Treatment of a non-axisymmetric casing comprising a plenum, with controlled opening
Patent Information
- Application Number
- EP2024702391
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-01-19
- Filing Date
- 2024-01-15
- Publication Date
- 2025-11-26
AI Technical Summary
Turbomachine compressors face efficiency degradation and pumping phenomena due to clearance between blades and casing, with existing non-axisymmetric casing treatments being inadequate for all operating regimes and prone to acoustic resonance issues.
A turbomachine compressor casing with a sliding ring in the annular cavity that can move between open and closed positions, allowing controlled communication between slots and an annular cavity, optimized by a pressurized air injection system and spring compression, to selectively engage or disengage the plenum for varying operating regimes.
This solution enhances the operating range of the compressor by delaying pumping mechanisms, reducing aerodynamic blocking, and avoiding acoustic resonance, while maintaining structural integrity and minimizing mass increase.
Smart Images
Figure FR2024050055_25072024_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title of the invention: Treatment of non-axisymmetric casing with controlled opening plenum
[0003] Technical Field
[0004] The present invention relates to the general field of turbomachine compressors, and more particularly to the treatment of the casing of turbomachine compressors.
[0005] Prior art
[0006] Turbomachine compressors consist of blades rotating inside a casing which seals the air stream with the outside of the engine.
[0007] It is known that the clearance between the ends of the compressor's moving blades and the casing forming the internal wall of the air flow vein degrades the efficiency of the turbomachine engine.
[0008] Furthermore, this clearance can modify and degrade the operation of the compressor until the appearance of a surge phenomenon which results from the air flow detaching from the surface of the blades. Controlling the air circulation at the tip of the blades is a major challenge to obtain both good aerodynamic efficiency of the compressor and a sufficient margin against the surge phenomenon.
[0009] In order to limit the impact of this parasitic flow between the tip 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.
[0010] The presence of these slots will locally modify the flow. The objective is to influence the appearance of the mechanisms responsible for the compressor surge. 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.
[0011] 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.
[0012] The presence of the annular cavity (plenum) in a TCNA is not necessarily of interest at all operating regimes. Indeed, for certain regimes, the slots are sufficient to ensure operability. In addition, the cavity necessarily has acoustic natural modes. If these natural modes are excited, acoustic resonance phenomena are likely to appear and cause compressor surge. Also, for certain compressors and for certain operating regimes, the TCNA without all or part of the annular cavity may have a better efficiency than the TCNA with annular cavity.
[0013] It is therefore desirable to be able to have a compressor casing having several TCNA configurations, namely a casing in which the communication between the slots and the annular cavity can be controlled.
[0014] Statement of the invention
[0015] To this end, the invention provides 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 comprising a plurality of slots hollowed out in the thickness of the inner annular wall, the slots being arranged next to each other in a circumferential direction and each extending in an axial direction, characterized in that the casing further comprises a sliding ring present in the annular cavity of said casing, the sliding ring being movable in the axial direction between an open position in which said slots present in the inner annular wall of the casing open into the annular cavity and a closed position in which the sliding ring covers at least certain slots so that they do not open into the annular cavity,the housing further comprising an actuating device for moving the sliding ring between the open and closed positions.,
[0016] The casing of the invention therefore makes it possible to optimize the treatment of non-axisymmetric casings according to the operating ranges of the compressor. Indeed, for the speeds which require it, the sliding ring is placed in the open position, which makes it possible to benefit from an additional margin for pumping by allowing the slots of the casing to open into the annular cavity or plenum. For the speeds or operating ranges where only the effect of the slots of the casing is necessary for the treatment, the sliding ring is placed in the closed position, which makes it possible in particular to avoid the acoustic modes which can develop in the annular cavity and which depend in particular on the rotation speed.
[0017] The use of a sliding 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.
[0018] According to a particular characteristic of the invention, the sliding ring is formed from a single piece. In this case, the actuating device may comprise a pressurized air injection system in communication with one or more injection orifices present in the downstream bottom of the annular cavity, a plurality of springs being held in compression between an upstream bottom of the annular cavity and the sliding ring. According to another particular characteristic of the invention, the sliding ring is divided into several annular sectors capable of sliding individually in the annular cavity in the axial direction. This makes it possible to selectively control the closing of the slots in the casing and to reduce the volume of the annular cavity for operating regimes where a reduced plenum volume is useful.In this case, the actuating device comprises a pressurized air injection system in communication with at least one injection orifice present in the downstream bottom of the annular cavity opposite each annular sector of the sliding ring, at least one spring being held in compression between an upstream bottom of the annular cavity and each annular sector of the sliding ring.
[0019] According to another particular characteristic of the invention, the sliding ring comprises cavities on its internal face opposite the external face of the internal annular wall, the cavities being positioned on the internal face of the sliding ring at locations determined so that the cavities coincide with the slots in the closed position. The cavities of the sliding ring may have an aerodynamic shape, such as for example a crescent shape, which makes it possible to reconstitute slots with an aerodynamic shape and thus limit losses.
[0020] According to another particular characteristic of the invention, the dimensions of the slots of the movable ring and of the openings of the casing are equal.
[0021] The invention also relates to a turbomachine compressor comprising a casing according to the invention.
[0022] 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 limiting in nature.
[0024] [Fig. 1] Figure 1 is a schematic and partial view of a turbomachine compressor with a casing equipped with a sliding ring in the open position according to an embodiment of the invention, [Fig. 2] Figure 2 is a schematic and partial view of a turbomachine compressor with a casing equipped with a sliding ring in the closed position according to an embodiment of the invention,
[0025] [Fig. 3] Figure 3 is an inclined view of the compressor of Figure 1,
[0026] [Fig. 4] Figure 4 is an inclined view of the compressor of Figure 2,
[0027] [Fig. 5] Figure 5 is a schematic perspective view of the sliding ring of the compressor casing of Figures 1 to 4,
[0028] [Fig. 6] Figure 6 is a detail view of a portion of the sliding ring of Figure 5.
[0029] Description of the embodiments
[0030] Figures 1 to 4 schematically and partially represent a turbomachine compressor 300 according to one embodiment of the invention. The compressor 300 comprises a rotor 200 equipped with a plurality of moving blades 210 surrounded by a casing 100.
[0031] The casing 100 comprises an inner annular wall 110 and an outer annular wall 120 each extending lengthwise in a circumferential direction D. c , in width along an axial direction D A and in thickness along a radial direction DR. The internal annular wall 110 and the external annular wall 120 delimit between them an annular cavity 130 forming a plenum.
[0032] The internal annular wall 110 comprises a plurality of slots 115 hollowed out (or cut out) in the thickness of the wall, each slot 115 opens onto both the internal face 111 and the external face 112 of the internal annular wall 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 110 along the circumferential direction D c . Each slot 115 extends over a determined length L115 in the axial direction D. A . In the example described here, the slots 145 are inclined at 45° relative to the radial direction DR.
[0034] 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.
[0035] According to the invention, the casing 100 further comprises a sliding ring 140 present in the annular cavity 130 and shown in full in FIG. 6. The sliding ring 140 is movable in the axial direction D A between an open position in which the slots 115 present in the internal annular wall 110 of the casing open into the annular cavity 130 (figures 1 and 3) and a closed position in which the sliding ring covers at least part of the slots 115 (figures 2 and 4). In the closed position, the slots covered by the sliding ring do not open into the annular cavity.
[0036] More precisely, the sliding ring 140 moves along the external face 112 of the internal annular wall 110 in the axial direction D A The sliding ring 140 has a length LI in the axial direction. 40 greater than or equal to the length L of the slots. The length L M o of the ring 140 is also determined so that the annular cavity 130 extends in the axial direction DA over a length LI 30 substantially equivalent to the length Lus of the slots 115 when the sliding ring is in the open position (figure 1).
[0037] In the example described here, the sliding ring 140 is in one piece so that, in the closed position, the ring covers all the slots 115 of the internal annular wall 110. In this case, no slot opens into the annular cavity 130.
[0038] According to a particular characteristic, the sliding ring 140 comprises cavities 145 on its internal face 141 opposite the external face 112 of the internal annular wall 110. The cavities 145 are positioned on the internal face 141 of the sliding ring at locations determined so that the cavities 145 coincide with the slots 115 in the closed position. In the example described here, the cavities 145 are oriented at 45° like the slots 115. The cavities 145 can have various shapes. They can in particular have an aerodynamic shape such as a lunule shape as shown in FIG. 6. In the closed position, the sliding ring 140 provided with the cavities 145 makes it possible to reconstitute slots with aerodynamic shapes, thus limiting losses.
[0039] The annular cavity 130 is closed on the upstream side by an upstream bottom 131 secured to the internal and external annular walls 110 and 120 and on the downstream side by a removable downstream flange or bottom 132. The removable flange 132 comprises one or more injection orifices 1320 opening into the annular cavity 130 opposite a downstream face 143 of the sliding ring 140.
[0040] The casing 100 comprises an actuating device formed here by an air injection system 10 connected to each injection orifice 1320. The injection of a pressurized air flow A via each orifice 1320 makes it possible to control the movement of the sliding ring 140 into the closed position (figure 2). The removable flange 132 is provided with O-rings 133 and 134 in order to ensure sealing between the vein and the exterior. Similarly, the sliding ring 140 is provided with O-rings 147 and 148 in order to ensure sealing between the ring and the exterior.
[0041] Several return springs 20 are further held in compression between the upstream bottom 131 of the annular cavity 130 and the upstream face 144 of the sliding ring 140. The return springs 20 are uniformly distributed in the annular cavity 130 in the circumferential direction D c The return springs 20 keep the sliding ring in the open position as long as no pressurized air is injected via the injection ports 1320.
[0042] According to an alternative embodiment, the sliding ring can be divided into several annular sectors capable of sliding individually in the annular cavity in the axial direction. In this case, the downstream flange or bottom comprises at least one injection orifice opposite each annular sector. The actuating device still comprises an air injection system but which is selectively connected, for example by means of valves, to each injection orifice so as to inject pressurized air independently for each annular sector. Each annular sector can also slide in guide rails present on the external face of the internal annular wall and / or on the internal face of the external annular wall of the casing. When the ring is provided with cavities, each annular sector comprises a number of cavities corresponding to the number of slots in the part of the internal annular wall to be covered.
[0043] It is thus possible to control, by selective injection of air under pressure, the movement into the closed position of only part of the annular sectors, the other annular sectors being held in the open position by the return springs.
[0044] The actuating device is not limited to the use of a pressurized air injection system. The actuating device may also use pistons or cylinders housed in the removable flange 132 or any other suitable actuating system.
[0045] Regardless of the embodiment, the slots in the housing can all be identical.
[0046] Regardless of the embodiment, the cavities of the sliding ring may all be identical. Advantageously, the cavities of the sliding ring and the slots of the housing have the same dimensions, i.e. they have the same length and the same width; and the distance between the slots of the housing is equal to the distance between the associated cavities of the sliding ring. This makes it possible to obtain cavities of the sliding ring coinciding with the slots of the housing.
[0047] Whatever the embodiment, the casing can be a single piece.
[0048] Whatever the embodiment, the number of slots in the casing (and therefore the number of cavities in the sliding ring) is between 40 and 850, for example between 45 and 810, for example between 60 and 210. Indeed, the casing treatment requires between 3 and 8 slots per rotor blade and a rotor comprises between 15 and 90 blades. This range of values therefore makes it possible to cover all the possibilities.
[0049] Regardless of the embodiment, the housing and sliding ring can be made of the same material. This allows both parts to undergo the same thermal and mechanical stresses and therefore ensures that the opening or closing of slots in the housing will always be possible, even in the event of thermal expansion.
[0050] Alternatively, the casing and the sliding ring can be made of different materials, but it is necessary that these two materials have similar or even identical physical properties so that their thermal expansion is similar.
[0051] The expression "between ... and ..." must be understood as including the limits.
Claims
Claims
1. Casing (100) of a turbomachine compressor (300) comprising an inner annular wall (110) and an outer annular wall (120) delimiting between them an annular cavity (130), the inner annular wall of the casing comprising a plurality of slots (115) hollowed out in the thickness of the inner annular wall, the slots being arranged next to each other in a circumferential direction (D c ) and each extending in an axial direction (D), the casing further comprising a sliding ring (140) present in the annular cavity (130) of said casing, the sliding ring being movable in the axial direction (D A) between an open position in which said slots (115) present in the inner annular wall (110) of the casing open into the annular cavity (130) and a closed position in which the sliding ring (140) covers at least some slots (115), the casing further comprising an actuating device for moving the sliding ring (140) between the open and closed positions, characterized in that the sliding ring (140) has cavities (145) on its inner face (141) facing the outer face (112) of the inner annular wall (110), the cavities being positioned on the inner face of the sliding ring at locations determined so that the cavities (145) coincide with the slots (115) in the closed position.
2. A housing according to claim 1, wherein the sliding ring (140) is formed in one piece.
3. Casing according to claim 2, in which the actuating device comprises a pressurized air injection system (10) in communication with one or more injection orifices (1320) present in the downstream bottom (132) of the annular cavity (130), a plurality of springs (20) being held in compression between an upstream bottom (131) of the annular cavity and the sliding ring (140).
4. A housing according to claim 1, wherein the sliding ring is divided into several annular sectors capable of sliding individually in the annular cavity in the axial direction.
5. Casing according to claim 4, in which the actuating device comprises a pressurized air injection system in communication with at least one injection orifice present in the downstream bottom of the annular cavity opposite each annular sector of the sliding ring, at least one spring being held in compression between an upstream bottom of the annular cavity and each annular sector of the sliding ring.
6. Casing according to any one of claims 1 to 5, in which the cavities (145) of the sliding ring (140) have an aerodynamic shape.
7. A housing according to any one of claims 1 to 6, wherein the dimensions of the cavities (145) of the sliding ring (140) and the slots (115) of the housing are equal.
8. A turbomachine compressor (300) comprising a casing (100) according to any one of claims 1 to 7.