Non-axisymmetric casing treatment with pilot-operated opening and plenum

Abstract

Non-axisymmetric card processing with controlled opening with plenum A turbomachine compressor casing (300) comprises an inner annular wall (310) and an outer annular wall (320) delimiting between them an annular cavity (330), the inner annular wall of the casing being provided with first slots (315). The casing comprises a movable ring (200) comprising the outer annular wall (320) and a plurality of closure bars (230) present opposite the outer face (312) of the inner annular wall (310), the bars delimiting between them second slots (240). The movable ring (200) slides between an open position in which the second slots (240) coincide with the first slots (315) and a closed position in which the closure bars (230) close the first slots (315). Figure for abstract: Fig. 2

Description

Title of the invention: Treatment of non-axisymmetric casing with controlled opening with 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 implementation of a TCNA formed by slots possibly associated with an annular cavity (plenum) is not necessarily of interest at all operating regimes. Indeed, the mechanisms responsible for the surge start only appear when the compressor is heavily loaded, which mainly corresponds to the transient phases (acceleration and deceleration). During the other operating phases corresponding to a large part of the compressor operating time, the presence of a TCNA results in a loss of efficiency.

[0009] It is therefore desirable to be able to have a compressor housing in which a TCNA can be selectively implemented, namely a housing in which it is possible to close all the constituent elements of the TCNA. 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 inner annular wall of the casing being provided with first slots hollowed out in the thickness of the inner annular wall, the first slots being arranged next to each other in a circumferential direction and each extending in an axial direction, characterized in that the casing comprises a fixed ring comprising the inner annular wall of the casing provided with the first slots, an upstream flange and a downstream flange extending in a radial direction from the inner annular wall, the upstream and downstream flanges being arranged on either side of the first slots in the axial direction and a movable ring present between the upstream and downstream flanges,the movable ring comprising the outer annular wall and a plurality of closure bars present opposite the outer face of the inner annular wall, the closure bars being arranged next to each other in the circumferential direction and delimiting between them second slots, the closure bars having a width equivalent to the width of the first slots, said closure bars extending in the radial direction from the outer face of the inner annular wall over a height less than the height of the annular cavity, and in that the movable ring slides in the circumferential direction between an open position in which the second slots coincide with the first slots and a closed position in which the closure bars close the first slots,the housing further comprising an actuating device for moving the movable ring between the opening and closing positions.

[0011] The casing of the invention therefore makes it possible to optimize the treatment of non-axisymmetric casing according to the operating ranges of the compressor. Indeed, for the speeds which require it, the movable ring is placed in the open position, which makes it possible to implement the treatment of non-axisymmetric casing with plenum and thus to benefit from an additional margin for pumping. For other speeds or operating ranges, the sliding ring is placed in the closed position in order to interrupt the implementation of the treatment of non-axisymmetric casing with plenum, which makes it possible to promote the efficiency of the compressor.

[0012] The use of a movable ring in the annular cavity of the casing further provides an optimized integration solution for compressor casings while limiting the increase in the overall mass of the casing and ensuring structural strength of the entire casing.

[0013] According to a particular characteristic of the invention, the movable ring comprises a ferrule and an annular cover, the closure bars being fixed between the ferrule and the annular cover.

[0014] According to another particular characteristic of the invention, one end of the closure bars comprises an anti-rotation element cooperating with a corresponding housing present in the ferrule, the opposite end of the closure bars being fixed to the annular cover by screws.

[0015] According to another particular characteristic of the invention, the actuating device comprises a rotary motor equipped with a cam cooperating with the movable ring, the cam being configured to slide the movable ring between the opening and closing positions.

[0016] According to another particular characteristic of the invention, the casing further comprises a tension spring connecting the movable ring to the fixed ring, the tension spring being configured to hold the movable ring in the open position.

[0017] According to another particular characteristic of the invention, the fixed ring and the movable ring are made of the same material.

[0018] The invention also relates to a turbomachine compressor comprising a casing according to the invention. Brief description of the drawings

[0019] 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 limiting in nature.

[0020] [Fig.l] [Fig.l] is a schematic perspective view of a turbomachine compressor casing according to one embodiment of the invention,

[0021] [Fig.2] [Fig.2] is a schematic view along a meridian section plane of the casing of [Fig.l],

[0022] [Fig.3] [Fig.3] is a schematic view along a meridian section plane of the casing of [Fig.l],

[0023] [Fig.4] [Fig.4] is a detail view of a portion of the movable ring of the casing of [Fig.l],

[0024] [Fig.5] [Fig.5] is another detail view of a portion of the movable ring of the casing of [Fig.l],

[0025] [Fig.6] [Fig.6] is a detail view of a portion of the casing of [Fig.l] showing a device for actuating the movable ring,

[0026] [Fig.7] [Fig.7] is a partial schematic view along an axial sectional plane of the casing of [Fig.l] showing the movable ring in a closed position,

[0027] [Fig.8] [Fig.8] is a partial schematic view along an axial sectional plane of the casing of [Fig.l] showing the movable ring in an open position. Description of the embodiments

[0028] Figures 1 to 3 schematically represent a casing 300 of a turbomachine compressor according to an embodiment of the invention, the casing 300 surrounding a rotor equipped with a plurality of moving blades (not shown in Figures 1 to 3).

[0029] The casing 300 comprises an internal annular wall 310 and an external annular wall 320 each extending in length along a circumferential direction Dc, in width along an axial direction DA and in thickness along a radial direction Dr. The internal annular wall 310 and the external annular wall 320 delimit between them an annular cavity 330 forming a plenum (figures 2 and 3).

[0030] The internal annular wall 310 comprises a plurality of slots 315 hollowed out (or cut out) in the thickness of the wall, each slot 315 opens onto both the internal face 311 and the external face 312 of the internal annular wall 310 so as to put a flow vein E into communication with the annular cavity 330, the arrow E indicating the direction of the flow in the casing and, consequently, the upstream and downstream sides thereof.

[0031] The slots 315 are arranged uniformly next to each other in the internal annular wall 310 in the circumferential direction Dc. Each slot 315 extends over a determined length L3i5 in the axial direction DA and over a width 1315 in the circumferential direction Dc.

[0032] The slots 315, the slots 240 described below and the annular cavity 330 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.

[0033] According to the invention, the casing 300 comprises a fixed or master ring 100 and a movable ring 200 capable of sliding around the fixed ring as explained in detail below.

[0034] The fixed ring 100 is in one piece and comprises the internal annular wall 310 of the casing 300 provided with the slots 315, an upstream flange 110 and a downstream flange 120 extending in a radial direction DR from the internal annular wall 310, the upstream and downstream flanges being arranged on either side of the slots 315 in the axial direction Da.

[0035] The movable ring 200 is arranged between the upstream flange 110 and the downstream flange 120 of the fixed ring 100. The movable ring 200 comprises a shell 210 and a cover 220 together defining the external annular wall 320 of the casing 300. The movable ring further comprises closure bars 230 mounted between a side wall 211 of the shell 210 and a side wall 221 of the cover 220. More precisely, the closure bars 230 are first each positioned on the side wall 211 of the shell 210 by means of an anti-rotation element 231 present at a first end 230a of the bars 230 which cooperates with a housing 2110 of corresponding shape present in the side wall 211 of the shell 210. By way of non-limiting example, the anti-rotation element 231 may correspond to a projection or a tenon of square or rectangular shape and the housing 2110 to a cavity or mortise of complementary square or rectangular shape.

[0036] Once all the closure bars 230 are thus positioned in the side wall 211 of the ferrule 210, the cover 220 is centered on the ferrule 210 and held in its centering position by screws 222 ([Fig. 5]). The closure bars 230 are secured to the cover 220 by countersunk head screws 223 screwed into a second end 230b of the bars (Figures 2 to 5).

[0037] When the movable ring 200 is mounted on the fixed ring 100, the closure bars 230 are opposite the external face 312 of the internal annular wall 310. The closure bars are arranged next to each other in the circumferential direction Dc and delimit between them slots 240 (Figures 4, 7 and 8). The casing treatment is mainly implemented by the slots 240 whose dimensions make it possible to guide the flow locally in an effective manner in order to prevent the occurrence of the mechanisms responsible for the compressor starting to surge. The influence of the slots 315 on the casing treatment is much less significant due to their small volume compared to that of the slots 240. The cavity 330 makes it possible to increase the gain in margin in pumping of the casing treatment.

[0038] The closing bars 230 have, along the circumferential direction Dc, a width l230 equivalent to the width l3i5 of the slots 315 present in the internal annular wall 310 along the circumferential direction ([Fig.7]). The slots 240 have along the circumferential direction Dc a width l240 equivalent to the width l316 of the solid portions 316 of the internal wall 310 present between the slots 315 ([Fig.7]). The closure bars 230 have, along the radial direction DR, a height H230 less than the height of the annular cavity 330 delimited between the internal annular wall 310 and the external annular wall 320.

[0039] As in the example described here, the movable ring 200 can be formed of two annular portions 200a and 200b ([Fig.l]). In this case, the two annular portions 200a and 200b are assembled together by screws 201 which ensure the positioning and maintenance thereof, but they can, instead, be assembled by any other assembly means, for example a system composed of a centering pin and a screw and nut assembly for holding in position. Having a movable ring formed of at least two annular portions makes it easier to mount the movable ring on the fixed ring.

[0040] In order to slide the movable ring 200 around the fixed ring 100, the casing 300 comprises a rotary electric motor 350 provided with a cam 351 ([Fig.6]). By pivoting, the cam 351 makes it possible to move the movable ring 200 along the circumference of the inner annular wall 310 of the casing 300. The cam 351 can bear on a portion 325 projecting from the outer face of the outer annular wall 320 of the casing in order to slide the movable ring 200. The electric motor 350 and the cam 325 make it possible to move the movable ring 200 by at least an amplitude equal to the width of a slot 315.

[0041] The casing 300 may also comprise a tension spring 360 connected to the movable ring 200 by a pin 370 fixed on said movable ring and to the fixed ring 100 by a pin 371 fixed between the upstream flange 110 and the downstream flange 120 of said fixed ring ([Fig.6]). The tension spring 360 is configured to automatically return the movable ring 200 to an active casing treatment position, i.e. to the position of the movable ring 200 in which the closure bars do not close the slots 315 of the casing. This position is defined as the default safety position of the casing.

[0042] The movable ring 200 slides in the circumferential direction between a closed position and an open position of the casing treatment. More specifically, [Fig. 7] illustrates the movable ring in the closed position in which the closure bars 230 close the slots 315 of the inner annular wall 310. Thus, in the closed position, the air flow F circulating inside the casing does not flow into the slots 244 and does not enter the annular cavity 330. There is therefore no TCNA implemented in the closed position, the slots 315 having a negligible aerodynamic effect. [Fig. 8] illustrates the movable ring in the open position in which the slots 240 present between the closure bars 230 coincide with the slots 315. Thus, in the open position, the air flow F circulating inside the casing can enter the annular cavity 330, which makes it possible to activate the TCNA with annular cavity or “plenum”.

[0043] Whatever the embodiment, the number of slots in the casing may be between 50 and 200, for example 180.

[0044] Regardless of the embodiment, the fixed ring and the movable ring can be made of the same material. This allows the two parts to undergo the same thermal and mechanical stresses and therefore ensures that the opening or closing of slots in the casing will always be possible, even in the event of thermal expansion.

[0045] Alternatively, the fixed ring and the movable ring can be made of different materials, but it is necessary for these two materials to have similar or even identical physical properties so that their thermal expansion is similar.

Claims

Claims

1. Turbomachine compressor casing (300) comprising an inner annular wall (310) and an outer annular wall (320) delimiting between them an annular cavity (330), the inner annular wall of the casing being provided with first slots (315) hollowed out in the thickness of the inner annular wall, the first slots (315) being arranged next to each other in a circumferential direction (Dc) and each extending in an axial direction (DA), characterized in that the casing comprises a fixed ring (100) comprising the inner annular wall (310) of the casing provided with the first slots (315), an upstream flange (110) and a downstream flange (120) extending in a radial direction (DR) from the inner annular wall (310), the upstream and downstream flanges being arranged on either side of the first slots (315) along the axial direction (DA) and a movable ring (200) present between the upstream and downstream flanges (110, 120),the movable ring comprising the outer annular wall (320) and a plurality of closure bars (230) present opposite the outer face (312) of the inner annular wall (310), the closure bars being arranged next to each other in the circumferential direction (Dc) and delimiting between them second slots (240), the closure bars (230) having a width (l230) equivalent to the width (l315) of the first slots (315), said closure bars extending in the radial direction (DR) from the outer face (312) of the inner annular wall (310) over a height (H23o) less than the height of the annular cavity (330), and in that the movable ring (200) slides in the circumferential direction (Dc) between an open position in which the second slots (240) coincide with the first slots (315) and a closing position in which the closing bars (230) close the first slots (315),the housing further comprising an actuating device for moving the movable ring between the open and closed positions.,

2. A housing according to claim 1, wherein the movable ring (200) comprises a ferrule (210) and an annular cover (220), the closure bars (230) being fixed between the ferrule and the annular cover.

3. A housing according to claim 2, wherein one end (230a) of the closure bars (230) comprises an anti-rotation element (231) cooperating with a corresponding housing (2110) present in the ferrule (210), the opposite end (230b) of the closure bars being fixed to the annular cover (220) by screws (223).

4. A housing according to any one of claims 1 to 3, wherein the actuating device comprises a rotary motor (350) equipped with a cam (351) cooperating with the movable ring (200), the cam being configured to slide the movable ring between the opening and closing positions.

5. A housing according to any one of claims 1 to 4, further comprising a tension spring (360) connecting the movable ring (200) to the fixed ring (100), the tension spring being configured to maintain the movable ring in the open position.

6. A housing according to any one of claims 1 to 5, wherein the fixed ring (100) and the movable ring (200) are made of the same material.

7. A turbomachine compressor comprising a casing (300) according to any one of claims 1 to 6.

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