Treatment for a casing with axial diffusion plenum

Abstract

The invention relates to a turbomachine compressor casing comprising an inner annular wall (101) and an outer annular wall (102) delimiting between them an annular cavity (150) extending in length in an axial direction (DA) between a front bottom (151) and a rear bottom (152) and in height in a radial direction (DR) between an inner face (1021) of the outer annular wall and an outer face (1011) of the inner annular wall, the inner annular wall of the casing comprising a plurality of slots (110) which open into the annular cavity, are arranged one next to the other in a circumferential direction (DC) and extend in length in the axial direction between the front bottom and the rear bottom and in height in the radial direction, characterized in that, in the axial direction, the annular cavity comprises a first portion (155) situated above, in the radial direction, an upstream part of the slots and a second portion (156) situated downstream of the first portion, the height of the annular cavity in the first portion (H155) being greater than that of the second portion (H156).

Description

[0001] Description

[0002] Title of the invention: Crankcase treatment with axial diffusion plenum

[0003] Technical Field

[0004] The present invention relates to the general field of turbomachinery compressors, and more particularly to the treatment of turbomachinery compressor casings.

[0005] Previous technique

[0006] Turbomachine compressors consist of blades driven in rotation inside a casing which ensures the air stream is sealed from the outside of the engine.

[0007] It is known that the play existing between the ends of the moving blades of the compressor and the casing forming the inner wall of the air flow duct degrades the efficiency of the turbomachine engine.

[0008] Furthermore, this play can alter and degrade the compressor's operation, potentially leading to a surge phenomenon resulting from the airflow separating from the blade surface. Controlling the airflow at the blade tips is crucial for achieving both good aerodynamic efficiency of the compressor and a sufficient margin against surge.

[0009] To limit the impact of this parasitic flow between the blade tips and the casing, the internal surface of the casing can be locally treated by creating slots within its thickness opposite the blades. The casing treatments considered in the present invention are of the "axial slot" type, corresponding to a series of slots arranged along the circumference of the casing (in the azimuthal direction). These slots are located vertically ("above") a compressor wheel. These treatments are therefore asymmetrical with respect to the compressor's axis of rotation: they are thus non-axisymmetric casing treatments, or NACF. The presence of these slots will locally modify the flow. The objective is to influence the onset of the mechanisms responsible for the compressor's surge.Effective crankcase treatment will increase the compressor's operating range by delaying the onset of these mechanisms, particularly by reducing aerodynamic wheel lock-up.

[0010] Some TCNA designs propose adding an annular cavity or "plenum" to the casing, as described, for example, in document WO 94 / 20759. This is equivalent to adding a cavity above the slots. This cavity extends around the entire circumference of the casing and connects the slots. This cavity is not directly open to the vein and is not connected to a secondary air circuit. The fluid must pass through the slots to enter and exit the cavity. The addition of the plenum tends to enhance the TCNA's ability to increase the pump margin.

[0011] The annular cavity is useful because it allows a fraction of fluid to be drawn through a slot downstream of the leading edge of the blades and reinjected through different slots upstream of the leading edge of the blades, thus improving the efficiency of crankcase treatment (compared to crankcase treatment without an annular cavity). However, this mechanism is not optimal because the pressure gradient between the plenum and the vein can be low and intermittently cause vorticity in the slot, preventing fluid reinjection. This intermittent reduction in the reinjection flow rate negatively impacts the efficiency of the NAC.

[0012] It is therefore desirable to be able to retain the advantages of TCNA with plenum, and to improve its ability to reinject a fraction of the fluid upstream of the rotor without degrading its ability to draw a fraction of the fluid above the rotor.

[0013] Description of the invention

[0014] The present invention therefore relates to a turbomachine compressor housing comprising an internal annular wall and an external annular wall delimiting between them an annular cavity extending lengthwise along an axial direction between a front end and a rear end, and heightwise along a radial direction between an internal face of the external annular wall and an external face of the internal annular wall. The internal annular wall of the housing comprises a plurality of slots opening into the annular cavity. The slots are arranged side by side along a circumferential direction and extend lengthwise along the axial direction between the front end and the rear end, and heightwise along the radial direction. The invention is characterized in that, along the axial direction, the annular cavity comprises a first portion located above, along the radial direction,of an upstream portion of the plurality of slits and a second portion located downstream of said first portion, the height of the annular cavity in the first portion being greater than that of the second portion.

[0015] Conservation of angular momentum implies a reduction in the tangential velocity of the downstream sampled flow, which is then reinjected into the upstream flow channel. This reduction in tangential velocity attenuates vortices appearing in the slots and improves the reinjection capacity of the non-axissymmetric crankcase treatment. This change in height induces a radial velocity component oriented towards the channel in the flow within the annular cavity. This radial velocity promotes the reinjection of the flow into the main flow channel.

[0016] According to a particular feature of the invention, the height of the slots is variable along the axial direction.

[0017] The variation in the height of the slits is, for example, discrete along the axial direction.

[0018] A discrete variation means that the height varies in steps or increments; in other words, the variation is not gradual. Having a discrete variation in the height of the slots simplifies their manufacture.

[0019] The variation in the height of the slits can also be gradual along the axial direction.

[0020] The gradual variation in the slit height helps limit heat loss in the annular cavity. Heat loss can also be called recirculating flow heat loss, as it involves momentum loss through heat conversion resulting from the formation of local recirculating flows. Indeed, the gradual variation prevents...

[0021] "step" at the level of the change in height of the slot and to limit the phenomena of air recirculation that may occur at the step.

[0022] According to a particular feature of the invention, along the axial direction, the height of the slots increases until reaching a maximum height at a first point in a direction extending from the front bottom to the rear bottom of the annular cavity, and then remains constant until the rear bottom of the annular cavity. According to another particular feature of the invention, along the axial direction and in a direction extending from the front bottom to the rear bottom of the annular cavity, the height of the annular cavity is maximum up to a second point, then decreases until a third point, and then is minimum until the rear bottom of the annular cavity.

[0023] The first point can be located upstream of the second point along the axial direction.

[0024] According to another particular feature of the invention, the housing comprises a treatment ring having the inner annular wall and a master ring having the outer annular wall, the treatment ring being fixed on the master ring.

[0025] According to another particular feature of the invention, the processing ring and the master ring are made of the same material.

[0026] Another object of the invention is a turbomachine compressor comprising a casing according to the invention.

[0027] Brief description of the drawings Other features and advantages of the present invention will become apparent from the description given below, with reference to the attached drawings which illustrate examples of embodiment without any limiting character.

[0028] [Fig. 1] Figure 1 schematically and in perspective represents a turbomachine compressor comprising a casing according to the invention.

[0029] [Fig. 2] Figure 2 schematically and partially represents a cross-sectional view along the radial and axial directions of a compressor housing according to an embodiment of the invention.

[0030] [Fig. 3] Figure 3 represents, schematically and partially, a cross-sectional view along the axial and circumferential directions of the compressor housing of Figure 2.

[0031] [Fig. 4] Figure 4 represents, schematically and partially, a cross-sectional view along the radial and circumferential directions of the compressor housing of Figure 2.

[0032] [Fig. 5] Figure 5 schematically and partially represents a cross-sectional view along the radial and axial directions of a compressor housing according to another embodiment of the invention.

[0033] [Fig. 6] Figure 6 schematically and partially represents a cross-sectional view along the radial and axial directions of a compressor housing according to another embodiment of the invention.

[0034] Description of the implementation methods

[0035] Figure 1 represents a schematic perspective view of a turbomachine compressor 101. The compressor 101 comprises around its axis A300 a rotor 120 equipped with a plurality of movable blades 121 surrounded by a casing 100 according to the invention.

[0036] The housing 100 includes a processing ring 130 and a master ring 140 which is structural. The processing ring 130 is fixed to the master ring 140, for example the processing ring 130 may include a flange which is fixed to a flange of the master ring 140.

[0037] The treatment ring 130 and the master ring 140 are made of the same material or of materials having similar coefficients of thermal expansion in order to avoid differential expansions between the two rings 130, 140 which could lead to mechanical stresses and / or sealing problems in the housing 100.

[0038] As illustrated in Figures 2 to 4, the master ring 140 comprises an external annular wall 102 while the treatment ring 130 comprises an internal annular wall 101 opposite the external annular wall 102.

[0039] The inner annular wall 101 and the outer annular wall 102 each extend in length along a circumferential direction DC, in width along an axial direction DA corresponding to the axis of the A300 compressor and in height (or thickness) along a radial direction DR.

[0040] The internal annular wall 101 and the external annular wall 102 define between them an annular cavity 150 forming a plenum. The internal annular cavity 150 extends vertically along the radial direction DR between an internal face 1021 of the external annular wall 102 and an external face 1011 of the internal annular wall 101; and longitudinally along the axial direction DA between an anterior fundus 151 and a posterior fundus 152.

[0041] The internal annular wall 101 comprises a plurality of slots 110 cut or grooved into the thickness of the internal annular wall 101. Each slot 110 opens onto both an internal face 1012 of the internal annular wall and the external face 1011 of the internal annular wall 101, so as to connect a vein of the main flow E in the compressor 101 with the annular cavity 150, the arrow E indicating the direction of the flow in the compressor 101, and consequently, the upstream and downstream sides thereof.

[0042] The slots 110 are arranged uniformly next to each other in the inner annular wall 101 along the circumferential direction DC. Each slot 110 extends lengthwise along a longitudinal axis that may be parallel to the axial direction DA or form an angle between -60° and +60° with the axial direction DA. Each slot 110 extends heightwise along the radial direction DR over a height H 110.

[0043] The slits 110 have a height H 110 that varies along the axial direction DA and is between H 110min and H110max. The height H 150 of the annular cavity 150 is then defined by the space between the external face 1011 of the internal annular wall 101 and the internal face 1021 of the external annular wall 102.

[0044] In particular, in Figure 2, along the axial direction DA, the height H 110 of the slots 110 increases until it reaches a maximum height HllOmax at a first point along the direction of the flow E (or along the direction extending from the front bottom 151 to the rear bottom 152 of the annular cavity 150), then is constant until the rear bottom 152 of the annular cavity 150.

[0045] As is known, the slots 110 and the annular cavity 150 into which they open constitute a non-axissymmetric crankcase treatment or TCNA which allows local modification of the flow in order to reduce the mechanisms responsible for the compressor starting to pump.

[0046] The TCNA thus formed is present above the blade head of the blades 121 in the radial direction DR and is placed astride the trailing edge of the blades.

[0047] According to the invention, the annular cavity 150 comprises a first portion 155 located above the upstream part of the slots 110 and a second portion 156 located downstream of said first portion 155. The term "above" means above in the radial direction DR. The height H 155 of the first portion 155 of the annular cavity 150 is greater than the height H156 of the second portion 156. The variation in height between the first portion 155 and the second portion 156 of the annular cavity 150 is obtained thanks to the variable height H 110 of the slits 110, which is between H 110min and H110max, and thanks to the difference in height along the radial direction DR of the anterior bottom 151 and the posterior bottom 152 of the annular cavity 150. Furthermore, the variation in the height H 110 of the slits 110 is gradual.In Figure 2, along the axial direction DA and according to the direction of flow E (or along the direction extending from the front bottom 151 to the rear bottom 152 of the annular cavity 150), the height H150 of the annular cavity 150 is maximum up to a second point, then decreases up to a third point, and is constant up to the rear bottom 152 of the annular cavity 150. In other words, the height H150 of the annular cavity is equal to its maximum height H155 between the front bottom 151 and the second point, then decreases up to the third point to reach its minimum height H156, and remains constant at its minimum height H156 between the third point and the rear bottom 152.

[0048] The first point, the point at which the maximum height HllOmax of the slits is reached, is located upstream of the second point along the axial direction.

[0049] Thanks to the invention, air from the flow vein E is taken by the slots 110 at the level of the second portion 156 of the annular cavity 150 and flows in the annular cavity 150 towards the first portion 155 before being reinjected into the flow vein E upstream of the blades 121 of the rotor 120. The variation in height H150 of the annular cavity 150 makes it possible in particular to decrease the velocity of the air taken in order to redirect it towards the flow vein E, and the gradual variation in height H110 of the slots makes it possible to limit the thermodynamic losses by heating or thermodynamic losses by recirculating flows in the annular cavity 150.

[0050] Figure 5 schematically and partially represents a cross-sectional view along the radial and axial directions of a compressor housing 200 according to a second embodiment of the invention. In accordance with the invention and as explained with reference to Figures 1 to 4, the housing comprises an internal annular wall 201 and an external annular wall 202 delimiting between them an annular cavity 250 extending lengthwise along the axial direction DA between the front end 251 and the rear end 252 and heightwise along the radial direction DR between the inner face 2021 of the external annular wall 202 and the outer face 2011 of the internal annular wall 201.The internal annular wall 201 comprises a plurality of slots 210 opening into the annular cavity 250, the slots 210 being arranged next to each other along the circumferential direction DC and extending lengthwise along the axial direction DA between the front bottom 251 and the rear bottom 252 and heightwise along the radial direction DR.

[0051] The annular cavity 250 has a first portion 255 located above, in the radial direction DR, the upstream part of the slots 210 and a second portion 256 located downstream of said first portion 255. The height H255 of the first portion 255 of the annular cavity 250 is greater than the height H256 of the second portion 256. The terms "upstream" and "downstream" are defined with respect to the direction of flow E in the compressor casing 200.

[0052] Compared to the previous embodiment, the variation in height of the annular cavity 250 between the first 255 and second 256 portions is achieved by the variable height H210 of the slots 210 and by the different heights, along the radial direction DR, of the front bottom 251 and the rear bottom 252 of the annular cavity 250. Furthermore, the variation in height H210 of the slots 210 is discrete; thus, the slots 210 have either a height equal to H210min or a height equal to H210max. This simplifies the manufacturing of the slots 210. Figure 6 schematically and partially shows a cross-sectional view along the radial and axial directions of a compressor housing 300 according to a third embodiment.According to the invention and as explained with reference to Figures 1 to 4, the housing comprises an inner annular wall 301 and an outer annular wall 302 defining between them an annular cavity 350 extending lengthwise along the axial direction DA between the front bottom 351 and the rear bottom 352 and heightwise along the radial direction DR between the inner face 3021 of the outer annular wall 302 and the outer face 3011 of the inner annular wall 301. The inner annular wall 301 comprises a plurality of slots 310 opening into the annular cavity 350, the slots 310 being arranged next to each other along the circumferential direction DC and extending lengthwise along the axial direction DA between the front bottom 351 and the rear bottom 352 and heightwise along the radial direction DR.

[0053] The annular cavity 350 has a first portion 355 located above, in the radial direction DR, the upstream part of the slots 310 and a second portion 356 located downstream of said first portion 355. The height H355 of the first portion 355 of the annular cavity 350 is greater than the height H356 of the second portion 356. The terms "upstream" and "downstream" are defined with respect to the direction of flow E in the compressor casing 300.

[0054] Compared to previous embodiments, the height variation of the annular cavity 350 is achieved by varying the height H310 of the slots 310, which varies between H310min and H310max. The front bottom 351 and the rear bottom 352 of the annular cavity 350 have the same height along the radial direction DR.

[0055] In this embodiment, the height variation between the two portions 355 and 356 of the annular cavity 350 does indeed reduce the velocity of the air, drawn from the second portion 356, in the annular cavity 350 before it passes through the first portion 355 and is reinjected into the compressor flow stream. However, it does not induce a radial velocity component directed towards the flow stream.

[0056] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. Compressor (101) housing (100, 200, 300) of a turbomachine comprising an inner annular wall (101, 201, 301) and an outer annular wall (102, 202, 302) delimiting between them an annular cavity (150, 250, 350) extending lengthwise in an axial direction (DA) between a front end (151, 251, 351) and a rear end (152, 252, 352) and heightwise in a radial direction (DR) between an inner face (1021, 2021, 3021) of the outer annular wall (102, 202, 302) and an outer face (1011, 2011, 3011) of the inner annular wall (101, 201, 302) 301), the internal annular wall of the housing comprising a plurality of slots (110, 210, 310) opening into the annular cavity, the slots being arranged next to each other in a circumferential direction (DC) and extending lengthwise in the axial direction between the front bottom and the rear bottom and heightwise in the radial direction, along the axial direction, the annular cavity comprises a first portion (155, 255, 355) located above, along the radial direction, an upstream part of the plurality of slots and a second portion (156, 256, 356) located downstream of said first portion, the height of the annular cavity in the first portion (H 155, H255, H355) being greater than that of the second portion (H 156, H256, H356), the housing being characterized in that the height (H110, H210, H310) of the slots is variable along the axial direction.

2. Housing according to claim 1, wherein the variation of the height (H210) of the slots is discrete along the axial direction.

3. Housing according to claim 1, wherein the variation in height (H 110, H310) of the slots is gradual along the axial direction.

4. Housing according to any one of claims 1 to 3, wherein, along the axial direction, the height (H 110) of the slots increases until reaching a maximum height (H110max) at a first point in a direction extending from the front bottom to the rear bottom of the annular cavity, and then is constant until the rear bottom of the annular cavity.

5. Housing according to any one of claims 1 to 4, wherein, along the axial direction and in a direction extending from the front bottom to the rear bottom of the annular cavity, the height (H 150) of the annular cavity is maximum (H 155) up to a second point, decreasing until a third point downstream of said second point, and then is constant (H 156) until the rear bottom of the annular cavity.

6. Housing according to claim 5 in combination with claim 4, wherein the first point is located upstream of the second point in the axial direction.

7. Carter (100) according to any one of claims 1 to 6 comprising a processing ring (130) having the inner annular wall (101) and a master ring (140) having the outer annular wall (102), the processing ring being fixed on the master ring.

8. Carter according to claim 7, wherein the processing ring and the master ring are made of the same material.

9. Turbomachine compressor (101) comprising a casing (100) according to any one of claims 1 to 8.

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