U.S. patent application number 09/802917 was filed with the patent office on 2001-10-11 for method and apparatus for expanding operating range of centrifugal compressor.
This patent application is currently assigned to Ishikawajima-Harima Jukogyo K. K.. Invention is credited to Nakao, Hidefumi.
Application Number | 20010028839 09/802917 |
Document ID | / |
Family ID | 18619960 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010028839 |
Kind Code |
A1 |
Nakao, Hidefumi |
October 11, 2001 |
Method and apparatus for expanding operating range of centrifugal
compressor
Abstract
In a centrifugal compressor, a housing 6 has an annular
treatment cavity 8 in a shroud wall 5. The shroud wall 5 has a
first opening 9 providing communication between an installed zone
of an impeller 1 and the treatment cavity 8, and a second opening
providing communication between the treatment cavity 8 and a zone
upstream of the first opening so as to circulate air a during a
low-flow-rate operation. Louvers 11 are arranged in the second
opening 10 in circumferentially equidistantly spaced apart
relationship with each other and inclined reversely to a rotative
direction of the impeller 1 so that the air a sucked to the
treatment cavity 8 is, when discharged through the second opening
10, subjected to directional flow guide action with a whirling
direction reverse to the rotative direction of the impeller.
Inventors: |
Nakao, Hidefumi;
(Kiyose-shi, JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
Ishikawajima-Harima Jukogyo K.
K.
Chiyoda-ku
JP
|
Family ID: |
18619960 |
Appl. No.: |
09/802917 |
Filed: |
March 12, 2001 |
Current U.S.
Class: |
415/1 ; 415/58.2;
415/58.4 |
Current CPC
Class: |
Y10S 415/914 20130101;
F04D 29/685 20130101; F04D 29/4213 20130101 |
Class at
Publication: |
415/1 ; 415/58.4;
415/58.2 |
International
Class: |
F04D 029/44 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2000 |
JP |
2000-106855 |
Claims
What is claimed is:
1. A method for expanding an operating range of a centrifugal
compressor, the centrifugal compressor including a shroud wall
extending ahead of an outer periphery of an impeller to provide an
air inlet, an annular treatment cavity in the shroud wall and first
and second openings on the shroud wall, the first opening providing
communication between the treatment cavity and an impeller-side
portion of the air inlet, the second opening providing
communication between the treatment cavity and a portion of the air
inlet located somewhat ahead of the impeller-side portion of the
air inlet, wherein, during a low-flow-rate operation, part of the
air sucked through the impeller is fed through the first opening
into the treatment cavity and is discharged through the second
opening so as to be circulated, the method comprising discharging
the air, which has flowed through the first opening into the
treatment cavity, through the second opening as flow having a
direction within a range from a direction with no whirling
component to a whirling direction reverse to the rotative direction
of the impeller.
2. An apparatus for expanding an operating range of a centrifugal
compressor, the centrifugal compressor including a shroud wall
extending ahead of an outer periphery of an impeller to provide an
air inlet, an annular treatment cavity in the shroud wall and first
and second openings on the shroud wall, the first opening providing
communication between the treatment cavity and an impeller-side
portion of the air inlet, the second opening providing
communication between the treatment cavity and a portion of the air
inlet located somewhat ahead of the impeller-side portion of the
air inlet, wherein, during a low-flow-rate operation, part of the
air sucked through the impeller is fed through the first opening to
the treatment cavity and is discharged through the second opening
so as to be circulated, the apparatus comprising a number of
louvers arranged in the second opening of the shroud wall, angular
arrangement of the louvers being within a range from radial
arrangement to arrangement inclined reversely to the rotative
direction of the impeller.
3. An apparatus according to claim 2, wherein, instead of the
louvers in the second opening, a number of guide plates are
arranged in the treatment cavity, angular arrangement of the guide
plates being within a range from radial arrangement to arrangement
inclined reversely to the rotative direction of the impeller.
4. An apparatus according to claim 2, wherein guide plates are
arranged in the treatment cavity as if to be extended from their
corresponding louvers.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method and apparatus for
expanding an operating range of a centrifugal compressor which is,
for example, used as an air feeder to a turbocharger for
supercharging an engine or used as an air supply in an ordinary
manufacturing plant or used together with a gas turbine.
[0002] Conventionally, a turbocharger for supercharging an engine
may comprise a turbine with a vane wheel, a centrifugal compressor
with an impeller and a bearing casing which integrally connects the
turbine to the centrifugal compressor. The vane wheel is connected
to the impeller through a shaft rotatably supported in the bearing
casing and is rotated by exhaust gases from the engine to rotate
the impeller via the shaft. Thus, intake air is compressed by the
centrifugal compressor and supplied to the engine.
[0003] A centrifugal compressor for use with a turbocharger of the
type described above has a characteristic such that, as shown in
FIG. 1, compressor's characteristic curves I may exceed a surge
line S into a surging region X of lower flow rate. Therefore, if
the surge line S can be successfully shifted to position S' where
the flow rate is lower, the centrifugal compressor can be applied
in a wider or expanded operating range to the engine.
[0004] A conventional proposal in this connection is disclosed for
example in JP-A-05-060097 (Japanese Patent No. 3038398). It is
directed to, as shown in FIGS. 2A and 2B, a centrifugal compressor
of the type wherein a housing 6 has a shroud wall 5 to provide a
scrolled compression duct 3 on an outer periphery of an impeller 1
via a diffuser 2, the shroud wall 5 extending ahead of the diffuser
2 to provide an air inlet 4, and wherein a vane wheel (not shown)
of a turbine is connected via a shaft to the impeller 1 and is
rotated by exhaust gases from an engine to rotate the impeller 1
via the shaft, whereby intake air is compressed and supplied to the
engine. The apparatus comprises: a throttle portion 7 on the shroud
wall 5 adjacent to the air inlet 4 and convergent toward the
impeller 1 such that air a is throttled by the throttle portion 7
and sucked through the impeller 1; an annular treatment cavity 8 in
the shroud wall 5; and circumferentially extending, first and
second slots or openings 9 and 10 on the shroud wall 5, the first
opening 9 providing communication between the treatment cavity 8
and an impeller-side portion of the air inlet 4 or portion of the
air inlet 4 adjacent to the impeller 1, the second opening 10
providing communication between the treatment cavity 8 and a
portion of the air inlet 4 located somewhat ahead of the
impeller-side portion of the air inlet 4, i.e., somewhat behind an
end of the throttle portion 7. Thus, the first opening 9, treatment
cavity 8 and second opening 10 provide a mechanism for expanding
the operating range by which, during a low-flow-rate operation,
part of the air a sucked by the impeller 1 is circulated to attain
reduction of the flow rate in terms of the surge line.
[0005] In an operation of the conventional centrifugal compressor,
the air a is sucked through the air inlet 4 by the rotation of the
impeller 1 into a suction zone of the impeller 1 and is supplied
through the compression duct 3 to a target zone. During a
low-flow-rate operation, the air a which has flowed into the
impeller 1 is increased in pressure due to the action of the
impeller 1 to have high pressure in comparison with the air inlet 4
and treatment cavity 8, so that part of the air a having passed
through blades of the impeller 1 can be fed through the first
opening 9 and treatment cavity 8 and discharged through the second
opening 10 back to the impeller 1. In this way, air flow
circulation can be attained through the use of static pressure.
[0006] As described above, in the prior structure, part of the air
a sucked by the impeller 1 can be circulated so that entering into
the surging region can be successfully avoided even under the
operating condition where the flow rate is so low as to reach the
surging region. In other words, the surge line S shown in FIG. 1
can be shifted into the position S' where the flow rate is low.
[0007] In the above-described centrifugal compressor, however, the
air a circulated via the first opening 9, treatment cavity 8 and
second opening 10 into the impeller 11 has flow direction as shown
in FIG. 2B aligned with the rotative direction (as indicated by
arrow r) of the impeller 1 or flows in so-called forward direction
to the rotation of the impeller 1. Thus, as compared with a case
where the air a is not circulated, expansion of the operating range
may be indeed achieved; but, turning of the flow angle between
before and after the impeller 1 is so small that inconveniently
decreased is the Euler head which is pressure ratio between entry
and exit sides of the impeller 1.
BRIEF SUMMARY OF THE INVENTION
[0008] An object of the present invention is, therefore, to achieve
expansion of an operating range of a centrifugal compressor of the
type as described above with no decrease in the Euler head.
[0009] The invention was made to solve the above problem. According
to one aspect of the invention, there is provided a method for
expanding an operating range of a centrifugal compressor, the
centrifugal compressor including a shroud wall extending ahead of
an outer periphery of an impeller to provide an air inlet, an
annular treatment cavity in the shroud wall and first and second
openings on the shroud wall, the first opening providing
communication between the treatment cavity and an impeller-side
portion of the air inlet, the second opening providing
communication between the treatment cavity and a portion of the air
inlet located somewhat ahead of the impeller-side portion of the
air inlet, wherein, during a low-flow-rate operation, part of the
air sucked through the impeller is fed through the first opening
into the treatment cavity and is discharged through the second
opening so as to be circulated. The method comprises discharging
the air, which has flowed through the first opening into the
treatment cavity, through the second opening as flow having a
direction within a range from a direction with no whirling
component to a whirling direction reverse to or conflict with the
rotative direction of the impeller. According to another aspect of
the invention, there is provided an apparatus for expanding an
operating range of a centrifugal compressor, the centrifugal
compressor including a shroud wall extending ahead of an outer
periphery of an impeller to provide an air inlet, an annular
treatment cavity in the shroud wall and first and second openings
on the shroud wall, the first opening providing communication
between the treatment cavity and an impeller-side portion of the
air inlet, the second opening providing communication between the
treatment cavity and a portion of the air inlet located somewhat
ahead of the impeller-side portion of the air inlet, wherein,
during a low-flow-rate operation, part of the air sucked through
the impeller is fed through the first opening to the treatment
cavity and is discharged through the second opening so as to be
circulated. The apparatus comprises a number of louvers arranged in
the second opening of the shroud wall, angular arrangement of the
louvers being within a range from radial arrangement to arrangement
inclined reversely to the rotative direction of the impeller.
[0010] During the low-flow-rate operation, the air fed through the
first opening into the treatment cavity is, when passed through the
second opening, guided by the louvers so that it is discharged as
flow having a direction within a range from a direction with no
whirling component to a whirling direction reverse to the rotative
direction of the impeller. This prevents decrease in the Euler
head.
[0011] Instead of the louvers in the second opening, a number of
guide plates may be arranged in the treatment cavity, angular
arrangement of the guide plates being within a range from radial
arrangement to arrangement inclined reversely to the rotative
direction of the impeller. In this structure, the flow in the
treatment cavity is restricted by the guide plates each having a
larger area than the louver, thereby providing directional flow
guide action within a range from a direction with no whirling
component to a whirling direction reverse to the rotative direction
of the impeller. As a result, discharged through the second opening
is the air with strong directivity not aligned with the rotative
direction of the impeller.
[0012] Alternatively, guide plates may be arranged in the treatment
cavity as if to be extended from their corresponding louvers. This
allows the air sucked into the treatment cavity to be subjected to
the directional flow guide action exerted by the guide plates and
by the louvers. As a result, the air is discharged through the
second opening with strong directivity not aligned with the
rotative direction of the impeller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a diagram illustrating the relationship between
flow rate and pressure in a conventional centrifugal
compressor;
[0014] FIG. 2A is a schematic fragmentary sectional side elevation
of a conventional centrifugal compressor;
[0015] FIG. 2B is a view looking in the direction of arrow 2B in
FIG. 2A;
[0016] FIG. 3A is a schematic fragmentary sectional side elevation
illustrating an embodiment of the invention;
[0017] FIG. 3B is a view looking in the direction of arrow 3B in
FIG. 3A;
[0018] FIG. 4A is a schematic fragmentary sectional side elevation
illustrating a further embodiment of the invention;
[0019] FIG. 4B is a view looking in the direction of arrow 4B in
FIG. 4A;
[0020] FIG. 5 is a diagram illustrating the relationship between
flow rate and pressure in a centrifugal compressor according to the
further embodiment shown in FIGS. 4A and 4B;
[0021] FIG. 6A is a schematic fragmentary sectional side elevation
illustrating a still further embodiment of the invention;
[0022] FIG. 6B is a view looking in the direction of arrow 6B in
FIG. 6A;
[0023] FIG. 7A is a side view illustrating a modification of the
guide plate; and
[0024] FIG. 7B is a side view illustrating a further modification
of the guide plate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] FIGS. 3A and 3B illustrate an embodiment of the invention.
In the apparatus for expanding an operating range of a centrifugal
compressor which is similar in basic construction to the prior
apparatus shown in FIGS. 2A and 2B, a second opening 10 on a shroud
wall 5 is directed to the impeller 1 and has a number (for example,
6 to 22 pieces) of louvers 11 arranged in the opening 10 in
circumferentially spaced apart relationship from each other. More
specifically, the louvers 11 are arranged in the opening 10 at
circumferentially equidistantly or arbitrarily spaced intervals
such that they are inclined (for example at about 65.degree.)
reversely to the rotative direction of the impeller. It is to be
noted that, in FIGS. 3A and 3B, the same elements found also in
FIGS. 2A and 2B are identified with the same reference
numerals.
[0026] During a low-flow-rate operation, part of the air a that has
passed through the impeller 1 under the pressure raised by the
impeller 1, passes through the first opening 9 into the treatment
cavity 8. During travel in the treatment cavity 8 toward the second
opening 10, the air a is whirled in the same direction as the
rotative direction of the impeller 1. Then, now that the second
opening 10 has the louvers 11 disposed therein in angular
arrangement inclined reversely to the rotative direction of the
impeller 1, the air a is subjected to the directional guide action
exerted by the louvers 11 during passage through the second opening
10 to the entry side of the impeller 1. As a result, the air is
discharged as flow having a direction reverse to the rotative
direction of the impeller 1. Accordingly, expansion of the
operating range of the centrifugal compressor can be successfully
attained with no decrease in the Euler head.
[0027] FIGS. 4A and 4B illustrate a further embodiment of the
invention. In an apparatus for expanding an operating range of a
centrifugal compressor that is similar in construction to that
shown in FIGS. 3A and 3B, instead of disposing the louvers 11 in
the second opening 10, a number (for example, 6 to 22 pieces) of
guide plates 12 are disposed in the treatment cavity 8 in
circumferentially spaced apart relationship from each other. More
specifically, the guide plates 12 are arranged in the treatment
cavity 8 at equidistantly or arbitrarily spaced intervals such that
they are inclined reversely (for example, at about 65.degree.) to
the rotative direction of the impeller 1.
[0028] In the structure shown in FIGS. 4A and 4B, the air a sucked
in the treatment cavity 8 through the first opening 9 is not only
restrained from flowing in the forward direction to the rotative
direction of the impeller 1 by the guide plates 12 each having an
area larger than the louver 11 shown in FIGS. 3A and 3B, but also
is subjected to directional flow guide action by the same guide
plates 12 so as to flow in a whirling direction reverse to the
rotative direction of the impeller 1. As a result, the air a is
discharged through the second opening 10 as flow with strong
directivity reverse to the rotative direction of the impeller 1.
Accordingly, in comparison with the embodiment shown in FIGS. 3A
and 3B, the Euler head can be stabilized further securely and thus
expansion of the operating range of the centrifugal compressor can
be attained further expansively. In the case where the guide plates
12 are disposed in the treatment cavity 8 so as to be inclined in a
direction reverse to the rotative direction of the impeller 1 as
shown in FIGS. 4A and 4B, as is understood from FIG. 5, the surge
line can be shifted (just like FIG. 1) to the position S' where the
flow rate is low, and so, the compressor's characteristic curve I
can be shifted above with respect to the operation line E for the
engine. This contributes to ensuring further stable operating
condition.
[0029] FIGS. 6A and 6B illustrate a still further embodiment of the
invention. In the apparatus for expanding the operating range of
the centrifugal compressor that is similar in construction to that
shown in FIGS. 3A and 3B, guide plates 12 are disposed in the
treatment cavity 8 as if to be extended from their corresponding
louvers 11. That is, the guide plate 12 are integrally aligned with
the corresponding louvers 11.
[0030] In the structure shown in FIGS. 6A and 6B, the circulating
air a is subjected to directional flow guide action by the guide
plates 12 in the treatment cavity 8 and then, during passage
through the second opening 10, further subjected to the directional
flow guide action exerted by the louvers 11. As a result, the air a
is discharged through the second opening 10 as flow with further
strong directivity in a direction reverse to the rotative direction
of the impeller 1. Accordingly, obtained are effects and advantages
equivalent or superior to as achieved in the previously-described
embodiments.
[0031] FIG. 7A and 7B illustrate modifications of the guide plates
12 employed in the embodiment shown in FIGS. 4A and 4B (or FIGS. 6A
and 6B). The guide plates 12 shown in the figures have their width
dimension short of the axial length of the treatment cavity 8. The
guide plate 12 shown in FIG. 7A is so designed that its one end
does not reach an inner edge of the treatment cavity 8 adjacent to
the first opening 9. On the other hand, the guide plate 12 shown in
FIG. 7B is so designed that its other end does not reach an inner
edge of the treatment cavity 8 adjacent to the second opening
10.
[0032] Either of the guide plates 12 shown in FIGS. 7A and 7B will
allow the air a to be discharged through the second opening 10 as
flow in a whirling direction reverse to the rotative direction of
the impeller 1.
[0033] It is to be understood that the present invention is not
limited to the above-mentioned embodiments and that various changes
and modifications may be made without departing from the scope and
spirit of the invention. For example, though the embodiments
described above deal only with the louvers 11 and/or guide plates
12 inclined reversely to the rotative direction of the impeller 1,
they may be arranged radially (0.degree.) so that air is discharged
through the second opening 10 as flow with a direction having no
whirling component toward the center of the rotation axis. In the
reversely inclined arrangement of the louvers 11 and/or guide
plates 12, the inclination angle is preferably set to at most
70.degree. since stabilization effects upon the Euler head remain
unchanged even if the inclination angle is set to be over
70.degree.. Though the embodiments described above are only
directed to a centrifugal compressor with a throttle portion 7
adjacent to an air inlet 4, the invention may be also applicable to
a centrifugal compressor with no throttle portion.
[0034] As described heretofore, according to the invention, there
is provided a method for expanding an operating range of a
centrifugal compressor, the centrifugal compressor including a
shroud wall extending ahead of an outer periphery of an impeller to
provide an air inlet, an annular treatment cavity in the shroud
wall and first and second openings on the shroud wall, the first
opening providing communication between the treatment cavity and
the impeller-side portion of the air inlet, the second opening
providing communication between the treatment cavity and a portion
of the air inlet located somewhat ahead of the impeller-side
portion of the air inlet, wherein, during a low-flow-rate
operation, part of the air sucked through the impeller is fed
through the first opening into the treatment cavity and is
discharged through the second opening so as to be circulated. The
method comprises discharging the air, which has flowed through the
first opening into the treatment cavity, through the second opening
as flow having a direction within a range from a direction with no
whirling component to a whirling direction reverse to the rotative
direction of the impeller. There is also provided an apparatus for
expanding an operating range of a centrifugal compressor, the
centrifugal compressor including a shroud wall extending ahead of
an outer periphery of an impeller to provide an air inlet, an
annular treatment cavity in the shroud wall and first and second
openings on the shroud wall, the first opening providing
communication between the treatment cavity and the impeller-side
portion of the air inlet, the second opening providing
communication between the treatment cavity and a portion of the air
inlet located somewhat ahead of the impeller-side portion of the
air inlet, wherein, during a low-flow-rate operation, part of the
air sucked through the impeller is fed through the first opening to
the treatment cavity and is discharged through the second opening
so as to be circulated. The apparatus comprises a number of louvers
arranged in the second opening of the shroud wall, the arrangement
of the louvers being within a range from radial arrangement to
arrangement inclined reversely to the rotative direction of the
impeller. As a result, the air is, when discharged through the
second opening, subjected to directional flow guide action by the
louvers within a range from a direction with no whirling component
to a whirling direction reverse to the rotative direction of the
impeller. This makes it possible to achieve expansion of the
operating range with no decrease in the Euler head. Instead of the
louvers in the second opening, a number of guide plates may be
arranged in the treatment cavity, angular arrangement of the guide
plates being within a range from radial arrangement to arrangement
inclined reversely to the rotative direction of the impeller. In
this alternative structure, the air can be subjected to directional
flow guide action, in the relatively wide area of treatment cavity,
within a range from a direction with no whirling component to a
whirling direction reverse to the rotative direction of the
impeller. As a result, air is discharged through the second opening
as flow with strong directivity not aligned with the rotative
direction of the impeller, thereby stabilizing the Euler head.
Alternatively, the guide plates may be disposed in the treatment
cavity as if to be integrally extended from their corresponding
louvers. In this structure, the circulating air can be subjected to
the directional flow guide action continuously exerted by the guide
plates and by the louvers, within a range from a direction with no
whirling component to a whirling direction reverse to the rotative
direction of the impeller. As a result, the air is discharged
through the second opening as flow with further strong directivity,
thereby further stabilizing the Euler head.
* * * * *