U.S. patent application number 10/914562 was filed with the patent office on 2005-06-09 for compressor diffuser.
Invention is credited to Allen, John F., Arnold, Steve D., Chen, Hua, Ellis, Stephen W., McArdle, Nathan J., Slupski, Kevin.
Application Number | 20050123394 10/914562 |
Document ID | / |
Family ID | 34681731 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050123394 |
Kind Code |
A1 |
McArdle, Nathan J. ; et
al. |
June 9, 2005 |
Compressor diffuser
Abstract
A compressor diffuser for a vehicle engine turbocharger, the
diffuser comprising: a diffuser housing having a gas flow path
having a side wall connecting a gas inlet to a gas outlet; a
plurality of pivotally mounted diffuser vanes arranged in the flow
path to control gas flow, and a vane angle control device for
adjusting the angle of each of the plurality of vanes in the flow
path; the control device comprising a unison ring coupled to the
plurality of vanes in such a way that rotation of the unison ring
pivots each of the vanes by interaction of a cam surface with a
respective cam follower.
Inventors: |
McArdle, Nathan J.;
(Bradford, GB) ; Ellis, Stephen W.; (Deeside,
GB) ; Chen, Hua; (Blackburn, GB) ; Arnold,
Steve D.; (Rancho Palos Verdes, CA) ; Allen, John
F.; (El Segundo, CA) ; Slupski, Kevin;
(Redondo Beach, CA) |
Correspondence
Address: |
John Christopher James
Honeywell International Inc.
Suite #200
23326 Hawthorne Boulevard
Torrance
CA
90505
US
|
Family ID: |
34681731 |
Appl. No.: |
10/914562 |
Filed: |
August 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10914562 |
Aug 9, 2004 |
|
|
|
10727845 |
Dec 3, 2003 |
|
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Current U.S.
Class: |
415/164 |
Current CPC
Class: |
F04D 29/422 20130101;
F05D 2250/52 20130101; F01D 17/165 20130101; F05D 2220/40 20130101;
F04D 29/462 20130101; F04D 25/04 20130101 |
Class at
Publication: |
415/164 |
International
Class: |
F01D 017/12 |
Claims
1. A compressor for a turbocharger comprising: a diffuser assembly
comprising a diffuser housing defining a gas inlet and a gas outlet
pneumatically connected by a gas flow path, a plurality of
pivotally mounted diffuser vanes arranged in the flow path, and a
vane angle control device for adjusting the angle of the diffuser
vanes wherein the vane control device further comprises a unison
ring coupled to the diffuser vanes in such a way that rotation of
the unison ring pivots each of the diffuser vanes by interaction of
a cam surface with a respective cam follower; and, an impeller
assembly positioned adjacent the diffuser assembly, the impeller
assembly comprising an impeller wheel having a plurality of
impeller blades adjoined thereto, a shroud wall extending
circumferentially around the impeller blades, a venting chamber
defined by the shroud wall and removed from the impeller wheel,
wherein the shroud wall comprises at least one vent pneumatically
connecting the impeller wheel to said venting chamber.
2. A compressor according to claim 1 further comprising means for
controlling the airflow through each vent.
3. A compressor according to claim 2 wherein the means for
controlling the airflow through the or each vent comprises a
sliding cover.
4. A compressor according to claim 2 wherein the means for
controlling the airflow through the or each vent comprises a
rotatable cover.
5. A compressor according to claim 2 wherein the airflow through
the or each vent is independently controllable.
6. A compressor according to claim 1 wherein a portion of the
plurality of impeller blades comprise splitter blades and the
remainder of plurality of impeller blade comprise full blades,
wherein said full blades extend greater axial distance from the
impeller wheel than the splitter blades.
7. A compressor according to claim 1 wherein all of said plurality
of impeller blades are full blades.
8. A compressor according to claim 1 wherein the unison ring is
mounted for rotation in a recess in the diffuser housing such that
the side of the unison ring exposed to the gas flow in the gas path
is generally flush with the remainder of the diffuser housing
making up a side wall of the flow path, so that the exterior
circumferential edge of the ring is not in the flow path.
9. A compressor according to claim 8 wherein the impeller wheel has
a diameter and the unison ring has a thickness about 5% of the
impeller wheel diameter.
10. A compressor according to claim 1 wherein each diffuser vane
comprises a leading end and a trailing end and each is pivotally
mounted about a pivot point adjacent the leading end.
11. A compressor according to claim 1 wherein the cam follower has
a generally elongate oval shape in cross section to engage the cam
surface over a contact surface.
12. A compressor according to claim 1 wherein the cam follower is
formed as a tab on each vane and the respective cam surfaces are
formed on the unison ring.
13. A compressor diffuser according to claim 1 wherein each cam
surface is formed as an internal surface of an elongate slot in the
unison ring, and wherein the slot has an arcuate form.
14. A compressor according to claim 11 wherein the elongate oval
shape of the cam follower comprises a central generally rectangular
region and two curved end regions.
15. A compressor according to claim 14 wherein the elongate oval
shape of the cam follower further comprises a region having a
trapezium cross-section formed between the rectangular region and
each curved end section, so as to present at least three generally
planar sides on each side of the cam follower.
16. A compressor according to claim 11 wherein the cam surface is
contoured to be complementary to the engaging surface of the cam
follower so as to maximize the area of the contact surface between
the cam and the cam follower.
17. A compressor according to claim 1 wherein each vane has an
elongate isosceles triangle shape with the apex of the triangle
forming said one end, and the angle subtended at the apex of the
triangle is between about 5 degrees and 15 degrees.
18. A compressor according to claim 1 wherein at least one side of
each vane is curved.
19. A compressor according to claim 1 wherein the vane angle
control device further comprises a rack and pinion driven crank
shaft.
20. A compressor according to claim 19 wherein the vane angle
control device further comprises a spring biased variable current
solenoid.
21. A compressor according to claim 20 wherein the crank shaft is
coupled to the solenoid via a cam on the crank shaft to provide
direct position feedback to the solenoid.
22. A compressor according to claim 1 wherein each vane is
pivotally mounted by means of a pivot pin on the vane which engages
with a hole in the diffuser housing, and wherein the pivot pin and
the cam follower are mounted on the same side of the vane and the
pivot pin extends beyond the tab.
23. A turbocharger comprising a compressor according to claim
1.
24. A turbocharger according to claim 23 further comprising means
for controlling the airflow through the or each vent.
25. A compressor for a turbocharger, comprising a diffuser assembly
adjoined to an impeller assembly, the diffuser comprising: a
diffuser housing defining a gas flow path having a side wall
connecting a gas inlet to a gas outlet and a plurality of diffuser
vanes arranged in the flow path to control gas flow; and, the
impeller assembly comprising: an impeller wheel having a plurality
of impeller blades attached thereto, a venting chamber and a
compressor housing shroud wall extending around the impeller blades
and separating the impeller wheel from said venting chamber,
wherein the shroud wall comprises at least one vent pneumatically
connecting the impeller wheel to said venting chamber.
26. A compressor according to claim 25 wherein all of said
plurality of impeller blades are full blades extending from the
impeller wheel to a similar axial position.
27. A compressor according to claim 26 wherein the diffuser vanes
are pivotally mounted such that their angle relative to the flow
path can be adjusted.
Description
BACKGROUND AND DESCRIPTION
[0001] The present invention relates to a diffuser for a compressor
for a vehicle engine turbocharger.
[0002] A turbocharger for an internal combustion engine comprises a
turbine side receiving exhaust gas from the engine to drive a
turbine wheel connected to a shaft on which is mounted a compressor
impeller wheel. Exhaust gas from the engine turns the turbine wheel
and thus the shaft and causes rotation of the compressor impeller
wheel. Intake air is drawn into the impeller wheel and its pressure
boosted before it is fed to the engine and mixed with fuel for the
combustion process. The increased pressure of the engine intake air
increases the performance of the engine.
[0003] A turbocharger compressor operates at relatively low
temperatures but relatively high pressure compared to the
turbine.
[0004] It is important to control the flow of gas in turbochargers
to ensure a steady flow and avoid surges and stalls. A diffuser
typically is positioned in the flow path from the compressor wheel
to the air outlet to control the flow of air by means of vanes in
the gas flow path which even out or diffuse the air flow.
[0005] These vanes may be fixed in position or may be arranged to
be moveable to vary their angle so as to better suit the gas flow
in the diffuser to the operating conditions of the engine.
[0006] According to one aspect of the present invention there is
provided a compressor for a vehicle engine turbocharger. The
compressor comprises a diffuser assembly and an impeller assembly.
The diffuser assembly comprises: a diffuser housing having a gas
flow path having a side wall connecting a gas inlet to a gas
outlet; a plurality of pivotally mounted diffuser vanes arranged in
the flow path to control gas flow, and a vane angle control device
for adjusting the angle of each of the plurality of vanes in the
flow path; the control device comprising a unison ring coupled to
the plurality of vanes in such a way that rotation of the unison
ring relative to the vanes pivots each of the vanes by interaction
of a cam surface with a respective cam follower. The impeller
assembly, located upstream of the diffuser, comprises an impeller
wheel and a plurality of impeller blades, a venting chamber and a
shroud wall extending around the impeller blades, separating the
blades from said venting chamber, wherein the shroud wall comprises
at least one vent pneumatically connecting the impeller to said
venting chamber.
[0007] Venting in the shroud wall acts to pull extra air into the
compressor when the compressor is in a choke condition and to
recirculate the air flow back toward the intake when the compressor
is in surge condition. This suction and recirculation action is
driven by pressure differentials between the intake and diffuser
section. The larger the pressure differential, the larger the flow
of air through the venting hole(s).
[0008] Some of the impeller blades may extend only partially across
the space between the impeller wheel and the shroud wall. This form
of the blades is known as "splitter blades". The "splitter blades"
form of impeller is generally considered to have a better flow
range, i.e. operates over a wider range of operating conditions,
because the removal of part, typically about half, of the blade,
opens up the throat area of the inducer and allows the flow to
adjust itself in choking conditions.
[0009] While such splitter blades can be used with the present
invention, the impeller blades in the present invention are
preferably all full blades, extending from the wheel across the
flow path to substantially adjacent the shroud wall.
[0010] This has been found to increase the frequency of noise to
levels above human sensitivity, and to reduce the noise level of
the compressor because blade loading is decreased. Also,
surprisingly, to have a flow range comparable with that of an
impeller having splitter blades. This may be at least partly
because the full blades cause a larger pressure change in the
inducer throat region when the inducer is choked and thus causes
increased suction to compensate the choke flow. It has also been
found that when vents are provided in the shroud wall the full
bladed impeller is more effective in the surge region than splitter
blades.
[0011] In one of the more advanced embodiments of the present
invention, there are two or more vents in the shroud wall and the
air flow through them is controlled, advantageously independently
of each other, for example by a sliding or rotating cover.
[0012] The design can be further simplified by having the unison
ring comprise a substantial part of the flow path side wall, for
example between 40-80% of the distance between the trailing edge of
the impeller blade and the diffuser exit.
[0013] According to a preferred embodiment of the present invention
the unison ring is mounted for rotation in a recess in the diffuser
housing such that the side of the ring exposed to the gas path is
generally flush with the remainder of the diffuser housing making
up the flow path side wall.
[0014] Preferably each diffuser vane comprises a leading end and a
trailing end and is pivotally mounted about a pivot point close to
the leading edge.
[0015] The unison ring is coupled to the plurality of vanes in such
a way that rotation of the unison ring pivots each of the vanes by
interaction of a cam surface with a respective cam follower, and
the cam follower has a generally elongate oval shape in cross
section to engage the cam surface over a contact surface. The cam
follower may be formed as a tab on each vane and the respective cam
surfaces are formed as an internal surface of an elongate slot in
the unison ring. The slot preferably has an arcuate form. The
elongated oval shape of the cam follower may comprise a central
generally rectangular region and two curved end regions, and a
region having a trapezium cross-section formed between the
rectangular region and each curved end section, so as to present at
least three generally planar sides on each side of the cam
follower. The cam surface is preferably contoured to be
complementary to the engaging surface of the cam follower so as to
maximize the area of the contact surface between the cam and the
cam follower. Each vane may have an elongate isosceles triangle
shape with the apex of the triangle forming said one end, wherein
the angle subtended at the apex of the triangle is between about 5
degrees and 15 degrees, preferably about 10 degrees. At least one
side of each vane may be curved or straight. The vane angle control
device preferably further comprises a rack and pinion driven crank
shaft, and a spring biased variable current solenoid, wherein the
crank shaft is coupled to the solenoid via a cam on the crank shaft
to provide direct position feedback to the solenoid. Each vane may
be pivotally mounted by means of a pivot pin on the vane which
engages with a hole in the diffuser housing. The pivot pin may be
formed by grinding and may be mounted on the same side of the vane
as the cam follower with the pivot pin extending beyond the tab
formed by injection molding.
[0016] According to another aspect of the invention there is
provided a compressor for a turbocharger, comprising a diffuser
assembly and an impeller assembly, the diffuser assembly comprising
a diffuser housing having a gas flow path having a side wall
connecting a gas inlet to a gas outlet and a plurality of diffuser
vanes arranged in the flow path to control gas flow. The impeller
assembly, located upstream of the diffuser assembly, has a
plurality of impeller blades mounted on an impeller wheel, a
venting chamber and a shroud wall extending around the impeller
blades and separating them from said venting chamber, wherein the
shroud wall comprises at least one vent pneumatically connecting
the impeller to said venting chamber. Preferably the impeller
blades are all full blades extending from substantially adjacent
the base of the impeller wheel to substantially adjacent the shroud
wall extending to an inlet portion of the shroud wall.
[0017] The invention can provide for a more robust and controllable
compressor with better operating conditions and performance. It can
be used for compressor wheels with or without splitter blades but
it works most efficiently for compressor wheels without splitter
blades.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a better understanding of the present invention and to
show how the same may be carried into effect, reference is made to
the accompanying drawings in which:
[0019] FIG. 1 is a cross-section of a vehicle engine turbocharger
compressor incorporating a diffuser according to the present
invention;
[0020] FIG. 2 is a plan view of a part of the compressor diffuser
shown in FIG. 1;
[0021] FIG. 3 is a plan view of a vane forming part of the
compressor diffuser in FIGS. 1 and 2 illustrating its path of
movement;
[0022] FIG. 4 is a plan view of an alternative design shape for the
vane;
[0023] FIG. 5 is a cross-sectional view of the vane of FIG. 3;
[0024] FIGS. 6a and 6b are cross-sectional views of alternative
arrangements of the vane of FIG. 3.
[0025] FIG. 7 is a graph showing pressure ratio plotted against
corrected air flow for the embodiment of FIG. 1.
[0026] FIG. 8 is a perspective view, from the side, of a compressor
wheel used in a preferred embodiment of the invention.
[0027] FIG. 9 is a front view of a compressor wheel which may be
used in an alternative embodiment of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0028] In FIG. 1 a turbine housing 12 is adapted to receive exhaust
gas from a vehicle engine and channel the gas to a turbine wheel 14
coupled to one end of a shaft 16. The exhaust gas drives the
turbine wheel 14 and thus rotates the shaft 16. The other end of
the shaft 16 is connected to a compressor wheel 18, which is
mounted in a compressor housing 19. The compressor wheel 18 rotates
with the shaft 16 and draws in air through the intake 20. The
pressure of this air is boosted by the compressor wheel 18 and
channeled through a diffuser section 22 of the compressor to an air
outlet 24 and ultimately to the vehicle engine for use in the
combustion process.
[0029] Compressor wheel 18 comprises a hub to which impeller blades
40 are attached. The blades 40 may be what are known in the
industry as full blades or splitter blades. Full blades are shown
in FIG. 8 and a mixture of full and splitter blades is shown in
FIG. 9. The full impeller blades 40 occupy the gap between the hub
and an inner shroud wall 41 and have an outer edge substantially
matching the profile of the inner surface of the shroud wall 41 to
ensure a close tolerance. Splitter blades 50 do not extend as far
axially forward as full blades. They are typically located between
the full blades 40 as shown in FIG. 9. Compressors with splitter
blades tend to be noisier than the compressors with full blades
because the frequency of the noise is in the audible range and the
noise level higher due to the extra loading on the blades.
Returning to FIG. 1, there is an outer shroud wall 42 surrounding
the inner shroud wall 41 and forming an annular venting chamber 43.
FIG. 1 illustrates a single vent 44 that connects the venting
chamber 43 to the impeller chamber within the inner shroud wall 41.
Such a venting arrangement provides a bleed path and improve the
surge characteristics of the compressor by providing a vent path
for back to return a small amount of pressurized gas to the intake.
This arrangement is known as a ported shroud. More than one vent
may be provided and each vent may take many forms such as
individual bores or circumferential slots (with bridging support
struts). Such vents may be arranged so that the airflow through
them can be varied, for example with moveable covers so as to
optimize the compressor performance depending upon operating
conditions. These covers may be slidable or rotatable depending
upon the form of the vents.
[0030] The compressor wheel may comprise splitter blades or full
blades but full blades may be preferred in applications where the
noises generated by the vents in the shroud wall are of concern. It
has also been found that full bladed compressor wheel also makes
the vented shroud more effective in improving the flow range of the
compressor.
[0031] An arrangement of variable position vanes 26 is disposed in
the diffuser section 22 and these cooperate with a unison ring 28
which controls their orientation relative to the air flow path. The
unison ring 28 is rotatably disposed within the compressor housing
19 and is arranged to engage and rotate all of the compressor vanes
in unison by cooperation of slots 32 in the unison ring 28 with
tabs 34 on the vanes 26 acting as cam members.
[0032] The unison ring 28 is set into a recess in the wall of the
diffuser section 22 and forms a part of the wall thereof. Since the
diffuser effectively has two faces we are referring here to one
half of the diffuser wall. This provides for a more robust
arrangement and is more cost effective since less parts are
required. Also the unison ring 28 has a pressure gradient across it
which tends to move it axially toward the vanes 26 thus effectively
eliminating any clearance gap between the vane side and the
diffuser housing. Such a gap is a source of efficiency loss in
known arrangements. The unison ring 28 may effectively be located
radially inside of the vanes. It does not open to the gas path,
that is to say that its outer peripheral edge is totally located
within the recess and the side adjacent the gas path is arranged
flush with the rest of the diffuser wall.
[0033] The unison ring 28 is a robust and hard wearing item which
has a thickness of about 5% of the compressor wheel tip diameter. A
thicker ring tends to reduce the effects of wear through contact
but a thinner one reduces wear through vibration.
[0034] On the opposite wall of the diffuser section 22 an insert
ring 30 is located, again set in an indentation in the compressor
housing 19.
[0035] The arrangement of the vanes 26 and the unison ring 28 is
shown more clearly in FIG. 2. The vanes 26 are wedge shaped i.e.
are relatively narrow tapering triangular members, each pivoted at
pivot point 36 close to the apex of the triangle. Each has a tab 34
acting as a cam member to cooperate with the slot 32 on the unison
ring 28. Each cam member tab 34 has a relatively large surface area
configured to provide a maximum area contact with the slots 32 on
the unison ring 28. In particular the tabs 34 are generally larger
than pins and has a generally elongate oval shape. The slots 32 are
shaped to match the shape of the tabs 34. Such a tab and slot
arrangement does not wear out as quickly as a pin and slot
arrangement and provides better and more accurate connection and
thus more accurate movement of the vanes. The major axis of each
tab 34 is set at an inclined angle with respect to the longitudinal
axis of each of the vanes 26 and the angle of each slot 32 in the
unison ring 28 is adapted accordingly.
[0036] This is shown more clearly in FIG. 3 which illustrates a
series of positions which the tab 34 occupies in the slot 32 as it
slides along the slot in response to the unison ring being rotated.
This pivots the vane 26 about pivot point 36, close to its leading
edge.
[0037] An alternative shape and configuration of the tabs 34 is
shown in FIG. 4. In this embodiment the vanes 26 are curved or
cambered and take the shape of a fin with a wide end at the
trailing edge where the tab 34 is located, tapering to a narrow end
at the leading edge where the pivot 36 is located. The tab 34, or
cam follower, may be molded with the vane 26.
[0038] The pivot point 36 of each vane 26 is set close to the apex
of the triangle to ensure higher efficiency. It is generally
desired to locate the pivot point of each vane within 10% of the
apex and preferably within 10% of the trailing edges of the
compressor wheel. This ensures that the leading edge of the vanes
26 is always at approximately the same distance from the compressor
wheel 18 regardless of the angle of orientation of the vane and
improves performance.
[0039] The pivot point 36 of each vane 34 is made as close to the
apex of the triangular wedge as is practically possible to assist
the aerodynamic loading of the vanes 34, reducing stress on the
vanes 34 under high compressor pressures.
[0040] The arrangement of the present invention provides a
relatively simple and robust operating mechanism with relatively
few parts, making it more hard wearing and cost effective to
produce and assemble. Control of the vanes is particularly accurate
and sensitive since a wider angle of rotation of the unison ring is
required for a given rotation of the vanes.
[0041] The unison ring 28 is rotated by a crank mechanism 38 to
alter the angle of the vanes 34. One possible version of this crank
mechanism 38 is described in U.S. 2003/0167767, which is
incorporated herein by reference. The crank mechanism 38 is located
at the top of the diffuser section 22.
[0042] FIG. 5 is a cross-sectional representation of a vane 26
showing the tab 34 close to the trailing edge, engaged in a slot 32
in the unison ring 28. The pivot 36 is close to the leading edge of
the vane and is on the opposite side of the vane to the tab 34.
However, the pivot pin could be mounted on the same side of the
vane as the tab 34 as shown in FIG. 6a, in which the pivot pin 36
is formed integrally with the vane 26, and FIG. 6b, in which the
pivot pin 36 is fixed to the vane 26 and less space is available
for the unison ring 28.
[0043] Adjusting the angle of the vanes 26 in the diffuser by
rotating the unison ring 28, causes the diffuser inlet and outlet
areas to be adjusted and thus the diffuser flow area can be set at
different values to suit different air mass flow rates. This helps
to stabilize the diffuser flow and delay a compressor surge and
thus extends the operating range of the compressor.
[0044] A combination of at least one vent 44 in the shroud wall 41
and the variable vanes 26 in the diffuser improves the operating
range of the compressor and improves stability at higher compressor
pressure ratios. Improved choke flows are also achievable with such
an arrangement.
[0045] Referring to FIG. 7, it will be seen that the combination of
ported shroud and variable vanes produces a more advantageous
performance map than would otherwise be expected. The lines 50-56
joining the solid point markers represent the performance of a
compressor using a variable diffuser and a vented shroud for
compressor corrected speeds between 95,000 and 210,000 rpm. The
lines 60-66 joining the shaded point markers, represent the
performance of a compressor without a vented shroud for the same
values of corrected compressor speeds. The corrected speed is the
compressor physical speed corrected to a standard reference inlet
condition. The numbers 62% to 75% on the Figure show compressor
total to total efficiency.
[0046] It will clearly be seen that the results for the combination
of the vented shroud and the variable values shown by the
compressor map comprising lines 50-56 provides higher pressure
ratios for given airflows and given corrected compressor speeds and
thus results in superior performance, particularly at high
compressor speeds.
[0047] Normally at higher pressure ratios, it is very difficult to
achieve a wide flow range, but the vent 44 reduces the surge flow
and increases the choke flow and thus improves the flow range
whilst increasing the attainable compressor pressure ratios, and
its efficiency. The combination also addresses the known problem of
vaned diffusers having a tendency toward instability in that the
vent 44 tends to make the compressor more stable.
* * * * *