Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LEANED DESWIRL VANES BEHIND A CENTRIFUGAL COMPRESSOR IN A
GAS TURBINE ENGINE
TECHNICAL FIELD
[0001] The present invention relates to a gas turbine engine and, more
particularly, to a deswirl assembly having leaned deswirl vanes for use in the
gas
turbine engine.
BACKGROUND
[0002] A gas turbine engine may be used to power various types of vehicles and
systems. A typical gas turbine engine includes a fan section, a compressor
section, a
combustor section, a turbine section, and an exhaust section. The fan section
induces
air from the surrounding environment into the engine and accelerates a
fraction of the
air toward the compressor section. The compressor section compresses the
pressure
of the air to a relatively high level and directs the air to the combustor
section. A
steady stream of fuel is injected into the combustor section, and the injected
fuel is
ignited to significantly increase the energy of the compressed air. The high-
energy
compressed air then flows into and through the turbine section, causing
rotationally
mounted turbine blades therein to rotate and generate energy. The air exiting
the
turbine section is exhausted from the engine via the exhaust section, and the
energy
remaining in the exhaust air aids the thrust generated by the air flowing
through a
bypass plenum.
[0003] In some engines, the compressor section is implemented with a
centrifugal
compressor. A centrifugal compressor typically includes at least one impeller
that is
rotationally mounted to a rotor and surrounded by a shroud. When the impeller
rotates, it compresses and imparts tangential velocity to the air received
from the fan
section and the shroud directs the air radially outward into a diffuser. The
diffuser
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decreases the radial and tangential velocity of the air and increases the
static pressure
of the air and directs the air into a deswirl assembly. The deswirl assembly
includes
an annular housing having a plurality of straight radially extending vanes
mounted
therein that straighten and reduce the tangential velocity component of the
air flow
before it enters the combustor section. The combustor section in some engines
is
implemented with an axial through-flow combustor that includes an annular
combustor disposed within a combustor housing that defines a plenum. The
straightened air enters the plenum and travels axially through the annular
combustor
where it is mixed with fuel and ignited.
[0004] Recently, conventional deswirl assemblies have included downcanted
outlets to improve aerodynamic coupling between the diffuser and combustor.
However, it has been found that these deswirl assemblies generate greater flow
angle
variation across the span of the flowpath at the deswirl vane leading edge and
therefore may not adequately condition air flow to a sufficiently low mach
number in
an acceptably efficient manner unless the overall axial length andlor radial
envelope
of the assembly is increased. Because engines are continually designed to be
smaller,
the size increase may not be acceptable in newer aircraft. As a result, the
configuration of the deswirl assembly has had to be redesigned. One preferred
configuration includes vanes that are shaped so that the vane can accept a
large
variation in air angle at its leading edge. The vanes may also be configured
such that
the pressure side of each vane faces radially inwardly. However, although this
configuration optimizes airflow through the deswirl assembly, manufacture of
the
assembly is relatively time-consuming and costly because each vane may need to
be
individually formed and shaped.
[0005] Hence, there is a need for an improved downcanted deswirl assembly that
includes a plurality of vanes that are configured to aerodynamically couple a
centrifugal compressor and an axial through-flow combustor. Additionally, it
is
desirable for the deswirl assembly to be relatively inexpensive and simple to
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manufacture. Moreover, it is desirable for the deswirl assembly to suitably
direct and
condition the air flowing therethrough for optimal engine performance.
BRIEF SUMMARY
[0006] The present invention provides a deswirl assembly for receiving air
flow
from a diffuser. The deswirl assembly includes an annular housing and a
plurality of
vanes. The annular housing includes an inner annular wall, an outer annular
wall
disposed concentric to the inner annular wall, and a flowpath defined
therebetween.
The plurality of vanes is disposed in the flowpath in a substantially annular
pattern.
Each vane has a leading edge, a trailing edge, a convex surface, and concave
surface,
and each of the convex and concave surfaces extends between the leading and
trailing
edges. Additionally, each vane extends between and is angled relative to the
inner
and the outer annular walls such that the concave surface faces the outer
annular wall
and the convex surface faces the inner annular wall.
[0007] In one embodiment, and by way of example only, the deswirl assembly
including an annular housing, and a first and a second plurality of vanes. The
annular
housing includes an inner annular wall, an outer annular wall disposed
concentric to
the inner annular wall, and a flowpath defmed therebetween. The first
plurality of
vanes is disposed in the flowpath in a substantially annular pattern, and each
vane has
a leading edge, a trailing edge, a convex surface, and concave surface, each
of the
convex and concave surfaces extending between the leading and trailing edges,
each
vane extends between and is angled relative to the inner and the outer annular
walls
such that the concave surface faces the outer annular wall and the convex
surface
faces the inner annular wall and each vane has an axial cross section shape,
and each
axial cross section shape is substantially the same. The second plurality of
vanes is
disposed in the flowpath in a substantially annular pattern downstream of the
first
plurality of vanes. Each vane has a leading edge, a trailing edge, a convex
surface,
and concave surface, each of the convex and concave surfaces extends between
the
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leading and trailing edges, and each vane extends between and is angled
relative to
the inner and the outer annular walls such that the concave surface faces the
outer
annular wall and the convex surface faces the inner annular wall.
Additionally, each
vane of the second plurality of vanes has an axial cross section shape, and
each axial
cross section shape is substantially the same.
[0008] In still another embodiment, a system is provided for aerodynamically
coupling air flow from a centrifugal compressor to an axial combustor, where
the
compressor and combustor are disposed about a longitudinal axis. The system
includes a diffuser, a deswirl assembly, combuster inner and outer annular
liners, a
combustor dome, and a curved annular plate. The diffuser has an inlet, an
outlet and a
flow path extending therebetween, where the diffuser inlet is in flow
communication
with the centrifugal compressor, and the diffuser flow path extends radially
outward
from the longitudinal axis. The deswirl assembly includes an annular housing
and a
plura.lity of vanes. The annular housing includes an inner annular wall, an
outer
annular wall disposed concentric to the inner annular wall, and a flowpath
defmed
therebetween. The plurality of vanes is disposed in the flowpath in a
substantially
annular pattern. Each vane has a leading edge, a trailing edge, a convex
surface, and
concave surface, and each of the convex and concave surfaces extends between
the
leading and trailing edges. Additionally, each vane extends between and is
angled
relative to the inner and the outer annular walls such that the concave
surface faces
the outer annular wall and the convex surface faces the inner annular wall.
The
combustor inner annular liner is disposed about the longitudinal axis, and the
inner
annular liner has an upstream end. The combustor outer annular liner is
disposed
concentric to the combustor inner annular liner and forms a combustion plenum
therebetween. The outer annular liner has an upstream end. The combustor dome
is
coupled to and extends between the combustor inner and outer annular liner
upstream
ends. The curved annular plate is coupled to the combustor inner and outer
annular
liner upstream ends to form a combustor subplenum therebetween, and the curved
annular plate has a first opening and a second opening formed therein. The
first
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opening is aligned with the deswirl assembly outlet to receive air discharged
therefrom.
[0009] Other independent features and advantages of the preferred deswirl
assembly will become apparent from the following detailed description, taken
in
conjunction with the accompanying drawings which illustrate, by way of
example, the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a simplified cross section side view of an exemplary multi-
spool
turbofan gas turbine jet engine according to an embodiment of the present
invention;
[0011] FIG. 2 is a cross section view of a portion of an exemplary combustor
that
may be used in the engine of FIG. 1;
[0012] FIG. 3 is a cutaway view of a portion of an exemplary deswirl assembly
that may be implemented into the combustor shown in FIG. 2 forward looking
aft;
[0013] FIG. 4 is the portion of the exemplary deswirl assembly shown in FIG. 3
aft looking forward; and
[0014] FIG. 5 is a top view of the exemplary deswirl assembly shown in FIG. 3.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0015] Before proceeding with the detailed description, it is to be
appreciated that
the described embodiment is not limited to use in conjunction with a
particular type of
turbine engine. Thus, although the present embodiment is, for convenience of
explanation, depicted and described as being implemented in a multi-spool
turbofan
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gas turbine jet engine, it will be appreciated that it can be implemented in
various
other types of turbines, and in various other systems and environments.
[0016] An exemplary embodiment of a multi-spool turbofan gas turbine jet
engine
100 is depicted in FIG. 1, and includes an intake section 102, a compressor
section
104, a combustion section 106, a turbine section 108, and an exhaust section
110.
The intake section 102 includes a fan 112, which is mounted in a fan case 114.
The
fan 112 draws air into the intake section 102 and accelerates it. A fraction
of the
accelerated air exhausted from the fan 112 is directed through a bypass
section 116
disposed between the fan case 114 and an engine cowl 118, and provides a
forward
thrust. The remaining fraction of air exhausted from the fan 112 is directed
into the
compressor section 104.
[0017] The compressor section 104 includes two compressors, an intennediate
pressure compressor 120, and a high pressure compressor 122. The intermediate
pressure compressor 120 raises the pressure of the air directed into it from
the fan
112, and directs the compressed air into the high pressure compressor 122. The
high
pressure compressor 122 compresses the air still further, and directs the high
pressure
air into the combustion section 106. In the combustion section 106, which
includes an
annular combustor 124, the high pressure air is mixed with fuel and combusted.
The
combusted air is then directed into the turbine section 108.
[0018] The turbine section 108 includes three turbines disposed in axial flow
series, a high pressure turbine 126, an intermediate pressure turbine 128, and
a low
pressure turbine 130. The combusted air from the combustion section 106
expands
through each turbine, causing it to rotate. The air is then exhausted through
a
propulsion nozzle 132 disposed in the exhaust section 110, providing
additional
forward thrust. As the turbines rotate, each drives equipment in the engine
100 via
concentrically disposed shafts or spools. Specifically, the high pressure
turbine 126
drives the high pressure compressor 122 via a high pressure spool 134, the
intermediate pressure turbine 128 drives the intermediate pressure compressor
120 via
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an intermediate pressure spool 136, and the low pressure turbine 130 drives
the fan
112 via a low pressure spool 138.
[0019] Turning now to FIG. 2, an exemplary cross section of the area between
the
high pressure compressor 122 and annular combustor 124 is illustrated. In
addition to
the compressor 122 and combustor 124, FIG. 2 depicts a diffuser 204 and a
deswirl
assembly 206, each disposed about a longitudinal axis 207. The high pressure
compressor 122 is preferably a centrifugal compressor and includes an impeller
208
and a shroud 210 disposed in a compressor housing 211. The impeller 208, as
alluded
to above, is driven by the high pressure turbine 126 and rotates about the
longitudinal
axis 207. The shroud 210 is disposed around the impeller 208 and defines an
impeller
discharge flow passage 212 therewith that extends radially outwardly.
[0020] The diffuser 204 is coupled to the shroud 210 and is configured to
decrease the velocity and increase the static pressure of air that is received
therefrom.
In this regard, any one of numerous conventional diffusers 204 suitable for
operating
with a centrifugal compressor may be employed. In any case, the diffuser 204
includes an inlet 214, an outlet 216, and a flow path 218 that each
communicates with
the passage 212, and the flow path 218 is configured to direct the received
air flow
radially outwardly.
[0021] The deswirl assembly 206 communicates with the diffuser 204 and is
configured to substantially remove swirl from air received therefrom, to
thereby
decrease the Mach number of the air flow. The deswirl assembly 206 includes an
inner annular wall 220, an outer annular wall 222, and two pluralities of
vanes 224,
226 disposed therebetween. The walls 220, 222 defme a flow path 228 that is
configured to redirect the air from its radially outward direction to a
radially inward
and axially downstream direction. In this regard, the walls 220, 222 are
formed such
that the flow path 228 extends between an inlet 230 and outlet 232 in an arc
233 so
that when the air exits the outlet 232, it is directed at an angle and toward
the
longitudinal axis 207 and the annular combustor 124. As the angle of the arc
233 is
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increased the variation of the air angle between the inner wall 220 and out
wall 222 is
increased.
[0022] As briefly mentioned above, the two pluralities of vanes 224, 226 are
disposed between the walls 220, 222. To secure the vanes 224, 226 to the
assembly
206, each wall 220, 222 includes two sets of slots 234, 236, 238, 240 that are
formed
in annular patterns along two axial positions. Preferably, the slots 234, 236,
238, 240
are formed downstream of the arc 233. Each of the vanes 224, 226 includes at
least a
top 242, 244 and a bottom 246, 248 that extend through the slots 234, 236,
238, 240.
The vanes 226, 228 may be secured to the walls 220, 222 in any one of numerous
fashions, such as, for example, by brazing.
[0023] To condition the airflow to a sufficiently low Mach number, each vane
preferably has a substantially identical predetermined shape and is positioned
in the
flow path 228 at a predetermined angle relative to the walls 220, 222.
Exemplary
vanes 300, which are shown as being implemented into the two pluralities of
vanes
224, 226, are depicted in FIGs. 3 and 4. As briefly mentioned above, FIG. 3 is
a
cutaway view of the deswirl assembly 200 looking at the vanes 300 from forward
to
aft, while FIG. 4 is the deswirl assembly shown in FIG. 3 looking at the vanes
300
from aft to forward.
[0024] Each vane 300 includes a leading edge 302 and a trailing edge 304. A
concave pressure surface 306 and a convex suction surface 308 extend between
the
leading and trailing edges 302, 304. The vanes 300 preferably each have a
uniformly
shaped curved axial cross-section from top 310 to bottom 312. In this regard,
a
number of the vanes 300 having substantially identical shapes may be mass
produced
from a single sheet of material. Specifically, the sheet of material may be
suitably
pressed into an appropriate curve shape to form the concave and convex
surfaces 306,
308 and a plurality of the vanes 300 may be cut from the single sheet of
material.
[0025] As mentioned previously, each vane 300 of the two pluralities of vanes
224,
226 is disposed at an angle relative to the walls 220, 222. Preferably, the
vanes 300
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are each placed such that the concave pressure surface 306 faces outwardly
toward the
outer annular wall 222 and the convex suction surface 308 faces inwardly
toward the
inner annular wall 220. Angling the vanes 300 in this preferred embodiment
reduces
the variation in air angle between the walls 220,222. In one exemplary
embodiment,
the vanes 300 are disposed such that an angle between the concave pressure
surface
208 the inner annular wall 220 is about 110.8 . However, it will be
appreciated that
the particular angle at which the vanes 224, 226 are disposed depends on the
overall
configuration of the walls 220, 222.
[0026] The degree to which the vanes 224, 226 are angled may also detennine
how
the two pluralities of vanes 224, 226 are placed relative to each another. In
one
example, as shown in FIGs. 3 and 4, the vanes of the fust plurality of vanes
224 are
equally spaced apart from one another and the trailing edge of each vane is
disposed
around a first circumferential position 242 around the inner annular wall 220,
while
the vanes of the second plurality of vanes 226 are also equally spaced apart
from one
another but the leading edge of each is disposed around a second
circumferential
position 244. Although the first and second circumferential positions 242, 244
are
shown in this embodiment as non-overlapping and the first circumferential
position
242 is disposed upstream of the second circumferential position 244, the first
circumferential position 242 may alternatively be disposed downstream of the
second
circumferential position 244, or may overlap.
[0027] Additionally, the second plurality of vanes 226 are preferably
staggered
between the first plurality of vanes 224. For instance, as shown in FIG. 5
viewing the
vanes 300 from forward 250 to aft 252, one vane 226b of the second plurality
of
vanes 226 is preferably disposed between two vanes 224a, 224b of the first
plurality
of vanes 224 and biased toward the pressure surface 306 of vane 224b. In one
exemplary embodiment, a distance 254 between vane 226b of the second plurality
of
vanes 226 and vane 224b of the first plurality of vanes 224 is about 35% of
the
distance 256 between vanes 224a, 224b of the first plurality of vanes 224. It
will be
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appreciated, however, that the particular distances between all of the vanes
may
largely depend on the angling thereof relative to the walls 220, 222.
[0028] It will further be appreciated that although two pluralities of vanes
226, 228
are included in the embodiment shown in FIG. 2, the deswirl assembly 200 may
alternatively only include a single plurality of vanes. In still other
embodiments,
more than two pluralities of vanes 226, 228 may need to be employed.
[0029] An improved downcanted deswirl assembly has now been provided that
includes a plurality of vanes that are configured to aerodynamically couple a
centrifugal compressor and an axial through-flow combustor. Additionally, the
deswirl assembly is relatively inexpensive and simple to manufacture and is
capable
of directing and conditioning the air flowing therethrough for optimal engine
performance
[0030] While the invention has been described with reference to a preferred
embodiment, it will be understood by those skilled in the art that various
changes may
be made and equivalents may be substituted for elements thereof without
departing
from the scope of the invention. In addition, many modifications may be made
to
adapt to a particular situation or material to the teachings of the invention
without
departing from the essential scope thereof. Therefore, it is intended that the
invention
not be limited to the particular embodiment disclosed as the best mode
contemplated
for canying out this invention, but that the invention will include all
embodiments
falling within the scope of the appended claims.
