U.S. patent application number 13/483377 was filed with the patent office on 2012-12-13 for inner peripheral surface shape of casing of axial-flow compressor.
This patent application is currently assigned to HONDA MOTOR CO., LTD.. Invention is credited to Toshiyuki Arima, Giles Endicott, Markus Olhofer, Bernhard Sendhoff, Toyotaka Sonoda.
Application Number | 20120315136 13/483377 |
Document ID | / |
Family ID | 47173182 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120315136 |
Kind Code |
A1 |
Sonoda; Toyotaka ; et
al. |
December 13, 2012 |
INNER PERIPHERAL SURFACE SHAPE OF CASING OF AXIAL-FLOW
COMPRESSOR
Abstract
A generating line of a casing surrounding an outer periphery of
vanes of a stator disposed downstream of a rotor of the axial-flow
compressor includes: a recessed region recessed outward in a radial
direction from a position forward of a front edge of each of the
vanes to a position rearward of a rear edge of the vane; and a
protruding region bulging inward in the radial direction at an
intermediate position of the recessed region in a front-rear
direction thereof. Thus, a distribution of static pressure in the
radial direction on a surface of the vane is improved by a first
recessed portion forward of the protruding region, and the static
pressure on the tip side is raised by a second recessed portion
rearward of the protruding region.
Inventors: |
Sonoda; Toyotaka; (Wako-shi,
JP) ; Arima; Toshiyuki; (Wako-shi, JP) ;
Endicott; Giles; (Offenbach/Main, DE) ; Olhofer;
Markus; (Offenbach/Main, DE) ; Sendhoff;
Bernhard; (Offenbach/Main, DE) |
Assignee: |
HONDA MOTOR CO., LTD.
Tokyo
JP
|
Family ID: |
47173182 |
Appl. No.: |
13/483377 |
Filed: |
May 30, 2012 |
Current U.S.
Class: |
415/210.1 |
Current CPC
Class: |
Y02T 50/60 20130101;
F04D 29/544 20130101; F05D 2220/36 20130101; F04D 29/526 20130101;
F01D 5/143 20130101; F01D 25/162 20130101; F01D 5/145 20130101 |
Class at
Publication: |
415/210.1 |
International
Class: |
F01D 9/04 20060101
F01D009/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2011 |
DE |
102011076804.1 |
Claims
1. An inner peripheral surface shape of a casing of an axial-flow
compressor, the casing surrounding an outer periphery of vanes of a
stator which are disposed in a radial arrangement and rearwardly of
a rotor of the axial-flow compressor, wherein a generating line of
the casing comprises a recessed region and a protruding region, the
recessed region being recessed outward in a radial direction from a
position frontwardly of a front edge of each of the vanes to a
position rearwardly of a rear edge of the vane, the protruding
region bulging inward in the radial direction at an intermediate
position of the recessed region in a front-rear direction.
2. The inner peripheral surface shape of a casing of an axial-flow
compressor according to claim 1, wherein the recessed region
comprises a first recessed portion on a front side, a second
recessed portion on a rear side, a first protruding portion
continuous to a front portion of the first recessed portion, a
second protruding portion forming said protruding region, and a
third protruding portion continuous to a rear portion of the second
recessed portion.
3. The inner peripheral surface shape of a casing of an axial-flow
compressor according to claim 2, wherein the first protruding
portion, the first recessed portion, the second protruding portion,
the second recessed portion, and the third protruding portion are
smoothly continuous to each other.
4. The inner peripheral surface shape of a casing of an axial-flow
compressor according to claim 1, wherein each of the vanes is swept
so that a tip-side end portion thereof is positioned rearwardly of
a hub-side end portion thereof.
5. The inner peripheral surface shape of a casing of an axial-flow
compressor according to claim 2, wherein each of the vanes is swept
so that a tip-side end portion thereof is positioned rearwardly of
a hub-side end portion thereof.
6. The inner peripheral surface shape of a casing of an axial-flow
compressor according to claim 3, wherein each of the vanes is swept
so that a tip-side end portion thereof is positioned rearwardly of
a hub-side end portion thereof.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an inner peripheral surface
shape of a casing of an axial-flow compressor, the casing
surrounding an outer periphery of vanes of a stator which are
disposed in a radial arrangement and downstream of a rotor of the
axial-flow compressor.
[0003] 2. Description of the Related Art
[0004] An inner peripheral surface (a peripheral surface on a tip
side) of a fan casing surrounding an outer periphery of a fan
stator of a turbofan engine is formed to have a substantially
cylindrical shape having the center at the position of a shaft. In
many cases, the shape of a generating line thereof (a line at which
a plane passing the shaft crosses the inner peripheral surface of
the fan casing) is a straight line. In addition, in some cases,
stator vanes of the fan stator of the turbofan engine extend from a
hub side to a tip side while being swept rearward (inclining
rearward) so as to reduce shock-wave loss and reduce noises.
[0005] Japanese Patent Application Laid-open No. 2008-274926
describes a fan casing surrounding an outer periphery of inlet
guide vanes (stator vanes) of a turbine. The fan casing has an
inner peripheral surface a generating line of which is in a shape
including outer peripheral protruding portions Cv2, Cv4 protruding
inward in a radial direction on the upstream side and outer
peripheral recessed portions Cc2, Cc4 recessed outward in the
radial direction on the downstream side. With this shape, a
secondary flow flowing inward in the radial direction, i.e., from
the tip side to the hub side, can thus be suppressed to reduce
pressure loss.
[0006] In addition, Japanese Patent Application Laid-open No.
7-247996 describes a casing surrounding an outer periphery of
stator vanes of a compressor of a gas turbine engine. The casing
has an inner peripheral surface a generating line of which is in a
shape including a recessed portion 18 recessed outward in a radial
direction. With this shape, the flow rate on the back surface side
(on the suction surface side) of the stator vanes is reduced to
prevent separation, and thus pressure loss is reduced.
[0007] Meanwhile, in the case of stator vanes of a fan stator each
being swept rearward from the hub side to the tip side,
particularly, a low-momentum fluid migration flowing from the hub
side to the tip side along the surfaces of the stator vanes is
accelerated, so that the pressure loss is increased. This
acceleration is caused by the phenomena that the static pressure
gradient in a peripheral direction, i.e., from the pressure surface
side to the suction surface side of the stator vane near an end
wall at the hub side increases at the rear part of the cascade, and
that a static pressure contour extending from the hub side to the
tip side on the suction surface of each stator vane is inclined
against a mainstream.
SUMMARY OF THE INVENTION
[0008] The present invention has been made in view of the
aforementioned circumstances. An object of the invention is to
suppress a low-momentum fluid migration flowing from a hub side to
a tip side of stator vanes of an axial-flow compressor and thus to
reduce the pressure loss.
[0009] In order to achieve the object, according to a first feature
of the present invention, there is provided an inner peripheral
surface shape of a casing of an axial-flow compressor, the casing
surrounding an outer periphery of vanes of a stator which are
disposed in a radial arrangement and rearwardly of a rotor of the
axial-flow compressor, wherein a generating line of the casing
comprises a recessed region and a protruding region, the recessed
region being recessed outward in a radial direction from a position
frontwardly of a front edge of each of the vanes to a position
rearwardly of a rear edge of the vane, the protruding region
bulging inward in the radial direction at an intermediate position
of the recessed region in a front-rear direction.
[0010] According to a second feature of the present invention, in
addition to the first feature, there is provided the inner
peripheral surface shape of a casing of an axial-flow compressor,
wherein the recessed region comprises a first recessed portion on a
front side, a second recessed portion on a rear side, a first
protruding portion continuous to a front portion of the first
recessed portion, a second protruding portion forming said
protruding region, and a third protruding portion continuous to a
rear portion of the second recessed portion.
[0011] According to a third feature of the present invention, in
addition to the second feature, there is provided the inner
peripheral surface shape of a casing of an axial-flow compressor,
wherein the first protruding portion, the first recessed portion,
the second protruding portion, the second recessed portion, and the
third protruding portion are smoothly continuous to each other.
[0012] According to a fourth feature of the present invention, in
addition to any one of the first to third features, there is
provided the inner peripheral surface shape of a casing of an
axial-flow compressor, wherein each of the vanes is swept so that a
tip-side end portion thereof is positioned rearwardly of a hub-side
end portion thereof.
[0013] According to the above features, the generating line of the
casing surrounding the outer periphery of the vane of the stator
disposed rearwardly of the rotor of the axial-flow compressor
includes the recessed region and the protruding region, the
recessed region being recessed outward in the radial direction from
the position frontwardly of the front edge of the vane to the
position rearwardly of the rear edge of the vane, the protruding
region bulging inward in the radial direction at the intermediate
position of the recessed region in the front-rear direction
thereof. Accordingly, the distribution of the static pressure in
the radial direction on the surface of the vane is improved by a
part of the recessed region frontwardly of the protruding region,
and the static pressure on the tip side is raised by a part of the
recessed region rearwardly of the protruding region. Thereby, a
low-momentum fluid migration flowing from the hub side to the tip
side is suppressed, and thus the pressure loss can be reduced.
[0014] In addition, the recessed region includes the first recessed
portion on the front side, the second recessed portion on the rear
side, the first protruding portion continuous to the front portion
of the first recessed portion, the second protruding portion
forming the protruding region, and the third protruding portion
continuous to the rear portion of the second recessed portion, and
is continuous among them smoothly. This makes smooth an air flow
along the inner peripheral surface of the casing.
[0015] Moreover, the vane is swept so that the tip-side end portion
thereof is positioned rearwardly of the hub-side end portion
thereof. Thus, the shock-wave loss can be reduced, and noises can
be reduced. Although the sweep of the vane makes it easier for the
low-momentum fluid to move from the hub-side end portion to the
tip-side end portion, the low-momentum fluid migration can be
effectively suppressed due to the inner peripheral surface shape of
the casing of the present invention.
[0016] Note that a fan rotor 15 in an embodiment corresponds to the
rotor of the present invention; a fan stator 16 in the embodiment
corresponds to the stator of the present invention; stator vanes 23
in the embodiment correspond to the vanes of the present invention;
and a second protruding portion 35 in the embodiment corresponds to
the protruding region of the present invention.
[0017] The aforementioned and other objects, features, and
advantages will be clear from a description to be given in detail
below of a preferable embodiment with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 to FIG. 8 show the embodiment of the present
invention:
[0019] FIG. 1 is a schematic view showing an overall configuration
of a turbofan engine;
[0020] FIG. 2 is an enlarged view of a portion 2 in FIG. 1;
[0021] FIGS. 3A and 3B are sectional views taken along a line 3-3
in FIG. 2;
[0022] FIGS. 4A and 4B are views taken in directions of arrows 4A
and 4B in FIGS. 3A and 3B, respectively;
[0023] FIGS. 5A and 5B are views showing wake states of stator
vanes;
[0024] FIGS. 6A and 6B are views showing flow lines along suction
surfaces of the stator vanes;
[0025] FIG. 7 is a graph showing changes of the total pressure loss
involved with the change of the mass flow; and
[0026] FIG. 8 is a graph showing distribution of the total pressure
loss of the stator vanes in a span direction.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] A description is given below of an embodiment of the present
invention with reference to the attached drawings.
[0028] Note that in this specification, an upstream side and a
downstream side of an air flow direction are defined as "front" and
"rear", respectively, and an inner side in a radial direction and
an outer side in the radial direction with an axis L being the
center are defined as a hub side and a tip side, respectively.
[0029] As shown in FIG. 1, a turbofan engine E for an aircraft
includes an outer casing 11 and an inner casing 12 which have
substantially cylindrical shapes and are rotary bodies with an axis
L being the center. Inside the outer casing 11 and the inner casing
12, a low-pressure shaft 13 and a high-pressure shaft 14 are
coaxially arranged, the low-pressure shaft 13 being located on the
axis L, the high-pressure shaft 14 being fitted around an outer
periphery of the low-pressure shaft 13 in such a manner as to be
freely and relatively rotatable.
[0030] A fan rotor 15 is provided at a front end of the
low-pressure shaft 13, and a fan stator 16 is provided rearwardly
of the fan rotor 15. A front portion of the outer casing 11 forms
an outer portion 17A of a fan casing 17. The fan rotor 15 faces, on
a tip side thereof, an inner peripheral surface of the outer
portion 17A of the fan casing 17. In addition, the fan stator 16 is
fixed, on the tip side thereof, to the inner peripheral surface of
the outer portion 17A of the fan casing 17, while the fan stator 16
is fixed, on a hub side thereof, to an outer peripheral surface of
an inner portion 17B of the fan casing 17.
[0031] A low-pressure compressor 18 is provided to the low-pressure
shaft 13 rearwardly of the fan stator 16, and a low-pressure
turbine 19 is provided to a rear end of the low-pressure shaft 13.
In addition, a high-pressure compressor 20 facing a rear portion of
the low-pressure compressor 18 is provided at a front end of the
high-pressure shaft 14, and a high-pressure turbine 21 facing a
front portion of the low-pressure turbine 19 is provided at a rear
end of the high-pressure shaft 14. Further, multiple combustion
chambers 22 are disposed between the high-pressure compressor 20
and the high-pressure turbine 21.
[0032] Thus, air compressed by the fan rotor 15 rotating together
with the low-pressure shaft 13 is rectified by the fan stator 16.
Thereafter, part of the air is exhausted rearward through a bypass
duct 24 formed between the outer casing 11 and the inner casing 12.
The remaining is supplied to the inside of the inner casing 12,
compressed by the low-pressure compressor 18 rotating together with
the low-pressure shaft 13 and by the high-pressure compressor 20
rotating together with the high-pressure shaft 14, and then mixed
with fuel in the combustion chambers 22 to be supplied for
combustion. The fuel gas exhausted from the combustion chambers 22
passes through the high-pressure turbine 21 to drive the
high-pressure shaft 14, further passes through the low-pressure
turbine 19 to drive the low-pressure shaft 13, and then is
exhausted rearward from a rear end of the inner casing 12 to meet
the air passing through the bypass duct 24.
[0033] FIG. 2 shows one of stator vanes 23 of the fan stator 16
disposed between the outer portion 17A and the inner portion 17B of
the fan casing 17. In the stator vane 23, a hub-side end portion
23c inward in a radial direction is connected to an outer
peripheral surface of the inner portion 17B of the fan casing 17,
and a tip-side end portion 23d outward in the radial direction is
connected to the inner peripheral surface of the outer portion 17A
of the fan casing 17. A front edge 23a and a rear edge 23b of the
stator vane 23 are swept in such a manner that the tip-side end
portion 23d deflects rearward relative to the hub-side end portion
23c. Accordingly, a 1/4 cord line 23e of the stator vane 23 is also
swept in such a manner that the tip side deflects rearward relative
to the hub side. Thereby, an element in a cord direction of the
flow rate of an air flow flowing along a surface of the stator vane
23 is reduced, and thus the critical Mach number is increased to
delay an occurrence of a shock wave. Thus, the shock-wave loss can
be reduced, and noises can be reduced.
[0034] The present invention is characterized by a shape, near the
tip-side end portion 23d of the stator vane 23, of the inner
peripheral surface of the outer portion 17A of the fan casing 17.
Since the fan casing 17 is basically a substantially cylindrical
member which is a rotary body with the axis L being the center, a
shape of an inner peripheral surface of the fan casing 17 is
represented by a shape of a generating line (a line of intersection
with a plane passing the axis L).
[0035] The shape of the generating line of the inner peripheral
surface of the outer portion 17A of the fan casing 17 to which the
tip-side end portion 23d of the stator vane 23 is connected
includes a recessed region 31 basically recessed outward in the
radial direction from a position frontwardly of the front edge 23a
to a position rearwardly of the rear edge 23b. The recessed region
31 includes a first recessed portion 32, a second recessed portion
33, a second protruding portion 35, a first protruding portion 34,
and a third protruding portion 36. The first recessed portion 32 is
located between a position slightly frontwardly of the front edge
23a of the tip-side end portion 23d of the stator vane 23 and a
position slightly frontwardly of the rear edge 23b thereof. The
second recessed portion 33 is located rearwardly of the rear edge
23b of the stator vane 23. The second protruding portion 35 bulges
inward in the radial direction at a position slightly frontwardly
of the rear edge 23b in such a manner as to connect the first and
second recessed portions 32, 33. The first protruding portion 34
connects a front end of the first recessed portion 32 to the inner
peripheral surface of the outer portion 17A of the fan casing 17.
The third protruding portion 36 connects a rear end of the second
recessed portion 33 to the inner peripheral surface of the outer
portion 17A of the fan casing 17. In other words, the recessed
region 31 is formed by smoothly connecting the first protruding
portion 34, the first recessed portion 32, the second protruding
portion 35, the second recessed portion 33, and the third
protruding portion 36 from the front to the rear. Positions of
connecting points of the first protruding portion 34, the first
recessed portion 32, the second protruding portion 35, the second
recessed portion 33, and the third protruding portion 36 are
inflexion points at which the direction of the curvature of the
generating line changes.
[0036] Note that the dashed lines in FIG. 2 show the shapes of an
inner peripheral surface of the fan casing 17 and an outer
peripheral surface of the inner casing 12 in Comparative
Example.
[0037] FIGS. 3A and 3B and FIGS. 4A and 4B show static pressure
distributions around the stator vanes 23. FIGS. 3A and 3B show
static pressure distributions on a cross section (of the tip-side
end portion 23d of the stator vane 23) taken along the line 3-3 in
FIG. 2. FIGS. 4A and 4B show static pressure distributions on the
suction surfaces (back surfaces) of the respective stator vanes 23
corresponding to views taken along the arrows 4A and 4B in FIGS. 3A
and 3B. FIGS. 3A and 3B and FIGS. 4A and 4B show that darker color
portions (densely shaded portions) exhibit higher pressures and
lighter color portions (coarsely shaded portions) exhibit lower
pressures.
[0038] According to the embodiment, the first and second recessed
portions 32, 33 are formed in the inner peripheral surface of the
outer portion 17A of the fan casing 17 to which the tip-side end
portion 23d of the stator vane 23 is connected. Thus, the flow rate
of the air flow flowing along the first and second recessed
portions 32, 33 is lowered, and thereby the static pressure is
raised.
[0039] As is clear with reference to Comparative Example and the
embodiment in FIG. 3A to FIG. 5B, it is proved that, due to an
effect of the first recessed portion 32 of the fan casing 17, the
static pressure of the pressure surface of each of the stator vanes
23 in the embodiment is raised in comparison with Comparative
Example (see FIGS. 3A and 3B). Furthermore, it is proved that, due
to an effect of the second recessed portion 33 of the fan casing
17, the static pressure rearwardly of the rear edge 23b of the
stator vane 23 in the embodiment is raised in comparison with
Comparative Example (see FIGS. 4A and 4B).
[0040] In addition, as is clear from FIGS. 4A and 4B, a static
pressure contour along the suction surface of the stator vane 23 in
the embodiment becomes upright in comparison with Comparative
Example due to the effect of the first recessed portion 32 of the
fan casing 17. In other words, in the embodiment, the static
pressure contour is approximately aligned with the radial
direction. In contrast, in Comparative Example, the static pressure
contour outward in the radial direction is swept back rearward.
Accordingly, a static pressure distribution is formed in which a
region (a lower side in the figure) inward in the radial direction,
of the static pressure contour, exhibits a higher pressure and a
region (an upper side in the figure) outward in the radial
direction, of the static pressure contour, exhibits a lower
pressure. This induces a secondary flow flowing from the hub-side
end portion 23c to the tip-side end portion 23d of the stator vane
23. On the other hand, in the embodiment, the static pressure
contour has almost no sweepback angle, and thus the secondary flow
is hardly induced.
[0041] Meanwhile, a rotor hub of the fan rotor 15 located
frontwardly of the fan stator 16 has a diameter increased from the
front to the rear in such a manner as to have a conical shape. This
easily induces the secondary flow in the air flow passing along the
stator vane 23 of the fan stator 16, the secondary flow flowing
from the inner side in the radial direction to the outer side in
the radial direction. Moreover, when the stator vane 23 is swept,
the air flow easily flows from the hub side to the tip side, making
the secondary flow further stronger. As described above, when the
secondary flow flowing from the inner side in the radial direction
to the outer side in the radial direction along the stator vane 23
is generated, a low-momentum wake (a following wake) generated on
the hub-side end portion 23c of the stator vane 23 easily spreads
outward in the radial direction, as shown in Comparative Example in
FIG. 5B. This causes a problem of increased pressure loss in the
fan stator 16.
[0042] According to the embodiment, however, the static pressure
contour along the suction surface of the stator vane 23 becomes
upright due to the effect of the first recessed portion 32 of the
fan casing 17, so that the secondary flow flowing from the hub side
to the tip side is suppressed. In addition, the static pressure
rearwardly of the rear edge 23b of the tip-side end portion 23d of
the stator vane 23 is raised due to the effect of the second
recessed portion 33 of the fan casing 17, so that the secondary
flow flowing from the hub side to the tip side is suppressed.
Thereby, as shown in the embodiment in FIG. 5A, a region where the
low-momentum wake spreads is minimized, and thus the pressure loss
can be reduced.
[0043] FIGS. 6A and 6B show flow lines of the air flow along the
suction surface of the stator vane 23. Comparative Example shows
that the air flow flowing in from the front edge 23a along the
hub-side end portion 23c of the stator vane 23 deflects largely
outward in the radial direction at the rear edge 23b to increase a
wake region Wh on the hub side, while the embodiment shows that the
secondary flow flowing from the hub side to the tip side is
suppressed to reduce a wake region Wh on the hub side. Here, the
static pressure rearwardly of the rear edge 23b of the tip-side end
portion 23d of the stator vane 23 is raised due to the effect of
the second recessed portion 33 of the fan casing 17, and thereby
the secondary flow flowing from the tip side to the hub side is
generated, so that a wake region Wt on the tip side in the
embodiment is slightly larger than that in Comparative Example. The
wake regions, however, are made smaller as a whole, and thereby the
pressure loss can be reduced.
[0044] FIG. 7 is a graph showing changes of the total pressure loss
in changing the mass flow rate. It is proved that in the mass flow
rate in an illustrated range, the total pressure loss in the
embodiment is approximately 20% lower than the total pressure loss
in Comparative Example.
[0045] FIG. 8 is a graph showing a distribution of the total
pressure loss of the stator vane 23 in a span direction in a case
of mass flow rate=1.0. It is proved that due to the increased wake
region Wt on the tip side in the embodiment in some region (80% to
90% region in the span direction) on the tip side, the total
pressure loss in the embodiment is increased in comparison with
Comparative Example. However, the total pressure loss in the
embodiment in the other region is lower than the total pressure
loss in Comparison Example.
[0046] An embodiment of the present invention has been described
above, but the present invention is not limited to the
aforementioned embodiment, and various design changes can be made
without departing from the gist of the present invention.
[0047] For example, in the embodiment, the present invention is
applied to the fan casing 17 of the turbofan engine E for an
aircraft, but is not only applicable to a turbofan engine for any
application other than that for an aircraft but also applicable to
a casing of an axial-flow compressor for any application.
[0048] In addition, although the stator vanes 23 in the embodiment
are swept, the present invention is applicable to stator vanes
which are not swept.
* * * * *