Twisted slotted crankcase with plenum

Abstract

TWISTED SLOT CASE WITH PLENUM An aspect of the invention relates to an aircraft turbomachine, comprising a housing (2) of a turbomachine rotor of axis X comprising an inner wall with axial slots (20), each slot (20) comprising two flanks (20d, 20g) inclined with respect to a radius R of axis X, each slot (20) opening onto a peripheral cavity (5), further comprising a rotor (3) which comprises blades (30) arranged opposite the slots (20), it is characterized in that each slot (20) has an upstream part (200) of its axial length with a flank (200d, 200g) inclined at an angle αam with respect to the radius R and a downstream part (201) of its axial length with a flank (201d, 201g) inclined at an angle αav, different from αam. In this way, the air intake angle αav and the air injection angle αam can be adjusted to optimize the intake and reinjection functions of the slot. Figure to be published with the abbreviation: Figure 4

Description

Title of the invention: SLOTTED CRANKCASE WITH PLENUM TECHNICAL FIELD OF THE INVENTION

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

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

[0003] It relates to the passive control of flows via the technology of casing treatments 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 start-up, 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, i.e., "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 thirty percent (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 in which a "plenum" is added, which amounts to adding 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 The peripheral cavity is not directly open to the vein and is not connected to a secondary air circuit: the fluid must pass through the slits to enter and exit the peripheral cavity.

[0009] Adding the plenum modifies the behavior of the housing. In particular, it alters the balance between improved operability and its impact on efficiency. This solution offers a good balance between operability and efficiency.

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

[0011] These solutions present a major drawback: since 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 of the slots, 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 side of the slot (the 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] It has also been proposed to redirect the air between a first position on the rotor head profile and a second position upstream of the leading edge using a series of small individual channels inserted into the rotor housing. However, the drawback is that the technology is not capable of adapting to changes in the flow within the rotor: depending on the operating conditions, the optimal positions and orientations for intake / reinjection are not necessarily the same. Furthermore, this type of housing treatment is complicated to implement: machining and assembling the channels is complex. Summary of the invention

[0013] The invention offers a solution to the problems mentioned above, by making it possible to improve the aerodynamics and to keep the advantages of the treatment of the axial slotted housing with plenum while improving its ability to reinject air upstream of the rotor without degrading its ability to draw air above the rotor.

[0014] One aspect of the invention relates to an aircraft turbomachine comprising a turbomachine rotor housing of axis X comprising an inner wall with axial slots, each slot comprising two flanks inclined with respect to a radius R of axis X, each slot opening onto a peripheral cavity also called a plenum, The turbomachine, which also includes a rotor with blades arranged opposite the slots, is characterized in that each slot has an upstream portion of its axial length with a flank inclined at an angle aam to the radius R, and a downstream portion of its axial length with a flank inclined at an angle aav, different from aam. In this way, the air intake angle aav and the air injection angle aam can be adjusted to optimize the intake and reinjection functions of the slot.

[0015] The invention thus makes it possible to reduce losses in the part devoted to injection into the vein while maintaining good sampling quality on the downstream part.

[0016] The inclination of the downstream portion of the slot facilitates sampling by adapting to the flow gyration induced by the rotation of the blades. The differently inclined upstream portion of the slot improves the flow's ability to pass from the plenum to the slot, and then from the slot to the upstream rotor flow in the stream. The vortex that forms when the pressure gradient between the plenum and the stream is low is reduced, or even eliminated, and the induced losses are reduced.

[0017] By decoupling the downstream inclination from the upstream inclination, the designer can choose an injection angle adapted to the upstream rotor aerodynamics without penalizing the sampling.

[0018] The reinjection angle will be chosen to act on the upstream aerodynamic behavior of the flow.

[0019] Advantageously, the difference in inclination between aam and aav is such that aam = aav - ô, with ô between 10° and 70°. Below 10°, the difference between the upstream and downstream parts is insufficient to observe a significant deviation in injection compared to a straight slot in the prior art. Above 70°, the difference is too large and not industrially feasible. ô is denoted as the twist angle.

[0020] Advantageously, the width of the slots differs between the upstream and downstream sections. This allows the porosity of the slot / vein interface to be varied between the upstream and downstream sections of the casing treatment. This porosity transition occurs at the same point as the change in inclination. The porosity change between the upstream and downstream sections can be between -30% and +30%. Porosity is defined as (slot width x number of slots) / casing perimeter, and this porosity is between 40% and 60%, preferably greater than 40%.

[0021] According to a first embodiment, the two sides of an upstream and / or downstream part of a slot are parallel. In this case, the porosity is radially constant, and the vein / slit interface and the slot / plenum interface have identical widths.

[0022] According to a second embodiment, the two flanks of an upstream and / or downstream portion of a slot have different inclinations. Thus, the porosity is different between the interface slits / vein and the slits / plenum interface. This radial variation in porosity is obtained by the different inclination between the left and right lateral surfaces of the slits.

[0023] According to this second variant, the two sides of the upstream part diverge towards the peripheral cavity. In this way, the airflow exiting the plenum can be accelerated.

[0024] In this case, the porosity is radially variable. The porosity of the vein / slits interface is defined by considering the slit width and the casing perimeter at the level of the slit opening on the vein, and the porosity of the plenum / slits interface is defined by considering the slit width and the casing perimeter at the level of the slit opening on the plenum.

[0025] Advantageously, the upstream and downstream portions of the slots are separated by a wall. The upstream and downstream portions of the slots are separated. The upstream and downstream portions can thus be manufactured on separate parts.

[0026] Advantageously, the angle aav is between 20° and 70°, preferably between 35° and 55°. Optimally, the angle aav will be 45°.

[0027] Advantageously, the rotor is capable of rotating in one direction and the angle aav is inclined in the direction of rotation of the rotor. Conventionally, the definition of inclination is that a positive angle corresponds to an inclination in the direction of rotation of the rotor; the angle aav of inclination of the downstream part of the slots is positive.

[0028] Advantageously, the rotor comprises blades with a leading edge and a trailing edge defining a profile inclined with respect to the X axis, the profile having a length Lx along the X axis, the upstream and downstream parts of a slot are connected by a transition zone of length lx located in an interval d between 10% Lx upstream of the leading edge and 5% Lx downstream of the leading edge.

[0029] From an aerodynamic point of view, the transition zone is ideally located just before the leading edge (between 5% Lx upstream of the leading edge and the leading edge). Depending on the rotor size, the length of the slots can vary significantly (between 10 cm for a large fan and 1 cm for a high-pressure compressor rotor). For small slots, machining and integration constraints mean that the transition may end slightly after the leading edge, but should not exceed 10% Lx.

[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 by way of 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 embodiment of the invention,

[0035] [Fig.4] is a cross-sectional view of the slots in [Fig.3],

[0036] [Fig.5] is a close-up perspective view of a second embodiment of the invention,

[0037] [Fig.6] is a cross-sectional view of the slots in [Fig.5],

[0038] [Fig.7] is a close-up perspective view of a third embodiment of the invention,

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

[0040] [Fig.9] is a close-up perspective view of a fourth embodiment of the invention. DETAILED DESCRIPTION

[0041] The figures are presented for illustrative purposes only and are in no way limiting of the invention.

[0042] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0043] Assembly 1 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 [Fig. 1], the housing 2 has slots 20 uniformly distributed around its entire inner periphery on an inner wall 21. These 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 slots 20.

[0044] 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.

[0045] The blades 30 comprise a leading edge 300 and a trailing edge 301, and have a length Lx along the X-axis, as illustrated [Fig. 2]. The leading edge 300 of the blades is opposite the slots 20 and covers only a portion of them. In this way, the step-off is evenly distributed between the two slot inlets on the vein side and the plenum side, thus ensuring good strength of the part.

[0046] It is possible to foresee without departing from the scope of the present invention that the transition zone can be machined so that the inlet of the slot on the vein or plenum side is rectangular, the inlet of the slot on the other side then has a more significant step-off.

[0047] Each slot 20 is divided into an upstream portion 200 (upstream of the leading edge relative to the direction of the main flow A) and a downstream portion 201 (downstream of the leading edge relative to the direction of the main flow A) connected by a transition zone 202. Each slot comprises two flanks 20d and 20g, which are divided into two upstream flanks 200d and 200g and two downstream flanks 201d and 201g. They open onto a peripheral cavity 5 also called plenum.

[0048] In the first example illustrated in Figures 3 and 4, the two upstream sides 200d and 200g are inclined at an angle aam with respect to the radius R of axis X, and the two downstream sides 201d and 201g are inclined at an angle aav with respect to the radius R of axis X. The two angles aam and aav are different and, in this case, of opposite signs. The downstream part 201 is oriented in the same direction (positive in the trigonometric direction) with respect to the radius R as the direction of rotation S of the blades 30, while the downstream part is oriented in the opposite direction (negative in the trigonometric direction) to the direction of rotation S of the blades 30. Air flows in the plenum 5 in the same direction S as the blades, entering through the downstream part 201 and exiting through the upstream part 200.

[0049] In the second example of Figures 5 and 6, the two upstream sides 200d and 200g are separated by a shorter distance Eam than the two downstream sides 201d and 201g, which are separated by a distance Eav. The air exiting the peripheral cavity 5 through the narrower upstream part 200 is thus accelerated.

[0050] In the third example illustrated in Figures 7 and 8, the upstream flanks 200d right and 200g left have different inclinations aamd of the right flank 200d and aamg of the left flank 200g to create a convergent shape of the peripheral cavity 5 towards the vein 4, which allows the air exiting the peripheral cavity 5 to be accelerated. This difference in inclination aamd of the right flank 200d and aamg of the left flank 200g is only achieved on the upstream part 200, because it is not necessary to accelerate the air entering the peripheral cavity 5 as it is pushed by the blades 30.

[0051] Fig. 9 shows a fourth example where the upstream part 200 and the forward part 201 of the slot 20 are separated not by a transition zone 202 as in the previous examples but by a circular wall 203. We therefore have two rows of slots upstream 200 and downstream 201 arranged axially and inclined differently.

[0052] The different examples can be combined, so it is possible to provide different widths of the upstream 200 and downstream 201 parts combined with different inclinations aamd of the right flank 200d and aamg of the left flank 200g of the upstream part, with or without circular wall 203. It is possible to provide several parts: one for the downstream parts of the slots 200, one for the upstream parts of the slots 201, one for the wall 202.

[0053] Air circulation occurs as follows: • Air enters the turbomachine, • the rotor blades 30 of the rotor 3 draw the rotating air into the channel 4 and some of it enters the downstream parts 201 of the slots 20 to reach the peripheral cavity 5, • Air flows in the peripheral cavity 5 in the same direction as the rotor 3 and in the opposite direction to the air of arrow A (the air velocity has a negative axial component). In the peripheral cavity 5, the flow is counter-current to the air in the duct; this is because, in the plenum, the air can flow in the correct direction relative to the pressure gradient, whereas in the duct it is pushed by the rotor. • springs out through the upstream part 200 of the slots 20, thanks to the axial reversal of the flow in the plenum which allows a sampling downstream of the slots and a reinjection upstream of the slots.

[0054] The inclination aav of the downstream part 201 is preferably oriented in the direction of rotation of the rotor 3 in order to facilitate the entry of air Ae from the vein 4 towards the peripheral cavity 5. The inclination aam of the upstream part 200 is preferably oriented in the opposite direction to the rotation of the rotor 3 in order to facilitate the exit of air As from the peripheral cavity 5 towards the vein 4. The downstream inclination aav and the upstream inclination aam are oriented according to the requirements.

Claims

Demands

1. Aircraft turbomachine, comprising a housing (2) of an aircraft turbomachine rotor of axis X comprising an inner wall with axial slots (20), each slot (20) comprising two flanks (20d, 20g) inclined with respect to a radius R of axis X, each slot (20) opening onto a peripheral cavity (5), further comprising a rotor (3) which comprises blades (30) arranged opposite the slots (20), characterized in that each slot (20) has an upstream portion (200) of its axial length with a flank (200d, 200g) inclined at an angle aam with respect to the radius R and a downstream portion (201) of its axial length with a flank (201d, 201g) inclined at an angle aav, different from aam.

2. Turbomachine according to claim 1, characterized in that the difference in inclination between aam and aav is such that aam = aav- ô with ô between 10° and 70°.

3. Turbomachine according to any one of the preceding claims, characterized in that the width of the slots (20) is different between the upstream part (200) and the downstream part (201).

4. Turbomachine according to any one of the preceding claims, characterized in that the two flanks (200d, 200g, 201d, 201g) of an upstream (200) and / or downstream (201) part of a slot (20) are parallel.

5. Turbomachine according to any one of claims 1 to 3, characterized in that the two flanks (200d, 200g, 201d, 201g) of an upstream (200) and / or downstream (201) part of a slot (20) have different inclinations.

6. Turbomachine according to the preceding claim, characterized in that the two flanks (200d, 200g) of the upstream part (200) are divergent towards the peripheral cavity (5).

7. Turbomachine according to any one of the preceding claims characterized in that the upstream (200) and downstream (201) parts of the slots (20) are separated by a wall (203).

8. Turbomachine according to any one of the preceding claims, characterized in that the angle aav is between 20° and 70°, preferably between 35° and 55°.

9. Turbomachine according to any one of the preceding claims, characterized in that the rotor (3) is able to rotate in one direction and that the angle aav is inclined in the direction of rotation of the rotor (3).

10. 9 Turbomachine according to any one of the preceding claims, characterized in that the rotor (3) comprises blades (30) with a leading edge (300) and a trailing edge (301) defining a profile inclined with respect to the X axis, the profile having a length Lx along the X axis, that the upstream (200) and downstream (201) parts of a slot (20) are connected by a transition zone (202) of length lx located in an interval d between 10% Lx upstream of the leading edge (300) and 5% Lx downstream of the leading edge (300).

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