Axial compressor with casing treatment for an aircraft turbine engine

Abstract

The invention relates to an axial compressor (10) with casing treatment for an aircraft turbine engine, comprising an annular casing (12) comprising at least one annular row of air outlet orifices (20) and at least one annular row of air inlet orifices (22), the air inlet orifices (22) being connected to the air outlet orifices (20) by channels (24) allowing air recirculation from the air inlet orifices (22) to the air outlet orifices (20), the compressor (10) further comprising a shroud (32) which is housed in a slot (26) of the casing (12) and which comprises apertures (34), this shroud (32) being radially extensible and rotatable in the slot (26).

Description

[0001] DESCRIPTION

[0002] TITLE: AXIAL CRANKCASE-TREATED COMPRESSOR FOR AN AIRCRAFT TURBOMACHINE

[0003] Technical field of the invention

[0004] The present invention relates to an axial compressor with casing treatment for an aircraft turbomachine, as well as an aircraft turbomachine comprising such a compressor.

[0005] Technical background

[0006] The technical background includes documents CA-A1-3 137 137, US-B1-11,965,528, US-A1-2020 / 332673 and US-A1-2023 / 184121.

[0007] An aircraft turbomachine typically comprises, from upstream to downstream along its longitudinal axis, at least one compressor, one combustion chamber, and at least one turbine. Air entering the turbomachine is compressed in the compressor and mixed with fuel before being burned in the combustion chamber. The combustion gases expand in the turbine and drive its rotor, which in turn drives the compressor rotor. The turbomachine may consist of two or more sections, for example, a low-pressure section and a high-pressure section.

[0008] A compressor or turbine comprises one or more stages, each with a rotating impeller (or blade) and a stationary blade. A blade is formed by a plurality of vanes extending radially around the axis of the turbomachine. The stationary blade of a compressor is generally called a stator, and the stationary blade of a turbine is generally called a distributor. The stationary blades of a compressor or turbine are supported by a casing that surrounds the rotating blades. The radial clearances between the rotating blades and the casing must be as small as possible to optimize the turbomachine's performance. Among compressors, a distinction is made between axial and centrifugal compressors. An axial compressor has an axially oriented compression stream, while a centrifugal compressor has a radially oriented compression stream.

[0009] In the field of small axial compressors, where the impellers can be very small, maintaining a clearance size compatible with a large pumping margin is difficult, if not impossible. Indeed, flow within the impeller head clearance can quickly become the primary cause of instability if this clearance exceeds values ​​on the order of 2% of j / h (clearance height or radial dimension (j) divided by blade height or radial dimension (h)). Furthermore, some impeller configurations can experience instability phenomena in the clearance even with j / h values ​​below 2%.

[0010] To improve the pumping margin in case of instability related to clearance, various Carter Treatments (CT) can be used. These Carter Treatments have the property of modifying clearance flows either by disrupting the formation of clearance vortices with axisymmetric grooves, or by drawing some of the flow from the clearance from high-pressure areas near the trailing edges of the blades and injecting flow into areas of lower static pressure near the leading edges of the blades (in this case, these are non-axisymmetric Carter Treatments).

[0011] The present invention applies to this latter category of Carter Treatment and more particularly to a configuration seeking to implement a recirculation at the head of the moving wheels from downstream to upstream.

[0012] Recirculating crankcase treatments offer considerable margin improvement potential. They also have the advantage of not requiring flow from other modules. However, their drawback in current technology is a negative impact on compressor efficiency. Without active control to modify the impeller's behavior based on load, increasing the pump margin through higher injection and withdrawal flow rates leads to a decrease in efficiency.

[0013] One aim of the invention is therefore to find a solution that limits the action of these Carter Treatments to the points in the cycle or mission that require them, while neutralizing their negative effects on cycle points that do not need them. Indeed, if it is possible to return to a configuration almost equivalent to the absence of Carter Treatment for points along the operating line, it is also possible to return to the original efficiency at these same points. Furthermore, in most aircraft cycles and missions that engines must perform, acceleration phases or periods of high fuel demand contribute only slightly to overall fuel consumption, which explains the advantage of such a solution.

[0014] Summary of the invention

[0015] The invention relates to an axial compressor with casing treatment for an aircraft turbomachine, this axial compressor comprising an annular casing extending around an axis and surrounding at least one wheel rotating about this axis, this wheel comprising blades each having a leading edge and a trailing edge, the casing comprising an axial annular section having at least one annular row of air outlet orifices which have a radial orientation and are formed at the leading edge of the blades, and at least one annular row of air inlet orifices which have a radial orientation and are formed between the leading and trailing edges of the blades, the air inlet orifices being connected to the air outlet orifices by channels allowing air recirculation from the air inlet orifices to the air outlet orifices,the section further comprising an annular slot which is formed in the thickness of the casing at the level of said at least one row of air inlet orifices, and which separates each of the air inlet orifices into two parts, a first part of each of the orifices passing through an internal annular wall of the casing which is located radially inside the slot, and a second part of each of the orifices passing through an external annular wall of the casing which is located radially outside the slot, the compressor further comprising a ferrule which is housed in the slot and which has through-holes in a radial direction, this ferrule being rotationally movable in the slot around the axis at least from a first position in which it blocks the fluidic communication between the first and second parts of each of the air inlet orifices,up to a second position in which its openings ensure fluidic communication between the first and second parts of each of the air inlet orifices, the ferrule being split and having an extensible diameter so as to be able to press radially against the external wall during operation in order to hermetically seal the second parts of the orifices when the ferrule is in its first position.

[0016] The compressor according to the invention therefore includes a crankcase treatment (also called CRT for Crankcase Treatment) of the air recirculation type. This means that during operation, air flows from upstream to downstream through the impeller, and a portion of this air is drawn in through the air inlet ports and recirculated from downstream to upstream to the air outlet ports for reinjection into the compressor's air stream. The pressure difference between the area where the air inlet ports are located and the area where the air outlet ports are located is sufficient to generate this recirculation. The pressure ratio between these two zones can be at least 1.2 or 1.3, that is to say that the pressure in the zone where the air inlet ports are located can be at least 1.2 to 1.3 greater than the pressure in the zone where the air outlet ports are located.

[0017] According to the invention, the air inlet ports are divided into two parts, between which a ferrule is interposed. This ferrule allows or prevents fluid communication between the two parts. The ferrule thus functions as a recirculation control valve. The advantage of this configuration is that only the inner portions of the air inlet ports open into the compressor housing when the ferrule is in its first closed position, and are therefore only likely to disrupt the airflow in the housing. The smaller the radial dimension of these inner portions of the air inlet ports—that is, the smaller the thickness (or radial dimension) of the inner wall of the housing—the less disruption and pressure drop there will be in the airflow within the compressor housing. The ferrule also provides a sealing function for the outer portions of the air inlet ports.To achieve this, it is able to press itself radially outwards against the outer wall of the crankcase to seal the outer portions of the air inlet ports. The air pressure in the aforementioned area is sufficient to force the ferrule radially outwards. This is made possible by the ferrule's ability to increase its diameter and thus be extensible in a radial direction. It is therefore understood that as the ferrule moves within the slot in the crankcase, it is able to slide circumferentially along the outer wall of the crankcase.

[0018] Although the compressor according to the invention is described below with a single ferrule of this type, the compressor could include a second similar ferrule mounted to slide in another slot at the air outlet ports of the crankcase.

[0019] The invention addresses the aforementioned need and, in particular, allows the crankcase treatment to be adapted to the points in the cycle or mission that require it, while neutralizing its negative effects on cycle points that do not. When the ferrule is in the closed position, the crankcase treatment can be considered inactive, or the crankcase can be considered as having no crankcase treatment. When the ferrule is in the open position, the crankcase treatment is active.

[0020] The compressor according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0021] - the inner wall has a thickness less than that of the outer wall; -- the inner wall has a thickness less than or equal to 1 mm; - the ferrule has a thickness less than that of the outer wall, or even less than that of the inner wall;

[0022] - the ferrule has a thickness less than that of the slot;

[0023] - the ferrule is connected to a jack mechanism for its rotational drive around the axis;

[0024] - the section includes at least two or three annular rows of air inlet ports;

[0025] - the air inlet openings of one of the rows, or of each row, differ in their shape and / or dimensions from the air inlet openings of the other row or rows;

[0026] - the ferrule comprises circumferential ends which overlap each other in a radial direction and which are able to move apart from each other by sliding one over the other as the diameter of the ferrule increases;

[0027] - the air inlet openings are regularly distributed around the axis, and the air outlet openings are regularly distributed around the axis;

[0028] - the number of lights in the ferrule is identical to the number of air inlet ports, and the lights in the ferrule have the same shapes and dimensions as the air inlet ports;

[0029] - the air outlet ports are located just upstream of the leading edges of the blades;

[0030] -- the air inlet ports are located between the trailing edges of the blades and points located halfway between the leading and trailing edges of the blades;

[0031] - at least some of the air inlet and / or air outlet ports are inclined with respect to radial axes;

[0032] - the air inlet openings are separated from each other by a distance which is greater than a diameter or a transverse dimension of these openings measured in a circumferential direction around the axis;

[0033] - the ferrule and the casing are made of the same material or of materials having identical behavior in thermal expansion; - the channels have an axial length representing between 30 and 100% of a blade chord measured between the leading and trailing edges of the blades.

[0034] The present invention also relates to an aircraft turbomachine, comprising a compressor as described above.

[0035] Brief description of the figures

[0036] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0037] [Fig.1] Figure 1 is a partial schematic perspective view of an axial compressor with crankcase treatment according to the invention,

[0038] [Fig. 2] Figure 2 is a schematic cross-sectional view of the compressor in Figure 1, and shows a movable ferrule of this compressor in a position,

[0039] [Fig. 3] Figure 3 is a view similar to that of Figure 2 and shows the movable ferrule of this compressor in another position.

[0040] [Fig. 4] Figure 4 is a partial schematic view of an axial compressor with casing treatment according to the invention, and shows a means of driving its ferrule, and

[0041] [Fig.5] Figure 5 is a schematic view of a ferrule for a compressor according to the invention.

[0042] Detailed description of the invention

[0043] Figure 1 shows a crankcase-treated axial compressor 10 for an aircraft turbomachine.

[0044] An aircraft turbomachine typically comprises, from upstream to downstream along its longitudinal axis X, at least one compressor 10 of the type shown in Figure 1, a combustion chamber, and at least one turbine. Air entering the turbomachine is compressed in the compressor 10, mixed with fuel, and then burned in the combustion chamber. The combustion gases expand in the turbine and drive its rotor, which in turn drives the compressor rotor. The turbomachine may comprise two or more sections, for example, a low-pressure section and a high-pressure section.

[0045] A compressor 10 or a turbine comprises one or more stage(s), each having a wheel (or moving blade) and a fixed blade.

[0046] A blade, whether fixed or moving, such as the moving blade 12 in Figure 1, is formed by a plurality of blades 14 which extend radially with respect to the X axis of the turbomachine.

[0047] A fixed compressor blade is generally called a rectifier, and a fixed turbine blade is generally called a distributor. The fixed blades of a compressor or turbine are supported by an annular housing 16 which surrounds the moving blades 12 of that compressor or turbine.

[0048] The radial clearances J between the blades 14 of a moving blade 12 and the casing 16 must be as small as possible to optimize the performance of the turbomachine.

[0049] The compressor 10 illustrated in Figure 1 is partially shown. Figure 1 shows in particular a part (or an angular sector) of the casing 16 and only one of the blades 14 of the moving blade 12 or of the wheel.

[0050] Each of the blades 14 comprises a leading edge 14a and a trailing edge 14b and preferably has an aerodynamic profile comprising an intrados 14c and an extrados 14d.

[0051] We denote by C the chord of a blade 16, namely the distance measured axially (along the axis of rotation of the wheel which coincides with the longitudinal axis X of the turbomachine) between the leading edge 14a and trailing edge 14b of the blade.

[0052] In Figure 1, the airflow in the compressor duct is represented by double-lined arrows, with the flow occurring from left to right in this figure. Only an axial portion of the compressor 10 is shown in Figure 1; this portion is referred to as section 18.

[0053] The particularity of the crankcase 12 and in particular of its section 18 is that it includes a crankcase treatment (or TC for Crankcase Treatment).

[0054] According to the invention, this crankcase treatment is of the non-axisymmetric and recirculating type.

[0055] The section 18 includes at least one annular row of air outlet orifices 20 which have a radial orientation and are formed at the leading edge 14a of the blades 14, and at least one annular row of air inlet orifices 22 which have a radial orientation and are formed between the leading edge 14a and trailing edge 14b of the blades 14.

[0056] The air inlet ports 22 are preferably evenly distributed around the X-axis. The section 18 may comprise one, two, three, or even more rows of these ports 22. These rows are preferably axially spaced apart from each other. In the example shown in Figure 1, the section 18 comprises two annular rows of these ports 22.

[0057] In the example shown in Figure 4, section 18 comprises three annular rows of these orifices 22. In this Figure 4, the flow of air in the compressor vein is represented by the double-lined arrows, this flow being from bottom to top in this figure.

[0058] The orifices 22 of the row or of each row preferably have an identical shape and dimensions but which may vary from the shape and dimensions of the other row or rows.

[0059] In the case of Figure 1, we see that the orifices 22 of the two rows have a circular or oblong shape, and that the orifices 22 of the upstream row have dimensions smaller than those of the orifices of the downstream row.

[0060] In the case of Figure 4, we see that the orifices 22 of the upstream and downstream rows are circular, and that the orifices 22 of the intermediate row are oblong. We also see that the orifices 22 of these rows have different dimensions. The rows of orifices 22 preferably have the same number of orifices 22, and the orifices 22 of the rows are preferably axially aligned with each other, at least partially.

[0061] In the case of Figure 1, we see that the orifices 22 of the two rows are axially aligned.

[0062] In the case of figure 4, we see that the orifices 22 of the upstream and downstream rows are aligned, and that the orifices 22 of the intermediate row are arranged in a staggered pattern with respect to the orifices of the other rows.

[0063] The orifices 22 are preferably located between a circumference C1 passing through the middle of the chords C of the blades 14 and a circumference C2 passing through the trailing edges 14b of the blades 14, as illustrated in figure 1.

[0064] The air inlet ports 22 are connected to the air outlet ports 20 by channels 24 allowing air recirculation from the air inlet ports 22 to the air outlet ports 20.

[0065] The housing 12 or the section 18 preferably comprises a multitude of channels 24 distributed around the X-axis and formed within the thickness of the housing 12 or mounted radially outside the housing. These channels 24 are schematically represented by dashed lines in Figures 1 and 4.

[0066] In Figure 1, recirculation occurs from right to left. In Figure 4, recirculation occurs from top to bottom.

[0067] The number of channels 24 is preferably equal to the number of orifices 22 per row, although this is not a limiting factor. Each of the channels 24 may be in fluidic communication with only one of the orifices 22 in each row or with several orifices in each row, and may be in fluidic communication with orifices 22 in several rows.

[0068] In the case of Figure 1 for example, each of the channels 24 can be in fluidic communication with one of the orifices 22 of each row.

[0069] In the case of Figure 4, for example, each of the channels 24 could also be in fluidic communication with one of the orifices 22 in each row. The air outlet orifices 20 are preferably regularly distributed around the X-axis. The section 18 can comprise one, two, three, or even more rows of these orifices 20. These rows are preferably axially separated from each other.

[0070] In the example shown in Figure 1, section 18 comprises a single annular row of these orifices 20.

[0071] The 20 holes of the row or each row preferably have the same shape and dimensions but may vary from the shape and dimensions of the other row or rows.

[0072] In the case of Figure 1, we see that the orifices 20 have a circular shape. The row or rows of orifices 20 preferably have the same number of orifices 20 as the row or rows of orifices 22, as is the case in Figure 1.

[0073] The orifices 20 are preferably located between a circumference C3 situated upstream of the leading edges 14a of the blades 14 and a circumference C4 situated downstream of the leading edges 14a of the blades 14, as illustrated in figure 1.

[0074] Each of the channels 24 can be in fluidic communication with one of the orifices 20 of each row or several orifices 20 of the row or each row, and can be in fluidic communication with orifices 20 of several rows.

[0075] In the case of Figure 1 for example, each of the channels 24 can be in fluidic communication with one of the orifices 20 of the row.

[0076] The channels 24 have an axial length L5 which preferably represents between 30 and 100% of the chord C of the blades 14.

[0077] The section 18 further includes an annular slot 26 which is formed in the thickness of the casing 12 at the level of the rows of air inlet orifices 22, and which separates each of the air inlet orifices 22 into two parts.

[0078] The slot 26 extends continuously over 360° all around the housing 12. We see in figure 1 in particular that it preferably has a length L1 which is greater than the length L2 of the housing 12 on which the rows of orifices 22 extend.

[0079] A first part 22a of each of the orifices 22 passes through an internal annular wall 28 of the housing 12 which is located radially inside the slot 26.

[0080] A second part 22b of each of the orifices 22 passes through an external annular wall 30 of the housing 12 which is located radially outside the slot 26.

[0081] Preferably, as can be seen in figures 2 and 3, the inner wall 28 has a thickness E1 (or radial dimension) less than the thickness E2 (or radial dimension) of the outer wall 30. Also preferably, the slot 26 has a thickness E3 (or radial dimension) less than the thickness E2 and which may be identical to the thickness E1.

[0082] E1, for example, is on the order of 1 mm

[0083] The compressor 10 further includes a ferrule 32 which is housed in the slot 26 and which has radially passing through ports 34.

[0084] Preferably, as can be seen in figures 2 and 3, the ferrule 32 has a thickness E4 (or radial dimension) less than the thickness E2 (or radial dimension) and which may be less than or equal to the thickness E1.

[0085] Thickness E4 is preferably less than thickness E3, as illustrated in these figures.

[0086] A preferred embodiment of the ferrule 32 is illustrated in Figure 5. The ferrule 32 is slotted and has an extensible diameter. For this purpose, the ferrule 32 comprises circumferential ends 32a, 32b which overlap each other in a radial direction and which are able to move apart from each other (see double arrow) by sliding over each other as the diameter of the ferrule 32 increases.

[0087] The ferrule 32 is rotationally movable within the slot 26 around the X-axis, at least from a first position in which it blocks fluid communication between the first and second parts 22a, 22b of each of the air inlet ports 22 (Figure 3), to a second position in which its openings 34 ensure fluid communication between the first and second parts 22a, 22b of each of the air inlet ports 22 (Figure 2). In the second position, the openings 34 are radially aligned with the parts 22a, 22b of the ports 22. In the first position, each of the openings 34 is located between two adjacent ports 22 in a circumferential direction.

[0088] The elastic deformation capacity of the ferrule 32 allows it to be able to press radially against the outer wall 30 in operation, as illustrated in figures 2 and 3, in order to seal tightly the second parts 22b of the orifices 22 when the ferrule is in its first position.

[0089] As illustrated in Figures 2 to 4, the slots 34 are preferably evenly distributed around the axis. The ferrule 32 can comprise one, two, three, or even more rows of these slots 34. These rows are preferably axially spaced apart from each other.

[0090] More preferably, the number of rows of lights 34 is preferably equal to the number of rows of orifices 22. More preferably, the number of lights 34 in the or each row is identical to the number of orifices 22 in the or each corresponding row.

[0091] Furthermore, the lights 34 of the or of each row preferably have a shape and dimensions identical to those of the orifices 22 of the or of each corresponding row.

[0092] As can be seen in Figure 4, the ferrule 32 is connected to a jack mechanism 36 for its rotational drive around the axis. The jack mechanism 36 comprises, for example, a cylinder 36a fixed to the housing 12 and a piston rod 36b, one end of which is connected to the ferrule 32 by a joint 38.

[0093] The ferrule 32 and the housing 12 can be made of the same material or of materials having identical thermal expansion behavior. Although not shown in the drawings, at least some of the ports 20, 22, or even the openings 34, could be inclined with respect to radial axes.

[0094] Furthermore, although the compressor 10 is described above with a single ferrule 32, the compressor 10 could include a second similar ferrule mounted to slide in another slot at the air outlet ports 20 of the housing 12.

Claims

DEMANDS 1. Axial compressor (10) with casing treatment for an aircraft turbomachine, this axial compressor (10) comprising an annular casing (12) extending around an axis (X) and surrounding at least one wheel rotating about this axis, this wheel comprising blades (16) each having a leading edge (14a) and a trailing edge (14b), the casing (12) comprising an axial annular section (18) having at least one annular row of air outlet ports (20) having a radial orientation and formed at the leading edge (14a) of the blades (16), and at least one annular row of air inlet ports (22) having a radial orientation and formed between the leading (14a) and trailing (14b) edges of the blades (16), the air inlet ports (22) being connected to the air outlet ports (20) by channels (24) allowing the recirculation of air from the air inlet ports (22) to the air outlet ports (20),the section (18) further comprising an annular slot (26) formed in the thickness of the housing (12) at the level of said at least one row of air inlet orifices (22), and which separates each of the air inlet orifices (22) into two parts, a first part (22a) of each of the orifices (22) passing through an internal annular wall (28) of the housing (12) which is located radially inside the slot (26), and a second part (22b) of each of the orifices (22) passing through an external annular wall (30) of the housing (12) which is located radially outside the slot (26), the compressor (10) further comprising a ferrule (32) which is housed in the slot (26) and which has radially through openings (34), this ferrule (32) being rotationally movable in the slot (26) about the axis (X) at least from a first position in which it blocks fluidic communication between the first and second parts (22a,22b) of each of the air inlet orifices (22), up to a second position in which its openings (34) ensure fluidic communication between the first and second parts (22a, 22b) of each of the air inlet orifices (22), the ferrule (32) being split and having an extensible diameter, so as to be able to press radially against the outer wall (30) in operation in order to seal tightly the second parts (22b) of the orifices (22) when the ferrule (32) is in its first position.

2. Compressor (10) according to claim 1, in which the inner wall (28) has a thickness (E1) less than that (E2) of the outer wall (30).

3. Compressor (10) according to claim 1 or 2, in which the shell (32) has a thickness (E4) less than that (E2) of the outer wall (30), or even less than that (E1) of the inner wall (28).

4. Compressor (10) according to any one of the preceding claims, wherein the ferrule (32) has a thickness (E4) less than that of the slot (E3).

5. Compressor (10) according to any one of the preceding claims, in which the ferrule (32) is connected to a jack mechanism (36) for its rotational drive around the axis (X).

6. Compressor (10) according to any one of the preceding claims, wherein the section (18) comprises at least two or three annular rows of air inlet ports (22).

7. Compressor (10) according to claim 6, wherein the air inlet ports (22) of one of the rows, or of each row, differ in their shape and / or dimensions from the air inlet ports (22) of the other row or rows.

8. Compressor (10) according to any one of the preceding claims, wherein the ferrule (32) comprises circumferential ends (32a, 32b) which overlap each other in a radial direction and which are able to move apart from each other by sliding over each other when the diameter of the ferrule (32) increases.

9. Compressor (10) according to any one of the preceding claims, wherein the air inlet ports are regularly distributed around the axis, and the air outlet ports are regularly distributed around the axis.

10. Compressor (10) according to any one of the preceding claims, wherein the number of ferrule openings is identical to the number of orifices air inlet, and the ferrule lights have the same shapes and dimensions as the air inlet ports.

11. Compressor (10) according to any one of the preceding claims, in which the air outlet ports are located just upstream of the leading edges of the blades.

12. Compressor (10) according to any one of the preceding claims, wherein at least some of the air inlet ports and / or air outlet ports are inclined with respect to radial axes.

13. Compressor (10) according to any one of the preceding claims, wherein the air inlet ports are separated from each other by a distance which is greater than a diameter or a transverse dimension of these ports measured in the circumferential direction around the axis.

14. Compressor (10) according to any one of the preceding claims, wherein the channels (24) have an axial length (L5) representing between 30 and 100% of a chord (C) of the blades (16) measured between the leading (14a) and trailing (14b) edges of the blades (16).

15. Aircraft turbomachine, comprising a compressor (10) according to any one of the preceding claims.

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