The present invention relates to a variable geometry turbine, particularly, but not
exclusively, for use in a turbocharger of an internal combustion engine.
Turbochargers are known devices for supplying air to the intake of an internal
combustion engine at pressures above atmospheric pressure (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
10 compressor wheel that is mounted on the other end of the shaft and 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 housings.
15
In known turbochargers, the turbine comprises a turbine chamber within which the
turbine wheel is mounted, an inlet passageway defined between facing radial walls
arranged around the turbine chamber, an inlet volute arranged around the inlet
passageway, and an outlet passageway extending from the turbine chamber. The
20 passageways and chambers communicate in such a way that pressurised exhaust gas
admitted to the inlet volute flows through the inlet passageway to the outlet passageway
via the turbine and rotates the turbine wheel. It is also known to trim turbine performance
by providing vanes, referred to as nozzle vanes, in the inlet passageway so as to deflect
gas flowing through the inlet passageway towards the direction of rotation of the turbine
25 wheel.
Turbines may be of a fixed or variable geometry type. Variable geometry turbines differ
from fixed geometry turbines in that the size of the inlet passageway can be varied to
optimise gas flow velocities over a range of mass flow rates so that the power output of
30 the turbine can be varied to suit varying engine demands. For instance, when the volume
of exhaust gas being delivered to the turbine is relatively low, the velocity of the gas
reaching the turbine wheel is maintained at a level that ensures efficient turbine operation
by reducing the size of the inlet passageway.
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In one known type of variable geometry turbine, an axially moveable wall member,
generally referred to as a "nozzle ring", defines one wall of the inlet passageway. The
position of the nozzle ring relative to a facing wall of the inlet passageway is adjustable
to control the axial width of the inlet passageway. Thus, for example, as gas flowing
5 through the turbine decreases, the inlet passageway width may also be decreased to
maintain gas velocity and to optimise turbine output. Such nozzle rings comprise a
generally annular wall and inner and outer axially extending flanges. The flanges extend
into a cavity defined in the turbine housing, which is a part of the housing that in practice
is provided by the bearing housing, which accommodates axial movement of the nozzle
10 ring.
The nozzle ring may be provided with vanes that extend into the inlet passageway and
through slots provided on the facing wall of the inlet passageway to accommodate
movement of the nozzle ring. Alternatively, vanes may extend from the fixed wall through
15 slots provided in the nozzle ring. Generally the nozzle ring is supported on rods
extending parallel to the axis of rotation of the turbine wheel and is moved by an actuator
that axially displaces the rods. Various forms of actuators are known for use in variable
geometry turbines, including pneumatic, hydraulic and electric actuators that are
mounted externally of the turbocharger and connected to the variable geometry system
20 via appropriate linkages.
25
It may be desirable to provide a variable geometry turbine at least partially addresses
one or more problems associated with known variable geometry turbines, whether
identified herein or otherwise.
According to a first aspect of the present invention there is provided a variable geometry
turbine comprising: a turbine housing defining an inlet and an outlet; a turbine wheel
rotatably mounted in the turbine housing between the inlet and the outlet such that the
turbine wheel can rotate about an axis; a movable wall member mounted in the housing
30 so as to be movable relative to the housing between at least a first position and a second
position, the movable wall member partially defining an inlet passageway between the
inlet and the turbine wheel, the inlet passageway being radially outboard of the turbine
wheel, a dimension of the inlet passageway being dependent on the position of the
movable wall member relative to the housing; and a plurality of vanes extending across
35 the inlet passageway, the vanes being circumferentially spaced; wherein in cross section
4
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each of the vanes has an elongate shape extending from a leading edge which is closer
to the inlet to a trailing edge which is closer to the turbine wheel and wherein a
perpendicular thickness of the vane 5% along the length of the vane from the leading
edge is at least 50% of the maximum perpendicular thickness of the vane.
It will be appreciated that as used here the perpendicular thickness of the vane is
intended to mean the thickness perpendicular to a camber line of the vane.
The variable geometry turbine according to this aspect of the invention has vanes which
10 have more bulbous leading edges, and which may have larger radii of curvature, than
the vanes typically used in such variable geometry turbines. This is advantageous over
existing designs, as now discussed.
The use of such a bulbous or blunt leading edge is contrary to the existing teaching in
15 the art, which would prompt the skilled person to select a smaller thickness at the leading
edge or the vanes in order to achieve better separation of the flow over the vanes (in
turn, increasing the efficiency of the turbine). However, the inventors have realized that
for a variable geometry turbine, the angle of attack of the flow of fluid over the vanes is
dependent on the position of the movable wall member. The inlet passageway between
20 the inlet and the turbine wheel is partially defined by the movable wall member and may
also be partially defined by a second wall member (which may, for example, be fixed
relative to the housing or integral therewith). The position of the movable wall member
may be characterized by a distance between the movable wall member and the second
wall member. This distance may be referred to as a variable geometry gap, or "VG gap".
25
By increasing the thickness at the leading edge such that a perpendicular thickness of
the vane 5% along the length of the vane from the leading edge is at least 50% of the
maximum perpendicular thickness of the vane, the variable geometry turbine according
to this aspect of the invention will operate with a relatively high efficiency over a larger
30 range of angles of attack (and therefore, equivalently, over a larger range of positions of
the movable wall member or VG gaps). Whereas prior art turbines may be very efficient
for a particular position of the movable wall member and very inefficient at other positions
of the movable wall member, the variable geometry turbine according to this aspect of
the invention can operate with a relatively high efficiency over a significantly larger range
35 of positions of the movable wall member.
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Typically, it may be intended for a variable geometry turbine to operate at a particular
design configuration (or design point) and convention wisdom would suggest that the
vanes be arranged to maximize the efficiency of the turbine under these conditions. For
5 example, a variable geometry turbine may be optimized for a flush gap arrangement
wherein the VG gap substantially matches a width of a leading edge (or tip) of the turbine
wheel.
Although the variable geometry turbine may operate at the design configuration for the
10 majority of the time, the variable geometry will also operate at other VG gaps. The
inventors have realized that with prior art arrangements, whilst being the most efficient
(time-averaged) arrangement, the efficiency at some other configurations that are far
from the design configuration could be significantly smaller. Perhaps more importantly,
the inventors have realized that with prior art arrangements some off design
15 configurations large static pressure fluctuations can be induced at the leading edge of
the turbine wheel, which can increase high cycle fatigue to the detriment of the lifetime
of the variable geometry turbine. This is addressed by the variable geometry turbine
according to this aspect of the invention.
20 The perpendicular thickness of the vane 5% along the length of the vane from the leading
edge may be at least 55% of the maximum perpendicular thickness of the vane. The
perpendicular thickness of the vane 5% along the length of the vane from the leading
edge is at least 60% of the maximum perpendicular thickness of the vane. In some
embodiments, the perpendicular thickness of the vane 5% along the length of the vane
25 from the leading edge may be at least 70% of the maximum perpendicular thickness of
the vane or even 80% of the maximum perpendicular thickness of the vane.
30
A perpendicular thickness of the vane 95% along the length of the vane from the leading
edge may be at least 40% of the maximum perpendicular thickness of the vane.
Advantageously, such an arrangement increases the foreign object damage (FOD)
tolerance of the vanes.
The perpendicular thickness of the vane 95% along the length of the vane from the
35 leading edge may be at least 45% of the maximum perpendicular thickness of the vane.
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The perpendicular thickness of the vane 95% along the length of the vane from the
leading edge may be at least 50% of the maximum perpendicular thickness of the vane.
The perpendicular thickness of the vane 95% along the length of the vane from the
leading edge may be at least 55% of the maximum perpendicular thickness of the vane.
5 The perpendicular thickness of the vane 95% along the length of the vane from the
leading edge may be at least 60% of the maximum perpendicular thickness of the vane.
The vanes and the turbine wheel may be arranged such that a ratio of a radius of the
trailing edge of each of the vanes to a radius of a leading edge of the turbine wheel is
10 1.2 or greater.
The ratio of the radius of the trailing edge of each of the vanes to the radius of the leading
edge of the turbine wheel may be in the range 1.2 to 1.25.
15 Whilst increasing the foreign object damage (FOD) tolerance of the vanes, increasing
the dimension at the trailing edge (for example such that a perpendicular thickness of
the vane 95% along the length of the vane from the leading edge is at least 40% of the
maximum perpendicular thickness of the vane) can increase the length of the wake
formed downstream of each vane. Advantageously, increasing the ratio of the radius of
20 the trailing edge of each of the vanes to the radius of the leading edge of the turbine
wheel to 1.2 or greater may allow this wake to dissipate sufficiently so as to reduce the
forcing function at a tip of the turbine wheel.
The vanes and the turbine wheel may be arranged such that a ratio of a radius of the
25 leading edge of each of the vanes to a radius of the trailing edge of each of the vanes is
1.2 or greater.
30
35
The vanes and the turbine wheel may be arranged such that a ratio of a solidity ratio of
the vanes in in the range 1.1 to 1.3.
The ratio of the length of the passageway defined between each pair of adjacent vanes
to the width of said passageway may be referred to as the solidity ratio. A higher solidity
ratio results in a larger vane overlap. In turn, this results in increases control over the
flow between adjacent vanes.
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The leading edge of the vanes may be provided with an elliptical end treatment having a
ratio of the major axis to the minor axis of at least 1.5.
The elliptical end treatment may have a ratio of the major axis to the minor axis of 1.5.
5 Alternatively, the elliptical end treatment may have a ratio of the major axis to the minor
axis of 2.0.
10
The vanes may be arranged so as to produce a double wake variation in the static
pressure around a circumference of the turbine wheel.
The static pressure trace around a circumference of the turbine at the trailing edge of
each of the vanes may be referred to as the forcing function. Naively, one may expect
the forcing function to have some areas of low pressure corresponding to the wake of
each vane interspersed by areas of high pressure corresponding to the flow of fluid
15 through the passageway defined between each pair of adjacent vanes. That is, one may
expect the forcing function to be dominated by a Fourier component that corresponds to
the number of the plurality of vanes (which may be referred to as a vane order oscillation).
Whilst increasing the foreign object damage (FOD) tolerance of the vanes, increasing
20 the dimensions of the trailing edge of the vanes can increase the length of the wake
formed downstream of each vane.
Shaping the vanes such that each vane produces a double wake in the forcing function
reduces the overall amplitude of the forcing function. Advantageously, this can reduce
25 the overall magnitude of the forcing function sufficiently such that even if the wake of the
vanes has not fully dissipated the forcing function may be at an acceptably low level.
The vanes may have a shape at least partially defined by a thickness distribution that
exponentially reduces from the leading edge to the trailing edge and having an end
30 treatment at each of the leading and trailing edges.
Such a thickness distribution may induce a double wake. The thickness distribution may
be the thickness distribution in Table 7. The actual thickness of the vanes, with the end
treatment at each of the leading and trailing edges, may be the thickness distribution in
35 Table 14.
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The vanes may have a shape at least partially defined by an angular distribution that is
more tangential at the leading edge than the trailing edge.
5 Such an angular distribution may aid in the induction of a double wake. The angular
distribution may be the angular distribution in Table 8.
According to a second aspect of the invention there is provided a variable geometry
turbine comprising: a turbine housing defining an inlet and an outlet; a turbine wheel
10 rotatably mounted in the turbine housing between the inlet and the outlet such that the
turbine wheel can rotate about an axis; a movable wall member mounted in the housing
so as to be movable relative to the housing between at least a first position and a second
position, the movable wall member partially defining an inlet passageway between the
inlet and the turbine wheel, the inlet passageway being radially outboard of the turbine
15 wheel, a dimension of the inlet passageway being dependent on the position of the
movable wall member relative to the housing; and a plurality of vanes extending across
the inlet passageway, the vanes being circumferentially spaced; wherein in cross section
each of the vanes has an elongate shape extending from a leading edge which is closer
to the inlet to a trailing edge which is closer to the turbine wheel and wherein a
20 perpendicular thickness of the vane 95% along the length of the vane from the leading
edge is at least 40% of the maximum perpendicular thickness of the vane; and wherein
the vanes and the turbine wheel are arranged such that a ratio of a radius of the trailing
edge of each of the vanes to a radius of a leading edge of the turbine wheel is 1.2 or
greater.
25
Advantageously, increasing a dimension of the trailing edge of each of the vanes such
that a perpendicular thickness of the vane 95% along the length of the vane from the
leading edge is at least 40% of the maximum perpendicular thickness of the vane
increases the foreign object damage tolerance of the vanes. Whilst increasing the
30 foreign object damage (FOD) tolerance of the vanes, increasing the dimension of the
trailing edge can increase the length of the wake formed downstream of each vane.
However, advantageously, increasing the ratio of the radius of the trailing edge of each
of the vanes to the radius of the leading edge of the turbine wheel to 1.2 or greater may
allow this wake to dissipate sufficiently so as to reduce the forcing function at a tip of the
35 turbine wheel.
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The perpendicular thickness of the vane 95% along the length of the vane from the
leading edge may be at least 45% of the maximum perpendicular thickness of the vane.
The perpendicular thickness of the vane 95% along the length of the vane from the
5 leading edge may be at least 50% of the maximum perpendicular thickness of the vane.
10
The perpendicular thickness of the vane 95% along the length of the vane from the
leading edge may be at least 55% of the maximum perpendicular thickness of the vane.
The perpendicular thickness of the vane 95% along the length of the vane from the
leading edge may be at least 60% of the maximum perpendicular thickness of the vane.
A perpendicular thickness of the vane 5% along the length of the vane from the leading
edge may be at least 50% of the maximum perpendicular thickness of the vane.
The use of such a bulbous or blunt leading edge provides increased tolerance to different
15 angles of attack and can reduce the forcing function.
The ratio of the radius of the trailing edge of each of the vanes to the radius of the leading
edge of the turbine wheel may be in the range 1.2 to 1.25.
20 The vanes and the turbine wheel may be arranged such that a ratio of a radius of the
leading edge of each of the vanes to a radius of the trailing edge of each of the vanes is
1.2 or greater.
The vanes and the turbine wheel may be arranged such that a ratio of a solidity ratio of
25 the vanes in in the range 1.1 to 1.3.
The ratio of the length of the passageway defined between each pair of adjacent vanes
to the width of said passageway may be referred to as the solidity ratio. A higher solidity
ratio results in a larger vane overlap. In turn, this results in increases control over the
30 flow between adjacent vanes.
The leading edge of the vanes may be provided with an elliptical end treatment having a
ratio of the major axis to the minor axis of at least 1.5.
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The elliptical end treatment may have a ratio of the major axis to the minor axis of 1.5.
Alternatively, the elliptical end treatment may have a ratio of the major axis to the minor
axis of 2.0.
5 According to a third aspect of the invention there is provided a variable geometry turbine
comprising: a turbine housing defining an inlet and an outlet; a turbine wheel rotatably
mounted in the turbine housing between the inlet and the outlet such that the turbine
wheel can rotate about an axis; a movable wall member mounted in the housing so as
to be movable relative to the housing between at least a first position and a second
10 position, the movable wall member partially defining an inlet passageway between the
inlet and the turbine wheel, the inlet passageway being radially outboard of the turbine
wheel, a dimension of the inlet passageway being dependent on the position of the
movable wall member relative to the housing; and a plurality of vanes extending across
the inlet passageway, the vanes being circumferentially spaced; wherein in cross section
15 each of the vanes has an elongate shape extending from a leading edge which is closer
to the inlet to a trailing edge which is closer to the turbine wheel and wherein the vanes
are arranged so as to produce a double wake variation in the static pressure around a
circumference of the turbine wheel.
20 The static pressure trace around a circumference of the turbine at the trailing edge of
each of the vanes may be referred to as the forcing function. Naively, one may expect
the forcing function to have some areas of low pressure corresponding to the wake of
each vane interspersed by areas of high pressure corresponding to the flow of fluid
through the passageway defined between each pair of adjacent vanes. That is, one may
25 expect the forcing function to be dominated by a Fourier component that corresponds to
the number of the plurality of vanes (which may be referred to as a vane order oscillation).
Whilst increasing the foreign object damage (FOD) tolerance of the vanes, increasing
the dimensions of the trailing edge of the vanes can increase the length of the wake
30 formed downstream of each vane.
Shaping the vanes such that a each vane produces a double wake in the forcing function
reduces the overall amplitude of the forcing function. Advantageously, this can reduce
the overall magnitude of the forcing function sufficiently such that even if the wake of the
35 vanes has not fully dissipated the forcing function may be at an acceptably low level.
11
5
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The vanes may have a shape at least partially defined by a thickness distribution that
exponentially reduces from the leading edge to the trailing edge and having an end
treatment at each of the leading and trailing edges.
Such a thickness distribution may induce a double wake. The thickness distribution may
be the thickness distribution in Table 7. The actual thickness of the vanes, with the end
treatment at each of the leading and trailing edges, may be the thickness distribution in
Table 14.
The vanes may have a shape at least partially defined by an angular distribution that is
more tangential at the leading edge than the trailing edge.
Such an angular distribution may aid in the induction of a double wake. The angular
15 distribution may be the angular distribution in Table 8.
According to a fourth aspect of the invention there is provided a variable geometry turbine
comprising: a turbine housing defining an inlet and an outlet; a turbine wheel rotatably
mounted in the turbine housing between the inlet and the outlet such that the turbine
20 wheel can rotate about an axis; a movable wall member mounted in the housing so as
to be movable relative to the housing between at least a first position and a second
position, the movable wall member partially defining an inlet passageway between the
inlet and the turbine wheel, the inlet passageway being radially outboard of the turbine
wheel, a dimension of the inlet passageway being dependent on the position of the
25 movable wall member relative to the housing; and a plurality of vanes extending across
the inlet passageway, the vanes being circumferentially spaced; wherein in cross section
each of the vanes has an elongate shape extending from a leading edge which is closer
to the inlet to a trailing edge which is closer to the turbine wheel and wherein the vanes
have a shape at least partially defined by a thickness distribution that exponentially
30 reduces from the leading edge to the trailing edge and having an end treatment at each
of the leading and trailing edges.
The thickness distribution may be the thickness distribution in Table 7. The actual
thickness of the vanes, with the end treatment at each of the leading and trailing edges,
35 may be the thickness distribution in Table 14.
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The vanes may have a shape at least partially defined by an angular distribution that is
more tangential at the leading edge than the trailing edge.
5 The angular distribution may be the angular distribution in Table 8.
According to a fifth aspect of the invention there is provided a variable geometry turbine
comprising: a turbine housing defining an inlet and an outlet; a turbine wheel rotatably
mounted in the turbine housing between the inlet and the outlet such that the turbine
10 wheel can rotate about an axis; a movable wall member mounted in the housing so as
to be movable relative to the housing between at least a first position and a second
position, the movable wall member partially defining an inlet passageway between the
inlet and the turbine wheel, the inlet passageway being radially outboard of the turbine
wheel, a dimension of the inlet passageway being dependent on the position of the
15 movable wall member relative to the housing; and a plurality of vanes extending across
the inlet passageway, the vanes being circumferentially spaced; wherein in cross section
each of the vanes has an elongate shape extending from a leading edge which is closer
to the inlet to a trailing edge which is closer to the turbine wheel and wherein the vanes
have a shape defined by the curves in Tables 9, 10, 11 and 12 multiplied by a scale
20 factor.
The scale factor may be 1. Alternatively the scale factor may be less than or greater
than 1.
25 It will be appreciated that the four curves given in Tables 9 to 12 define a shape and
position of a single vane in a plane perpendicular to the axis. It will be appreciated that
for the plurality of vanes to have a shape defined by the curves in Tables 9, 10, 11 and
12, all of the vanes have the shape as defined by the four curves given in Tables 9 to 12
but, in general, are disposed at different positions with respect to the axis. The vanes
30 may be arranged evenly around the axis. The variable geometry turbine may comprise
14 vanes. Therefore, the positions of all the vanes may be given by rotating the x-y coordinates
of the four curves given in Tables 9 to 12 about the origin by n · 360/14
degrees, where n is an integer between 1 and 14 inclusive.
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According to a sixth aspect of the invention there is provided a variable geometry turbine
comprising: a turbine housing defining an inlet and an outlet; a turbine wheel rotatably
mounted in the turbine housing between the inlet and the outlet such that the turbine
wheel can rotate about an axis; a movable wall member mounted in the housing so as
5 to be movable relative to the housing between at least a first position and a second
position, the movable wall member partially defining an inlet passageway between the
inlet and the turbine wheel, the inlet passageway being radially outboard of the turbine
wheel, a dimension of the inlet passageway being dependent on the position of the
movable wall member relative to the housing; and a plurality of vanes extending across
10 the inlet passageway, the vanes being circumferentially spaced; wherein in cross section
each of the vanes has an elongate shape extending from a leading edge which is closer
to the inlet to a trailing edge which is closer to the turbine wheel and wherein the vanes
have a shape at least partially defined by the thickness distribution in Table 1 and the
angular distribution in Table 2.
15
The actual thickness of the vanes, with an end treatment at each of the leading and
trailing edges, may be the thickness distribution in Table 13.
According to a seventh aspect of the invention there is provided variable geometry
20 turbine comprising: a turbine housing defining an inlet and an outlet; a turbine wheel
rotatably mounted in the turbine housing between the inlet and the outlet such that the
turbine wheel can rotate about an axis; a movable wall member mounted in the housing
so as to be movable relative to the housing between at least a first position and a second
position, the movable wall member partially defining an inlet passageway between the
25 inlet and the turbine wheel, the inlet passageway being radially outboard of the turbine
wheel, a dimension of the inlet passageway being dependent on the position of the
movable wall member relative to the housing; and a plurality of vanes extending across
the inlet passageway, the vanes being circumferentially spaced; wherein in cross section
each of the vanes has an elongate shape extending from a leading edge which is closer
30 to the inlet to a trailing edge which is closer to the turbine wheel and wherein the vanes
have a shape defined by the curves in Tables 3, 4, 5 and 6 multiplied by a scale factor.
35
The scale factor may be 1. Alternatively the scale factor may be less than or greater
than 1.
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It will be appreciated that the four curves given in Tables 3 to 6 define a shape and
position of a single vane in a plane perpendicular to the axis. It will be appreciated that
for the plurality of vanes to have a shape defined by the curves in Tables 3, 4, 5 and 6,
all of the vanes have the shape as defined by the four curves given in Tables 3 to 6 but,
5 in general, are disposed at different positions with respect to the axis. The vanes may
be arranged evenly around the axis. The variable geometry turbine may comprise 14
vanes. Therefore, the positions of all the vanes may be given by rotating the x-y coordinates
of the four curves given in Tables 3 to 6 about the origin by n · 360/14 degrees,
where n is an integer between 1 and 14 inclusive.
10
According to an eighth aspect of the invention there is provided a movable wall member
for use in the variable geometry turbine of any of the first, second, third, fourth, fifth, sixth
or seventh aspects of the invention.
15 According to an ninth aspect of the invention there is provided a method for designing
the vanes for a variable geometry turbine, the method comprising: selecting a thickness
distribution; and applying an edge treatment to each of the leading edge and trailing
edge, the edge treatment for the leading edge being elliptical in cross-section, having a
ratio between the minor and major lengths of 1.5 or more; such that a perpendicular
20 thickness of the resultant vane 5% along the length of the vane from the leading edge is
at least 50% of the maximum perpendicular thickness of the vane.
Optionally, the method may further comprise: selecting a radius of the trailing edge of
the vanes such that a ratio of the radius of the trailing edge of the vanes to a radius of a
25 leading edge of the turbine wheel is within the range 1.2 to 1.25.
30
35
Optionally, the method may further comprise: selecting an outer diameter of the vane
leading edge such that the ratio of the radius of the leading edge of the vanes to the
radius of the trailing edge of the vanes is 1.2.
Optionally, the selection of the thickness distribution and the application of the edge
treatment to each of the leading edge and trailing edge may be such that a perpendicular
thickness of the resultant vane 95% along the length of the vane from the leading edge
is at least 40% of the maximum perpendicular thickness of the vane.
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According to an tenth aspect of the invention there is provided a method for designing
the vanes for a variable geometry turbine having a turbine wheel, the method comprising:
selecting a radius of the trailing edge of the vanes such that a ratio of the radius of the
trailing edge of the vanes to a radius of a leading edge of the turbine wheel is within the
5 range 1.2 to 1.25; and selecting an outer diameter of the vane leading edge such that
the ratio of the radius of the leading edge of the vanes to the radius of the trailing edge
of the vanes is 1.2.
According to an eleventh aspect of the invention there is provided a method for designing
10 the vanes for a variable geometry turbine having a turbine wheel, the method comprising:
selecting a thickness distribution of the vanes to provide a rapid reduction in vane
thickness between the leading and trailing edges.
The method may further comprise: selecting an angular distribution of the vanes wherein
15 the angular distribution is more tangential at the leading edge than at the trailing edge.
It will be appreciated that where appropriate any of the above aspects may incorporate
one or more features of any of the other aspects.
20 Specific embodiments of the present invention will now be described, by way of example,
with reference to the accompanying drawings, of which:
Figure 1
25 Figure 2
Figure 3
30
Figure 4
Figure SA
35
shows a turbocharger which may incorporate a variable geometry turbine
in accordance with an embodiment of the present invention;
illustrates the steps of a conventional method or process for designing the
vanes for a variable geometry turbine of the type of turbine shown in
Figure 1;
illustrates the steps of a first new method or process according to an
embodiment of the invention for designing the vanes for a variable
geometry turbine of the type of turbine shown in Figure 1;
illustrates the steps of a second new method or process according to an
embodiment of the invention for designing the vanes for a variable
geometry turbine of the type of turbine shown in Figure 1;
shows an arrangement of vanes designed according to the known method
shown in Figure 2 in a plane perpendicular to the turbocharger axis;
16
5
10
15
20
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Figure 58
Figure SC
Figure 6A
Figure 68
Figure 6C
Figure 7A
Figure 78
Figure 7C
PCT /EP2020/059014
15
shows the thickness distribution of the vanes shown in Figure SA as a
percentage along the length of the vanes;
shows the angular distribution of the vanes shown in Figure SA as a
percentage along the length of the vanes;
shows an arrangement of vanes designed according to the new method
shown in Figure 3 in a plane perpendicular to the turbocharger axis;
shows the thickness distribution of the vanes shown in Figure 6A as a
percentage along the length of the vanes;
shows the angular distribution of the vanes shown in Figure 6A as a
percentage along the length of the vanes;
shows an arrangement of vanes designed according to the new method
shown in Figure 4 in a plane perpendicular to the turbocharger axis;
shows the thickness distribution of the vanes shown in Figure 7 A as a
percentage along the length of the vanes;
shows the angular distribution of the vanes shown in Figure 7 A as a
percentage along the length of the vanes;
Figures SA to 8C illustrate the performance of the arrangement of vanes shown in
Figures 9A to 9C
Figure SA for an exhaust flow for which the arrangement has been
designed;
illustrate the performance of the arrangement of vanes shown in
Figure SA for an exhaust flow for which the arrangement has not
been designed;
Figures 1 OA to 1 OC illustrate the performance of the arrangement of vanes shown in
Figure 6A for an exhaust flow for which the arrangement has been
25 designed;
Figures 11A to 11 C illustrate the performance of the arrangement of vanes shown in
Figure 6A for an exhaust flow for which the arrangement has not
been designed;
Figures 12A to 12C illustrate the performance of the arrangement of vanes shown in
30 Figure 7 A for an exhaust flow for which the arrangement has been
designed;
Figures 13A to 13C illustrate the performance of the arrangement of vanes shown in
Figure 7 A for an exhaust flow for which the arrangement has not
been designed;
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Figure 14
Figure 1S
PCT /EP2020/059014
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shows the static pressure variation over an angular region of the turbine
wheel corresponding to a single vane for the arrangements shown in
Figures SA and 7 A; and
shows the actual thicknesses of the vanes shown in Figures SA, 6A and
7 A respectively, as a percentage of the vane length.
Figure 1 shows a turbocharger 1 which may incorporate a variable geometry turbine in
accordance with an embodiment of the present invention. The turbocharger 1 comprises
a turbine housing 2 and a compressor housing 3 interconnected by a central bearing
10 housing 4. A turbocharger shaft S extends from the turbine housing 2 to the compressor
housing 3 through the bearing housing 4. A turbine wheel 6 is mounted on one end of
the shaftS for rotation within the turbine housing 2, and a compressor wheel? is mounted
on the other end of the shaft S for rotation within the compressor housing 3. The shaft S
rotates about turbocharger axis 8 on bearing assemblies located in the bearing housing
1S 4.
20
It will be appreciated that the turbine housing 2 and an axial end of the bearing housing
4 together form a housing of the variable geometry turbine, in which the turbine wheel 6
is supported for rotation about turbocharger axis 8.
The turbine housing 2 defines an inlet volute 9 to which exhaust gas from an internal
combustion engine (not shown) is delivered. The exhaust gas flows from the inlet volute
9 to an axial outlet passage 10 via an inlet passageway 11 and the turbine wheel 6. The
inlet passageway 11 is defined between two axially spaced walls. In particular, the inlet
2S passageway 11 is defined on one side by a face of a movable wall member 12, commonly
referred to as a "nozzle ring," and on the opposite side by a shroud 13. The shroud 13
covers the opening of a generally annular recess 14 in the turbine housing 2.
As will be appreciated by the skilled person, the inlet volute 9 may comprise a generally
30 toroidal volume (defined by the turbine housing 2) and an inlet arranged to direct exhaust
gas from an internal combustion engine tangentially into the generally toroidal volume.
As exhaust gas enters the inlet volute 9 it flows circumferentially around the generally
toroidal volume and radially inwards towards the inlet passageway 11. In the vicinity of
the inlet, there is provided a wall or "tongue" 18 which serves to separate the generally
3S toroidal volume in the vicinity of the inlet of the volute 9 from the inlet passageway 11 of
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the turbine. The tongue 18 may help to guide the exhaust gas circumferentially around
the generally toroidal volume and may also aid the mixing of the generally linear gas
flowing into the volute 9 with the circumferential gas flow around the generally toroidal
volume. In the cross section shown in Figure 1, the tongue 18 is visible on one side of
5 the axis 8 only.
The movable wall member 12 supports an array of circumferentially and equally spaced
inlet vanes 15 each of which extends across the inlet passageway 11. The vanes 15 are
orientated to deflect gas flowing through the inlet passageway 11 towards the direction
10 of rotation of the turbine wheel 6. The shroud 13 is provided with suitably configured
slots for receipt of the vanes 15 such that as the movable wall member 12 moves axially
towards the shroud 13, a distal end of each of the vanes 15 moves through one of said
slots and protrudes into the recess 14.
15 Accordingly, by appropriate control of the actuator (which may for instance be pneumatic
or electric), the axial position of the movable wall member 12 can be controlled. The
speed of the turbine wheel 6 is dependent upon the velocity of the gas passing through
the inlet passageway 11. For a fixed rate of mass of gas flowing into the inlet passageway
11, the gas velocity is a function of the width of the inlet passageway 11, the width being
20 adjustable by controlling the axial position of the movable wall member 12. As the width
of the inlet passageway 11 is reduced, the velocity of the gas passing through it
increases. Figure 1 shows the nozzle ring 12 disposed between a fully open position
and a fully closed position such that the width of inlet passageway 11 is greater that a
minimum width and smaller than a maximum width.
25
The (axial) width of the inlet passageway 11 between the movable wall member 12 and
the shroud 13 may be referred to as a variable geometry gap or a VG gap.
It will be appreciated that the exhaust gases spiral generally radially inwards through the
30 inlet passageway 11 towards the turbine wheel 6. Accordingly, it will be appreciated that,
unless stated otherwise, as used herein the leading edge of a vane 15 shall be
understood to be a radially outer end of the vane 15 and the trailing edge of a vane 15
shall be understood to be a radially inner end of the vane 15.
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Gas flowing from the inlet volute 9 to the outlet passage 10 passes over the turbine wheel
6 and as a result torque is applied to the shaft 5 to drive the compressorwheel7. Rotation
of the compressor wheel 7 within the compressor housing 2 pressurises ambient air
present in an air inlet 16 and delivers the pressurised air to an air outlet volute 17 from
5 which it is fed to an internal combustion engine (not shown).
10
15
The movable wall member (or nozzle ring) 12 comprises a generally annular wall 20 and
radially inner and outer flanges 21, 22 extending axially from the generally annular wall
20.
A cavity 25 is provided in the housing of the variable geometry turbine for receipt of the
radially inner and outer flanges 21, 22 of the moveable member 12. It will be appreciated
that the cavity 25 is formed on an axial end of the bearing housing 4, which cooperates
with the turbine housing 2 to form the housing of the variable geometry turbine.
As the movable wall member 12 moves axially, the extent to which the radially inner and
outer flanges 21, 22 of the moveable member 12 are received in the cavity 25 varies.
The moveable wall member 12 is moveable between a fully opened position and a fully
closed position. When disposed in the fully opened position, the radially inner and outer
20 flanges 21, 22 of the moveable member 12 may contact a base surface 26 of the cavity
25. That is, a portion of the base surface 26 of the cavity 25 may serve as a physical
stop to limit the range of axial movement of the moveable member 12.
Inner and outer sealing rings 27, 28 are provided to seal the movable wall member 12
25 with respect to surfaces of the cavity 25, whilst allowing the movable wall member 12 to
slide within the cavity 25. The inner sealing ring 27 is supported within an annular groove
formed in a radially inner curved surface of the cavity 25 and bears against the inner
flange 21 of the movable wall member 12. The outer sealing ring 28 is supported within
an annular groove formed in a radially outer curved surface of the cavity 25 and bears
30 against the outer flange 22 of the movable wall member 12.
In some embodiments a plurality of axially extending apertures may be provided through
the generally annular wall 20 of the moveable wall member 12. The apertures may be
referred to as balancing apertures. The balancing apertures may connect the inlet 11 to
35 the cavity 25, such that the inlet 11 and the cavity 25 are in fluid communication via the
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apertures. In use, the balancing apertures serve to reduce pressure differences across
the generally annular wall 20 of the movable wall member 12 and thereby reduce loads
applied to the face of the generally annular wall 20 of the movable wall member 12.
5 In use, as air flows radially inwards through the turbine inlet 11, it flows between adjacent
vanes 15, which can be regarded as defining a vane passage. The turbine inlet 11 has
a reduced radial flow area in the region of the vane passage with the effect that the inlet
gas speed increases through the vane passage with a corresponding drop in pressure
in this region of the movable wall member 12.
10
Embodiments of the present invention relate to variable geometry turbines of the type of
turbine shown in Figure 1 which have new arrangements of inlet vanes 15 which extend
across the inlet passageway 11. In particular, embodiments of the present invention
relate to vanes 15 having new shapes and configurations with respect to known vanes
15 15. In some embodiments of the present invention, other parts of the variable geometry
turbine may be similar to corresponding parts of known variable geometry turbines, the
novelty lying in the shapes and configurations of the vanes 15. Therefore, some
embodiments of the present invention may relate merely to a novel movable member 12
(or nozzle ring) or even merely to a novel vane 15.
20
As explained further below, some embodiments of the present invention relate to vanes
15 having shapes and configurations which would be contrary to prejudices of the skilled
person. Some embodiments of the present invention relate to new methods for
designing arrangements of inlet vanes 15 which extend across the inlet passageway 11
25 of a variable geometry turbine of the type of turbine shown in Figure 1.
Some embodiments of the present invention relate to new inlet vanes 15 which have a
shape and configuration which results in a reduction in the amplitude of azimuthal (static)
pressure variations around the circumference of the turbine wheel 6. Such azimuthal
30 pressure variations around the circumference of the turbine wheel 6 may be referred to
herein as a forcing function. In particular, some embodiments of the present invention
relate to new inlet vanes 15 which have a shape and configuration which results in a
reduction in the amplitude of azimuthal pressure variations around the circumference of
the turbine wheel 6 over a range of different VG gaps. This is beneficial since large
35 pressure fluctuations around the circumference of the turbine wheel 6 (which the blades
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of the turbine wheel 6 move through) will cause oscillating deformation or vibration of the
blades of the turbine wheel 6. In turn, this can lead to high cycle fatigue.
Some embodiments of the present invention relate to new inlet vanes 15 which have a
5 larger, more bulbous (or, alternatively, less pointy) leading edge profile with respect to
known vanes 15. This is advantageous over existing designs, as now discussed.

CLAIMS:
1. A variable geometry turbine comprising:
a turbine housing defining an inlet and an outlet;
a turbine wheel rotatably mounted in the turbine housing between the inlet and
the outlet such that the turbine wheel can rotate about an axis;
a movable wall member mounted in the housing so as to be movable relative to
the housing between at least a first position and a second position, the movable wall
member partially defining an inlet passageway between the inlet and the turbine wheel,
10 the inlet passageway being radially outboard of the turbine wheel, a dimension of the
inlet passageway being dependent on the position of the movable wall member relative
to the housing; and
a plurality of vanes extending across the inlet passageway, the vanes being
circumferentially spaced;
15 wherein in cross section each of the vanes has an elongate shape extending from
20
25
a leading edge which is closer to the inlet to a trailing edge which is closer to the turbine
wheel and wherein a perpendicular thickness of the vane 5% along the length of the
vane from the leading edge is at least 50% of the maximum perpendicular thickness of
the vane.
2. The variable geometry turbine of claim 1 wherein a perpendicular thickness of
the vane 95% along the length of the vane from the leading edge is at least 40% of the
maximum perpendicular thickness of the vane.
3. The variable geometry turbine of claim 1 or claim 2 wherein the vanes and the
turbine wheel are arranged such that a ratio of a radius of the trailing edge of each of the
vanes to a radius of a leading edge of the turbine wheel is 1.2 or greater.
4. The variable geometry turbine of any preceding claim wherein the vanes and the
30 turbine wheel are arranged such that a ratio of a radius of the leading edge of each of
the vanes to a radius of the trailing edge of each of the vanes is 1.2 or greater.
5. The variable geometry turbine of any preceding claim wherein the vanes and the
turbine wheel are arranged such that a ratio of a solidity ratio of the vanes in the range
35 1.1 to 1.3.
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6. The variable geometry turbine of any preceding claim wherein the leading edge
of the vanes is provided with an elliptical end treatment having a ratio of the major axis
to the minor axis of at least 1.5.
7. A variable geometry turbine comprising:
a turbine housing defining an inlet and an outlet;
a turbine wheel rotatably mounted in the turbine housing between the inlet and
the outlet such that the turbine wheel can rotate about an axis;
a movable wall member mounted in the housing so as to be movable relative to
the housing between at least a first position and a second position, the movable wall
member partially defining an inlet passageway between the inlet and the turbine wheel,
the inlet passageway being radially outboard of the turbine wheel, a dimension of the
inlet passageway being dependent on the position of the movable wall member relative
15 to the housing; and
a plurality of vanes extending across the inlet passageway, the vanes being
circumferentially spaced;
wherein in cross section each of the vanes has an elongate shape extending from
a leading edge which is closer to the inlet to a trailing edge which is closer to the turbine
20 wheel and wherein a perpendicular thickness of the vane 95% along the length of the
vane from the leading edge is at least 40% of the maximum perpendicular thickness of
the vane; and
wherein the vanes and the turbine wheel are arranged such that a ratio of a radius
of the trailing edge of each of the vanes to a radius of a leading edge of the turbine wheel
25 is 1.2 or greater.
30
8. The variable geometry turbine of claim 7 wherein a perpendicular thickness of
the vane 5% along the length of the vane from the leading edge is at least 50% of the
maximum perpendicular thickness of the vane.
9. The variable geometry turbine of claim 7 or claim 8 wherein the vanes and the
turbine wheel are arranged such that a ratio of a radius of the leading edge of each of
the vanes to a radius of the trailing edge of each of the vanes is 1.2 or greater.
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10. The variable geometry turbine of any one of claims 7 to 9 wherein the vanes and
the turbine wheel are arranged such that a ratio of a solidity ratio of the vanes in in the
range 1.1 to 1.3.
11. The variable geometry turbine of any one of claims 7 to 10 wherein the leading
edge of the vanes is provided with an elliptical end treatment having a ratio of the major
axis to the minor axis of at least 1.5.
12. A variable geometry turbine comprising:
a turbine housing defining an inlet and an outlet;
a turbine wheel rotatably mounted in the turbine housing between the inlet and
the outlet such that the turbine wheel can rotate about an axis;
a movable wall member mounted in the housing so as to be movable relative to
the housing between at least a first position and a second position, the movable wall
15 member partially defining an inlet passageway between the inlet and the turbine wheel,
the inlet passageway being radially outboard of the turbine wheel, a dimension of the
inlet passageway being dependent on the position of the movable wall member relative
to the housing; and
a plurality of vanes extending across the inlet passageway, the vanes being
20 circumferentially spaced;
25
30
wherein in cross section each of the vanes has an elongate shape extending from
a leading edge which is closer to the inlet to a trailing edge which is closer to the turbine
wheel and wherein the vanes have a shape at least partially defined by the thickness
distribution in Table 1 and the angular distribution in Table 2.
13. The variable geometry turbine of claims 12 wherein the actual thickness of the
vanes, with an end treatment at each of the leading and trailing edges, is the thickness
distribution in Table 13.
14. A variable geometry turbine comprising:
a turbine housing defining an inlet and an outlet;
a turbine wheel rotatably mounted in the turbine housing between the inlet and
the outlet such that the turbine wheel can rotate about an axis;
a movable wall member mounted in the housing so as to be movable relative to
35 the housing between at least a first position and a second position, the movable wall
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member partially defining an inlet passageway between the inlet and the turbine wheel,
the inlet passageway being radially outboard of the turbine wheel, a dimension of the
inlet passageway being dependent on the position of the movable wall member relative
to the housing; and
a plurality of vanes extending across the inlet passageway, the vanes being
circumferentially spaced;
wherein in cross section each of the vanes has an elongate shape extending from
a leading edge which is closer to the inlet to a trailing edge which is closer to the turbine
wheel and wherein the vanes have a shape defined by the curves in Tables 3, 4, 5 and
10 6 multiplied by a scale factor.
15
15. A movable wall member for use in the variable geometry turbine of any preceding
claim.
16. A method for designing the vanes for a variable geometry turbine, the method
comprising:
selecting a thickness distribution; and
applying an edge treatment to each of the leading edge and trailing edge, the
edge treatment for the leading edge being elliptical in cross-section, having a ratio
20 between the minor and major lengths of 1.5 or more;
25
30
such that a perpendicular thickness of the resultant vane 5% along the length of
the vane from the leading edge is at least 50% of the maximum perpendicular thickness
of the vane.
17. The method of claim 16 further comprising:
selecting a radius of the trailing edge of the vanes such that a ratio of the radius
of the trailing edge of the vanes to a radius of a leading edge of the turbine wheel is
within the range 1.2 to 1.25.
18. The method of claim 16 or claim 17 further comprising:
selecting an outer diameter of the vane leading edge such that the ratio of the
radius of the leading edge of the vanes to the radius of the trailing edge of the vanes is
1.2.
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19. The method of any one of claims 16 to 18, wherein the selection of the thickness
distribution and the application of the edge treatment to each of the leading edge and
trailing edge is such that a perpendicular thickness of the resultant vane 95% along the
length of the vane from the leading edge is at least 40% of the maximum perpendicular
5 thickness of the vane.
20. A method for designing the vanes for a variable geometry turbine having a turbine
wheel, the method comprising:
selecting a radius of the trailing edge of the vanes such that a ratio of the radius
10 of the trailing edge of the vanes to a radius of a leading edge of the turbine wheel is
within the range 1.2 to 1.25; and
15
selecting an outer diameter of the vane leading edge such that the ratio of the
radius of the leading edge of the vanes to the radius of the trailing edge of the vanes is