Casing with slots comprising a plurality of stages

Abstract

A first object of the invention relates to an aircraft turbomachine comprising a turbomachine rotor of axis X and a rotor casing, said casing comprising an inner wall with straight axial slots (20), each straight axial slot (20) comprises two flanks (20d, 20g) that are inclined with respect to a radius R of axis X. The straight axial slots (20) are arranged in a first peripheral ring and they are extended by curved slots (22) connecting an upstream part (200) of one straight axial slot (20) to a downstream part (201) of another straight axial slot (20). The curved slots allow the downstream part of one or a plurality of straight axial slots of the first ring to communicate with the upstream part of another or a plurality of other straight axial slots that are azimuthally offset, that is to say circumferentially offset.

Description

DESCRIPTION TITLE: SLOTTED CRANKCASE WITH MULTIPLE STAGES TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of enclosed turbomachinery and more particularly enclosed turbomachinery compressors.

[0002] The present invention relates to the external wall of these turbomachines or casings, located radially above the rotors of axial compressors of booster type (Low Pressure Compressor: CoBP) or high pressure compressor (CoHP) or blowers.

[0003] It concerns the passive control of flows via crankcase treatment technology with plenum, which are local modifications in the shape of the external envelope of the aerodynamic duct, radially above the rotor wheels, with a peripheral cavity or plenum. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0004] To influence the activation of the mechanisms responsible for the compressor's pumping action, it is known to modify the internal profile of the casing by creating axial slots. These slots are arranged along the circumference of the casing in the azimuthal direction. They are located vertically, or "radially above" the compressor blades, and are inclined.

[0005] The presence of these slots will locally modify the flow. Effective casing treatment will increase the compressor's operating range by delaying the onset of these mechanisms, particularly by reducing aerodynamic blockage at the rotor head. The overall slot shape is ideally optimized to minimize pressure losses within the slot and facilitate fluid circulation. The slots are positioned straddling the leading edge of the rotor head profile: the upstream portion of the slots is upstream of the leading edge and the downstream portion of the slots is downstream of the leading edge, generally within the first 30% of the rotor head profile.

[0006] The terms "upstream" and "downstream" are used in relation to the direction of the main flow in the compressor.

[0007] The main drawback of this solution is its tendency to negatively impact compressor efficiency by generating additional losses.

[0008] There are also solutions that add a "plenum," which is essentially a peripheral cavity above the slots. This peripheral cavity extends around the entire circumference of the housing. Its axial length is identical to the axial length of the slots. It connects the upper parts of the slots to each other. This peripheral 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 peripheral cavity.

[0009] Adding the plenum modifies the crankcase's behavior. Specifically, it alters the balance between improved operability and reduced efficiency. This solution offers a good balance between operability and efficiency.

[0010] It was proposed to play with the orientation of the slits, with walls that do not have the same circumferential inclination.

[0011] These solutions present a major drawback: because the circumferential inclination of the slots is always in the direction of rotor rotation to ensure proper crankcase treatment, as this inclination facilitates fluid penetration into the slots and is essential on the downstream side, it is problematic on the upstream side. Indeed, while the downstream side operates primarily in extraction mode, the upstream side operates primarily in injection mode, and the optimal reinjection angle is not compatible with this inclination. Thus, vortices can appear intermittently in the upstream part of the slot (a vortex forms when the pressure gradient between the plenum and the vein is low). When present, this vortex blocks reinjection. This intermittent reduction in the reinjection flow rate negatively impacts the effectiveness of the crankcase treatment.

[0012] On the other hand, the air circulating in the plenum can reach a significant speed since it covers the entire periphery of the crankcase and it is not possible to control where the reinjection into the vein will take place.

[0013] It has also been proposed to redirect the air between a first position on the rotor head profile downstream of the leading edge of a blade and a second position upstream of the leading edge of the same blade using a series of small ducts. Individual units are inserted into the rotor housing. However, the drawback is that the technology cannot adapt to changes in the rotor flow: depending on the operating speed, the optimal positions and orientations for sampling / reinjection are not necessarily the same. Furthermore, this type of housing treatment is complicated to implement: machining and assembling the pipes is complex. SUMMARY OF THE INVENTION

[0014] The invention offers a solution to the problems mentioned above, by improving aerodynamics and retaining the advantages of the axial slotted casing treatment with plenum while improving its ability to reinject air upstream of the rotor without degrading its ability to draw air above the rotor.

[0015] A first object of the invention relates to an aircraft turbomachine comprising a turbomachine rotor with axis X and a housing, said housing comprising an inner wall with straight axial slots, each straight axial slot comprising two flanks inclined with respect to a radius R of axis X. It is characterized in that the straight axial slots are arranged in a first peripheral ring and are extended by curved slots connecting an upstream portion of one straight axial slot to a downstream portion of another straight axial slot. The curved slots allow communication between the downstream portion of at least one straight axial slot of the first ring and the upstream portion of at least one other straight axial slot offset azimutally, that is to say, circumferentially offset.

[0016] The invention thus makes it possible to reduce losses in the section dedicated to injection into the vein while maintaining good sampling quality in the downstream section. The air entering the downstream section of the straight axial slit is channeled through the curved slit until it exits through the upstream section of another straight axial slit.

[0017] Unlike the concept where the upper part consists of a circumferential cavity or "plenum", in which the flow can have a significant circumferential velocity (> 100 m / s), in the present invention, the presence of curved slots above the first ring strongly limits this circumferential component by recovering the flow taken downstream and bringing it towards one or more straight axial slot(s) offset azimutally. This circumferentially separates the extraction and reinjection into the vein.

[0018] Compared to local recirculation concept solutions via a pipe, the invention allows differentiation of the circumferential position of sampling and reinjection, while maintaining suction through a straight axial slot above the blade.

[0019] An axial slit extends axially and includes a radial depth measured between an internal radial opening and an external radial bottom.

[0020] Advantageously, the outer radial end of a straight axial slit comprises an opening onto a curved slit and another opening onto a different curved slit. Advantageously, the curved slits connect the upstream portion of a straight axial slit n to the downstream portion of a straight axial slit n+i, where i is an integer between 1 and 4. The circumferential offset between sampling and injection into the vein is one to four straight axial slits; that is, each curved slit connects the upstream portion of a straight axial slit of position n to the downstream portion of a straight axial slit n+i, circumferentially offset by one, two, three, or four straight axial slits. The air will therefore exit offset from its entry position by one to four straight axial slits.

[0021] Advantageously, the curved slits connect the upstream part of p straight axial slits to the downstream part of p straight axial slits, where p is an integer between 1 and 4. In this way, the air entering the downstream part of these p straight axial slits will be directed towards the upstream part of p straight axial slits, circumferentially offset by at least one straight axial slit.

[0022] Advantageously, the downstream portion of the p straight axial slits is connected by curved slits to the upstream portion of the straight axial slits, offset by a number p of straight axial slits. Thus, the air entering the downstream portion of these p straight axial slits will be directed towards the upstream portion of other p straight axial slits, circumferentially offset by p straight axial slits.

[0023] Advantageously, the curved slots have an S shape. This S shape constitutes baffles which selectively direct air from downstream to upstream; the more or less curved shape of the S is chosen according to the parameters of the compressor.

[0024] Advantageously, the curved slots are arranged in a second peripheral ring radially superimposed on the first peripheral ring. The fabrication and assembly of these two superimposed peripheral rings is easy, as the first ring is nested within the second.

[0025] Advantageously, the set of straight axial slots represents a sum of openings between 40% and 60%, preferably greater than or equal to 40% of the internal wall of the housing covered by said straight axial slots.

[0026] Advantageously, straight axial slits have a radial height less than the height of curved slits.

[0027] A second aspect of the invention relates to an assembly of a rotor and a housing having at least one of the preceding characteristics, the rotor comprising blades arranged opposite the slots.

[0028] Advantageously, the rotor rotates in one direction, and the straight axial slots are inclined in the direction of rotor rotation. Conventionally, the definition of inclination is that a positive angle corresponds to an inclination in the direction of rotor rotation; therefore, the inclination of the straight axial slots is positive. Thus, the radially external bottom of a straight axial slot is angularly offset in the direction of rotation relative to the radially internal opening of the same right axial slot. In other words, when viewing the rotor from the side where it rotates counterclockwise, a ray passing through the center of the internal opening is angularly to the right of the ray passing through the radially external bottom of the axial slot.

[0029] A third aspect of the invention relates to a turbomachine comprising an assembly according to the second aspect of the invention.

[0030] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0031] The figures are presented as an example and in no way limit the invention.

[0032] [Fig. 1] is an overall perspective view of a rotor and a housing according to the invention,

[0033] [Fig. 2] is a radial view of the housing with a blade,

[0034] [Fig. 3] is a close-up perspective view of a first example of an embodiment of the invention seen from the vein,

[0035] [Fig. 4] is a radial cross-sectional view of the first example in Figure 3, viewed from outside the rotor.

[0036] [Fig. 5] is a cross-sectional view of the slots in figures 3 and 4,

[0037] [Fig. 6] is a close-up perspective view of a second embodiment of the invention seen from the vein,

[0038] [Fig. 7] is a radial cross-sectional view of the second example in Figure 6, viewed from outside the rotor.

[0039] [Fig. 8] is a cross-sectional view of the slots in figures 6 and 7,

[0040] [Fig. 9] is a close-up perspective view of a third embodiment of the invention seen from the vein,

[0041] [Fig. 10] is a radial cross-sectional view of the third example in Figure 9, viewed from outside the rotor.

[0042] [Fig. 11] is a cross-sectional view of the slots in figures 9 and 10,

[0043] [Fig. 12] is a close-up perspective view of a fourth embodiment of the invention seen from the vein,

[0044] [Fig. 13] is a radial cross-sectional view of the fourth example in Figure 12, viewed from outside the rotor.

[0045] [Fig. 14] is a cross-sectional view of the slots in figures 12 and 13. DETAILED DESCRIPTION

[0046] The figures are presented for illustrative purposes only and are in no way limiting to the invention.

[0047] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0048] Assembly 1, according to one aspect of the invention, comprises a housing 2 and a rotor 3. The rotor 3 is equipped with blades 30 and rotates about an axis X in the direction of arrow S. As shown in Figure 1, the housing 2 comprises, on an inner wall 21, straight axial slots 20 uniformly distributed around its entire inner periphery. These straight axial slots 20 represent a sum of openings between 40% and 60%, preferably greater than or equal to 40% of the inner wall of the housing covered by said straight axial slots 20.

[0049] Air flows along arrow A, the direction of airflow defining the upstream and downstream sections. This air flows in a channel 4 located between the housing 2 and the hub 31.

[0050] The blades 30 comprise a leading edge 300 and a trailing edge 301, and have a length Lx along the X axis, as illustrated in Figure 2. The leading edge 300 of the blades 30 is opposite the straight axial slots 20 and covers only a part of them.

[0051] Each straight axial slot 20 comprises two parallel flanks 20d and 20g inclined in the direction of rotation of the rotor 3. These straight axial slots 20 are arranged in a first peripheral ring 2A, which constitutes a first stage. The straight axial slots 20 extend into curved slots 22, which constitute a second stage. The curved slots 22 comprise two parallel flanks 22d and 22g oriented radially. This second stage can be implemented in the housing 2 or in a second peripheral ring 2B in which the first peripheral ring is nested.

[0052] The leading edge 300 of the blades defines an upstream part 200 and a downstream part 201 of the right axial slot 20.

[0053] In the first example illustrated in figures 3, 4 and 5, the curved slots 22 connect a downstream part 201 n+1 of a straight axial slot 20 of position n+1 to an upstream part 200n of a straight axial slot 20 of position n. In the present description, the positions n increment in the opposite direction of rotation S of the rotor 3, that is to say that n increases in the direction of rotation S.

[0054] The air flows through the curved slots 22 in the same direction S as the blades, it enters through the downstream part 201 n+1 of a straight axial slot 20n+1 and exits through the upstream part 200n of the straight axial slot 20n.

[0055] In the second example of figures 6 to 8, the curved slots 22 connect a downstream part 201 n-1 of a straight axial slot 20 of position n-1 to an upstream part 200n of a straight axial slot 20 of position n. In this example, the air flows in the curved slots 22 in the opposite direction to the direction of rotation S of the blades 30, it enters through the downstream part 201 n-1 of a straight axial slot 20n-1 and exits through the upstream part 200n of the straight axial slot 20n.

[0056] The third example, illustrated in Figures 9 to 11, involves curved slots 22 connecting a downstream portion 201n+2 of a straight axial slot 20 at position n+2 to an upstream portion 200n of a straight axial slot 20 at position n, representing an offset of two straight axial slots. In this example, air flows through the curved slots 22 in the same direction of rotation S as the blades 30; it enters through the downstream portion 201n+2 of a straight axial slot 20n+2 and exits through the upstream portion 200n of the straight axial slot 20n.

[0057] Up to four straight axial slots 20 apart can be connected by a curved slot 22, in the direction of rotation or in the opposite direction.

[0058] The fourth example illustrated in figures 12 to 14, the curved slots 22 connect the downstream parts 201 n+3 and 201 n+2 of two straight axial slots 20 of position n+2 and n+3 to an upstream part 200n of two straight axial slots 20 of position n and n+1, i.e. an offset of four straight axial slots between the last upstream inlet and the first downstream outlet in the direction of rotation of the rotor 3. In this example, the air flows in the curved slots 22 in the direction of rotation S that the blades 30, it enters through the downstream part 201 n+3 or 201 n+4 of a straight axial slot 20n+3 or 20n+4 and exits through the upstream part 200n or 200n+1 of the straight axial slot 20n or 20n+1. This shift results in fewer losses and better performance in certain configurations.

[0059] Up to four straight axial slits 20 can be grouped with a single curved slit 22.

[0060] The air circulation occurs as follows: air enters the turbomachine, the rotor blades 30 drive the rotating air into the duct 4, and a portion enters the downstream parts 201 of the straight axial slots 20. the air is directed by the curved slits of the downstream part of at least one straight axial slit 20 towards the upstream part of at least one straight axial slit 20 offset by one or more straight axial slits, the air exits through the upstream part 200 of at least one straight axial slit 20.

Claims

DEMANDS

1. Aircraft turbomachine comprising a turbomachine rotor of axis X and a housing (2) of said rotor, said housing (2) comprising an inner wall (21) with straight axial slots (20), each straight axial slot (20) comprising two flanks (20d, 20g) inclined with respect to a radius R of axis X, characterized in that the straight axial slots (20) are arranged in a first peripheral ring (2A) and are extended by curved slots (22) connecting an upstream part (200) of a straight axial slot (20) to a downstream part (201) of another straight axial slot (20).

2. Turbomachine according to claim 1, characterized in that the curved slots (22) connect the upstream part (200) of a straight axial slot (20) n to the downstream part (201) of a straight axial slot (20) n+i, with i is an integer between 1 and 4.

3. Turbomachine according to any one of the preceding claims, characterized in that the curved slots (22) connect the upstream part (200) of p straight axial slots (20) to the downstream part (201) of p straight axial slots (20).

4. Turbomachine according to the preceding claim, characterized in that the downstream part (201) of the p straight axial slots (20) are connected by the curved slots (22) to the upstream part (200) of the straight axial slots (20) offset by a number p of straight axial slots (20), with p being an integer between 1 and 4.

5. Turbomachine according to any one of the preceding claims, characterized in that the curved slots (22) have an S-shape.

6. Turbomachine according to any one of the preceding claims, characterized in that the curved slots (22) are arranged in a second peripheral ring (2B) radially superimposed on the first peripheral ring (2A).

7. Turbomachine according to any one of the preceding claims, characterized in that the straight axial slots (20) have a radial height less than the height of the curved slots (22). he

8. Turbomachine according to any one of the preceding claims, characterized in that the rotor (3) comprises blades (30) arranged opposite the right axial slots (20).

9. Turbomachine according to the preceding claim, characterized in that the rotor (3) rotates in a direction of rotation of turbomachine operation and that the flanks (20d, 20g) of the straight axial slots (20) are inclined in the direction of rotation of the rotor (3).

10. Turbomachine according to any one of the preceding claims, characterized in that the set of straight axial slots (20) represent a sum of openings greater than or equal to 40%, preferably between 40% and 60% of the inner wall of the casing covered by said straight axial slots (20).

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