Non-axisymmetric casing treatment with corrugated plenum

Abstract

Non-axisymmetric casing treatment with corrugated plenum A turbomachine compressor casing (300) comprises an inner annular wall (111) and an outer annular wall (121) delimiting between them an annular cavity (130), the annular cavity extending in an axial direction (DA) between a front end wall (131) and a rear end wall (132) and in a radial direction (DR) between an inner face (1210) of the outer annular wall and an outer face (1111) of the inner annular wall. The inner annular wall of the casing comprises a plurality of slots (115) opening into the annular cavity (130), the slots being arranged next to each other in a circumferential direction (DC).The inner face (1210) of the outer annular wall (120) comprises concave portions and convex portions arranged alternately in the circumferential direction so as to define in the inner cavity (130) undulations (140) in said circumferential direction (DC). Figure for the abstract: Fig. 3.

Description

Title of the invention: Treatment of non-axisymmetric casing with corrugated plenum Technical field

[0001] The present invention relates to the general field of turbo-machine compressors, and more particularly to the treatment of the casing of turbo-machine compressors. Prior art

[0002] Turbomachine compressors consist of blades rotated inside a casing which ensures the sealing of the air stream with the exterior of the engine.

[0003] It is known that the clearance existing between the ends of the moving blades of the compressor and the casing forming the internal wall of the air flow vein degrades the efficiency of the turbomachine engine.

[0004] Furthermore, this clearance can modify and degrade the operation of the compressor to the point of the appearance of a pumping phenomenon which results from the detachment of the air flow from the surface of the blades. Controlling the circulation of air at the tip of the blades constitutes a major challenge in order to obtain both good aerodynamic efficiency of the compressor and a sufficient margin against the pumping phenomenon.

[0005] In order to limit the impact of this parasitic flow between the end of the blades and the casing, the internal surface of the casing can be treated locally by digging slots arranged in the thickness of the casing 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 non-axisymmetric with respect to the axis of rotation of the compressor: they are therefore non-axisymmetric casing treatments or TCNA.

[0006] The presence of these slots will locally modify the flow. The objective is to influence the appearance of the mechanisms responsible for the compressor starting to surge. An effective crankcase treatment will increase the compressor's operability range by delaying the appearance of these mechanisms, in particular by reducing aerodynamic blockage at the wheel head.

[0007] Some TCNA concepts propose the addition of an annular cavity or "plenum" in the casing as described for example in document WO9420759, which amounts to adding a cavity above the slots. This cavity extends over the entire circumference of the casing and connects the slots together. 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 amplify the TCNA's ability to increase the pumping margin.

[0008] The annular cavity is useful for allowing a fraction of fluid to be taken through one slot and reinjected through different slots, which improves the efficiency of the casing treatment (compared to a casing treatment without an annular cavity). However, this mechanism is not optimal because the reinjection is distributed between several slots and some of these slots are not in a good position relative to the rotor at the time of reinjection.

[0009] It is therefore desirable to be able to better control the sampling and reinjection zones at the level of the slots. Statement of the invention

[0010] For this purpose, the invention proposes a turbomachine compressor casing comprising an inner annular wall and an outer annular wall delimiting between them an annular cavity, the annular cavity extending in an axial direction between a front bottom and a rear bottom and in a radial direction between an inner face of the outer annular wall and an outer face of the inner annular wall, the inner annular wall of the casing comprising a plurality of slots opening into the annular cavity, the slots being arranged next to each other in a circumferential direction, the slots extending lengthwise along a longitudinal axis between the front bottom and the rear bottom in the axial direction,characterized in that the internal face of the external annular wall facing the plurality of slots of the internal annular wall comprises concave portions and convex portions arranged alternately in the circumferential direction so as to define in the internal cavity undulations in said circumferential direction, the concave portions and the convex portions each extending between the front bottom and the rear bottom of the internal cavity in a longitudinal direction,

[0011] in that said longitudinal direction forms a non-zero angle with the longitudinal axis of the slots, ,

[0012] or in that said longitudinal direction is parallel to the longitudinal axis of the slots, each corrugation extending in this case in the circumferential direction over two or more adjacent slots.

[0013] In the case where the concave portions and the convex portions each extend between the front bottom and the rear bottom of the internal cavity in a longitudinal direction forming a non-zero angle with the longitudinal axis of the slots, the concave portions forming circulation channels for the flow in the internal cavity make it possible to shift the sampling zone and the reinjection zone of the fluid to the slot level. Depending on the value of the angle, it is possible to determine the slot(s) from which the fluid is taken into the internal cavity and the slot(s) from which the fluid is reinjected.

[0014] In the case where the concave portions and the convex portions each extend between the front bottom and the rear bottom of the internal cavity in a longitudinal direction parallel with the longitudinal axis of the slots and with each corrugation extending in the circumferential direction over two or more adjacent slots, it is also possible to have an exchange between several adjacent slots in the same circulation channel for the flow in the internal cavity and to shift the sampling zone and the reinjection zone of the fluid at the slots.

[0015] Thanks to the presence of corrugations, it is possible to better control the flow path in the annular cavity. Guiding the flow by the corrugations in the internal cavity makes it possible to optimize the operation of the non-axisymmetric casing treatment (TCNA). Indeed, it is thus possible to control the slot(s) through which a fraction of the flow is reinjected and, consequently, the time of reinjection relative to the position of the rotor, which makes it possible to increase the pumping margin gain. The operation of the TCNA is also optimized by reducing pressure losses during circulation in the internal cavity by limiting the azimuthal migration of the sampled flow.

[0016] The non-zero angle formed between the longitudinal direction of the concave portions and the convex portions and the longitudinal axis of the slots is between -60° and +60°, preferably between -40° and +40°.

[0017] According to another particular characteristic of the invention in the case of a non-zero angle formed between the longitudinal direction of the concave portions and the convex portions and the longitudinal axis of the slots, each concave portion has a width at least equal to a width of a slot in the internal annular wall.

[0018] According to another particular characteristic of the invention in the case of a non-zero angle formed between the longitudinal direction of the concave portions and the convex portions and the longitudinal axis of the slots, the number of undulations present on the internal face of the external wall is between 0.1 and 1 times the number of slots present in the internal annular wall.

[0019] According to another particular characteristic of the invention, the amplitude of the undulations formed by the concave portions and the convex portions arranged alternately in the circumferential direction is between 0.2 and 5 times the height of the slots in the internal annular wall.

[0020] According to another particular characteristic of the invention, the casing comprises a treatment ring comprising the internal annular wall and a master ring comprising the external annular wall, the treatment ring being fixed on the ring master.

[0021] According to another particular characteristic of the invention, the treatment ring and the master ring are made of the same material.

[0022] The invention also relates to a turbomachine compressor comprising a casing according to the invention. Brief description of the drawings

[0023] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate exemplary embodiments thereof which are not in any limiting nature.

[0024] [Fig-1] [Fig.l] is a schematic perspective view of a turbine compressor machine according to one embodiment of the invention,

[0025] [Fig.2] [Fig.2] is a schematic and partial view showing undulations present on the internal face of the master ring of the compressor of [Fig.l],

[0026] [Fig.3] [Fig.3] is a schematic and partial view of the casing of the compressor of [Fig.l],

[0027] [Fig.4] [Fig.4] is a radial sectional view along section plane IV-IV on the casing of [Fig.3],

[0028] [Fig.5] [Fig.5] is a radial sectional view along section plane VV on the casing of [Fig.3]. Description of the embodiments

[0029] [Fig.l] represents a turbomachine compressor 300 according to an embodiment of the invention. The compressor 300 comprises around its axis A300 a rotor 200 equipped with a plurality of mobile blades 210 surrounded by a casing 100.

[0030] The housing 100 includes a treatment ring 110 and a master ring 120 which is structural. In the example described herein, the treatment ring 110 includes a flange 116 which is attached to a flange 126 of the master ring 120.

[0031] As illustrated schematically and partially in [Fig. 3], the master ring 120 comprises an outer annular wall 121 while the treatment ring 110 comprises an inner annular wall 111 opposite the outer annular wall 121. The inner annular wall 111 and the outer annular wall 121 each extend in length along a circumferential direction Dc, in width along an axial direction DA corresponding to the axis of the compressor 300 and in thickness along a radial direction DR. The inner annular wall 111 and the outer annular wall 121 delimit between them an annular cavity 130 forming a plenum. The internal annular cavity 130 extends in the axial direction DA between a front bottom 131 and a rear bottom 132 and in the radial direction DR between an internal face 1210 of the external annular wall 121 and an external face 1111 of the internal annular wall 111.

[0032] The internal annular wall 111 comprises a plurality of slots 115 hollowed out (or cut out) in the thickness of the wall, each slot 115 opens both onto an internal face 1110 and onto the external face 1111 of the internal annular wall 111 so as to put a flow vein E into communication with the annular cavity 130, the arrow E indicating the direction of the flow in the compressor and, consequently, the upstream and downstream sides thereof.

[0033] The slots 115 are arranged uniformly next to each other in the inner annular wall 111 along the circumferential direction Dc. Each slot 115 extends in length along a longitudinal axis An5 over a determined length Ln5 and in height along the radial direction DR over a height Hn5. In the example described here, the longitudinal axis An5 of the slots 115 is parallel to the axial direction DA. However, it may form an angle with the axial direction DA between -60° and +60°.

[0034] In the example described here, the slots 115 are inclined at 45° relative to the radial direction DR. The slots 115 may be inclined at an angle other than 45° or be parallel to the radial direction DR.

[0035] In a known manner, the slots 115 and the annular cavity 130 into which they open constitute a non-axisymmetric casing treatment or TCNA which makes it possible to locally modify the flow in order to reduce the mechanisms responsible for the compressor starting to surge.

[0036] According to the invention, the internal face 1210 of the external annular wall 121 facing the plurality of slots 115 of the internal annular wall 111 comprises concave portions 1212 and convex portions 1213 arranged alternately in the circumferential direction Dc so as to define in the internal cavity 130 undulations in the circumferential direction Dc (figures 2, 4 and 5).

[0037] As illustrated in [Fig.2], the concave portions 1212 and the convex portions 1213 each extend between the front bottom 131 and the rear bottom 132 of the internal cavity 130 in a longitudinal direction Di40. The concave portions 1212 define circulation channels for channeling the flow in the internal cavity 130.

[0038] In the example described here, the longitudinal direction of the concave 1212 and convex 1213 portions forms an angle [3i40] with the longitudinal axis A1 15 of the slots 115. The angle |3i40 is between -60° and +60°, preferably between -40° and +40°. The concave portions forming circulation channels for the flow in the internal cavity, it is thus possible to offset the sampling zone and the reinjection zone of the fluid at the slots. Depending on the value of the angle [3i40], it is possible to determine the slot(s) from which the fluid is sampled in the internal cavity and the slot(s) from which the fluid is reinjected.

[0039] An example of a shift between the sampling zone and the reinjection zone in the internal cavity is illustrated in Figures 4 and 5 which correspond to radial sections of the casing of [Fig.3]. The section plane of [Fig.4] is located upstream of the leading edge 211 of the blades 210 of the rotor 200 in the axial direction and intersects the slots 115 in their upstream part. The section plane of [Fig.5] is located downstream of the leading edge 211 of the blades 210 of the rotor 200 in the axial direction and intersects the slots 115 in their downstream part. The slots 1151 to 1156 shown in Figures 4 and 5 correspond to the same slots of the internal annular wall 111. Similarly, the concave portion 12121 shown in Figures 4 and 5 corresponds to the same concave portion of the external annular wall 121 which defines a circulation channel 136.The concave portion 12121 has a different azimuthal position between figures 4 and 5 due to the angle |3i40 formed between the longitudinal direction Di40 of the concave and convex portions and the longitudinal axis An5 of the slots which here coincides with the axial direction DA corresponding to the axis of the compressor 300 ([Fig.3]). In the example described here, the angle [3i40 is approximately 37°.

[0040] Due to the inclination of the concave portion 1212i relative to the longitudinal axis of the slots, a fraction FE of the flow is taken by the slots 1154 and 1155 as shown in [Fig. 5]. The fraction FE is then channeled into the circulation channel 136 to be reinjected into the flow vein E by the slots 1153 and 1154 as shown in [Fig. 4]. It can be seen here that the inclined concave portions make it possible to channel the flow so that it passes from the slot 1155 to the slot 1153 during its passage in the internal cavity, that is to say with an azimuthal offset of two slots in the example considered here.

[0041] Each concave portion 1212 has a width li2i2 at least equal to a width 1 in of the slots 115 (figures 2 and 3).

[0042] The amplitude of the undulations corresponding to the height H1212 of the concave portions 1212 is between 0.2 and 5 times the height Hn5 of the slots 115 (figures 3 and 4).

[0043] The number of undulations is between 0.1 and 1 times the number of slots 115 present on the treatment ring 110.

[0044] The number of slots 115 present on the treatment ring 110 is between 2 and 10, the number of blades 210 of the rotor 200. The number of slots can typically be 5 for a blade.

[0045] The master ring and the treatment ring are preferably made of the same material or of materials having similar thermal expansion coefficients in order to avoid differential expansions between the two rings which could lead to mechanical stresses and / or sealing problems in the casing.

[0046] The expression “between ... and ...” must be understood as including the limits.

Claims

1.

2.

3.

4. Claims Casing (100) of a turbomachine compressor (300) comprising an inner annular wall (111) and an outer annular wall (121) delimiting between them an annular cavity (130), the annular cavity extending in an axial direction (DA) between a front bottom (131) and a rear bottom (132) and in a radial direction (DR) between an inner face (1210) of the outer annular wall and an outer face (1111) of the inner annular wall, the inner annular wall (111) of the casing comprising a plurality of slots (115) opening into the annular cavity (130), the slots being arranged next to each other in a circumferential direction (Dc), the slots extending lengthwise along a longitudinal axis (An5) between the front bottom (131) and the rear bottom (132) in the axial direction,characterized in that the inner face (1210) of the outer annular wall (121) facing the plurality of slots (115) of the inner annular wall (111) comprises concave portions (1212) and convex portions (1213) arranged alternately in the circumferential direction so as to define in the inner cavity (130) undulations (140) in said circumferential direction (Dc), the concave portions (1212) and the convex portions (1213) each extending between the front bottom (131) and the rear bottom (132) of the inner cavity (130) in a longitudinal direction (Di40), in that said longitudinal direction forms a non-zero angle (Pi40) with the longitudinal axis (An5) of the slots (115), or in that said longitudinal direction is parallel to the longitudinal axis of the slots, each undulation extending in the circumferential direction over two or more adjacent slits., Housing according to claim 1, in which the non-zero angle (Pi40) formed between the longitudinal direction (Di40) of the concave portions (1212) and the convex portions (1213) and the longitudinal axis (An5) of the slots (115) is between -60° and +60°. Housing according to claim 2, in which each concave portion (1212) has a width (11212) at least equal to a width of a slot (115) of the internal annular wall (111). Housing according to claim 2 or 3, in which the number of undulations present on the internal face (1210) of the external wall (121) is between 0.1 and 1 times the number of slots (115) present. in the inner annular wall (111).

5. A casing according to any one of claims 1 to 4, wherein the amplitude of the undulations formed by the concave portions (1212) and the convex portions (1213) arranged alternately in the circumferential direction (Dc) is between 0.2 and 5 times the height (Hn5) of the slots (115) of the inner annular wall (111).

6. A housing according to any one of claims 1 to 5, comprising a treatment ring (110) having the inner annular wall (111) and a master ring (120) having the outer annular wall (121), the treatment ring being fixed to the master ring.

7. A housing according to claim 6, wherein the treatment ring and the master ring are made of the same material.

8. A turbomachine compressor (300) comprising a casing (100) according to any one of claims 1 to 7.

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