VARIABLE GEOMETRY TURBINE
The present invention relates to a variable geometry turbine and has particular, but not
exclusive, application to variable geometry turbochargers.
Turbochargers are well known devices for supplying air to the intake of an internal
combustion engine at pressures above atmospheric (boost pressures). A conventional
turbocharger essentially comprises an exhaust gas driven turbine wheel mounted on a
rotatable shaft within a turbine housing. Rotation of the turbine wheel rotates a
compressor wheel mounted on the other end of the shaft within a compressor housing.
The compressor wheel delivers compressed air to the engine intake manifold. The
turbocharger shaft is conventionally supported by journal and thrust bearings, including
appropriate lubricating systems, located within a central bearing housing connected
between the turbine and compressor wheel housing.
The turbine stage of a conventional turbocharger comprises: a turbine housing defining
a turbine chamber within which the turbine wheel is mounted ; an annular inlet passage
defined in the housing between facing radially extending walls arranged around the
turbine chamber; an inlet arranged around the inlet passage; and an outlet passage
extending from the turbine chamber. The passages and chamber communicate such
that pressurised exhaust gas admitted to the inlet flows through the inlet passage to the
outlet passage via the turbine chamber and rotates the turbine wheel. It is known to
improve turbine performance by providing vanes, referred to as nozzle vanes, in the
inlet passage so as to deflect gas flowing through the inlet passage towards the
direction of rotation of the turbine wheel.
Turbines of this kind may be of a fixed or variable geometry type. Variable geometry
turbines differ from fixed geometry turbines in that the size of the inlet passage can be
varied to optimise gas flow velocities over a range of mass flow rates so that the power
output of the turbine can be varied in line with varying engine demands.
In one known type of variable geometry turbine, an axially moveable wall member
defines one wall of the inlet passage. The position of the movable wall member relative
to a fixed facing wall of the inlet passage is adjustable to control the axial width of the
inlet passage. Thus, for example, as exhaust gas flow through the turbine decreases,
the inlet passage width may be decreased to maintain the gas velocity and optimise
turbine output.
The axially movable wall member may be a "nozzle ring" that is provided with vanes
that extend into the inlet passage and through orifices provided in a shroud plate
defining the fixed facing wall of the inlet passage, the orifices being designed to
accommodate movement of the nozzle ring relative to the shroud. Typically the nozzle
ring may comprise a radially extending wall (defining one wall of the inlet passage) and
radially inner and outer axially extending walls or flanges that extend into an annular
cavity behind the radial face of the nozzle ring. The cavity is formed in a part of the
turbocharger housing (usually either the turbine housing or the turbocharger bearing
housing) and accommodates axial movement of the nozzle ring. The flanges may be
sealed with respect to the cavity walls to reduce or prevent leakage flow around the
back of the nozzle ring. In one common arrangement the nozzle ring is supported on
rods extending parallel to the axis of rotation of the turbine wheel and is moved by an
actuator, which axially displaces the rods.
In an alternative type of variable geometry turbocharger, the nozzle ring is fixed and
has vanes that extend from a fixed wall through orifices provided in a moving shroud
plate.
Actuators for moving the nozzle ring or movable shroud plate can take a variety of
forms, including pneumatic, hydraulic and electric and can be linked to the nozzle ring
or shroud plate in a variety of ways. The actuator will generally adjust the position of
the nozzle ring or movable shroud plate under the control of an engine control unit
(ECU) in order to modify the airflow through the turbine to meet performance
requirements.
In addition to the conventional control of a variable geometry turbocharger in an engine
fired mode (in which fuel is supplied to the engine for combustion) to optimise gas flow,
it is also known to take advantage of the facility to minimise the turbocharger inlet area
to provide an engine braking function in an engine braking mode (in which no fuel is
supplied for combustion) in which the inlet passage is reduced to smaller areas
compared to those in a normal engine fired mode operating range.
Engine brake systems of various forms are widely fitted to vehicle engine systems, in
particular to compression ignition engines (diesel engines) used to power large
vehicles such as trucks. The engine brake systems may be employed to enhance the
effect of the conventional friction brakes acting on the vehicle wheels or, in some
circumstances, may be used independently of the normal friction braking system, to
control, for example, the downhill speed of a vehicle. With some engine brake systems,
the brake is set to activate automatically when the engine throttle is closed (i.e. when
the driver lifts his foot from the throttle pedal) , and in others the engine brake may
require manual activation by the driver, such as depression of a separate brake pedal.
In one form of conventional engine brake system an exhaust valve in the exhaust line
is controlled to block partially the engine exhaust when braking is required. This
produces an engine braking torque by generating a high backpressure that retards the
engine by serving to increase the work done on the engine piston during the exhaust
stroke. This braking effect is transmitted to the vehicle wheels through the vehicle drive
chain.
With a variable geometry turbine, it is not necessary to provide a separate exhaust
valve. Rather, the turbine inlet passage may simply be "closed" to a minimum flow area
when braking is required. The level of braking may be modulated by control of the inlet
passage size by appropriate control of the axial position of the nozzle ring or movable
shroud plate. In a "fully closed" position in an engine braking mode the nozzle ring or
movable shroud plate may in some cases about the facing wall of the inlet passage.
A variable geometry turbocharger can also be operated in an engine fired mode so as
to close the inlet passage to a minimum width less than the smallest width appropriate
for normal engine operating conditions in order to control exhaust gas temperature.
The basic principle of operation in such an "exhaust gas heating mode" is to reduce the
amount of airflow through the engine for a given fuel supply level (whilst maintaining
sufficient airflow for combustion) in order to increase the exhaust gas temperature. This
has particular application where a catalytic exhaust after-treatment system is present.
In such a system performance is directly related to the temperature of the exhaust gas
that passes through it.
To achieve a desirable performance the exhaust gas temperature must be above a
threshold temperature (typically lying in a range of about 250 to O' ) under all
engine operating conditions and ambient conditions. Operation of the exhaust gas
after-treatment system below the threshold temperature range will cause the system to
build up undesirable accumulations.
These must be burnt off in a regeneration cycle to allow the system to return to
designed performance levels. In this regard, thermal management or engine
regeneration is a pre-determined engine process which uses exhaust gas heating, to
close the inlet passage to a minimum width less than the smallest width appropriate for
normal engine operating conditions, to heat the exhaust gas to a temperature that will
burn off the build-up undesirable accumulations.
In addition, prolonged operation of the exhaust gas after-treatment system below the
threshold temperature without regeneration will disable the system and cause the
engine to become non-compliant with government exhaust emission regulations.
For the majority of the operating range of, for example, a diesel engine, the exhaust
gas temperature will generally be above the required threshold temperature. However,
in some conditions, such as light load conditions and/or cold ambient temperature
conditions, the exhaust gas temperature can often fall below the threshold temperature.
In such conditions the turbocharger can in principle be operated in the exhaust gas
heating mode to reduce the turbine inlet passage width with the aim of restricting
airflow thereby reducing the airflow cooling effect and increasing exhaust gas
temperature.
For both engine braking and exhaust gas heating, it is important to allow some exhaust
gas flow through the turbine of the turbocharger. If the exhaust from an engine is
restricted to too great an extent, this can lead to excessive heat generation in the
engine cylinders, failure of exhaust valves, and the like. There must therefore be
provision for at least a minimum leakage flow through the turbine when the nozzle ring
or movable shroud plate is moved to a position in which the inlet width is small, or in a
fully closed position, for example during engine braking mode or exhaust gas heating
mode.
In this respect, due to their high efficiency modern variable geometry turbochargers can
generate such high boost pressures even at small inlet widths that their use in an
engine braking mode can be problematic as cylinder pressures can approach, or
exceed, acceptable limits unless countermeasures are taken (or braking efficiency is
sacrificed). Similarly, in relation to exhaust gas heating, the high boost pressures
achieved at small inlet widths can actually increase the airflow to the engine, offsetting
the effect of the restriction and thus reducing the desired heating effect. By way of
example, it is believed that in order to maintain the temperature of exhaust gas in an
engine idling at around OOOrpm, turbine efficiency must be 50% or less.
These problems have been addressed up to a point by EP1 435434, which discloses a
variable geometry turbine having an annular passageway defined between a radial wall
of a moveable wall member and a facing wall of the turbine housing. The moveable
wall member is mounted within an annular cavity provided within the housing and has
inner and outer annular surfaces. An annular seal is disposed between an annular
flange of the moveable wall member and the adjacent inner or outer annular surface of
the cavity. The turbine comprises a bypass arrangement in the form of a plurality of
radially extending bypass slots provided in the annular flange and distributed in the
circumferential direction. Each bypass slot extends through the radial thickness off the
annular flange.
The annular seal and bypass passageways move axially relative to one another as the
moveable wall member moves. The annular seal and bypass passages are axially
located such that as the annular wall member approaches the facing wall of the
housing, the bypass passages permit the flow of exhaust gas through the cavity to the
turbine wheel, thereby bypassing the annular inlet passageway.
However, with this known bypass arrangement it is only possible to provide this
reduction in efficiency at a certain axial position of the movable wall member.
Furthermore, this arrangement provides relatively little control over the amount of the
bypass flow that occurs at different axial positions of the movable wall member.
In this regard once the bypass slots (the circumferential array of bypass slots) are
moved inboard of the seal, the bypass slots are permanently fully open. Accordingly,
any further movement of the bypass slots inboard of the seal, i.e. any further inboard
movement of the moveable wall member does not affect the amount of bypass flow.
In addition, this arrangement may not provide a sufficient reduction in efficiency to
prevent over-pressurization of the engine cylinders during engine braking, or to off-set
the reduction in the cooling effect of the airflow during exhaust gas heating.
Furthermore, the above bypass arrangement can be prone to clogging due to the build¬
up of soot or other particulate matter, which can reduce the effectiveness of the bypass
passages, or even render them inoperable.
It is one object of the present invention to obviate or mitigate at least one of the above
disadvantages, and/or to provide an improved or alternative variable geometry turbine.
According to a first aspect of the present invention there is provided a variable
geometry turbine comprising :
a turbine wheel supported in a housing for rotation about a turbine axis;
an annular primary inlet passageway extending radially inwards towards the
turbine wheel, the primary inlet passageway being defined between a surface of a
radial wall of a moveable wall member and a surface of a facing wall of the housing ;
the moveable wall member being mounted within an annular cavity provided
within a housing, the movable wall member being moveable axially to vary the width of
the inlet passageway;
an annular seal being mounted to one of the movable wall member and an
adjacent housing member to provide a seal between adjacent surfaces of the movable
wall member and housing member respectively;
wherein a bypass passage is provided in the other of said movable wall
member and housing member, the bypass passage extending from an inlet bypass port
to an outlet bypass port, said inlet and outlet bypass ports being axially spaced from
each other and provided in said adjacent surface of said other of the movable wall
member and housing member;
a secondary inlet passageway fluidly connecting a region of the cavity outboard
of the seal to the turbine wheel such that flow in the secondary inlet passageway
bypasses at least a portion of the primary inlet passageway;
the bypass passage and the annular seal being arranged such that as the
movable wall member moves axially, the annular seal moves axially relative to the inlet
and outlet bypass ports so as to vary the extent of flow that may pass from a region of
the cavity inboard of the seal, through the bypass passage to the secondary inlet
passageway.
This is advantageous in that the axial position of the movable wall member determines
the level of bypass flow, i.e. the amount of flow that passes from a region of the cavity
inboard of the seal, through the inlet port, along the bypass passage, out of the outlet
bypass port and along the secondary inlet passageway to the turbine wheel. The
bypass flow provides a reduction in efficiency of the turbine since the bypass flow does
less work than the exhaust gas flow through the primary inlet passageway to the
turbine wheel. In this regard, where vanes extend across the primary inlet
passageway, the flow through the primary inlet passageway is turned in a tangential
direction by the vanes, causing the flow to do more work. Accordingly, the bypass flow
causes a reduction in efficiency of the turbine and a corresponding drop in compressor
outflow pressure (where the turbine is coupled to a compressor to form a
turbocharger), with an accompanying drop in engine cylinder pressure.
The axial position of the inlet and outlet bypass ports may be selected to provide a
reduction in efficiency at certain axial positions of the movable wall member (i.e. at
certain widths of the inlet passageway) such that, during exhaust gas heating and/or
thermal regeneration, the high boost pressures that would otherwise be achieved at
small inlet widths are reduced. This prevents an increase in the airflow to the engine,
that would offset the effect of the restriction and thus reduce the desired heating effect.
Accordingly, the above bypass arrangement may allow for improved exhaust gas
heating and/or thermal regeneration.
Furthermore, the axial position of the inlet and outlet bypass ports may be selected to
provide a reduction in efficiency at certain axial positions of the movable wall member
(i.e. at certain widths of the inlet passageway) such that, during engine braking the high
boost pressures that would otherwise be achieved at small inlet widths are reduced.
This avoids the cylinder pressures approaching, or exceeding, acceptable lim its.
Accordingly, the above bypass arrangement may allow for improved engine braking.
Since the extent of the bypass flow is varied in dependence on the axial position of the
movable wall member, the reduction in efficiency is varied in dependence on the axial
position of the movable wall member.
Providing a bypass passage having inlet and outlet bypass ports that are axially
spaced from each other and provided in said adjacent surface of the other of the
annular flange and wall member, allows the level of bypass flow to be controlled to a
greater extent than in the above known arrangement.
In this regard, where the bypass passage is provided in the housing member and the
seal is mounted to the movable wall member, as the movable wall member moves
inboard, from a fully open position, the seal moves inboard of the outlet bypass port,
thereby Opening' the outlet bypass port, i.e. allowing flow to pass from a region of the
cavity inboard of the seal, through the bypass inlet port, through the bypass passage
and out of the bypass outlet port to the secondary inlet passageway. Once the
outboard side of the seal passes the inboard side of the outlet bypass port, the outlet
bypass port is fully Opened'.
As the seal continues to move inboard relative to the inlet and outlet bypass ports, it
then begins to 'close' the inlet bypass port, i.e. reducing the flow that can pass through
the inlet bypass port into the bypass passage.
Accordingly, this allows the level of bypass flow to be controlled, after the outlet port
has been fully opened in dependence on the axial position of the movable wall
member, as the movable wall member moves inboard.
This is particularly advantageous since, in some situations, it is desirable to increase
the level of bypass flow to a maximum, for certain axial positions of the movable wall
member (i.e. certain widths of the inlet passageway) and then to decrease it again as
the movable wall member moves inboard from this position, i.e. as the width of the inlet
passageway is reduced. For example, during engine braking it may be desirable to
reduce the level of bypass flow at a very small width of the inlet passageway, so as to
allow for sufficient back pressure for engine braking to occur.
Furthermore, by varying the axial separation of the inlet and outlet bypass ports, the
level of bypass flow may be "tuned" to specific operating conditions, i.e. by providing
the desired levels of bypass flow at each axial position of the movable wall member.
In addition, the cross sectional area and axial position of the inlet port can be selected
to control the level of bypass flow at certain axial positions of the movable wall
member.
It will be appreciated that the same advantage is obtained wherein the bypass passage
is provided in the moveable wall member and the seal is mounted to the housing
member. However, in this case, as the moveable wall member moves inboard, from a
fully open position, the seal moves outboard of the inlet bypass port, thereby Opening'
the inlet bypass port, i.e. allowing flow to pass from a region of the cavity inboard of the
seal, through the bypass inlet port, through the bypass passage and out of the bypass
outlet port to the secondary inlet passageway. Once the inboard side of the seal
passes the outboard side of the inlet bypass port, the inlet bypass port is fully Opened'.
As the seal continues to move inboard relative to the inlet and outlet bypass ports, it
then begins to 'close' the outlet bypass port, i.e. reducing the flow that can pass
through the outlet bypass port into the bypass passage. Accordingly, this allows the
level of bypass flow to be controlled as above.
Furthermore, the bypass arrangement removes the need for a bypass valve, such as a
wastegate valve, that would otherwise be needed to vary the efficiency of the turbine.
Such a valve would require a large and costly actuator to operate the valve. The above
arrangement therefore removes the need for any such valve or actuator.
In addition, providing the inlet and outlet bypass ports in the same surface
advantageously provides a relatively compact bypass arrangement, as it is not
necessary for the bypass passageway to pass through the radial thickness of the
annular flange or wall member respectively, i.e. with the bypass passage extending in
the radial direction, between inlet and outlet ports provided on radially inner and outer
surfaces of the annular flange or wall member respectively.
It will be appreciated that references to 'inboard' and 'outboard' are in relation to the
primary inlet passageway. It will also be appreciated that, unless otherwise stated,
references to 'radially extending', 'radial', 'axially extending', 'axial, 'circumferentially
extending' and 'circumferential' are in relation to the turbine axis.
Optionally the moveable wall member has an annular flange extending axially from the
radial wall into said cavity and the annular seal is mounted to one of the annular flange
and the housing member.
The inlet bypass port may be provided inboard of the outlet bypass port.
The movable wall member may be axially movable relative to the facing wall of the
housing, between first and second configurations, wherein in the first configuration the
seal is positioned relative to the inlet and outlet bypass ports such that flow may pass
from a region of the cavity inboard of the seal to the secondary inlet passageway, via
the bypass passage and in the second configuration the seal is positioned relative to
the inlet and outlet bypass ports such that flow is substantially prevented from passing
from the region of the cavity inboard of the seal to the secondary inlet passageway, via
the bypass passage.
When the movable wall member is in the first configuration, the movable wall member
may be in a first position relative to the facing wall of the housing.
Optionally, when the movable wall member is in the first position, the seal is provided
at least partially outboard of the inlet bypass port such that it does not cover the inlet
bypass port or only partly covers an outboard portion of the inlet bypass port.
Optionally, when the movable wall member is in the first position, the seal is provided
at least partially inboard of the outlet bypass port such that is does not cover the outlet
bypass port or only partly covers an inboard portion of the outlet port. When the
movable wall member is in the first position, the seal may be disposed axially between
the inlet and outlet bypass ports.
The inlet and outlet bypass ports may be axially separated by a section of said other of
said movable wall member and said housing member.
The inlet and outlet ports may have substantially the same cross-sectional area. The
inlet and outlet ports may have substantially the same axial width. The outlet port may
have a cross-sectional area that is the same, or greater than, the cross-sectional area
of the inlet port.
When the movable wall member is in the second configuration, the movable wall
member may be in a second position relative to the facing wall of the housing.
When the movable wall member is in the second position, it may be closer to the facing
wall of the housing than when it is in the first position.
When the movable wall member is in the second position, the seal may substantially
cover the inlet bypass port or be provided inboard of the inlet bypass port such that
flow is substantially prevented from passing from the region of the cavity inboard of the
seal through the inlet bypass port and into the bypass passage.
In this respect, when the movable wall member is in the second position an inboard
side of the seal may be disposed inboard of an inboard side of the inlet bypass port.
When the movable wall member is in the second configuration, the movable wall
member may be in a third position relative to the facing wall of the housing.
When the movable wall member is in the third position, it may be axially further from
the facing wall of the housing than when the movable wall member is in the first
position.
When the movable wall member is in the third position, the seal may substantially
cover the outlet bypass port or be provided outboard of the outlet bypass port such that
flow is substantially prevented from passing from the bypass outlet port to the
secondary inlet passageway.
The inlet and outlet bypass ports may be separate ports defined by said surface of the
other of the movable wall member and housing member. The inlet and outlet bypass
ports may be defined only by said surface and not in combination with the seal. The
size of the inlet and outlet ports may be substantially fixed as the seal moves relative to
the inlet and outlet bypass ports, as the movable wall member moves axially. However,
it will be appreciated that the amount that these ports are open will depend on the axial
position of the movable wall member.
Each of the inlet and outlet bypass ports may be formed by an aperture provided in
said surface of said other of the movable wall member and housing member. The
aperture may have a substantially circular cross-sectional shape. Each of the inlet and
outlet ports may extend in the circumferential direction, either partly or substantially
along the circumferential extent of said other of the movable wall member and housing
member.
A plurality of said inlet ports may be provided in said adjacent surface of said other of
the movable wall member and housing member, distributed in the circumferential
direction along said surface. The inlet ports may be substantially aligned in the axial
direction. In this respect, the inlet ports may have substantially the same length in the
axial direction and have centres that are substantially axially aligned.
A plurality of said outlet ports may be provided in said adjacent surface of said other of
the movable wall member and housing member, distributed in the circumferential
direction along said surface. The outlet ports may be substantially aligned in the axial
direction. In this respect, the outlet ports may have substantially the same length in the
axial direction and have centres that are substantially axially aligned.
The bypass passage may extend in the circumferential direction such that it connects a
plurality of the inlet ports to a plurality of the outlet ports. The bypass passage may
extend partly or substantially along the circumferential extent of said other of the
movable wall member and housing member.
Alternatively, or additionally, there may be a plurality of said bypass passages, each
bypass passage extending from a respective inlet port to a respective outlet port. Each
bypass passage may extend from a respective inlet port that is substantially aligned, in
the circumferential direction, with a respective outlet port. The plurality of bypass
passages may be distributed in the circumferential direction.
The bypass passage may be arranged to direct the bypassed flow from the inlet
bypass port to the outlet bypass port.
The bypass passage may form a passage that is substantially enclosed between the
inlet and outlet ports. The bypass passage may be defined in whole, or in part, by said
other of said movable wall member and said housing member.
The, or each, bypass passage may comprise an inlet passage that fluidly connects the,
or a , bypass inlet port to a bypass chamber and an outlet passage that fluidly connects
the bypass chamber to the, or an, outlet bypass port.
The bypass chamber may extend in the circumferential direction partly or substantially
along the circumferential extent of said other of the movable wall member and housing
member.
The seal may be mounted to the movable wall member, with the bypass passage
provided in said adjacent housing member, the inlet and outlet bypass ports being
provided in said adjacent surface of the housing member. In this case, inlet and outlet
ports are axially fixed and the seal moves axially with the movable wall member.
Alternatively, the seal may be mounted to the adjacent housing member, with the
bypass passage provided in the movable wall member, the inlet and outlet bypass
ports being provided in said adjacent surface of the movable wall member. In this
case, the seal is axially fixed and the inlet and outlet ports move axially with the
movable wall member.
The adjacent housing member may be part of any housing of the variable geometry
turbine. In this regard, the housing member may be part of the housing in which the
turbine wheel is supported.
The variably geometry turbine may comprise a bearing housing that houses a bearing
assembly that rotatably supports a shaft on which the turbine wheel is mounted, for
rotation about said axis. In this case, the housing member may be part of the bearing
housing.
The adjacent housing member may comprise an axially extending annular sleeve. The
sleeve may be mounted to a radially inner surface of a housing of the variable
geometry turbine, for example a radially inner surface of the bearing housing or of the
housing in which the turbine wheel is supported. The sleeve may extend in the
circumferential direction, either partly or substantially about the turbine axis, to form the
shape of section of a cylinder or of a circumferential section of a cylinder.
The, or each, inlet and outlet passage are be provided in the sleeve, with the
respective bypass chamber provided in an adjacent housing of the variable geometry
turbine.
The annular cavity within which the moveable wall member is mounted may be
provided in any housing of the variable geometry turbine. For example, it may be
provided in the housing in which the turbine wheel is supported or in the bearing
housing.
The inlet and/or outlet bypass ports of the bypass passage may each have the same or
a smaller axial extent than the seal. The inlet and/or outlet bypass ports of the bypass
passage may each have the same or a smaller cross-sectional area than the seal.
The bypass passage may form a first bypass feature, wherein a second bypass
feature, defining a bypass flow path, is provided in said other of said moveable wall
member and said housing member, and is arranged such that as the movable wall
member moves axially, the annular seal moves axially relative to the second bypass
feature so as to vary the extent of flow that may pass from a region of the cavity
inboard of the seal, through the bypass flow path to the secondary inlet passageway.
The second bypass feature may be provided axially inboard or outboard of the first
bypass passage. Preferably, the second bypass feature is provided axially inboard of
the inlet bypass port of the bypass passage.
The second bypass feature may comprise a slot or recess, provided in said other of
said movable wall member and said housing member, that defines said flow path. The
recess may be of greater axial width than the seal.
Where the second bypass feature is provided in said sleeve, it may comprise a radially
extending slot that extends through the radial thickness of the sleeve such that a
radially outer end of the slot is in fluid communication with the cavity and a radially
inner end of the slot is provided in said adjacent surface.
The slot or recess may extend to an axially inboard end of the sleeve such that the slot
or recess is open to the cavity at its axially inboard end.
The slot or recess may be annular and may extend partly, or substantially, in the
circumferential direction about the turbine axis. The second bypass feature may
comprise a plurality of said recesses and/or slots, distributed in the circumferential
direction. The plurality of recess and/or slots maybe substantially axially aligned.
The bypass passage may form a first bypass passage, wherein the flow path of the
second bypass feature is a second bypass passage provided in said other of the
movable wall member or said housing member, the second bypass passage extending
from an inlet bypass port to an outlet bypass port, the second bypass passage and the
annular seal being arranged such that as the movable wall member moves axially, the
annular seal moves axially relative to the inlet and outlet bypass ports of the second
bypass passage so as to vary the extent of flow that may pass from a region of the
cavity inboard of the seal, through the second bypass passage to the secondary inlet
passageway.
The inlet and outlet bypass ports of the second bypass passage may be provided in the
same or different surfaces of said other of the annular flange and wall member.
Where the inlet and outlet bypass ports of the second bypass passage are provided in
different surfaces of said other of the annular flange and wall member, the inlet and
outlet bypass ports may be provided in radially inner and outer surfaces of said other of
the movable wall member and housing member, with the second bypass passage
extending in the radial direction. The second bypass passage may extend substantially
parallel to, or inclined relative to, the radial direction. In this respect, the inlet and outlet
bypass ports of the second bypass passage may substantially axially aligned or spaced
in the axial direction.
Where the inlet and outlet bypass ports of the second bypass passage are provided in
the same surface of said other of the movable wall member and housing member, the
second bypass passageway may have any of the above features of the first bypass
passageway or of said plurality of first bypass passageways.
In this respect, the inlet and outlet bypass ports of the second bypass passage may be
axially spaced from each other and provided in said adjacent surface of said other of
the movable wall member and housing member.
The second bypass feature may comprise a plurality of said inlet and outlet ports
provided in said adjacent surface of said other of the movable wall member and
housing member, distributed in the circumferential direction along said surface. The
second bypass passage may extend in the circumferential direction such that it
connects a plurality of the inlet ports to a plurality of the outlet ports. Alternatively, or
additionally, there may be a plurality of said second bypass passages, each bypass
passage extending from a respective inlet port to a respective outlet port.
When the movable wall member is in the second position, the seal may be disposed
between the first and second bypass features. Where the second bypass feature is
said second bypass passage, when the movable wall member is in the second position
the seal may be disposed between an adjacent respective inlet and outlet port of the
first and second bypass passages.
The movable wall member may be axially movable relative to the facing wall of the
housing, between third and fourth configurations, wherein in the third configuration the
seal is positioned relative to the second bypass feature such that flow may pass from a
region of the cavity inboard of the seal to the secondary inlet passageway, via the
second bypass flow path and in the fourth configuration the seal is positioned relative
to the second bypass feature such that flow is substantially prevented from passing
from the region of the cavity inboard of the seal to the secondary inlet passageway, via
the second bypass flow path.
When the movable wall member is in the third configuration, the movable wall member
may be in a fourth position relative to the facing wall of the housing.
In the case that the second bypass feature comprises said recess, when the movable
wall member is in the fourth position, the seal may be located within the axial extent of
the recess such that flow may pass from a region of the cavity inboard of the seal to the
secondary inlet passageway. In this case, an axially inboard side of the seal may be
located axially outboard of an axially inboard side of the recess and/or an axially
outboard side of the seal may be located axially inboard of an axially outboard side of
the recess.
In the case that the second bypass feature comprises said second bypass passage,
optionally when the movable wall member is in the fourth position, the seal does not
cover the inlet bypass port or only partially covers the inlet bypass port of the second
bypass passage.
Optionally, when the movable wall member is in the fourth position, the seal is provided
at least partially outboard of the inlet bypass port of the second bypass passage such
that it does not cover the inlet bypass port or only partly covers an outboard portion of
the inlet bypass port. When the movable wall member is in the fourth position, the seal
may be disposed axially between the inlet and outlet bypass ports of the second
bypass passage.
The inlet and outlet bypass ports of the second bypass passage may be axially
separated by a section of said other of said movable wall member and said housing
member.
When the movable wall member is in the fourth configuration, the movable wall
member may be in a fifth position relative to the facing wall of the housing.
When the movable wall member is in the fifth position, it may be closer to the facing
wall of the housing than when it is in the fourth position.
When the movable wall member is in the fifth position, the seal may substantially cover
the inlet bypass port or be provided inboard of the inlet bypass port of the second
bypass passage such that flow is substantially prevented from passing from the region
of the cavity inboard of the seal through the inlet bypass port and into the bypass
passage.
In this respect, when the movable wall member is in the fifth position an inboard side of
the seal may be disposed inboard of an inboard side of the inlet bypass port of the
second bypass passage.
When the movable wall member is in the fourth configuration, the movable wall
member may be in a sixth position relative to the facing wall of the housing.
When the movable wall member is in the sixth position, it may be axially further from
the facing wall of the housing than when the movable wall member is in the fourth
position.
When the movable wall member is in the sixth position, the seal may substantially
cover the outlet bypass port or be provided outboard of the outlet bypass port of the
second bypass passage such that flow is substantially prevented from passing from the
second bypass passage out of the bypass outlet port to the secondary inlet
passageway.
In this respect, when the movable wall member is in the sixth position an outboard side
of the seal may be disposed outboard of an outboard side of the outlet bypass port of
the second bypass passage.
An array of inlet guide vanes may extend across the annular primary inlet passageway
to define a radial vane passage.
The secondary inlet passageway may fluidly connect a region of the cavity outboard of
the seal to the turbine wheel such that flow in the secondary inlet passageway
bypasses the inlet guide vanes in the primary inlet passageway.
The movable wall member may be a shroud defining apertures for receipt of the vanes,
which are attached to a nozzle ring having a radial surface that corresponds to the
facing of the housing.
Alternatively, the movable wall member may be a nozzle ring which supports the vanes
for receipt in apertures defined by a shroud plate whose radial surface corresponds to
the facing wall of the housing.
It will be appreciated that, regardless of which component defines the facing wall of the
housing, the facing wall of the housing may itself be secured to the housing or it may
be movable. That is, in the embodiment where the movable wall member of the
present invention is a shroud for example, the vanes are supported by a nozzle ring
which may be secured to the housing or movable.
Optionally, a particulate filter is provided in the bypass passage such that flow passing
through the bypass passage passes through the filter, with the particulate filter being
contacted by particulate matter flowing through the filter.
The particulate filter may comprise a high surface area material. The high surface area
material may possesses a surface area that is sufficiently high to facilitate aerial
oxidation of particulate matter deposited on said high surface area material.
The surface area of the high surface area material may be sufficiently high to facilitate
aerial oxidation of particulate matter at a temperature of at least around 200 °C.
The surface area of the high surface area material may be sufficiently high to facilitate
aerial oxidation of particulate matter at a temperature of around 250 °C to 400 °C.
The particulate filter may comprise a metallic material and/or ceramic material.
The metallic material may be an iron or nickel based alloy.
The ceramic material may be a magnesium based ceram ic material.
The particulate filter may comprise a catalytic material suitable to catalyse the
conversion of particulate matter into one or more different species. The one or more
different species may comprise one or more fluids.
The catalytic material may incorporates a transition metal species.
The particulate filter may be a carbonaceous particulate filter. The carbonaceous
particulate filter may comprise a catalyst suitable to catalyse the conversion of
carbonaceous material to gaseous carbon dioxide and water.
The particulate filter may comprise a Diesel Particulate Filter catalyst material.
The particulate filter may comprise a mesh through which the flow may pass. The mesh
may be of stainless steel.
The filter may be arranged such that substantially all the flow that passes through the
bypass passage passes through the filter. The filter may extend substantially across
the entire cross-sectional area of the bypass passage.
Where the bypass passage comprises said bypass chamber, the filter may be disposed
within said bypass chamber.
The filter may be provided in said first and/or second bypass passages. The filter may
be provided in said recess such that flow passing through the recess passes through
the filter.
The mesh of the filter may have a cut-out section disposed at the inlet and/or outlet
bypass port of the bypass passageway.
The mesh may be housed within a frame. The frame may be a metal frame. The frame
may be of any suitable material.
According to a second aspect of the invention there is provided a turbocharger
comprising a variable geometry turbine according to the first aspect of the invention
and a compressor comprising a housing defining an inlet and an outlet, and a chamber
between the inlet and outlet, within which an impeller wheel is rotatably mounted such
that rotation of the impeller wheel compresses air received through the inlet and
passes the compressed air to the outlet, wherein the turbine wheel of the turbine is
coupled to the impeller wheel so as to drivably rotate the impeller wheel.
According to a third aspect of the invention there is provided an engine system
comprising an internal combustion engine and a turbocharger according to the second
aspect of the invention, arranged such that exhaust gas from the internal combustion
engine drivably rotates the turbine wheel of the turbine.
According to a fourth aspect of the invention there is provided a method of operating an
engine system according to the third aspect of the invention wherein the movable wall
member is moved between said first and second configurations when the engine
system is operated in an engine braking mode, a thermal regeneration mode or an
exhaust gas heating mode.
Preferably the movable wall member is moved between said first and second
configurations when the engine system is operated in a thermal regeneration mode or
an exhaust gas heating mode.
The movable wall member may be moved between said third and fourth configurations
when the engine system is operated in an engine braking mode, a thermal
regeneration mode or an exhaust gas heating mode.
Preferably the movable wall member is moved between said third and fourth
configurations when the engine system is operated in an engine braking mode.
Specific embodiments of the present invention will now be described, by way of
example only, with reference to the accompanying drawings, in which :
Figure 1 shows a cross-sectional view of a turbocharger;
Figure 2 shows a schematic cross-sectional view of a portion of a turbine according to
a first embodiment of the present invention;
Figure 3a shows a schematic cross-sectional view corresponding to that of Figure 2,
where the movable shroud is in a third axial position relative to a facing wall of a
housing of the turbine;
Figure 3b shows a schematic cross-sectional view corresponding to that of Figure 2,
where the movable shroud is in a first axial position relative to a facing wall of a
housing of the turbine;
Figure 3c shows a schematic cross-sectional view corresponding to that of Figure 2,
where the movable shroud is in a first axial position relative to a facing wall of a
housing of the turbine but located axially inboard of the position shown in Figure 3b;
Figure 3d shows a schematic cross-sectional view corresponding to that of Figure 2,
where the movable shroud is in a second axial position relative to a facing wall of a
housing of the turbine;
Figure 4a shows a schematic cross-sectional view of a portion of a turbine according to
a second embodiment of the present invention, where the movable shroud is in a third
axial position relative to a facing wall of a housing of the turbine;
Figure 4b shows a schematic cross-sectional view corresponding to that of Figure 4a,
where the movable shroud is in a first axial position relative to a facing wall of a
housing of the turbine;
Figure 4c shows a schematic cross-sectional view corresponding to that of Figure 4a,
where the movable shroud is in a second axial position relative to a facing wall of a
housing of the turbine;
Figure 4d shows a schematic cross-sectional view corresponding to that of Figure 4a,
where the movable shroud is in a fourth axial position relative to a facing wall of a
housing of the turbine;
Figure 5a shows a schematic cross-sectional view of a portion of a turbine according to
a third embodiment of the present invention, where the movable shroud is in a third
axial position relative to a facing wall of a housing of the turbine;
Figure 5b shows a schematic cross-sectional view corresponding to that of Figure 5a,
where the movable shroud is in a first axial position relative to a facing wall of a
housing of the turbine;
Figure 5c shows a schematic cross-sectional view corresponding to that of Figure 5a,
where the movable shroud is in a first axial position relative to a facing wall of a
housing of the turbine but located axially inboard of the position shown in Figure 5b;
Figure 5d shows a schematic cross-sectional view corresponding to that of Figure 5a,
where the movable shroud is in a second axial position relative to a facing wall of a
housing of the turbine;
Figure 5e shows a schematic cross-sectional view corresponding to that of Figure 5a,
where the movable shroud is in a sixth axial position relative to a facing wall of a
housing of the turbine;
Figure 5f shows a schematic cross-sectional view corresponding to that of Figure 5a,
where the movable shroud is in a fourth axial position relative to a facing wall of a
housing of the turbine;
Figure 5g shows a schematic cross-sectional view corresponding to that of Figure 5a,
where the movable shroud is in a fourth axial position relative to a facing wall of a
housing of the turbine but located axially inboard of the position shown in Figure 5f, and
Figure 5h shows a schematic cross-sectional view corresponding to that of Figure 5a,
where the movable shroud is in a fifth axial position relative to a facing wall of a
housing of the turbine.
Figure 6 shows an under plan view of a circumferential section of an annular sleeve of
the portion of the turbine shown in Figures 4a to 4d ;
Figure 7 shows an enlarged cross-sectional schematic view of the bypass passage
shown in Figure 2, where a filter is included in the bypass passage;
Figures 8a to 8c each show an enlarged view of different designs of filter that may be
used in the bypass passage shown in Figure 7 ;
Figure 9 shows a schematic cross-sectional view of a portion of a turbine according to
a further embodiment of the present invention, and
Figure 10 shows a schematic cross-sectional view of a portion of a turbine according to
a further embodiment of the present invention.
Referring to figure 1, this illustrates a variable geometry turbocharger comprising a
variable geometry turbine housing 1 and a compressor housing 2 interconnected by a
central bearing housing 3 . A turbocharger shaft 4 extends from the turbine housing 1 to
the compressor housing 2 through the bearing housing 3 . A turbine wheel 5 is mounted
on one end of the shaft 4 for rotation within the turbine housing 1, and a compressor
wheel 6 is mounted on the other end of the shaft 4 for rotation within the compressor
housing 2. The shaft 4 rotates about turbocharger axis 4a on bearing assemblies
located in the bearing housing 3 .
The turbine housing 1 defines an inlet volute 7 to which gas from an internal
combustion engine 500 is delivered via an exhaust path 501 (the engine 500 and
exhaust path 501 are shown schematically in Figure 1) . The exhaust gas flows from the
inlet volute 7 to an axial outlet passageway 8 via an annular inlet passageway 9 and
the turbine wheel 5 . The inlet passageway 9 is defined on one side by a face of a radial
wall of a movable annular wall member 11, comprising an annular shroud 12 , and on
the opposite side by a second wall member, also referred to as a nozzle ring 10 , which
forms the wall of the inlet passageway 9 facing the annular shroud 12. The shroud 12
defines an annular recess 13 in the annular wall member 11.
The nozzle ring 10 supports an array of circumferentially and equally spaced inlet
vanes 14 each of which extends across the inlet passageway 9. The vanes 14 are
orientated to deflect gas flowing through the primary inlet passageway 9 towards the
direction of rotation of the turbine wheel 5. When the annular shroud 12 is proximate to
the nozzle ring 10 the vanes 14 project through suitably configured slots in the shroud
12 , into the recess 13 .
The position of the annular wall member 11 is controlled by an actuator assembly of
the type disclosed in US 5,868,552. An actuator (not shown) is operable to adjust the
position of the annular wall member 11 via an actuator output shaft (not shown) , which
is linked to a yoke 15 . The yoke 15 in turn engages axially extending actuating rods 16
that support the annular wall member 11. Accordingly, by appropriate control of the
actuator (which may for instance be pneumatic, hydraulic or electric), the axial position
of the rods 16 and thus of the annular wall member 11 can be controlled. The speed of
the turbine wheel 5 is dependent upon the velocity of the gas passing through the inlet
passageway 9. For a fixed rate of mass of gas flowing into the inlet passageway 9 , the
gas velocity is a function of the width of the inlet passageway 9 , the width being
adjustable by controlling the axial position of the annular wall member 11. For a fixed
rate of mass of gas flowing into the inlet passageway 9 , up until the point at which the
vanes 14 choke the inlet passageway 9 the narrower the width of the inlet passageway
9, the greater the velocity of the gas passing through the inlet passageway 9.
Figure 1 shows the inlet passageway 9 fully open. The inlet passageway 9 may be
closed to a minimum by moving the annular shroud 1 of the annular wall member 11
towards the nozzle ring 10 . When the separation between the annular shroud 12 of the
annular wall member 11 and the nozzle ring 10 is a minimum (such that the width of
the inlet passageway is a minimum), the annular wall member 11 may be said to be in
a closed position.
The annular wall member 11 has axially extending radially inner and outer annular
flanges 17 and 18 that extend into an annular cavity 19 provided in the turbine housing
1. Inner and outer sealing rings 20 and 2 1 are provided to seal the annular wall
member 11 with respect to inner and outer annular surfaces of the annular cavity 19
respectively, whilst allowing the annular wall member 11 to slide within the annular
cavity 19 . The inner sealing ring 20 is supported within an annular groove formed in the
radially inner annular surface of the cavity 19 and bears against the inner annular
flange 17 of the annular wall member 11. The outer sealing ring 20 is supported within
an annular groove formed in the radially outer annular surface of the cavity 19 and
bears against the outer annular flange 18 of the annular wall member 11.
Gas flowing from the inlet volute 7 to the outlet passageway 8 passes over the turbine
wheel 5 and as a result torque is applied to the shaft 4 to drive the compressor wheel
6 . Rotation of the compressor wheel 6 within the compressor housing 2 pressurises
ambient air present in an air inlet 22 and delivers the pressurised air to an air outlet
volute 23 from which it is fed to an internal combustion engine (not shown).
Referring to Figure 2, there is shown a schematic cross-sectional view of a portion of a
turbine according to a first embodiment of the present invention. The turbine of this
embodiment is identical to the turbine of Figure 1 except of the differences described
below. Corresponding features are given the same reference numerals but
incremented by 100. The turbine of this embodiment is a turbine of a turbocharger
such as the turbocharger shown in Figure 1.
In the embodiment shown in Figure 2, the shroud 112 includes radially inner and outer
axially extending annular flanges 117 , 118 similar to those of the shroud 1 shown in
Figure 1. However, the outer annular flange 118 of the embodiment shown in Figure 2
is shorter than that of the outer annular flange 18 forming part of the conventional
arrangement shown in Figure 1.
At the outboard end of the inner annular flange 117 is a radially extending flange 125
which defines an annular groove 1 6 for receipt of an annular split seal ring 127. The
seal ring 127 is dimensioned so as to contact an adjacent, radially inner, surface of a
cylindrical sleeve 128 which extends axially from the bearing housing 103 into the
annular cavity 113 so as to provide a restriction to fluid flow in between the seal ring
127 and the cylindrical sleeve 128. In this regard, the contact between the seal ring
127 and the radially inner surface of the cylindrical sleeve 128 results in a substantial
seal that substantially prevents fluid from passing from a region of the cavity 113
inboard of the seal ring 1 7, past the seal ring 127 to a position outboard of the seal
ring 127 (and vice versa).
An annular primary inlet passageway 109 is defined between a radial surface 133 of
the nozzle ring 110 and an opposite radial surface 134 of a radial wall 135 of the
shroud 118 .
As in Figure 1, in the arrangement shown in Figure 2 , the nozzle ring 110 is fixed to the
turbine housing 10 1. The nozzle ring 1 0 supports an array of circumferentially spaced
inlet vanes 114 , each of which extends across the primary inlet passageway 109.
The vanes 114 are oriented to deflect gas flow in the direction or arrow X through the
primary inlet passageway 109 towards the direction of rotation of the turbine wheel (not
shown in Figure 2). When the annular shroud 112 is proximate to the nozzle ring 110
the vanes 114 project through suitably configured slots (not shown) in the shroud 112.
As can be seen in Figure 2 , the shroud 12 and the bearing housing 103 are arranged
so as to define a path for gas flowing towards the turbine wheel to flow into the annular
cavity 113 behind the shroud 112 . In this way, gas can flow around the relatively short
outer annular flange 1 8 to transmit relatively high pre-turbine pressure to the back of
the shroud 112. In an alternative arrangement, the shroud 112 may incorporate a
relatively long outer annular flange which can be sealed with respect to the bearing
housing 103 by a seal ring and a plurality of apertures defined by the shroud upstream
of the outer diameter of the vane passage to facilitate the flow of gas at pre-turbine
pressure to flow into the annular cavity 113 .
A secondary inlet flow passageway 190 fluidly connects a region of the cavity 113
axially outboard of the seal ring 127 to the turbine wheel. The secondary inlet
passageway 190 is arranged such that flow passing through the secondary inlet
passageway 190, from the cavity 113 to the turbine wheel, bypasses the inlet vanes
114 .
A bypass arrangement in the form of a plurality of circumferentially distributed bypass
passages 150 is provided in the cylindrical sleeve 128. Each bypass passage 150
extends from an inlet bypass port 15 1 to an outlet bypass port 152, said inlet and outlet
bypass ports 15 1, 152 being axially spaced from each other and provided in said
radially inner surface of the annular sleeve 128 that is adjacent to the seal 127. Each
of the inlet and outlet bypass ports 15 1, 152 has substantially the same axial extent as
the annular seal 127.
The bypass passages 150 are distributed in the circumferential direction and are
substantially axially aligned with each other.
Each bypass passage 150 comprises an inlet passage 154 that fluidly connects the
bypass inlet port 15 1 to a bypass chamber 157 and an outlet passage 155 that fluidly
connects the bypass chamber to the outlet bypass port 152. The outlet bypass port
152 is spaced axially from the inlet bypass port 15 1 in the axially outboard direction.
The bypass chamber 157 extends in the axial direction partway along the axial length
of the annular sleeve 128. The bypass chamber 157 also extends in the
circumferential direction partway along the circumference of the annular sleeve 128.
Similarly, the inlet and outlet bypass ports 15 1 , 152 have an annular cross-sectional
shape, extending in the circumferential direction partway along the circumference of
the radially inner surface of the sleeve 128 (see Figure 6). Accordingly, the inlet and
outlet bypass ports 15 1 , 152, the inlet and outlet passages 154, 155 and the bypass
chamber 157 are each annular extending in the circumferential direction partway along
the circumference of the annular sleeve 128.
As described in more detail below, the bypass passage 150 and the annular seal 127
are arranged such that as the shroud 112 moves axially, the annular seal 127 moves
axially relative to the inlet and outlet bypass ports 15 1 , 152, so as to vary the extent of
flow that may pass from a region of the cavity 113 inboard of the annular seal 1 7,
through the bypass passage 150, to the secondary inlet passageway 190.
Referring again to Figure 2 , a further split seal ring 130 is provided between the inner
annular flange 117 and an axially extending wall 13 1 of the bearing housing 103 that, in
part, defines the annular cavity 113 within which the shroud 112 is mounted.
In the embodiment shown in Figure 2 the wall 13 1 defines an annular groove 132 for
receipt of the seal ring 130 such that the inner annular flange 117 of the shroud 112
runs over the radially outer edge of the seal ring 130 during axial displacement of the
shroud 112 . The radial extent of the seal ring 130 is selected to define a
predetermined radial clearance between the seal ring 130 and the inner annular flange
117 . This sealing arrangement is configured so as to define a leakage flow path across
the seal ring 130, from inboard of the seal ring 130 to outboard of the seal ring 130 so
that said secondary inlet passageway 190 is in fluid communication with the turbine
wheel.
In an alternative embodiment, the seal ring 130 may be omitted.
Specifically, referring to Figures 3a to 3d, there is sequentially shown schematic crosssectional
views corresponding to that of Figure 2 , but where the movable shroud 112 is
moved progressively closer to the facing radial surface 133 of the radial wall of the
nozzle ring 110 .
In more detail, in Figure 3a the movable shroud 112 is in a third position relative to the
facing radial surface 133 of the nozzle ring 110 . In this position, the radially extending
flange 125 is axially positioned such that the annular seal 127 is disposed axially
outboard of the outlet port 152 of the bypass passageway 150. In this respect, the
axially inboard and outboard sides of the annular seal 127 are disposed axially
outboard of the outlet port 152. When the seal 127 is in this third position, flow is
substantially prevented from passing from a region of the cavity 113 inboard of the seal
127 to a region of the cavity 13 outboard of the seal 1 7 and therefore is substantially
prevented from passing to the secondary inlet passageway 190. Accordingly, flow is
substantially prevented from bypassing the primary inlet passageway 109, and
therefore from bypassing the vanes 114 (the path of the flow is shown by the arrow F).
When the movable shroud 112 is in the third position, it may occupy any axial position
in which it substantially covers the outlet bypass port 152, or is disposed axially
outboard of the outlet bypass port 152 such that it substantially prevents flow passing
from the bypass passage 150 to axially outboard of the seal 127, to the secondary inlet
passageway 190. In this third position, the seal 127 may partially cover the outlet port
152, with an outboard side of the seal 127 disposed axially outboard of the outboard
side of the outlet port 52, such that flow is substantially prevented from passing from
the outlet port 152 to axially outboard of the seal 1 7.
Referring to Figure 3b, the movable shroud 112 is shown in a first axial position relative
to the facing surface 133 of the nozzle ring 110 . When the shroud 112 is in this axial
position, the radially extending flange 125 and the annular seal 127 are axially located
between the inlet and outlet ports 15 1 , 152 of the bypass passage 150, such that the
inlet and outlet ports 15 1 , 152 are at least partially exposed so as to allow flow to pass
from the region of the cavity 113 inboard of the seal 127, through the bypass passage
150 to the secondary inlet passageway 190 and to the turbine wheel 105, thereby
bypassing the primary inlet passageway 109 and therefore the inlet guide vanes 114
(the path of the flow is shown by the arrow F).
Similarly, in Figure 3c the seal 127 is also shown in an alternative first axial position in
which the seal 127 is disposed slightly axially inboard of its position shown in Figure
3b. In the position shown in Figure 3c, the inlet port 15 1 is partially covered by the seal
127 and the outlet port 152 is entirely exposed, with the seal 127 disposed axially
inboard of the outlet port 152. The inlet port 15 1 is exposed to a sufficient extent to
allow flow to pass from the region of the cavity 113 inboard of the seal 127, through the
inlet port 15 1 , through the bypass port 150 to the secondary inlet port 157, and to the
turbine wheel 150, thereby bypassing the primary inlet passageway 109 and the inlet
guide vanes 1 4 .
It will be appreciated that when the shroud 112 is in its first position it may occupy a
range of axial positions in which it is disposed between the inlet and outlet ports 15 1 ,
152 such that it does not cover, or only partially covers, the inlet and/or outlet bypass
ports 15 1 , 152 such that flow may pass from the cavity 113 , through the bypass
passage 150 to the secondary inlet passage 157.
Referring to Figure 3d, the shroud 112 is shown in a second axial position. When the
shroud is in the second axial position it is disposed axially inboard of its position when it
is in the third axial position (shown in Figures 3b and 3c). In this regard, when the
shroud 112 is in the third axial position the annular seal 127 is disposed axially inboard
of its position when the shroud 112 is in the third axial position.
When the shroud 112 is in the second axial position, it is disposed axially inboard of the
inlet port 15 1 of the bypass passage 150. In this regard, the axially inboard and
outboard sides of the seal 127 are disposed axially inboard of the inlet port 15 1 of the
bypass passage 150. In this position, the seal 127 substantially prevents flow from
passing from the cavity 113 past the seal 127, to the secondary inlet passageway 190.
It will be appreciated that in this position, no flow passes from the cavity 113 through
the bypass passage 150.
When the shroud 112 is in the second axial position, the seal 127 may be axially
located such that it substantially covers, or at least partially covers, or is disposed
axially inboard of, the inlet bypass port 15 1 of the bypass passage 150, such that flow
may not pass from the region of the cavity 113 inboard of the seal 127 to the secondary
inlet passageway 190. Accordingly, it will be appreciated that when the movable
shroud 112 is in the second axial position, it may occupy a range of axial positions.
Accordingly, the movable shroud 112 is axially movable relative to the facing wall 133
of the nozzle ring 110, between first and second configurations, wherein in the first
configuration the seal 127 is positioned relative to the inlet and outlet bypass ports 15 1,
152 such that flow may pass from a region of the cavity 113 inboard of the seal 127 to
the secondary inlet passageway 190, via the bypass passage 150 and in the second
configuration the seal 127 is positioned relative to the inlet and outlet bypass ports
15 1 , 152 such that flow is substantially prevented from passing from the region of the
cavity 113 inboard of the seal 127 to the secondary inlet passageway 190, via the
bypass passage 150.
When the shroud 112 is in the first configuration it is in the first axial position. When
the shroud 112 is in the second configuration it is in the second or third axial positions.
The bypass arrangement of the above described embodiment is advantageous in that
the axial position of the movable shroud 112 determines the level of bypass flow, i.e.
the amount of flow that passes from a region of the cavity 113 inboard of the seal 127,
along the secondary inlet passageway 190 to the turbine wheel. The bypass flow
provides a reduction in efficiency of the turbine since the bypass flow does less work
than the exhaust gas flow through the primary inlet passageway 109 to the turbine
wheel. In this regard, the flow through the primary inlet passageway 109 is turned in a
tangential direction by the vanes 114 , causing the flow to do more work. Accordingly,
the bypass flow causes a reduction in efficiency of the turbine and a corresponding
drop in compressor outflow pressure, with an accompanying drop in engine cylinder
pressure.
The axial position of the inlet and outlet bypass ports 15 1 , 152 may be selected to
provide a reduction in efficiency at certain axial positions of the movable wall member
(i.e. at a certain width of the inlet passageway) such that, during exhaust gas heating
and/or thermal regeneration, the high boost pressures that would otherwise be
achieved at small inlet widths are reduced. This prevents an increase in the airflow to
the engine, that would offset the effect of the restriction and thus reduce the desired
heating effect. Accordingly, the above bypass arrangement may allow for improved
exhaust gas heating and/or thermal regeneration.
Furthermore, the axial position of the inlet and outlet bypass ports 15 1 , 152, may be
selected to provide a reduction in efficiency at certain axial positions of the movable
shroud 112 (i.e. at a certain width of the inlet passageway) such that, during engine
braking the high boost pressures that would otherwise be achieved at small inlet widths
are reduced. This avoids the cylinder pressures approaching, or exceeding, acceptable
limits. Accordingly, the above bypass arrangement may allow for improved engine
braking.
Since the extent of the bypass flow is varied in dependence on the axial position of the
movable shroud 11 , the reduction in efficiency is varied in dependence on the axial
position of the movable shroud 112.
Providing a bypass passage 150 having inlet and outlet bypass ports 15 1 , 152 that are
axially spaced from each other in this way allows the level of bypass flow to be
controlled to a greater extent than would otherwise be possible.
In this regard, where the bypass passage 150 is provided in the sleeve 128 and the
seal 127 is mounted to the movable shroud 112 , as the movable shroud 112 moves
inboard, from a fully open position, the seal 127 moves inboard of the outlet bypass
port 152, thereby Opening' the outlet bypass port 152, i.e. allowing flow to pass from a
region of the cavity inboard of the sea 127, through the bypass inlet port 15 1 through
the bypass passage 150 and out of the bypass outlet port 152 to the secondary inlet
passageway. Once the outboard side of the seal 127 passes the inboard side of the
outlet bypass port 152, the outlet bypass port 152 is fully Opened'. This is the position
shown in Figure 3 . In this position, the amount of bypass flow is at a maximum .
As the seal 127 continues to move inboard relative to the inlet and outlet bypass ports
15 1 , 152, it then begins to 'close' the inlet bypass port 15 1, i.e. reducing the flow that
can pass through the inlet bypass port 15 1 into the bypass passage 150.
Accordingly, this allows the level of bypass flow to be controlled, after the outlet port
152 has been fully opened, in dependence on the axial position of the movable shroud
112 , as the movable shroud 112 moves inboard.
This is particularly advantageous since, in some situations, it is desirable to increase
the level of bypass flow to a maximum , for a certain axial position of the movable
shroud 112 (i.e. a certain width of the inlet passageway) and then to decrease it again
as the movable shroud 112 moves inboard from this position, i.e. as the width of the
inlet passageway is reduced. For example, during engine braking it may be desirable
to reduce the level of bypass flow at a very small width of the inlet passageway, so as
to allow for sufficient back pressure for engine braking to occur.
Furthermore, by varying the axial separation of the inlet and outlet bypass ports
15 1,152, the level of bypass flow may be "tuned" to specific operating conditions, i.e.
by providing the desired levels of bypass flow at each axial position of the movable
shroud 112
In addition, the cross sectional area and axial position of the inlet port 15 1 can be
selected to control the level of bypass flow at certain axial positions of the movable
shroud 112 .
Furthermore, the bypass arrangement removes the need for a bypass valve, such as a
wastegate valve, that would otherwise be needed to vary the efficiency of the turbine.
Such a valve would require a large and costly actuator to operate the valve. The above
arrangement therefore removes the need for any such valve or actuator.
In addition, providing the inlet and outlet bypass ports 15 1, 152 in the same surface
advantageously provides a relatively compact bypass arrangement, as it is not
necessary for the bypass passageway 150 to pass through the radial thickness of the
sleeve 1 8, i.e. with the bypass passage extending in the radial direction, between inlet
and outlet ports provided on radially inner and outer surfaces of the sleeve 128.
Referring to Figures 4a to 4d, there is shown a schematic cross-sectional view of a
portion of a turbine according to a second embodiment of the present invention, where
the shroud 112 is progressively moved towards the facing radial surface 133 of the
nozzle ring 110. The turbine of the second embodiment is identical to that of the first
embodiment, except for the differences described below. Corresponding features are
given the same reference numerals.
The second embodiment differs from the first embodiment in that the bypass passage
150 is located at a position axially outboard of its position in the first embodiment. In
addition, a second bypass arrangement in the form of an array of annular bypass slots
160 is provided at an axially inboard end of the sleeve 1 8. The slots 160 are
distributed in the circumferential direction (see Figure 6) .
Each slot 160 extends in the axial direction part way along the axial extent of the
annular sleeve 128. Each slot 160 extends through the radial thickness of the sleeve
128 such that its radially outer end is in gas communication with the cavity. Each slot
160 extends axially inboard to the axially inboard end of the sleeve 28 such that the
sleeve 128 has an open inboard end. Accordingly flow is able to pass from the cavity
113 through the open end of the sleeve 128 into the slot 160. The slot 160 extends in a
circumferential direction partly along the circumference of the annular sleeve 128 (as
shown in Figure 6).
The movable shroud 112 is moved to corresponding positions to those as described for
the first embodiment. In this regard, in Figure 4a the movable shroud 112 is in said
third position relative to the facing radial surface 133 of the nozzle ring 110. In this
position, the radially extending flange 125 is axially positioned such that the annular
seal 127 is disposed axially outboard of the outlet port 152 of the bypass passageway
150. In this respect, the axially inboard and outboard sides of the annular seal 127 are
disposed axially outboard of the outlet port 152. When the seal 127 is in this third
position, flow is substantially prevented from passing from a region of the cavity 133
inboard of the seal 127 to the secondary inlet passageway 190 - i.e. to a region of the
cavity 113 outboard of the seal 127. Accordingly, flow is substantially prevented from
bypassing the vanes 114.
When the movable shroud 112 is in the third position, it may occupy any axial position
in which it substantially covers the outlet bypass port 152, or is disposed axially
outboard of the outlet bypass port 152 such that it substantially prevents flow passing
from the bypass passage 150 to axially outboard of the seal 127, to the secondary inlet
passageway 190. In this third position, the seal 1 7 may partially cover the outlet port
152, with an outboard side of the seal 127 disposed axially outboard of the outboard
side of the outlet port 152, such that flow is substantially prevented from passing from
the outlet port 152 to axially outboard of the seal 1 7.
Referring to Figure 4b, the shroud is shown in said second axial position. In this
position, the seal 127 is axially located between the inlet and outlet ports 15 1, 152 of
the bypass passage 150, such that the inlet and outlet ports 15 1 , 152 are substantially
completely exposed so as to allow flow to pass from a region of the cavity 113 inboard
of the seal 127, through the bypass passage 150 to the secondary inlet passageway
190 and to the turbine wheel 105, thereby bypassing the inlet guide vanes 114 .
As with the first embodiment, when the shroud 112 is in the first position it may occupy
a range of axial positions in which it is disposed between the inlet and outlet ports 15 1,
152 such that it does not cover, or only partially covers, the inlet and/or outlet bypass
ports 15 1 , 152, such that the flow may pass from a region of the cavity 13 inboard of
the seal 127, through the bypass passage 1 0 to the secondary inlet passage 157.
Referring to Figure 4c, the shroud 112 is shown in said second axial position. In this
position, the annular seal 127 is disposed axially inboard of its position when the
shroud 112 is in the third axial position.
When the shroud 112 is in the second axial position, it is disposed axially inboard of the
inlet port 15 1 of the bypass passage 150. In this regard, the axially inboard and
outboard sides of the seal are disposed axially inboard of the inlet port 15 1 of the
bypass passage 150. In this position, the seal substantially prevents flow from passing
from a region of the cavity 113 inboard of the seal 127, past the seal 127 to the
secondary inlet passageway 190.
When the shroud 112 is in the second axial position, the seal 127 may be axially
located such that it substantially covers, or at least partially covers, or is disposed
axially inboard of, the inlet bypass port 15 1 of the bypass passage 150, such that flow
may not pass from the region of the cavity 113 inboard of the seal 127 to the secondary
inlet passageway 190. Accordingly, it will be appreciated that when the movable
shroud 112 is in the second axial position, it may occupy a range of axial positions.
As with the first embodiment, the axial position of the inlet and outlet bypass ports 15 1,
152 of the bypass passage 150 may be selected to provide a reduction in efficiency at
certain axial positions of the movable wall member (i.e. at a certain width of the inlet
passageway) to provide improved exhaust gas heating and thermal regeneration, or
improved engine braking.
Referring to Figure 4d, the shroud 112 is shown in a fourth axial position. When the
shroud 112 is in the fourth axial position, it is disposed axially inboard of its position
when it is in the third axial position. When the shroud 112 is in the fourth axial position,
the seal 127 is disposed such that its axially outboard end is located axially inboard of
the axially outboard end of the slot 160. Accordingly, flow is able to pass from a region
of the cavity 113 inboard of the recess 160, through the slot 160 past the seal 127 to a
region of the cavity 113 inboard of the seal 127, through the secondary inlet
passageway 157, to the turbine wheel, thereby bypassing the inlet guide vanes 114 .
When the shroud 112 is in the first configuration it is in the first axial positions. When
the shroud 112 is in the second configuration it is in the second or third axial positions.
The shroud 112 may be axially movable relative to the facing wall of the nozzle ring,
between third and fourth configurations, wherein in the third configuration the seal is
positioned relative to the second bypass feature, in this embodiment the recess 160,
such that flow may pass from a region of the cavity 113 inboard of the seal 1 7 to the
secondary inlet passageway 190, through the bypass flow path of the second bypass
feature and in the fourth configuration the seal 127 is positioned relative to the second
bypass feature such that flow is substantially prevented from passing from the region of
the cavity 113 inboard of the seal 127 to the secondary inlet passageway 190, via the
bypass flow path.
When the shroud 112 is in the third configuration it is in the fourth axial position. When
the shroud is in the fourth configuration it is in the second axial position.
In this embodiment, the axial position of the inlet and outlet bypass ports 15 1, 152 of
the bypass passage 150 are selected to provide a reduction in efficiency at certain
axial positions of the movable wall member (i.e. at a certain width of the inlet
passageway) to provide improved exhaust gas heating and/or thermal regeneration.
The axial position of the slot 160 may be selected to provide a reduction in efficiency at
certain axial positions of the movable wall member (i.e. at a certain width of the inlet
passageway) to provide improved engine braking.
The axial positions of the movable shroud 112 during exhaust gas heating and/or
thermal regeneration are outboard of the axial positions of the movable shroud 112
during engine braking, i.e. the width of the inlet passageway 109 is greater during
exhaust gas heating and/or thermal regeneration than during engine braking. During
engine braking the movable shroud 112 may be moved to a position in which the width
of the inlet passageway 109 is a minimum, which may be zero, with the radial wall of
the movable shroud 112 abutting the facing wall 133 of the housing.
Referring to Figures 5A to 5H, there is shown a schematic cross-sectional view of a
portion of a turbine according to a third embodiment of the present invention, where the
shroud 112 is progressively moved towards the facing radial surface 133 of the nozzle
ring 110 . The turbine of the third embodiment is identical to that of the second
embodiment, except for the differences described below. Corresponding features are
given the same reference numerals.
The third embodiment differs from the second embodiment in that each bypass recess
160 is replaced with a second bypass passage 170. In this regard, each bypass
passage 150 forms a first bypass passage and each bypass passage 170 forms a
second bypass passage. The second bypass passage 1 0 is disposed axially inboard
of the first bypass passage 50 and is located slightly axially outboard of the end of the
annular sleeve 128. The second bypass passages 170 are distributed in the
circumferential direction and are substantially axially aligned with each other.
Each second bypass passage 170 is substantially identical in structure to each first
bypass passage 150. In this regard, each second bypass passage 170 extends from
an inlet bypass port 17 1 to an outlet bypass port 172, said inlet and outlet bypass ports
17 1 , 172 being axially spaced from each other and provided in the surface of the
annular sleeve 1 8 that is adjacent to the seal 127. Each of the inlet and outlet bypass
ports 17 1 , 172 have substantially the same axial extent than the annular seal 127.
Each second bypass passage 170 comprises an inlet passage 174 that fluidly connects
the inlet port 17 1 to a bypass chamber 177 and an outlet passage 175 that fluidly
connects the bypass chamber 177 to the outlet bypass port 172. The outlet bypass
port 172 is spaced axially from the inlet bypass port 17 1 in the axially outboard
direction.
The bypass chamber 177 extends in the axial direction part way along the axial length
of the annular sleeve 128. The bypass chamber 177 also extends in the
circumferential direction part way along the circumference of the annular sleeve 1 8.
As with the second embodiment, the shroud 112 is movable to said third, first and
second positions relative to the facing radial surface 133 of the nozzle ring 110 , as
shown in Figures 5A, 5B and 5C (Figures 5B and 5C show different axial positions of
the shroud 112 in which it is in said first position) and Figure 5D, respectively. The
positions correspond to those shown in Figures 4A, 4B and 4C, respectively.
Referring to Figure 5e, the movable shroud 112 is shown in a sixth axial position
relative to the facing radial surface 133 of the nozzle ring 110. In this position, the
annular seal 1 7 is disposed axially inboard of when it is in the second axial position.
In the sixth position, the radially extending flange 125 is axially positioned such that the
annular seal 127 is disposed such that it partially overlaps the outlet port 172 of the
second bypass passage 170, with the axially outboard side of the seal 127 being
disposed axially outboard of the axially outboard side of the outlet port 172. In this
regard, flow is substantially prevented from passing from a region of the cavity 113
inboard of the seal 127, to a region of the cavity 113 outboard of the seal 1 7. And
therefore to the secondary inlet passageway 190. Accordingly, flow is substantially
prevented from bypassing the guide vanes 114 .
When the movable shroud 112 is in the sixth position, it may occupy any axial position
in which it substantially covers the outlet bypass port 172, or is disposed axially
outboard of the outlet bypass port 172 such that it substantially prevents flow passing
from the bypass passage 170 to axially outboard of the seal 127, to the secondary inlet
passageway 190. In this sixth position, the seal 127 may partially cover the outlet port
172, with an outboard side of the seal 127 disposed axially outboard of the outboard
side of the outlet port 172, such that flow is substantially prevented from passing from
the outlet port 1 2 to axially outboard of the seal 127.
Referring to Figure 5F, the movable shroud 112 is shown in a fourth axial position.
When the shroud 112 is in this axial position, the radially extending flange 125 is
located such that the annular seal 127 is axially located between the inlet and outlet
ports 17 1 , 72 of the second bypass passage 170, such that the inlet and outlet ports
17 1 , 172 are substantially completely exposed so as to allow flow to pass from a
region of the cavity 113 inboard of the seal 127, through the second bypass passage
170 to the secondary inlet passageway 190 and to the turbine wheel 105, thereby
bypassing the inlet guide vanes 114 .
Similarly, in Figure 5G the seal 127 is shown in an alternative fourth axial position, in
which the seal 127 is disposed slightly axially inboard of its position shown in Figure
5F. In the position shown in Figure 5G, the inlet port 17 1 is partially covered by the
seal 127 and the outlet port 172 is entirely exposed, with the inlet seal 127 disposed
axially inboard of the outlet port 172. The inlet port 17 1 is exposed to a sufficient
extent to allow flow to pass from a region of the cavity 113 axially inboard of the seal
127, through the inlet port 17 1 , through the second bypass passage 170, out through
the outlet port 172 to the secondary inlet passage 170.
It will be appreciated that when the shroud 112 is in the fourth position, it may occupy a
range of axial positions in which it is disposed between the inlet and outlet ports 17 1 ,
172 such that it does not cover, or only partially covers, the inlet and/or outlet bypass
ports 17 1, 172 such that flow may pass from a region of the cavity 113 inboard of the
seal 127, through the bypass passage 170 to the secondary inlet passage. 170
Referring to Figure 5h, the movable shroud 112 is shown in a fifth axial position. In the
fifth axial position, the movable shroud 112 is axially located such that the annular seal
127 is disposed axially outboard of the inlet port 17 1 of the second bypass passage
170. In this respect, the axially inboard and outboard ends of the seal 127 are
disposed axially outboard of the outboard end of the inlet port 17 1.
When the shroud 112 is in the fifth axial position, it is disposed axially inboard of the
inlet port 17 1 of the second bypass passage 170. In this regard, the axially inboard
and outboard sides of the seal 127 are disposed axially inboard of the inlet port 17 1 of
the second bypass passage 170. In this position, the seal 127 substantially prevents
flow from passing from a region of the cavity 113 inboard of the seal 127, past the seal
127, to the secondary inlet passageway 190. It will be appreciated that in this position,
no flow passes from the region of the cavity 113 inboard of the seal 127 through the
bypass passage 170. Accordingly, no flow bypasses the inlet guide vanes 114 .
When the shroud 112 is in the fifth axial position, the seal 127 may be axially located
such that it substantially covers, or at least partially covers, or is disposed axially
inboard of, the inlet bypass port 17 1 of the second bypass passage 170, such that flow
may not pass from the region of the cavity 113 inboard of the seal 127 to the secondary
inlet passageway 190. Accordingly, it will be appreciated that when the movable
shroud 112 is in the fifth axial position, it may occupy a range of axial positions.
When the shroud 112 is in the first configuration it is in the first axial position. When
the shroud 112 is in the second configuration it is in the second or third axial positions.
When the shroud 112 is in the third configuration it is in the fourth axial position. When
the shroud is in the fourth configuration it is in the fifth or sixth axial positions.
In an exhaust gas heating mode, the engine 500 is operated in an engine fired mode
and the movable shroud 112 is moved inboard so as to close the inlet passage 109 to
a minimum width less than the smallest width appropriate for normal engine operating
conditions in order to control exhaust gas temperature. The basic principle of operation
in such an "exhaust gas heating mode" is to reduce the amount of airflow through the
engine for a given fuel supply level (whilst maintaining sufficient airflow for combustion)
in order to increase the exhaust gas temperature. This has particular application where
a catalytic exhaust after-treatment system is present.
In a thermal regeneration mode, the movable shroud 112 is moved inboard to close the
inlet passage 109 to a minimum width less than the smallest width appropriate for
normal engine operating conditions, to heat the exhaust gas to a temperature that will
burn off the build-up undesirable accumulations.
The axial position of the inlet and outlet bypass ports 15 1, 152 of the first bypass
passage 150 are selected to provide a reduction in efficiency at certain axial positions
of the movable wall member (i.e. at a certain width of the inlet passageway) to provide
improved exhaust gas heating and/or thermal regeneration.
In use, the movable shroud 112 is moved between said first and second configurations
when the engine system is operated in a thermal regeneration mode or an exhaust gas
heating mode.
In an engine braking mode, no fuel is supplied to the engine 500 for combustion and
the inlet passage 109 is reduced to smaller areas compared to those in a normal
engine fired mode operating range. In this respect, the movable shroud 12 is moved
inboard "close" the turbine inlet passage 109 to a minimum flow area. In a "fully
closed" position in an engine braking mode the movable shroud 112 may in some
cases about the facing wall 133 of the inlet passage.
The axial positions of the movable shroud 112 during exhaust gas heating and/or
thermal regeneration are outboard of the axial positions of the movable shroud 112
during engine braking, i.e. the width of the inlet passageway 109 is greater during
exhaust gas heating and/or thermal regeneration than during engine braking.
The axial position of the inlet and outlet bypass ports 17 1 , 172 of the second bypass
passage 170 are selected to provide a reduction in efficiency at certain axial positions
of the movable wall member (i.e. at a certain width of the inlet passageway) to provide
improved engine braking.
In use, the movable shroud 112 is moved between said third and fourth configurations
when the engine system is operated in an engine braking mode.
Referring to Figure 7 there is shown an enlarged schematic axial cross-sectional view
of the bypass passage 150 shown in Figure 2 where a particulate filter 600 is disposed
in the bypass passage 150.
The particulate filter 600 comprises a block 601 of DPF material. The block 601 of DPF
material captures particulate matter flowing through the bypass passage 150 and then
facilitates oxidation of the particulate matter to relatively harmless gaseous carbon
dioxide and water while the temperature within the DPF block 601 is sufficiently high
(e.g. 200 ° and above) to support the oxidation process. In certain applications it is
envisaged that during operation of the turbine the DPF material will almost always be at
a sufficiently high temperature to enable the oxidation process to take place. In such
applications it is envisaged that the DPF catalyst will be continually converting
particulate matter to gaseous carbon dioxide and water, which can then easily flow out
of the bypass passage 150, past the turbine wheel and out of the turbocharger outlet,
thereby avoiding the potentially deleterious effects of the build-up of particulate
deposits within the turbine.
The block 601 of DPF material comprises a silicon carbide honeycomb scaffold with a
layer of platinum and a base metal catalyst deposited on the scaffold. It will be
appreciated that this is only one example of a material that could be employed. Other
suitable catalytic materials could be based on a Corning cordierite, incorporating
different loadings of platinum and base metal oxides, sintered metal materials, or filters
incorporating metal foil substrates such as the diesel-oxycat filter marketed by Bosal
(UK) Ltd which incorporates a stacked corrugated metal flow substrate. Moreover, the
catalytic material may incorporate one or more alkali metal (e.g. potassium, caesium
etc), alkaline earth metal (e.g. magnesium, strontium etc), transition metal, lanthanide
or actinide (e.g. iron, cobalt, cerium etc), or compounds (e.g. oxides, nitrates etc) or
combinations thereof. For example, the DPF material may include one of more
compound or alloy selected from the group consisting of MgO, Ce0 2, Co30 4, Sr(N0 3)2,
Co-Sr, Co-Sr-K, Co-KN0 3-Zr0 2, K2Ti20 , Co-Zr0 2 and the like.
In applications where the operating temperature of the particulate filter is often likely to
be sufficiently high to facilitate aerial oxidation of particulate matter, the particulate filter
may not need to be provided with a catalyst, but may just include a material of
sufficiently high surface area to allow aerial oxidation to take place. As and when the
operational temperature of the high surface area material exceeds the combustion
temperature of the particulate matter, the particulate matter retained within the high
surface area material will be burned-off and oxidised to gaseous waste products which
can then easily flow out of the turbine outlet. The high surface area material could be
formed from any appropriate material such as wire, fibre mesh, one or more sintered
powders, an iron based alloy such as stainless steel, a nickel based alloy such as a
hastaloy, and/or a ceramic such as a magnesium based cordierite-like material.
The density of the material used in the particulate filter can be chosen to suit a
particular application. It is envisaged that if, for example, wire mesh was to be used in a
non-catalyst containing particulate filter then a density of around 20 to 50 %, more
preferably around 35 %, wire mesh may be appropriate. If a wire or fibrous material is
used the thickness and length of the material can be selected to suit a particular
application. By way of example, the wire/fibre may have a thickness of up to around a
few millimetres or more and may have a length of up to around 10 to 60 metres or
more. Particularly preferred dimensions are a thickness of around 0.1 to 0.5 mm, still
more preferably around 0 .15 to 0.35 mm, and a length of around 20 to 50 m, more
preferably around 30 to 40 and most preferably around 37 m. If, for example, steel
wire were used then 37 m of 0.35 mm wire would provide the filter with a surface area
of around 35-45,000 mm2, a volume of around 3-4,000 mm3 and a weight of around 25-
35 g . Such a filter may, for example, be suitable for use with a turbine wheel having a
diameter of around 80-90 mm. It may be desirable to scale the physical properties of
the wire/fibre used in relation to changes in the diameter of the turbine wheel to allow
appropriate design of a filter for use with larger or small turbine wheel than has been
used and tested previously. While the inventors do not wish to be bound by any
particular theory, it is anticipated that one way to achieve this might be to scale the
weight or volume of the filter material as the cube of the turbine wheel diameter and/or
scale the surface area of the filter material as the square of the turbine wheel diameter.
It will also be appreciated that the mechanical properties of the material for the
particulate filter in a high vibration environment will be an important consideration in
selecting a suitable material or combination of materials.
The filter 600 shown in Figure 7 is shown in an enlarged view in Figure 8a. Figure 8b
shows an alternative design of the filter 600, in which the block of DPF material 601 is
provided with a cut-out 603 across an area where the flow from the inlet passage 154
enters the bypass chamber 157. This advantageously increases the surface area of
the DPF material 601 in this region, which increases the filtering effect of the DPF
material 601 .
Referring to figure 8c there is shown a further alternative design of the filter. In this
design, a stainless steel mesh 601 ' coated with a platinum coating is used in place of
the block 601 of DPF material. The mesh 601 ' of DPF material is housed within a
metal frame 602, that is press fit into the bypass chamber 157 (e.g. into a suitable
flange surrounding the bypass chamber 157), It will be appreciated that the filter 601
of each of the designs may be mounted into the bypass chamber 157 in any suitable
way.
The filter 601 , 601 ' may additionally, or alternatively be provided in the second bypass
passage 170 (as with the first bypass passage 150) .
Referring to figure 9 there is shown a schematic cross-sectional view of a portion of a
turbine according to a further embodiment of the present invention. This embodiment
is identical to the embodiment shown in Figures 2 to 3d except for the differences
described below. Corresponding features are given the same reference numerals.
In this embodiment, for each bypass passage 150, the inlet and outlet passages 154,
155 are provided in the sleeve 128, with the bypass chamber 157 provided in the
bearing housing 103. Additionally, or alternatively, a corresponding arrangement may
be used for the second bypass passage 170.
Referring to Figure 10 , there is shown a schematic cross-sectional view of a portion of
a turbine according to a further embodiment of the present invention. This embodiment
is identical to that shown in Figures 2 to 3d, except for the differences described below.
Corresponding features are given the same reference numerals.
In this embodiment, the bypass passage 150 is provided in the movable shroud 112 is
movable, with the inlet and outlet ports 15 1 , 152 provided in a surface of the movable
shroud 112 adjacent to an opposed surface of the sleeve 128. The seal 127 is
mounted within a cavity in said opposed surface of the sleeve 128.
It will be appreciated that the same advantage is obtained with this embodiment, as
with the first embodiment. However, in this case, as the moveable shroud 112 moves
inboard, from a fully open position, the inlet bypass port 15 1 moves inboard of the seal
127, thereby Opening' the inlet bypass port 15 1 , i.e. allowing flow to pass from a region
of the cavity inboard of the seal 127, through the bypass inlet port 15 1 , through the
bypass passage 150 and out of the bypass outlet port 152 to the secondary inlet
passageway. Once the outboard side of the bypass inlet port 15 1 passes the inboard
side of the seal 127, the inlet bypass port is fully Opened'.
As the outlet bypass port 152 continues to move inboard, it passes the seal 127 which
then begins to 'close' the outlet bypass port 152, i.e. reducing the flow that can pass
through the outlet bypass port 152 into the bypass passage. Accordingly, this allows
the level of bypass flow to be controlled as above.
Numerous modifications and variations may be made to the exemplary design
described above without departing from the scope of the invention as defined in the
claims.
For example, in the described embodiments, the shroud 112 is axially movable and the
nozzle ring 110 is fixed. Alternatively, the shroud 112 may be axially fixed and the
nozzle ring 110 axially movable relative to the shroud 112 , whose radial surface
corresponds to the facing wall of the housing.
In this case, the seal 1 7 may be mounted on the nozzle ring 110, so as to move with
the nozzle ring relative to the bypass passage(s)/recess 150, 170, 160.
In the described embodiment, the movable wall member is mounted, for said axial
movement, in an annular cavity provided in the turbine housing. Alternatively, the
movable wall member may be mounted in an annular cavity provided in the bearing
housing.
In the described embodiment the first bypass passage 150, the second bypass
passage and/or the recess are provided in the cylindrical sleeve 128. Alternatively, or
additionally, the first bypass passage 150, the second bypass passage and/or the
recess may be provided in any housing of the variable geometry turbine, for example
the bearing housing.

CLAIMS
1. A variable geometry turbine comprising:
a turbine wheel supported in a housing for rotation about a turbine axis;
an annular primary inlet passageway extending radially inwards towards the
turbine wheel, the primary inlet passageway being defined between a surface of a
radial wall of a moveable wall member and a surface of a facing wall of the housing ;
the moveable wall member being mounted within an annular cavity provided
within a housing, the movable wall member being moveable axially to vary the width of
the inlet passageway;
an annular seal being mounted to one of the movable wall member and an
adjacent housing member to provide a seal between adjacent surfaces of the movable
wall member and housing member respectively;
wherein a bypass passage is provided in the other of said movable wall
member and housing member, the bypass passage extending from an inlet bypass port
to an outlet bypass port, said inlet and outlet bypass ports being axially spaced from
each other and provided in said adjacent surface of said other of the movable wall
member and housing member;
a secondary inlet passageway fluidly connecting a region of the cavity outboard
of the seal to the turbine wheel such that flow in the secondary inlet passageway
bypasses at least a portion of the primary inlet passageway;
the bypass passage and the annular seal being arranged such that as the
movable wall member moves axially, the annular seal moves axially relative to the inlet
and outlet bypass ports so as to vary the extent of flow that may pass from a region of
the cavity inboard of the seal, through the bypass passage to the secondary inlet
passageway.
A variable geometry turbine according to claim 1 wherein the movable wall
member is axially movable relative to the facing wall of the housing, between
first and second configurations, wherein in the first configuration the seal is
positioned relative to the inlet and outlet bypass ports such that flow may pass
from a region of the cavity inboard of the seal to the secondary inlet
passageway, via the bypass passage and in the second configuration the seal
is positioned relative to the inlet and outlet bypass ports such that flow is
substantially prevented from passing from the region of the cavity inboard of the
seal to the secondary inlet passageway, via the bypass passage.
A variable geometry turbine according to claim 2 wherein when the movable
wall member is in the first configuration, the movable wall member is in a first
position relative to the facing wall of the housing.
A variable geometry turbine according to claim 3 wherein and when the
movable wall member is in the first position, the seal is provided at least
partially outboard of the inlet bypass port such that it does not cover the inlet
port or only partially covers the inlet port.
A variable geometry turbine according to either of claims 3 or 4 wherein when
the movable wall member is in the first position, the seal is provided at least
partially inboard of the outlet bypass port such that it does not cover the outlet
port or only partly covers an inboard portion of the outlet port.
A variable geometry turbine according to any of claims 3 to 5 wherein when the
movable wall member is in the first position, the seal is disposed axially
between the inlet and outlet bypass ports.
A variable geometry turbine according to any preceding claim wherein the inlet
and outlet bypass ports are axially separated by a section of said other of said
movable wall member and said housing member.
A variable geometry turbine according to any preceding claim wherein the outlet
bypass port has a cross-sectional area that is the same, or greater than, the
cross-sectional area of the inlet bypass port.
A variable geometry turbine according to any of claims 2 to 6, or any of claims 7
or 8 when dependent on claim 2 wherein when the movable wall member is in
the second configuration, the movable wall member is in a second position
relative to the facing wall of the housing.
A variable geometry turbine according to claim 9 wherein when the movable
wall member is in the second position, it is closer to the facing wall of the
housing than when it is in the first position.
A variable geometry turbine according to either of claims 9 or 10 wherein when
the movable wall member is in the second position, the seal substantially
covers the inlet bypass port or is provided inboard of the inlet bypass port such
that flow is substantially prevented from passing from the region of the cavity
inboard of the seal through the inlet bypass port and into the bypass passage.
A variable geometry turbine according to any of claims 9 to 11 wherein when
the movable wall member is in the second configuration, the movable wall
member is in a third position relative to the facing wall of the housing.
A variable geometry turbine according to claim 12 wherein when the movable
wall member is in the third position, it is further from the facing wall of the
housing than when the movable wall member is in the first position.
A variable geometry turbine according to either of claims 1 or 13 wherein when
the movable wall member is in the third position, the seal substantially covers
the outlet bypass port or is provided outboard of the outlet bypass port such that
flow is substantially prevented from passing from the bypass outlet port to the
secondary inlet passageway.
A variable geometry turbine according to any preceding claim wherein a
plurality of said inlet ports are provided in said adjacent surface of said other of
the movable wall member and housing member, distributed in the
circumferential direction along said surface.
A variable geometry turbine according to any preceding claim wherein a
plurality of said outlet ports are provided in said adjacent surface of said other
of the movable wall member and housing member, distributed in the
circumferential direction along said surface.
A variable geometry turbine according to claim 16 when dependent on claim 15
wherein there are a plurality of said bypass passages, each bypass passage
extending from a respective inlet port to a respective outlet port.
A variable geometry turbine according to any preceding claim wherein the
bypass passage forms a passage that is substantially enclosed between the
inlet and outlet ports.
A variable geometry turbine according to any preceding claim wherein the
bypass passage comprises an inlet passage that fluidly connects the bypass
inlet port to a bypass chamber and an outlet passage that fluidly connects the
bypass chamber to the outlet bypass port.
A variable geometry turbine according to any preceding claim wherein the seal
is mounted to the movable wall member, with the bypass passage provided in
said adjacent housing member, the inlet and outlet bypass ports being provided
in said adjacent surface of the housing member.
A variable geometry turbine according to any preceding claim wherein the seal
is mounted to the adjacent housing member, with the bypass passage provided
in the movable wall member, the inlet and outlet bypass ports being provided in
said adjacent surface of the movable wall member.
A variable geometry turbine according to any preceding claim wherein the
adjacent housing member is part of the housing in which the turbine wheel is
supported.
A variable geometry turbine according to any preceding claim wherein the
variably geometry turbine comprises a bearing housing that houses a bearing
assembly that rotatably supports a shaft on which the turbine wheel is mounted,
for rotation about said axis and wherein the housing member is part of the
bearing housing.
A variable geometry turbine according to any preceding claim wherein the
adjacent housing member comprises an axially extending annular sleeve.
A variable geometry turbine according to claim 24 when dependent on claim 19
wherein the, or each, inlet and outlet passage is provided in the sleeve, with the
respective bypass chamber provided in an adjacent housing of the variable
geometry turbine.
A variable geometry turbine according to any preceding claim wherein the
bypass passage forms a first bypass feature, wherein a second bypass feature,
defining a bypass flow path, is provided in said other of said moveable wall
member and said housing member, and is arranged such that as the movable
wall member moves axially, the annular seal moves axially relative to the
second bypass feature so as to vary the extent of flow that may pass from a
region of the cavity inboard of the seal, through the bypass flow path to the
secondary inlet passageway.
A variable geometry turbine according to any preceding claim wherein the
second bypass feature comprises a slot or recess, provided in said other of said
movable wall member and said housing member, that defines said flow path.
A variable geometry turbine according to claim 27 wherein the slot or recess is
provided in the housing member, is provided at in inboard end of the housing
member and extends axially to the inboard end such that recess is open to the
cavity at its axially inboard end.
A variable geometry turbine according to claim 27 when dependent on claim 24
wherein the slot extends through the radial thickness of the sleeve such that a
radially outer end of the slot is in fluid communication with the cavity and a
radially inner end of the slot is provided in said adjacent surface.
A variable geometry turbine according to any of claims 27 to 29 wherein the
second bypass feature comprises a plurality of said recesses, distributed in the
circumferential direction.
A variable geometry turbine according to claim 26 wherein the bypass passage
forms a first bypass passage, wherein the flow path of the second bypass
feature is a second bypass passage provided in said other of the movable wall
member or said housing member, the second bypass passage extending from
an inlet bypass port to an outlet bypass port, the second bypass passage and
the annular seal being arranged such that as the movable wall member moves
axially, the annular seal moves axially relative to the inlet and outlet bypass
ports of the second bypass passage so as to vary the extent of flow that may
pass from a region of the cavity inboard of the seal, through the second bypass
passage to the secondary inlet passageway.
A variable geometry turbine according to claim 3 1 wherein the inlet and outlet
bypass ports of the second bypass passage are axially spaced from each other
and provided in said adjacent surface of said other of the annular flange and
wall member.
A variable geometry turbine according to any of claims 26 to 3 1 wherein the
movable wall member is axially movable relative to the facing wall of the
housing, between third and fourth configurations, wherein in the third
configuration the seal is positioned relative to the second bypass feature such
that flow may pass from a region of the cavity inboard of the seal to the
secondary inlet passageway, via the second bypass flow path and in the fourth
configuration the seal is positioned relative to the second bypass feature such
that flow is substantially prevented from passing from the region of the cavity
inboard of the seal to the secondary inlet passageway, via the second bypass
flow path.
A variable geometry turbine according to claim 33 wherein when the movable
wall member is in the third configuration, the movable wall member is in a fourth
position relative to the facing wall of the housing.
A variable geometry turbine according to claim 34 when dependent on any of
claims 27 to 30 wherein when the movable wall member is in the fourth
position, the seal is located within the axial extent of the recess such that flow
may pass from a region of the cavity inboard of the seal to the secondary inlet
passageway.
A variable geometry turbine according to claim 34 when dependent on either of
claims 3 1 or 32 wherein when the movable wall member is in the fourth
position, the seal does not cover the inlet bypass port or only partially covers
the inlet bypass port of the second bypass passage.
A variable geometry turbine according to claim 34 when dependent on either of
claims 3 1 or 32 wherein when the movable wall member is in the fourth
position, the seal does not cover the outlet bypass port or only partly covers the
outlet bypass port of the second bypass passage.
A variable geometry turbine according to claim 34 when dependent on either of
claims 3 1 or 32 wherein when the movable wall member is in the fourth
position, the seal is disposed axially between the inlet and outlet bypass ports
of the second bypass passage.
A variable geometry turbine according to any of claims 33 to 39 wherein when
the movable wall member is in the fourth configuration, the movable wall
member is in a fifth position relative to the facing wall of the housing.
A variable geometry turbine according to claim 39 wherein when the movable
wall member is in the fifth position, it is closer to the facing wall of the housing
than when it is in the fourth position.
A variable geometry turbine according to claim 40 wherein when the movable
wall member is in the fifth position, the seal substantially covers the inlet bypass
port or is provided inboard of the inlet bypass port of the second bypass
passage such that flow is substantially prevented from passing from the region
of the cavity inboard of the seal through the inlet bypass port and into the
bypass passage.
A variable geometry turbine according to any of claims 33 to 4 1 wherein when
the movable wall member is in the fourth configuration, the movable wall
member is in a sixth position relative to the facing wall of the housing.
A variable geometry turbine according to claim 42 wherein when the movable
wall member is in the sixth position, it is axially further from the facing wall of
the housing than when the movable wall member is in the fourth position.
A variable geometry turbine according to either of claims 42 or 43 wherein when
the movable wall member is in the sixth position, the seal substantially covers
the outlet bypass port or is provided outboard of the outlet bypass port of the
second bypass passage such that flow is substantially prevented from passing
from the second bypass passage out of the bypass outlet port to the secondary
inlet passageway.
A variable geometry turbine according to any preceding claim wherein an array
of inlet guide vanes extend across the annular primary inlet passageway to
define a radial vane passage.
A variable geometry turbine according to claim 45 wherein the secondary inlet
passageway fluidly connects a region of the cavity outboard of the seal to the
turbine wheel such that flow in the secondary inlet passageway bypasses the
inlet guide vanes in the primary inlet passageway.
A variable geometry turbine according to either of claims 45 or 46 wherein the
movable wall member is a shroud defining apertures for receipt of the vanes,
which are attached to a nozzle ring having a radial surface that corresponds to
the facing of the housing.
A variable geometry turbine according to either of claims 45 or 46 wherein the
movable wall member is a nozzle ring which supports the vanes for receipt in
apertures defined by a shroud plate whose radial surface corresponds to the
facing wall of the housing.
A variable geometry turbine according to any preceding claim wherein a
particulate filter is provided in the bypass passage such that flow passing
through the bypass passage passes through the filter, with the particulate filter
being contacted by particulate matter flowing through the filter.
A variable geometry turbine according to claim 49 wherein the particulate filter
comprises a high surface area material.
A variable geometry turbine according to either of claims 49 or 50 wherein the
particulate filter comprises a metallic material and/or ceramic material.
A variable geometry turbine according to any of claims 49 to 5 1 wherein the
particulate filter comprises a catalytic material suitable to catalyse the
conversion of particulate matter into one or more different species.
A variable geometry turbine according to any of claims 49 to 52 wherein the
particulate filter is a carbonaceous particulate filter.
A variable geometry turbine according to any of claims 49 to 53 wherein the
particulate filter comprises a Diesel Particulate Filter catalyst material.
A variable geometry turbine according to any of claims 49 to 54 wherein the
particulate filter comprises a mesh through which the bypass flow passes.
A variable geometry turbine according to any of claims 49 to 55 wherein the
filter is arranged such that substantially all the flow that passes through the
bypass passage passes through the filter.
A variable geometry turbine according to any of claims 49 to 56 wherein the
filter is disposed within said bypass chamber, and/or said first and/or second
bypass passages.
A variable geometry turbine according to any of claims 55 to 57 wherein the
mesh of the filter has a cut-out section disposed at the inlet and/or outlet bypass
port of the bypass passageway.
A turbocharger comprising a variable geometry turbine according to any
preceding claim and a compressor comprising a housing defining an inlet and
an outlet, and a chamber between the inlet and outlet, within which an impeller
wheel is rotatably mounted such that rotation of the impeller wheel compresses
air received through the inlet and passes the compressed air to the outlet,
wherein the turbine wheel of the turbine is coupled to the impeller wheel so as
to drivably rotate the impeller wheel.
An engine system comprising an internal combustion engine and a
turbocharger according to claim 59 arranged such that exhaust gas from the
internal combustion engine drivably rotates the turbine wheel of the turbine.
A method of operating an engine system according to claim 60, when
dependent on claim 2 , or any of claims 2 to 60 when dependent on claim 2,
wherein the movable wall member is moved between said first and second
configurations when the engine system is operated in an engine braking mode,
a thermal regeneration mode or an exhaust gas heating mode.
A method of operating an engine system according to claim 6 1 wherein the
movable wall member is moved between said first and second configurations
when the engine system is operated in a thermal regeneration mode or an
exhaust gas heating mode.
63. A method of operating an engine system according to either of claims 6 1 or 62
when dependent on claim 33, or any of claims 34 to 62 when dependent on
claim 33, wherein the movable wall member is moved between said third and
fourth configurations when the engine system is operated in an engine braking
mode, a thermal regeneration mode or an exhaust gas heating mode.
64. A method of operating an engine system according to claim 63 wherein the
movable wall member is moved between said third and fourth configurations
when the engine system is operated in an engine braking mode.
65. A variable geometry turbine substantially as described herein, with reference to
the description and drawings.
A turbocharger substantially as described herein, with reference
description and drawings.
67. An engine system substantially as described herein, with reference to the
description and drawings.
68. A method of operating an engine system substantially as described herein, with
reference to the description and drawings.