TURBINE HOUSING
The present invention relates to a turbine housing for a turbine assembly, and has
particular, but not exclusive, application to 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 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 throat defined
in the housing between facing radially extending walls and arranged around the turbine
chamber to form an inlet passage; and an outlet passage extending from the turbine
chamber. These components communicate such that pressurised exhaust gas
admitted to the housing flows through the throat 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 throat so as to deflect gas flowing
through the throat towards the direction of rotation of the turbine wheel.
The turbines of known turbochargers may be of a fixed or variable geometry type.
Variable geometry turbines differ from fixed geometry turbines in that the size of the
throat 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 throat. The position of the movable wall member relative to a
fixed facing wall of the throat is adjustable to control the axial width of the throat. Thus,
for example, as exhaust gas flow through the turbine decreases, the throat 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 throat and through orifices provided in a "shroud plate" that defines the fixed
facing wall of the throat, 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 throat) 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.
In another type of variable geometry turbine known as a swing vane turbocharger, the
inlet size (or flow size) of the turbine is controlled by an array of movable vanes
positioned in the turbine inlet. Each vane can pivot about an axis extending across the
inlet parallel to the turbocharger shaft and aligned with a point approximately half way
along the length of the vane. A vane actuating mechanism is linked to each of the
vanes and is displaceable in a manner which causes each of the vanes to move in
unison, such a movement enabling the cross sectional area available for the incoming
gas and the angle of approach of the gas to the turbine wheel to be controlled.
It is known to provide a turbocharger turbine with a valve-controlled bypass port
referred to as a wastegate, to enable control of the turbocharger boost pressure and/or
shaft speed. A wastegate valve (typically a poppet type valve) is controlled to open the
wastegate port (bypass port) when the boost pressure of the fluid in the compressor
outlet reaches pre-determined upper limit, thus allowing at least some of the exhaust
gas to bypass the turbine wheel. Typically the wastegate port opens into a wastegate
passage which diverts the bypass gas flow to the turbine outlet or vents it to the
atmosphere. The wastegate valve may be actuated by a variety of means, including
electric actuators, but is more typically actuated by a pneumatic actuator operated by
boost pressure delivered by the compressor wheel.
Some known internal combustion engines include Exhaust Gas Recirculation (EGR).
EGR is used to reduce nitrogen oxide (NOx) emissions of an internal combustion
engine. EGR works by recirculating a portion of an exhaust gas produced by the
internal combustion engine back to the engine cylinders, usually via the engine intake
manifold. Recirculating a portion of the exhaust gas results in a reduction in
temperature of the combustion which occurs in the engine cylinders. Because NOx
production requires a mixture of nitrogen and oxygen (as found in the air) to be
exposed to high temperatures, the lower combustion temperatures resulting from EGR
reduces the amount of NOx generated by the combustion. In some known internal
combustion engines a variable geometry turbine assembly (which forms part of a
turbocharger) is used to increase the pressure (also known as back pressure) of the
exhaust gas by partially closing the throat. This creates a pressure differential between
the exhaust gas and the engine intake such that the exhaust gas will flow via an
exhaust gas recirculation channel to the engine intake. However, the creation of back
pressure by the variable geometry turbine can impair the operating performance of the
internal combustion engine.
Exhaust gas is generally admitted to the throat of a turbocharger turbine through an
inlet volute provided within the turbine housing. The inlet volute has a volute passage
which spirals radially inwards from a first end to a second end and terminates at the
throat. Exhaust gas from the exhaust manifold of an engine enters the volute passage
at the first end, and emerges at the throat at significant angular velocity. The volute
passage generally decreases in cross section along its length, so as to increase the
velocity of the exhaust gas flow therethrough (and thereby increase the amount of
energy which can be extracted by the turbine wheel) and/or to increase the pressure in
the volute passage so that exhaust gas is urged out of the passage and into the throat.
Though some turbines utilise a single inlet volute, known turbines such as double flow
turbines and twin flow turbines utilise two inlet volutes each including a separate volute
passage. The two volute passages are separated by a dividing wall and each has a
separate throat. The two passages' throats meet at an inlet passage radially adjacent
to the turbine, with different portions of the inlet passage being supplied by the different
volute passages. In the case of a twin flow turbine each volute passage supplies a
different axial portion of the inlet passage, and in the case of a double flow turbine each
volute passage supplies a different circumferential portion of the inlet passage. In other
words, in a double flow turbine the two volute passages meet the inlet passage in the
same plane, whereas in a twin flow turbine the two volute passages meet the inlet
passage in axially adjacent planes.
One advantage of twin flow and double flow turbines is that they allow the segregation
of the exhaust gas flows from the engine cylinders which flows would otherwise
interfere with each other. Where exhaust from all cylinders feeds a single volute
passage, all engine cylinders are connected together by the exhaust manifold. An
exhaust gas flow pulse from a first cylinder at the end of its firing stroke and the start of
its exhaust stroke can therefore increase the local pressure in the exhaust manifold
near a second cylinder which is at the end of its exhaust stroke and the start of its
intake stroke (i.e. during its overlap period, in which the intake and exhaust valves of
that cylinder are both partially open so that exhaust scavenging can occur), preventing
full expulsion of exhaust gas therefrom. In twin flow or double flow turbines, however,
this first cylinder can be connected to one volute passage and the second cylinder can
be connected to the other. The exhaust flow from these two cylinders is therefore
partitioned (by the dividing wall between the volute passages) until it enters the turbine
inlet passage. This reduces or eliminates interference with exhaust scavenging
processes. This more efficient use of scavenging decreases exhaust gas temperatures
(and therefore NOx production), and improves turbine efficiency (thereby reducing
turbo lag and increasing boost pressures).
Double flow and twin flow turbines may also provide benefits in relation to EGR. By
increasing the number of engine cylinders connected to one of the volute passages,
and/or by reducing the cross sectional area of the passage, the exhaust pressure in
that volute passage can be increased. This allows the local pressure in one volute
passage to be increased to the point where (by connecting the exhaust recirculation
channel to this passage) the recirculated exhaust can be supplied at sufficient pressure
with a smaller rise in the overall exhaust pressure (and thus a smaller negative effect
on engine performance).
In conventional turbochargers, the or each inlet volute has a tongue which projects
along a longitudinal axis running substantially within a plane that is normal to the
turbine axis. The tongue projects between, and acts to partition, the second end of the
volute passage from a part of the passage immediately radially adjacent thereto. While
many volute passages do not rotate far beyond 360° around the turbine axis, in
figurative terms the tongue can be considered to separate at least the end of the
radially innermost 'coil' of the passage (i.e. at least the second end of the passage)
from the penultimate coil. The tongue terminates in a longitudinally distal tip, which is
conventionally positioned radially adjacent to the turbine wheel to provide minimal
clearance therewith, and acts to direct working fluid in the second end of the passage
into the turbine wheel. In conventional turbines the exhaust gas runs into the turbine
wheel radially (i.e. with no axial velocity component), so conventional turbine wheels
are designed to be most efficient when their inflow has no axial component.
Conventionally, therefore, the lateral centreline of the tongue tip is positioned
transverse to this direction (i.e. parallel to the turbine axis) so that the radially inner
surface of the tongue tip urges fluid into the turbine wheel accordingly (rather than
imparting an axial velocity component, as it would if aligned at an angle to the turbine
axis). Further, the casting processes by which the turbine housing is manufactured may
be more simple if the lateral centreline of the tongue tip is parallel to the turbine axis.
A key parameter in turbine design is the swirl angle (also known as whirl angle), which
is the angle between the radial direction and the direction in which fluid enters the
turbine wheel. For instance, if fluid enters a turbine radially then it has a swirl angle of
zero, and if it enters a turbine wheel tangentially it has a swirl angle of 90°. The swirl
angle in the turbine of a turbocharger is typically between around 20° and around 40°.
The swirl angle at a particular angular position about the turbine axis can be defined
as:
Where a is swirl angle, A is the area of the wheel (in circumferential cross section),
r is the radial distance to the centroid of A A is the area of the volute
passage at the angular position in question and r is the radial distance to the
centroid of that area.
In some applications, A a ag / r a age (hereafter referred to merely as 'A/r'), preferably
decreases linearly around the turbine axis. This can be useful in controlling the swirl
angle so as to optimise the mass flow of working fluid into the turbine. For most angular
positions about the circumference of the turbine wheel this can be achieved by
adjusting the size and shape of the volute passage. However, problems can arise in
the region of the tongue tip. As working fluid running along the volute passage passes
the tip of the tongue there is a sudden increase in the area of the passage and the
shape of that area (since the tongue no longer occupies any space in the passage).
This can lead to a sudden change in the A/r and therefore in the swirl angle. This
localised change in swirl angle can create a localised area of high/low force on the
turbine wheel around its circumference. This, in turn, can reduce the efficiency of the
turbine (for instance by inducing vibration of the turbine wheel) and/or lead to
premature failure (for instance from fatigue due to a point on the turbine undergoing
increased cyclic loading as it continually travels around the turbine axis and through the
localised region). For the reasons discussed below, this problem can be particularly
acute in turbochargers where the volute is axially asymmetric (such as twin flow
turbines and some double flow turbines), which can lead to such turbines being
rejected for use in applications to which they would otherwise be well suited.
It is one object of the invention to obviate or mitigate at least one of the aforesaid
disadvantages, and/or to provide an improved or alternative turbine housing, turbine
assembly or turbocharger.
According to a first aspect of the present invention there is provided a turbine housing
comprising a cavity for a turbine wheel, the cavity defining a turbine axis about which
the turbine wheel rotates in use, and an inlet volute comprising:
a volute passage spiralling radially inwards about the turbine axis from a first
end to a second end;
a substantially annular throat positioned between a radially inner portion of the
volute passage and a radially outer portion of the cavity to provide fluid communication
therebetween, the throat being defined between first and second axially-spaced walls;
a tongue projecting between a radially outer portion of the second end of the
volute passage and a radially inner portion of a part of the volute passage radially
outboard thereof, the tongue terminating at a distal tongue tip,
wherein the volute passage, throat and tongue tip are positioned whereby in a plane
containing the turbine axis and the tongue tip:
the throat defines a line of minimum clearance, which is a line running between
the points on the first and second walls which are the closest together;
the volute passage and tongue tip co-operatively define a preliminary inlet area;
the line of minimum clearance and the preliminary inlet area co-operatively
define a line of passage offset, which connects the centroid of the preliminary inlet area
and a point half way along the line of minimum clearance;
the tongue tip defines a tongue tip lateral centreline;
the line of passage offset is not perpendicular to the turbine axis; and
the tongue tip lateral centreline and the line of passage offset define an angle
therebetween of at least 60 degrees.
With the tongue tip lateral centreline arranged relative to the line of passage offset in
this way, the total cross sectional area of the tongue tip may be reduced, which may in
turn reduce the fluctuations in A/r across the tongue. Instead or in addition, this tongue
positioning may allow the radially inner and outer surfaces of the tongue to be a more
similar size to one another, which may reduce the magnitude of fluctuations in pressure
of fluid flow passing over the tongue tip. Either of these effects may allow the force
applied to the turbine by the fluid to be more constant, which may improve turbine
efficiency and/or reduce turbine wheel fatigue.
In some embodiments, the circumferential extent of the tongue is the same across its
lateral width (in other words the tongue has a 'flat' tip). For the avoidance of doubt,
where the circumferential extent of the tongue varies along its lateral width (e.g. if the
longitudinal extremity of the tongue is rounded or pointed) , the tongue tip may be
considered to be the point at which the tongue has narrowed to 80% of its original
lateral width, and the plane containing the turbine axis and the tongue tip is the plane
which contains the turbine axis and passes through this point on the tongue.
It will be apparent that two lines in a plane necessarily define an angle therebetween of
between 0 and 90 degrees. Reference to the angle between the tongue tip lateral
centreline and the line of passage offset refers to this angle, rather than any obtuse
angle also defined. For instance, a turbine housing where the tongue tip lateral
centreline and the line of passage offset are at an angle of 45 degrees falls outside the
first aspect of the invention, even though it may be considered that the tongue tip
lateral centreline and the line of passage offset also define an angle of 135 degrees.
The same applies in relation to other angles described herein.
The preliminary inlet area is the cross sectional area enclosed by the volute passage
and tongue tip in the plane containing the turbine axis and the tongue tip. For the
avoidance of doubt, reference to the tongue tip defining a lateral centreline is not
intended to imply that the tongue tip is necessarily symmetrical.
In some arrangements, there may be several pairs of points on the first and second
walls which are each spaced apart by the same distance (this distance being the
minimum clearance between the walls) . In such arrangements the line of minimum
clearance may be considered to run between any such pair of points. Alternatively, it
may be considered to run between the pair of points which are nearest to the cavity.
The line of passage offset may be positioned at an angle of no more than 80 degrees
to the turbine axis. For instance, the line of passage offset may be positioned at an
angle of no more than 75 degrees, no more than 70 degrees, no more than 60 degrees
or no more than 50 degrees to the turbine axis.
As discussed below, if line of passage offset is perpendicular then the effect of the
tongue tip on the change in A/r is more manageable. It follows that in some
circumstances the smaller the angle between the line of passage offset and the turbine
axis (i.e. the further from perpendicular the line of passage offset is to the turbine axis),
the greater the advantage provided by the present invention may be. The line of
passage offset being further from perpendicular to the turbine axis may also allow the
inlet volute to be moved further to one side of the turbine housing, thereby providing
more room for other components (such as lubricant conduits to and from a bearing
housing to which the turbine housing may be mounted or the bearing housing itself, or
components of a body in proximity to the turbine housing such as ducts or cables
running to or from an engine) .
The tongue tip lateral centreline and the line of passage offset may define an angle
therebetween of at least 75 degrees, preferably at least 80 degrees, and more
preferably at least 85 degrees.
One or more of the benefits of the first aspect of the invention may be increased by
positioning the tongue tip lateral centreline and line of passage offset nearer to
perpendicular to each other.
The sum of the angle at which the tongue tip lateral centreline intersects the first wall,
and the angle at which the tongue tip lateral centreline intersects the second wall, may
be at least 120 degrees.
According to a second aspect of the present invention there is provided a turbine
housing comprising a cavity for a turbine wheel, the cavity defining a turbine axis about
which the turbine wheel rotates in use, and an inlet volute comprising:
a volute passage spiralling radially inwards about the turbine axis from a first
end to a second end;
a substantially annular throat positioned between a radially inner portion of the
volute passage and a radially outer portion of the cavity to provide fluid communication
therebetween, the throat being defined between first and second axially-spaced walls;
a tongue projecting between a radially outer portion of the second end of the
volute passage and a radially inner portion of a part of the volute passage radially
outboard thereof, the tongue terminating at a distal tongue tip,
wherein the volute passage, throat and tongue tip are positioned whereby in a plane
containing the turbine axis and the tongue tip:
the throat defines a line of minimum clearance, which is a line running between
the points on the first and second walls which are the closest together;
the tongue tip defines a tongue tip lateral centreline; and
the sum of the angle at which the tongue tip lateral centreline intersects the first
wall, and the angle at which the tongue tip lateral centreline intersects the second wall,
is at least 120 degrees.
As outlined above, the sum of said angles reflects the extent to which the tongue tip is
positioned perpendicularly to the first and second walls. The tongue tip lateral
centreline being positioned nearer to perpendicular to first and second walls may
reduce the cross sectional area of the tongue tip, and/or may allow the radially inner
and outer surfaces of the tongue tip to be a more similar size to one another. This may
reduce the magnitude of fluctuations in A/r and/or pressure across the tongue to be
reduced, thereby improving turbine efficiency and/or turbine wheel fatigue life, as
described in relation to the first aspect of the invention.
As outlined above, it is to be noted that two lines in a plane necessarily define an angle
therebetween of between 0 and 90 degrees. Reference to the angle between the
tongue tip lateral centreline and the first wall or second wall refers to this angle, rather
than any obtuse angle also defined. Accordingly, the sum of said angles is necessarily
between 0 and 180 degrees.
Where in a turbine housing according to the invention said sum of angles is at least
120 degrees, said sum may be at least 140 degrees, at least 150 degrees or at least
155 degrees. Said sum of angles may be at least 160 degrees, at least 170 degrees or
at least 175 degrees. This may enhance one or more of the above advantages.
The tongue tip lateral centreline may be positioned substantially perpendicularly to the
first wall, at a location at which it is as close to perpendicular to the second wall as
possible. For instance, during the design process for a turbine housing according to the
invention, the desired position of a tongue tip may be determined by constraining its
position so that the tongue tip lateral centreline intersects the first wall at substantially
90 degrees, before moving the position of the tongue tip along the first wall (in the
aforementioned plane) to the position in which its lateral centreline would intersect the
second wall at as large an angle as possible.
The tongue tip lateral centreline may be positioned substantially perpendicularly to the
first wall, at a location at which its lateral centreline is as short as possible. For
instance, during the design process for a turbine housing according to the invention,
the desired position of a tongue tip may be determined by constraining its position so
that the tongue tip lateral centreline intersects the first wall at substantially 90 degrees,
before moving the position of the tongue tip along the first wall (in the aforementioned
plane) to the position in which its lateral extent is minimised.
The tongue tip lateral centreline may be positioned at an angle of at least 60 degrees,
for example at least 65 degrees, at least 70 degrees, at least 75 degrees, at least 80
degrees or at least 85 degrees, to the first wall. Instead or in addition, the tongue tip
lateral centreline may be positioned at an angle of at least 60 degrees, for example at
least 65 degrees, at least 70 degrees, at least 75 degrees, at least 80 degrees or at
least 85 degrees, to the second wall.
The tongue may be positioned so that the sum of the angles at which the tongue tip
lateral centreline is positioned relative to the first and second walls is at least 130
degrees, for instance at least 150 degrees, at least 160 degrees, at least 170 degrees
or at least 175 degrees. For the avoidance of doubt, the sum of the angles at which the
tongue tip lateral centreline is positioned relative to the first and second walls is the
angle at which the tongue tip lateral centreline intersects the first wall, plus the angle at
which the tongue tip lateral centreline intersects the second wall. In one embodiment,
the tongue may be positioned so that the sum of the angles at which the tongue tip
lateral centreline is positioned relative to the first and second walls is as large as the
geometry of the turbine housing will allow.
The tongue tip may be laterally tapered. For instance, a portion of the tongue tip which
is adjacent to the first wall may be thicker than a portion which is adjacent to the
second wall. The tongue tip being laterally tapered, for instance by around 2 degrees,
is commonplace as this can simplify the casting of a turbine housing. The tongue tip
may or may not taper evenly along its lateral extent. For instance it may be convex or
concave in lateral cross-section. For the avoidance of doubt, a tongue tip may be
considered to be laterally tapered even if it intersects the first and/or second wall at a
filleted or chamfered junction.
The turbine housing may have a mounting surface configured to be positioned against
a bearing housing, and the first wall may be positioned axially further from the
mounting surface than the second wall.
In some arrangements the first and second walls may axially overlap, and/or the axial
extent of the first and second walls may be difficult to determine. In such circumstances
the wall which is axially further from the mounting surface may be determined by
comparing the points on the walls between which the line of minimum clearance runs.
The one of said points which is axially nearer the mounting surface may be considered
to be provided by the wall which is axially nearer the mounting surface.
The tongue tip lateral centreline may be at an angle of no more than 25 degrees to the
line of minimum clearance, for instance it may be no more than 20 degrees to the line
of minimum clearance. Indeed, the tongue tip lateral centreline may be at an angle of
15 degrees or less to the line of minimum clearance, is preferably at an angle of 10
degrees or less to the line of minimum clearance, and is more preferably at an angle of
5 degrees or less to the line of minimum clearance.
The line of minimum clearance may lie substantially within the tongue tip. In such a
case, the line of minimum clearance and the tongue tip lateral centreline are preferably
substantially collinear.
With part of the tongue tip being positioned at the narrowest part of the throat in this
manner, the lateral width of the tongue can be minimised. This reduces the overall
cross sectional area of the tongue tip, thereby reducing the change in A/r across it.
As the tongue tip may obscure the shape of a portion of the throat in the plane
containing the turbine axis and the tongue tip, in some situations it may not be possible
to directly visually determine the position of the line of minimum clearance. For the
avoidance of doubt, in such arrangements the position of the line of minimum
clearance can be determined by interpolation. For instance, where the shape of the
throat is substantially constant around its circumference its shape in the region
occupied by the tongue tip can be readily inferred. Alternatively, the shape may be
determined by interpreting the angle and curvature of the first and second walls radially
above and below the tongue tip, and extrapolating the most likely overall shape.
The tongue tip lateral centreline may be at an angle of 15 degrees or less to the turbine
axis, is preferably at an angle of 10 degrees or less to the turbine axis, and is more
preferably at an angle of 5 degrees or less to the turbine axis.
Arranging the housing so that the tongue tip lateral centreline is at such an angle to the
turbine axis (while also being at an angle of 60° or more to the line of passage offset)
may allow the radially inner surface of the tongue to direct working fluid into the cavity
(i.e. the turbine wheel) in a direction nearer to the radial direction, in order to improve
turbine efficiency (as outlined above).
The housing may further comprise an additional inlet volute with an additional volute
passage spiralling radially inwards about the turbine axis from a first end to a second
end.
The housing comprising a second volute may provide one or more of the advantages
discussed above, in relation to double flow and twin flow turbines.
The volute passage and the additional volute passage may be separated by a dividing
wall.
The dividing wall may define the second wall of the throat. As an alternative, it may
define the first wall of the throat.
The volute passage and the additional volute passage may be substantially mirrorimages
of each other about a plane normal to the turbine axis. This may allow the flow
of working fluid into the turbine from both volute passages to be advantageously
uniform.
The volute passage and the additional volute passage may be inclined in opposite axial
directions. Where this is the case, the angles by which the volute passage and the
additional volute passages are inclined (represented by the angles from the radial
direction of the line of passage offset and the additional line of passage offset
respectively) may or may not be of substantially the same magnitude. The volute
passage and additional volute passage being inclined in opposite axial directions may
allow the net flow entering the cavity to be nearer radial in direction, which can be
advantageous in terms of efficiency of a turbine positioned within the cavity.
In one embodiment where the volute comprises an additional volute passage, the
turbine housing further comprises:
a substantially annular additional throat positioned between a radially inner
portion of the additional volute passage and a radially outer portion of the cavity to
provide fluid communication therebetween, the additional throat being defined between
first and second axially-spaced walls;
an additional tongue projecting between a radially outer portion of the second
end of the additional volute passage and a radially inner portion of a part of the
additional volute passage radially outboard thereof, the additional tongue terminating at
a distal additional tongue tip,
wherein the additional volute passage, additional throat and additional tongue tip are
positioned whereby in a plane containing the turbine axis and the additional tongue tip:
the additional throat defines an additional line of minimum clearance, which is a
line running between the points on the first and second walls of the additional throat
which are the closest together;
the additional volute passage and the additional tongue tip co-operatively define
an additional preliminary inlet area;
the additional line of minimum clearance and the additional preliminary inlet
area co-operatively define a line of additional passage offset, which connects the
centroid of the additional preliminary inlet area and a point half way along the additional
line of minimum clearance;
the additional tongue tip defines an additional tongue tip lateral centreline;
the line of additional passage offset is not perpendicular to the turbine axis; and
the additional tongue tip lateral centreline and the line of additional passage
offset define an angle therebetween of at least 60 degrees.
In the above embodiment the sum of the angle at which the additional tongue tip lateral
centreline intersects the first wall of the additional throat, and the angle at which the
additional tongue tip lateral centreline intersects the second wall of the additional
throat, may be at least 1 0 degrees.
In a further embodiment where the volute comprises an additional volute passage, the
turbine housing further comprises:
a substantially annular additional throat positioned between a radially inner
portion of the additional volute passage and a radially outer portion of the cavity to
provide fluid communication therebetween, the additional throat being defined between
two axially-spaced walls;
an additional tongue projecting between a radially outer portion of the second
end of the additional volute passage and a radially inner portion of a part of the
additional volute passage radially outboard thereof, the additional tongue terminating at
a distal additional tongue tip,
wherein the additional volute passage, additional throat and additional tongue tip are
positioned whereby in a plane containing the turbine axis and the additional tongue tip:
the additional throat defines an additional line of minimum clearance, which is a
line running between the points on the two axially-spaced walls of the additional throat
which are the closest together;
the additional volute passage and the additional tongue tip co-operatively define
an additional preliminary inlet area;
the additional line of minimum clearance and the additional preliminary inlet
area co-operatively define a line of additional passage offset, which connects the
centroid of the additional preliminary inlet area and a point half way along the additional
line of minimum clearance;
the additional tongue tip defines an additional tongue tip lateral centreline;
the line of additional passage offset is not perpendicular to the turbine axis; and
the additional tongue tip lateral centreline and the line of additional passage
offset define an angle therebetween of at least 60 degrees.
In another embodiment where the volute comprises an additional volute passage, the
turbine housing further comprises:
a substantially annular additional throat positioned between a radially inner
portion of the additional volute passage and a radially outer portion of the cavity to
provide fluid communication therebetween, the additional throat being defined between
first and second axially-spaced walls;
an additional tongue projecting between a radially outer portion of the second
end of the additional volute passage and a radially inner portion of a part of the
additional volute passage radially outboard thereof, the additional tongue terminating at
a distal additional tongue tip,
wherein the additional volute passage, additional throat and additional tongue tip are
positioned whereby in a plane containing the turbine axis and the additional tongue tip:
the additional tongue tip defines an additional tongue tip lateral centreline; and
the sum of the angle at which the additional tongue tip lateral centreline
intersects the first wall of the additional throat, and the angle at which the additional
tongue tip lateral centreline intersects the second wall of the additional throat, is at
least 120 degrees.
Arrangements falling within the above embodiments may provide one or more of the
advantages discussed above in relation to double flow and twin flow turbines, while
also allowing both of the volutes to provide one or more of the advantages discussed
above in relation to the first and second aspects of the invention.
One or more of the above optional features described in relation to the inlet volute may,
instead or in addition to applying to the inlet volute, apply in relation to the additional
volute.
In alternative embodiments the additional volute may have one or more, but less than
all, of the above features.
The plane containing the turbine axis and the tongue tip, and the plane containing the
turbine axis and the additional tongue tip, may be coplanar. This may allow any
disruption to the A/r across the tongue to have a more limited circumferential extent.
Alternatively, the plane containing the turbine axis and the tongue tip, and the plane
containing the turbine axis and the additional tongue tip, may not be coplanar (for
instance the plane containing the turbine axis and the tongue tip may intersect the
plane containing the turbine axis and the additional tongue tip at an angle of at least 5
degrees, at least 10 degrees or at least 20 degrees). This may allow the circumferential
positions of the two tongue tips to be staggered, which in turn may 'smooth' the
changes in A/r around the circumference of the turbine. Further, it may allow a change
in A/r across one tongue to be partially or entirely counteracted by a change in A/r
across the other tongue.
The volute passage and additional volute passage may merge at a substantially
annular inlet passage positioned immediately radially outwards from the cavity. The
inlet passage may allow flow from the two volute passages to be combined with less
resultant turbulence. The volute passage and the additional volute passage may
instead be in direct fluid communication with respective portions of the cavity. This may
advantageously reduce the amount of space occupied by the turbine housing.
The line of minimum clearance and the additional line of minimum clearance may be of
substantially equal length. This may allow the flow into the cavity (or the inlet passage,
where present) to be more even and therefore less turbulent. Alternatively, the line of
minimum clearance and the additional line of minimum clearance may differ from one
another in length. This may allow the fluid flow through each throat to be optimised
separately, (for instance to provide faster flow into a turbine at some axial positions
than at others).
The preliminary inlet area and the additional preliminary inlet area may not be of equal
magnitude. In other words, the preliminary inlet area and the additional preliminary inlet
area may differ from one another in magnitude. Their magnitudes may differ from one
another by at least 5%, at least 10% or at least 20% of the larger of the two areas. This
may allow one of the volute passages to be utilised for EGR with reduced overall
exhaust back pressure, as outlined above. The volute with the smaller preliminary inlet
area may also be used to provide advantageously increased flow velocity through a
wastegate, due to the presence of higher pressure therein. Alternatively, the
preliminary inlet area and the additional preliminary inlet area may have substantially
the same cross-sectional area.
The tongue tip lateral centreline (and/or the additional tongue tip lateral centreline,
where present) may be positioned at a radial distance from the turbine axis of around
1.1 - 1.3 times the radius of the turbine wheel.
The first and second walls may be movable relative to one another so as to adjust the
distance therebetween. For instance, the turbine housing may have a movable shroud
plate or nozzle ring as described above.
According to a third aspect of the present invention there is provided a turbine
assembly comprising a turbine wheel, and a turbine housing according to the first
aspect of the invention.
A turbine assembly according to the third aspect of the invention may provide a
complete assembly which may be fitted to an apparatus so as to provide one or more
of the advantages discussed in relation to the first and second aspects of the invention.
According to a fourth aspect of the present invention there is provided a turbocharger
comprising a turbine assembly according to the third aspect of the invention.
A turbocharger according to the fourth aspect of the invention may provide a
self-contained unit which provides one or more of the advantages discussed in relation
to the first and second aspects of the invention.
According to a fifth aspect of the present invention there is provided a turbine housing
comprising a cavity for a turbine wheel, the cavity defining a turbine axis about which
the turbine wheel rotates in use, and an inlet volute comprising:
a volute passage spiralling radially inwards about the turbine axis from a first
end to a second end;
a substantially annular throat positioned between a radially inner portion of the
volute passage and a radially outer portion of the cavity to provide fluid communication
therebetween, the throat being defined between two axially-spaced walls;
a tongue projecting between a radially outer portion of the second end of the
volute passage and a radially inner portion of a part of the volute passage radially
outboard thereof, the tongue terminating at a distal tongue tip,
wherein the volute passage, throat and tongue tip are positioned whereby in a plane
containing the turbine axis and the tongue tip:
the throat defines a line of minimum clearance, which is a line running between
the points on the two axially-spaced walls which are the closest together;
the volute passage and tongue tip co-operatively define a preliminary inlet area;
the line of minimum clearance and the preliminary inlet area co-operatively
define a line of passage offset, which connects the centroid of the preliminary inlet area
and a point half way along the line of minimum clearance;
the tongue tip defines a tongue tip lateral centreline;
the line of passage offset is not perpendicular to the turbine axis; and
the tongue tip lateral centreline and the line of passage offset define an angle
therebetween of at least 60 degrees.
One or more of the optional features discussed in relation to the first or second aspect
of the invention may also be applicable to the fifth aspect of the invention. Further, a
turbine housing according to the fifth aspect of the invention may form part of a turbine
assembly which also comprises a turbine wheel. Such a turbine assembly may form
part of a turbocharger.
Specific embodiments of the present invention will now be described, by way of
example only, with reference to the accompanying drawings (not to scale), in which:
Figure 1 shows a schematic longitudinal cross-section through a known
turbocharger;
Figure 2 shows an axial cross-section through the turbocharger of Figure 1;
Figure 3 shows a cross-section through an exemplary inlet volute;
Figure 4 shows a cross-section through an inlet volute of a turbine housing
according to a first embodiment of the invention;
Figure 5 shows a graph of the variation in A/r around the circumference of the
throats of the volutes of figures 3 and 4 ;
Figure 6 shows a cross-section through an inlet volute of a turbine housing
according to a second embodiment of the invention;
Figure 7 shows a cross-section through an inlet volute of a turbine housing
according to a third embodiment of the invention; and
Figure 8 shows a cross-section of the preliminary inlet areas of a turbine
housing according to a fourth embodiment of the invention.
Figure 1 shows a known turbocharger, which has a turbine assembly 2 joined to a
compressor assembly 4 by a bearing housing 6 . The turbine assembly 2 has a turbine
wheel 10 and a turbine housing 12. The turbine housing 12 has a mounting surface 13,
which in this case is annular in shape, that is positioned against the bearing housing 6 .
In other embodiments the mounting surface 13 may take a different form, for instance a
flat or concave surface provided on a mounting flange.
The turbine housing 12 has an inlet volute 14, an outlet passage 16, and a cavity 18
which defines a turbine axis 20. The turbine wheel 10 is located within the cavity 18
and is rotatable about the turbine axis 20. The inlet volute 14 defines a volute passage
22 which spirals radially inwards from a first end to a second end (not visible in Figure
1) , and terminates at an annular throat 24 which is immediately radially outwards of the
cavity 18. The volute passage 22, throat 24, cavity 18 and outlet passage 16 are
arranged in fluid communication so that working fluid (in this case exhaust gas) enters
the volute passage 22 at its first end, emerges from the second end of the volute
passage into the throat 24, then passes from the throat to the outlet passage 16
through the cavity 18 (thereby imparting energy to the turbine wheel 10). The inlet
volute 14 has a flange 26 positioned at the first end of the volute passage 16, for
connection to the exhaust manifold of an internal combustion engine (not shown).
The turbine wheel 10 is mounted on one end of a shaft 28 which is positioned in line
with the turbine axis 20 and rotatably received within bearings 30 in the bearing
housing 6 . The bearings 30 are connected to a lubricant port 32, through which
lubricant is fed while the turbocharger is in use. When energy is imparted to the turbine
wheel 10 by exhaust gas flowing through the cavity 18 from the throat 24 to the outlet
passage 16, the turbine wheel rotates within the cavity and rotates the shaft 28.
The compressor assembly 4 has a compressor wheel 34 and a compressor housing
36. The compressor housing 36 has an inlet passage 38, an outlet volute 40, and a
cavity 42 within which the compressor wheel 34 is located. The cavity 42 defines a
compressor axis 44, which is in line with the turbine axis 20. The outlet volute 40
spirals radially outwards from the cavity 42 and terminates in a hose connector 46 for
connection to the air intake of an engine (not shown). The compressor wheel is also
mounted on the shaft 28, so that as the shaft is rotated by the turbine, the compressor
wheel is rotated similarly. The inlet passage 38, cavity 42 and outlet volute 40 are
arranged in fluid communication so that atmospheric air is sucked through the inlet
passage 38 and into the cavity 42 by rotation of the compressor wheel 34, before being
forced out of the compressor wheel, under pressure, through the outlet volute 40.
Returning to the turbine assembly 2 , the inlet volute 14 also has a tongue 50, which is
shown more clearly in Figure 2 . This figure shows the inlet volute 14, and the volute
passage 22 spiralling radially inwards (about the turbine axis 20) towards the throat 24
from its first end 52 to its second end 54. The tongue 50 projects along its longitudinal
axis 56, which runs within a plane that is normal to the turbine axis (i.e. the plane of the
cross section shown in this figure), and terminates in a longitudinally distal tongue tip
58. As outlined above, the tongue acts to separate a radially outer portion of the
second end 54 of the volute passage 22 from a radially inner portion of a part of the
volute passage radially outboard from and adjacent to the second end (which in this
case is a portion near to the first end 52). As also outlined above, the tongue tip 58 acts
to direct flow of exhaust gas in the second end 54 of the volute passage 22 into the
throat 24.
The potential sudden change in A/r described previously may be more apparent from
Figure 2 . As exhaust gas flow runs through the first end 52 of the volute passage 22
(from right to left from the perspective of Figure 2) and begins to spiral (anticlockwise
from the perspective of Figure 2) inwards towards the throat 24, it crosses an imaginary
line 60. At that point, the radially inner boundary of the volute passage that was
provided by the radially outer surface of the tongue is no longer present. The total
cross-sectional area of the volute passage 22 at that point (Apassage) therefore increases
due to the tongue no longer occupying space and enclosing the passage, and similarly
the shape of that area (and thus the (radial) position of the centroid, rpassage) changes.
Depending on the magnitudes of these changes, this can bring about the sudden
change in A/r described above.
In the case of the volute shown in Figures 1 and 2 , the effect of the change in cross
sectional area across the tip of the tongue is manageable, however in other
circumstances the effect can be more dramatic.
Figure 3 shows a cross-section of an inlet volute 14 where the volute passage 22 has
been moved along the turbine axis (not visible, but running horizontally and positioned
downwards from the perspective of Figure 3) away from the mounting surface and
bearing housing (not visible, but positioned to the left from the perspective of Figure 3).
As such, the throat 24 is no longer positioned at the axial centre of the volute passage
22. Such a change of position of the volute passage 22 can be necessary if the
passage is large enough that it would otherwise obstruct access to the bearing housing
(for instance for connection of lubricant lines to a lubricant port).
The cross-section of Figure 3 is taken in a plane that contains the turbine axis (not
visible) and the tongue tip 58 (i.e. a plane at the same angular position as the dotted
line in Figure 2). It also shows the preliminary inlet area 62, which is the cross-sectional
area enclosed by the walls of the volute passage 22 and the tongue tip 58, and the
centroid 64 of this area. In addition, Figure 3 shows the line of minimum clearance 66,
which is the shortest distance between the two axially-spaced counterposed walls 68,
70 that define the throat 24. In other words, the line of minimum clearance 64 is a line
which runs between the points on the two walls 68, 70 which are the closest together.
The mid-point 72 of the line of minimum clearance 66, that is the point which is half¬
way along the line of minimum clearance (and which is therefore equidistant between
the walls 68, 70), is also marked on this drawing.
While the volute passage shown in Figures 1 and 2 is axially symmetrical, as outlined
above the volute passage 22 shown in Figure 3 is not. As a result, while in the passage
shown in Figures 1 and 2 the centroid of the preliminary inlet area would be directly
radially outwards from (i.e. axially aligned with) the mid-point of the line of minimum
clearance of the throat, this is not the case for the volute passage 22 of Figure 3 . The
centroid 64 of the preliminary inlet area 62 is axially displaced from the mid-point 72 of
the line of minimum clearance 66. As such, a line connecting these two points 64, 72,
hereafter referred to as the line of passage offset 74, is not perpendicular to the turbine
axis as it would be in the volute passage of Figures 1 and 2 .
With the volute passageway positioned so that the line of passage offset 74 is not
perpendicular to the turbine axis, and the tongue tip 58 positioned so that its lateral
centreline 76 is parallel to the turbine axis (i.e. transverse to the radial direction) as is
conventional, the lateral centreline of the tongue tip is at a relatively acute angle to the
line of passage offset 74. In this example, the angle 78 between the lateral centreline
58 of the tongue tip 58 and the line of passage offset 74 is 56 °. Due to this relatively
acute angle 78, the sudden change in A/r across the tongue tip 58 is more pronounced.
Figure 4 shows a cross-section of an inlet volute 14 according to a first embodiment of
the invention. The volute of Figure 4 is the same as the volute of Figure 3 with the
exception of the configuration of the tongue, therefore only the differences will be
discussed here.
In this embodiment, the tongue tip 58 has been adjusted so that its lateral centreline 76
is no longer parallel to the turbine axis (not shown, but horizontal from the perspective
of Figure 4) , but is at an angle 79 of 8 ° to it. The angle 78 between the lateral centreline
76 of the tongue tip 58 and the line of passage offset 74 is now 64 °. This increase in
the angle 78 between the tongue tip 58 and line of passage offset 74 reduces the
magnitude of the change in A/r across the tongue tip. In addition, this change in angle
of the tongue tip 58 decreases its cross sectional area (from the perspective of figure 4 ,
the right hand lateral end of tongue tip 58 has been moved downwards towards the
throat, shortening the overall lateral width of the tongue tip) , which further reduces the
change in A r.
Figure 5 illustrates the effect of this change, showing the change in A/r of the volute
passage 22 as angular displacement from the tongue tip 58 increases (exaggerated for
clarity) for the volute passages of Figure 3 (line 80) and Figure 4 (line 82). From this
figure, the improvement offered by this change in tongue tip angle 78 is clear, with line
82 being nearer to the linear decrease in A/r (line 84) that is desired.
Figure 6 shows a cross-section of an inlet volute 14 according to a second embodiment
of the invention. Like the volute 14 of the first embodiment, it has a volute passage 22,
a throat 24, and a tongue with a tip 58. The structure of these features correspond to
the equivalent features of the first embodiment. As with Figures 3 and 4 , Figure 6 is a
cross-section through a plane which contains the turbine axis (not visible) and the
tongue tip 58. Again, the figure is annotated to show the prelim inary inlet area 62 and
its centroid 64, the line of minimum clearance 66 and its mid-point 72, and the lateral
centreline 76 of the tongue tip 58. In this embodiment, the angle (not shown) between
the lateral centreline 76 of the tongue tip 58 and the line of passage offset 74 is 78 °.
In the second embodiment, the turbine housing 12 has an additional volute 14' with an
additional volute passage 22' separated from the volute passage 22 by a dividing wall
86. The additional volute 14' also has an additional throat 24' and an additional tongue
with an additional tongue tip 58'. The additional tongue tip 58' has a lateral centreline
76'. The features of the additional inlet volute 14' have equivalent structure and
function to those of the inlet volute 14. The two volute passages 22, 22' meet at an inlet
passage 87 positioned immediately radially outwards from the turbine wheel 10. In this
embodiment, the volute passage 22 and the additional volute passage 22' are both
inclined from the radial direction. More particularly, in this case both passages 22, 22'
are inclined from the radial direction in the same axial direction - both are inclined to
the right from the perspective of Figure 6 . This may provide an advantageous amount
of space to the other axial side of the turbine housing, which may for example allow a
particularly large bearing housing to be accommodated (or may allow particularly
uninhibited access to the bearing housing).
The plane of Figure 6 is also a plane which includes the turbine axis and the additional
tongue tip 58', and in this plane the additional volute passage, throat and tongue tip
22', 24', 58' define (in a corresponding manner) an additional preliminary inlet area 62'
with a centroid 64', an additional line of minimum clearance 66' with a mid-point 72',
and a line of additional passage offset 74'. In this embodiment the angle (not labelled)
between the additional tongue tip lateral centreline 76' and the line of additional
passage offset 74' is 90°. In other words, the additional tongue tip lateral centreline 76'
is perpendicular to the line of additional passage offset 74'.
In the second embodiment, the tongue tip 58 is positioned in the throat 24 such that the
line of minimum clearance 66 runs through (i.e. lies within) the tongue tip, and similarly
the additional tongue tip 58' is positioned in the additional throat 24' such that the
additional line of minimum clearance 66' runs through the additional tongue tip. It is
also apparent that the additional tongue tip lateral centreline 76' is near parallel (5°) to
the additional line of minimum clearance 66'. Further, it is noteworthy that the additional
preliminary inlet area 62' is smaller than the preliminary inlet area 62.
In this case, the additional preliminary inlet area 62' is around half the size of the
preliminary inlet area 62 (in other words the magnitudes of the two areas differ from
one another by around 50% of the larger area). In this case the additional line of
minimum clearance 66' is around two thirds the length of the line of minimum clearance
66. In other words the line of minimum clearance 66 and the additional line of minimum
clearance 66' differ in length from one another. In this case the additional line of
minimum clearance 66' is shorter than the line of minimum clearance 66, but in other
embodiments it may be longer. Further, although in this case the difference in
magnitudes of the two lines of minimum clearance is around 33% of the length of the
larger, in other embodiments this difference may be more than this (for instance 40%)
of less than this (for instance 20%).
In this embodiment, due to its smaller size the pressure is greater in the additional
volute passage 22'. The pressure in the additional volute passage 22' is therefore
higher, and this can utilised in an EGR system by opening a valve 88 and releasing
some of the exhaust gas in the additional volute passage back into the engine through
a recirculation duct 90. In an alternative embodiment, the valve 88 and duct 90 may be
used as a wastegate.
A cross-section of an inlet volute 14 according to a third embodiment of the invention is
shown in Figure 7 . Like the second embodiment, the housing 12 of the third
embodiment has an inlet volute 14 and an additional inlet volute 14' which meet at an
inlet passage 87. Only the differences between the second and third embodiments will
be described here.
While in the first and second embodiments the volute 14 or volutes 14, 14' were all
angled to the right (from the perspective of the figures) away from the radial direction in
order to provide access to a bearing housing, this is not the case in the third
embodiment. In this case, the inlet volute 14 and the additional inlet volute 14' are
angled away from the radial direction in opposite axial directions - the inlet volute 14 is
inclined to the left and the additional inlet volute is inclined to the right (from the
perspective of Figure 7). Nonetheless, since each of the two volutes 14, 14' are
individually offset relative to their respective throats (i.e. neither the line of passage
offset 74 nor the additional line of passage offset 74' are perpendicular to the turbine
axis), albeit in opposite directions, the invention may nonetheless be of benefit to each
volute passage 22, 22' individually.
In the third embodiment, the volute passage 22 and additional volute passage 22' are
mirror-images of each other about a plane normal to the turbine axis. Similarly, unlike
the second embodiment, in the third embodiment the throat 24 and additional throat 24'
have the same minimum clearance. In other words, the line of minimum clearance 66
and the additional line of minimum clearance 66' are the same length.
In addition, in this embodiment the tongue tip lateral centreline 76 is collinear with the
line of minimum clearance 66, and the additional tongue tip lateral centreline 76' is
collinear with the additional line of minimum clearance 66'. In this embodiment the
angle between the tongue tip lateral centreline 76 and the line of passage offset 74, is
76°, as is the angle between the additional tongue tip lateral centreline 76' and the
additional line of passage offset 74'.
Figure 8 shows the preliminary inlet area 62 and additional preliminary inlet area 62' of
a turbine housing according to a fourth embodiment of the invention. Figure 8 is a
magnified view but is shown to scale. As an indication of the actual size of the fourth
embodiment, the width 100 of the dividing wall is 6 mm. The turbine axis is not visible,
but is horizontal from the perspective of Figure 8 , with the bearing housing and the
mounting surface of the turbine housing (not visible) positioned to the left. The fourth
embodiment is similar to the second embodiment, therefore only the differences will be
described here.
In the fourth embodiment, the preliminary inlet area 62 is smaller than the additional
preliminary inlet area 62', in this case by a factor of around 2 (however, as explained
below, the selection of the preliminary inlet area and the additional preliminary inlet
area may be reversed). In other words, their magnitudes differ from one another by
around 50% of the larger of the two areas. The inlet volutes (not visible) are positioned
such that the line of passage offset 74 is at an angle of around 68 degrees to the
turbine axis, and such that the line of additional passage offset 74' is positioned at an
angle of around 24 degrees to the turbine axis. It is also noteworthy that the tongue tip
lateral centreline 76 is collinear with the line of minimum clearance 66, as was the case
in the third embodiment. In this embodiment, the additional tongue tip lateral centreline
76 is not collinear with the additional line of minimum clearance 66. Rather, they are
positioned at an angle of around 10 degrees to one another.
In this embodiment, the angle between the tongue tip lateral centreline 76 and the line
of passage offset 74 is around 68 degrees, and the angle between the additional
tongue tip lateral centreline 76' and the line of additional passage offset 74' is around
75 degrees. In this embodiment the tongue tip 58 and additional tongue tip 58' are
each laterally tapered, in this case each having an even taper of around 2 degrees, for
ease of manufacture. Each tongue tip 58, 58' narrows towards the dividing wall 86. In
this embodiment, the tongue tip lateral centreline 76 is substantially parallel to the
turbine axis (not visible), as is the line of minimum clearance 66, the additional tongue
tip lateral centreline 76' is positioned at an angle of around 50 degrees to the turbine
axis and the additional line of minimum clearance 66' is positioned at an angle of
around 60 degrees to the turbine axis. In this embodiment, the line of minimum
clearance 66 and the additional line of minimum clearance 66' are of substantially the
same length. In this case, each is around 6 mm long.
The tongue tip lateral centreline 76 meets the first wall 102 of the throat 24 at an angle
of around 90 degrees, and also meets the second wall 104 of the throat at an angle of
around 90 degrees. Accordingly, the sum of the angle at which the tongue tip lateral
centreline 76 intersects the first wall 102, and the angle at which the tongue tip lateral
centreline intersects the second wall 104, is around 180 degrees. The additional
tongue tip lateral centreline 76' meets the first wall 102' of the additional throat 24' at an
angle of around 78 degrees, and meets the second wall 104' of the additional throat 24'
at an angle of around 78 degrees. Therefore, the sum of the angle at which the
additional tongue tip lateral centreline 76' intersects the first wall 102', and the angle at
which the additional tongue tip lateral centreline intersects the second wall 104', is
around 156 degrees. Although in this case the tongue tip lateral centreline 76 meets
both walls 102, 104 at substantially the same angle and the additional tongue tip lateral
centreline 76' meets both walls 102', 104' at substantially the same angle, this is a
result of the particular geometry of the throats 24, 24' of the fourth embodiment. In
other embodiments this may not be the case.
In this embodiment, the wall described as the 'first' wall 102 is the wall of the throat 24
which is axially nearer to the mounting surface (not visible), and the second wall 104 is
the wall of the throat 24 which is defined by the dividing wall 86. Further, the first wall
102 is the wall on the side of the throat 24 at which the tongue tip 58 is thicker due to
its lateral taper. The first wall 102' is the wall of the additional throat 24' that is axially
further from the mounting surface (not visible), and is also the wall of the additional
throat 24' which is not defined by the dividing wall 86. The first wall 102' is also the wall
on the side of the additional throat 24' at which the additional tongue tip 58' is thicker
due to its lateral taper. In the case of both volute passages, it is to be understood that
in other embodiments the 'first' and 'second' walls of the throat in question may be
designated in any suitable fashion, for instance one or more of those described in the
appended claims.
In this embodiment, the dividing wall 86 is positioned with its centreline 106 at an angle
of around 40 degrees to the turbine axis. The line of minimum clearance 66 and the
tongue tip lateral centreline 76 (which are collinear, as outlined above) are each
positioned at an angle of around 40 degrees to the centreline 106 of the dividing wall
86. The additional tongue tip lateral centreline 76' is positioned at an angle of around
90 degrees to the centreline 106 of the dividing wall 86, and the additional line of
minimum clearance 66' is positioned at an angle of around 80 degrees to the centreline
106 of the dividing wall 86. It will be readily apparent from Figure 8 that in the case of
the fourth embodiment, the line of minimum clearance runs through the tongue tip and
the additional line of minimum clearance runs through the additional tongue tip.
Although in this embodiment the additional tongue tip lateral centreline 76' is positioned
substantially perpendicularly to the centreline 106 of the dividing wall 86, in one
modification of the fourth embodiment it is instead positioned substantially
perpendicularly to the first wall 102' and second wall 104' of the additional throat 24'. In
this modification, due to the particular geometry of the additional throat 24', the
additional tongue tip lateral centreline 76' would be substantially parallel to (and indeed
collinear with) the additional line of minimum clearance 66'. In this modification the
additional tongue tip lateral centreline 76' would be positioned at an angle of around 86
degrees to the line of additional passage offset 74', and positioned at an angle of
around 80 degrees to the to the centreline 106 of the dividing wall 86.
Numerous modifications and variations may be made to the exemplary designs
described above without departing from the scope of the invention as defined in the
claims. For instance, though in the above embodiments the line of additional passage
offset is not perpendicular to the turbine axis and the additional tongue tip lateral
centreline is at an angle of not less than 60° with the line of additional passage offset,
in other embodiments the additional inlet volute may be entirely conventional.
Furthermore, whilst the turbine housing described forms part of a turbine assembly in a
turbocharger, it will be appreciated that this need not be the case. For example, the
housing may be fitted to a turbine assembly that is to be linked to a crankshaft and/or
gear which transmits mechanical power to a flywheel or a power generating device.
It is to be noted that features or arrangements described in relation to the additional
inlet volute may be present in relation to the volute passage (instead or in addition),
and vice versa. For the avoidance of doubt, as both inlet volutes in the second, third
and fourth embodiments fall within the scope of the appended claims, the selection of
which inlet volute constitutes the additional inlet volute is arbitrary. In both cases the
two volutes may be categorised the other way round, i.e. with the additional inlet volute
being on the left from the perspective of the figures. In the illustrations of the above
embodiments each tongue tip has a slight taper along its lateral centreline. While this
feature may be preferable for manufacturing reasons, as it allows easier removal of the
mould during casting, it should not be construed as limiting.
Although the first and second aspects of the invention have been discussed in detail in
relation to different embodiments, it is to be understood that the arrangements
described may also be embodiments of other aspects of the invention. For example, in
relation to the first embodiment (illustrated in Figure 4), if the wall of the throat 24 to the
right from the perspective of the diagram is designated the 'first wall' and the opposite
wall of the throat is designated the 'second wall', the tongue tip lateral centreline 76
intersects the first wall at an angle of around 65 degrees and intersects the second wall
at an angle of around 82 degrees. Accordingly, the sum of said angles is around 147
degrees. Although the wall to the right of the throat (from the perspective of Figure 4)
has been designated as the 'first wall' in this example, since it is the wall of the throat at
which the tongue tip is thicker) and is the wall of the throat which is further from the
mounting surface, as outlined above this should not be construed as limiting. This wall
may equally be designated the 'second wall' and the other wall the 'first wall'.
It should be noted that the above embodiments are also within the scope of the fifth
aspect of the invention.
While the invention has been illustrated and described in detail in the drawings and
foregoing description, the same is to be considered as illustrative and not restrictive in
character, it being understood that only the preferred embodiments have been shown
and described and that all changes and modifications that come within the scope of the
invention as defined in the claims are desired to be protected. It should be understood
that while the use of words such as preferable, preferably, preferred or more preferred
utilized in the description above indicate that the feature so described may be more
desirable, it nonetheless may not be necessary and embodiments lacking the same
may be contemplated as within the scope of the invention, the scope being defined by
the claims that follow. In reading the claims, it is intended that when words such as "a,"
"an," "at least one," or "at least one portion" are used there is no intention to limit the
claim to only one item unless specifically stated to the contrary in the claim. When the
language "at least a portion" and/or "a portion" is used the item can include a portion
and/or the entire item unless specifically stated to the contrary. For the avoidance of
doubt, optional and/or preferred features as set out herein may be used either
individually or in combination with each other where appropriate and particularly in the
combinations as set out in the accompanying claims. The optional and/or preferred
features for each aspect of the invention set out herein are also applicable to any other
aspects of the invention, where appropriate.
CLAIMS
1. A turbine housing comprising a cavity for a turbine wheel, the cavity defining a
turbine axis about which the turbine wheel rotates in use, and an inlet volute
comprising:
a volute passage spiralling radially inwards about the turbine axis from a first
end to a second end;
a substantially annular throat positioned between a radially inner portion of the
volute passage and a radially outer portion of the cavity to provide fluid communication
therebetween, the throat being defined between first and second axially-spaced walls;
a tongue projecting between a radially outer portion of the second end of the
volute passage and a radially inner portion of a part of the volute passage radially
outboard thereof, the tongue terminating at a distal tongue tip,
wherein the volute passage, throat and tongue tip are positioned whereby in a plane
containing the turbine axis and the tongue tip:
the throat defines a line of minimum clearance, which is a line running between
the points on the first and second walls which are the closest together;
the volute passage and tongue tip co-operatively define a preliminary inlet area;
the line of minimum clearance and the preliminary inlet area co-operatively
define a line of passage offset, which connects the centroid of the preliminary inlet area
and a point half way along the line of minimum clearance;
the tongue tip defines a tongue tip lateral centreline;
the line of passage offset is not perpendicular to the turbine axis; and
the tongue tip lateral centreline and the line of passage offset define an angle
therebetween of at least 60 degrees.
2 . A turbine housing according to claim 1 wherein the tongue tip lateral centreline
and the line of passage offset define an angle therebetween of at least 75 degrees.
3 . A turbine housing according to claim 1 or 2 wherein the sum of the angle at
which the tongue tip lateral centreline intersects the first wall, and the angle at which
the tongue tip lateral centreline intersects the second wall, is at least 120 degrees.
4 . A turbine housing comprising a cavity for a turbine wheel, the cavity defining a
turbine axis about which the turbine wheel rotates in use, and an inlet volute
comprising:
a volute passage spiralling radially inwards about the turbine axis from a first
end to a second end;
a substantially annular throat positioned between a radially inner portion of the
volute passage and a radially outer portion of the cavity to provide fluid communication
therebetween, the throat being defined between first and second axially-spaced walls;
a tongue projecting between a radially outer portion of the second end of the
volute passage and a radially inner portion of a part of the volute passage radially
outboard thereof, the tongue terminating at a distal tongue tip,
wherein the volute passage, throat and tongue tip are positioned whereby in a plane
containing the turbine axis and the tongue tip:
the throat defines a line of minimum clearance, which is a line running between
the points on the first and second walls which are the closest together;
the tongue tip defines a tongue tip lateral centreline; and
the sum of the angle at which the tongue tip lateral centreline intersects the first
wall, and the angle at which the tongue tip lateral centreline intersects the second wall,
is at least 120 degrees.
5 . A turbine housing according to claim 3 or 4 wherein said sum is at least 150
degrees.
6 . A turbine housing according to claim 5 wherein the tongue tip lateral centreline
is positioned substantially perpendicularly to the first wall, at a location at which it is as
close to perpendicular to the second wall as possible.
7 . A turbine housing according to any one of claims 3 - 6 wherein the tongue tip
lateral centreline is positioned at an angle of at least 75 degrees to the first wall.
8 . A turbine housing according to any one of claims 3 - 7 wherein the tongue tip
lateral centreline is positioned at an angle of at least 75 degrees to the second wall.
9 . A turbine housing according to any one of claims 3 - 8 wherein the tongue tip
is laterally tapered, and a portion of the tongue tip which is adjacent to the first wall is
thicker than a portion which is adjacent to the second wall.
10. A turbine housing according to any one of claims 3 - 9 wherein the turbine
housing has a mounting surface configured to be positioned against a bearing housing,
and the first wall is positioned axially further from the mounting surface than the second
wall.
11. A turbine housing according to any preceding claim wherein the tongue tip
lateral centreline is at an angle of 15 degrees or less to the line of minimum clearance.
12. A turbine housing according to any preceding claim wherein the line of
minimum clearance lies substantially within the tongue tip.
13. A turbine housing according to claim 12, incorporating claim 11, wherein the
line of minimum clearance and the tongue tip lateral centreline are substantially
collinear.
14. A turbine according to any preceding claim wherein the tongue tip lateral
centreline is at an angle of 15 degrees or less to the turbine axis.
15. A turbine housing according to any preceding claim further comprising an
additional inlet volute with an additional volute passage spiralling radially inwards about
the turbine axis from a first end to a second end, the volute passage and the additional
volute passage being separated by a dividing wall;
16. A turbine housing according to claim 15 wherein the dividing wall defines the
second wall of the throat.
17. A turbine housing according to claim 15 or 16 further comprising:
a substantially annular additional throat positioned between a radially inner
portion of the additional volute passage and a radially outer portion of the cavity to
provide fluid communication therebetween, the additional throat being defined between
first and second axially-spaced walls;
an additional tongue projecting between a radially outer portion of the second
end of the additional volute passage and a radially inner portion of a part of the
additional volute passage radially outboard thereof, the additional tongue terminating at
a distal additional tongue tip,
wherein the additional volute passage, additional throat and additional tongue tip are
positioned whereby in a plane containing the turbine axis and the additional tongue tip:
the additional throat defines an additional line of minimum clearance, which is a
line running between the points on the first and second walls of the additional throat
which are the closest together;
the additional volute passage and the additional tongue tip co-operatively define
an additional preliminary inlet area;
the additional line of minimum clearance and the additional preliminary inlet
area co-operatively define a line of additional passage offset, which connects the
centroid of the additional preliminary inlet area and a point half way along the additional
line of minimum clearance;
the additional tongue tip defines an additional tongue tip lateral centreline;
the line of additional passage offset is not perpendicular to the turbine axis; and
the additional tongue tip lateral centreline and the line of additional passage
offset define an angle therebetween of at least 60 degrees.
18. A turbine housing according to claim 17 wherein the sum of the angle at which
the additional tongue tip lateral centreline intersects the first wall of the additional
throat, and the angle at which the additional tongue tip lateral centreline intersects the
second wall of the additional throat, is at least 120 degrees.
19. A turbine housing according to claim 15 or 16 further comprising:
a substantially annular additional throat positioned between a radially inner
portion of the additional volute passage and a radially outer portion of the cavity to
provide fluid communication therebetween, the additional throat being defined between
first and second axially-spaced walls;
an additional tongue projecting between a radially outer portion of the second
end of the additional volute passage and a radially inner portion of a part of the
additional volute passage radially outboard thereof, the additional tongue terminating at
a distal additional tongue tip,
wherein the additional volute passage, additional throat and additional tongue tip are
positioned whereby in a plane containing the turbine axis and the additional tongue tip:
the additional tongue tip defines an additional tongue tip lateral centreline;
the line of additional passage offset is not perpendicular to the turbine axis; and
the sum of the angle at which the additional tongue tip lateral centreline
intersects the first wall of the additional throat, and the angle at which the additional
tongue tip lateral centreline intersects the second wall of the additional throat, is at
least 120 degrees.
20. A turbine assembly comprising a turbine wheel, and a turbine housing
according to any preceding claim.
21. A turbocharger comprising a turbine assembly according to claim 20.