Axial compressor with casing treatment for an aircraft turbomachine
The movable ferrule in the casing treatment of small axial compressors controls air recirculation to adapt to operational needs, enhancing compressor efficiency by reducing airflow disruption and pressure loss.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2024-06-27
- Publication Date
- 2026-05-22
AI Technical Summary
In small axial compressors, maintaining a suitable clearance size to prevent instability while optimizing performance is challenging, as current Carter Treatments for recirculation increase efficiency but have negative effects on compressor efficiency when not needed.
A casing treatment with a movable ferrule that controls air recirculation by separating air inlet ports into two parts, allowing fluid communication only when needed, using pressure differences to manage recirculation and minimize airflow disruption.
The solution adapts the crankcase treatment to required operating conditions, maintaining efficiency by minimizing airflow disruption and pressure loss, thus optimizing compressor performance.
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Abstract
Description
Title of the invention: AXIAL COMPRESSOR WITH CRANKCASE TREATMENT FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention
[0001] 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. Technical background
[0002] An aircraft turbomachine conventionally comprises, from upstream to downstream along its longitudinal axis, at least one compressor, one combustion chamber, and at least one turbine. The air entering the turbomachine is compressed in the compressor and mixed with fuel, 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.
[0003] A compressor or turbine comprises one or more stages, each with a rotating wheel (or blade) and a stationary blade. A blade is formed by a plurality of blades extending radially about 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 of that compressor or turbine. The radial clearances between the rotating blades and the casing should be as small as possible to optimize the performance of the turbomachine.
[0004] Among compressors, a distinction is made between axial compressors and centrifugal compressors. An axial compressor has a compression stream oriented axially, while a centrifugal compressor has a compression stream oriented radially.
[0005] In the field of small axial compressors, where the impellers can be very small, it is difficult, if not impossible, to maintain a clearance size compatible with a large pumping margin. Indeed, flow in 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)). Moreover, some impeller configurations can experience instability phenomena in the clearance even with j / h values below 2%.
[0006] To improve the pumping margin in case of instability related to clearance, Carter Treatments (CT) can be used, of which there is a wide variety. These Carter Treatments have the property of modifying clearance flows either by disturbing the formation of clearance vortices by axisymmetric grooves, or by taking part of the flow in the clearance from the high pressure zones near the trailing edges of the blades and injecting flow into the lower static pressure zones near the leading edges of the blades (in this case, these are non-axisymmetric Carter Treatments).
[0007] 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.
[0008] Recirculating crankcase treatments have considerable margin improvement potential. They also have the advantage of not requiring flow from other modules. However, their drawback in current technology is that they have a negative effect on compressor efficiency. In the absence of active control that could modify the impeller's behavior according to its load, the more the pump margin is increased through higher injection and withdrawal flow rates, the more the efficiency tends to decrease.
[0009] One object 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 the 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 on the operating line, it is also possible to return to the original efficiency at these same points. Furthermore, in most of the cycles and missions of an aircraft that the engines must perform, the acceleration phases or periods of high fuel demand contribute only slightly to overall fuel consumption, which explains the advantage of such a solution. Summary of the invention
[0010] The invention relates to a casing-treated axial compressor 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 radially oriented air outlets formed at the leading edge of the blades, and at least one annular row of radially oriented air inlet ports formed between the leading and trailing edges of the blades, the air inlet ports being connected to the air outlet ports by channels allowing air recirculation from the air inlet ports to the air outlet ports, the section further comprising an annular slot formed in the thickness of the casing at the level of said at least one row of air inlet ports, and which separates each of the air inlet ports into two parts, a first part of each of the ports passing through an internal annular wall of the casing which is located radially inside the slot, and a second part of each of the ports passing through an external annular wall of the casing which is located radially outside the slot, the compressor further comprising a shell which is housed in the slot and which has radially through-holes,This ferrule being rotationally mobile within the slot around the axis, at least from a first position in which it blocks fluid communication between the first and second parts of each of the air inlet orifices, to a second position in which its openings ensure fluid communication between the first and second parts of each of the air inlet orifices, the ferrule being slotted 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.
[0011] 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 recirculates from downstream to upstream to the air outlet ports to be reinjected 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.
[0012] According to the invention, the air inlet ports are separated into two parts, between which a ferrule is interposed. This ferrule allows or prevents fluid communication between these parts. The ferrule thus functions as a recirculation control valve. The advantage of this configuration is that only the internal parts of the air inlet ports open into the compressor stream when the ferrule is in its first closed position, and are therefore likely to disrupt the airflow in the stream. The smaller the radial dimension of these internal parts of the air inlet ports—that is, the smaller the thickness (or radial dimension) of the inner wall of the casing—the less there will be of disturbance and pressure loss in the airflow in the compressor channel.
[0013] The distinctive feature of the ferrule is that it also serves to provide a tight seal for the external portions of the air inlet ports. To achieve this, it is designed to press radially outward against the outer wall of the housing to seal the external portions of the air inlet ports. The air pressure in the aforementioned area is sufficient to force the ferrule radially outward. This is made possible by the ferrule's ability to increase its diameter and thus be extensible in the radial direction. It is therefore understood that when the ferrule moves within the slot in the housing, it is also able to slide circumferentially along the outer wall of the housing.
[0014] 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 sliding in another slot at the air outlet ports of the casing.
[0015] The invention makes it possible to meet the aforementioned need and, in particular, to adapt the crankcase treatment to the points in the cycle or mission that require it, while neutralizing its negative effects on the cycle points that do not require it. When the ferrule is in the closed position, the crankcase treatment can be considered inactive, or the crankcase can be considered as not having any crankcase treatment. When the ferrule is in the open position, the crankcase treatment is active.
[0016] The compressor according to the invention may comprise one or more of the following features, taken individually or in combination with each other: • the inner wall has a thickness less than that of the outer wall;
[0017] — 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; • the ferrule has a thickness less than that of the slot; • The ferrule is connected to a jack mechanism for its rotational drive around the axis; • the section includes at least two or three annular rows of air inlet ports; • 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; • 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;
[0018] — the air inlet ports are regularly distributed around the axis, and the ports air outlets are regularly distributed around the axis;
[0019] — the number of lights in the ferrule is identical to the number of inlet ports of air, and the lights in the ferrule have shapes and dimensions identical to those of the air inlet ports;
[0020] — the air outlet ports are located just upstream of the leading edges of the blades;
[0021] — the air inlet ports are located between the trailing edges of the blades and the points located midway between the leading and trailing edges of the blades;
[0022] — at least some of the air inlet ports and / or air outlet ports are inclined with respect to radial axes;
[0023] — the air inlet ports are separated from each other by a distance which is greater than a diameter or transverse dimension of these orifices measured in a circumferential direction around the axis;
[0024] — the ferrule and the housing are made of the same material or of materials having identical behaviors 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.
[0025] The present invention also relates to an aircraft turbomachine, comprising a compressor as described above. Brief description of the figures
[0026] 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:
[0027] [Fig-1] [Fig.1] is a partial schematic perspective view of a compressor axial casing treatment according to the invention,
[0028] [Fig.2] [Fig.2] is a schematic cross-sectional view of the compressor of the [Fig. 1], and shows a movable ferrule of this compressor in a position,
[0029] [Fig. 3] [Fig. 3] is a view similar to that of [Fig. 2] and shows the movable ferrule of this compressor in a different position,
[0030] [Fig.4] [Fig.4] is a partial schematic view of an axial compressor crankcase treatment according to the invention, and shows a means of driving its ferrule, and
[0031] [Fig. 5] [Fig. 5] is a schematic view of a ferrule for a compressor according to the invention. Detailed description of the invention
[0032] Fig. 1 shows an axial compressor 10 with casing treatment for an aircraft turbomachine.
[0033] An aircraft turbomachine conventionally comprises, from upstream to downstream along its longitudinal axis X, at least one compressor 10 of the type shown in [Fig. 1], a combustion chamber, and at least one turbine. The air entering the turbomachine is compressed in the compressor 10 and mixed with fuel, 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.
[0034] A compressor 10 or a turbine comprises one or more stage(s) each comprising a wheel (or moving blade) and a fixed blade.
[0035] A blade, whether fixed or moving, such as the moving blade 12 of [Fig.1], is formed by a plurality of blades 14 which extend radially with respect to the X axis of the turbomachine.
[0036] 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 this compressor or turbine.
[0037] 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.
[0038] The compressor 10 illustrated in [Fig. 1] is partially shown. [Fig. 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.
[0039] 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.
[0040] C denotes 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.
[0041] In [Fig.1], the flow of air in the compressor vein is represented by the double-lined arrows, this flow being from left to right in this figure.
[0042] Only an axial part of the compressor 10 is shown in [Fig.1], this part being called a section 18.
[0043] The particularity of the casing 12 and in particular of its section 18 is that it includes a casing treatment (or TC for Casing Treatment).
[0044] According to the invention, this crankcase treatment is of the non-axisymmetric and recirculating type.
[0045] The section 18 comprises 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.
[0046] The air inlet orifices 22 are preferably regularly distributed around the X-axis. The section 18 may comprise one, two, three, or even more rows of these orifices 22. These rows are preferably axially spaced apart from each other. In the example shown in [Fig. 1], the section 18 comprises two annular rows of these orifices 22.
[0047] In the example shown in [Fig.4], the section 18 comprises three annular rows of these orifices 22. In this [Fig.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.
[0048] 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.
[0049] In the case of [Fig.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.
[0050] In the case of [Fig. 4], it can be seen that the orifices 22 of the upstream and downstream rows are circular, and that the orifices 22 of the intermediate row are oblong. It can also be seen that the orifices 22 of these rows have different dimensions.
[0051] The rows of orifices 22 preferably have the same number of orifices 22 and the orifices 22 of the rows are preferably aligned axially with each other, at least in part.
[0052] In the case of [Fig.1], we see that the orifices 22 of the two rows are axially aligned.
[0053] In the case of [Fig.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.
[0054] The orifices 22 are preferably located between a circumference Cl 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 [Fig.1].
[0055] The air inlet ports 22 are 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.
[0056] 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.
[0057] In the case of [Fig. 1], recirculation occurs from right to left. In the case of [Fig. 4], recirculation occurs from top to bottom.
[0058] The number of channels 24 is preferably equal to the number of orifices 22 per row, although this is not limiting. Each of the channels 24 can be in fluidic communication with only one of the orifices 22 of each row or several orifices of each row, and can be in fluidic communication with orifices 22 of several rows.
[0059] In the case of [Fig. 1] for example, each of the channels 24 can be in fluidic communication with one of the orifices 22 of each row.
[0060] In the case of [Fig.4] for example, each of the channels 24 could also be in fluidic communication with one of the orifices 22 of each row.
[0061] The air outlet orifices 20 are preferably regularly distributed around the X axis. The section 18 can include one row, two rows, three rows, or even more, of these orifices 20. These rows are preferably axially separated from each other or from each other.
[0062] In the example shown in [Fig.1], the section 18 comprises a single annular row of these orifices 20.
[0063] The orifices 20 of the 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.
[0064] In the case of [Fig.1], we see that the orifices 20 have a circular shape.
[0065] The row or each row of orifices 20 preferably has the same number of orifices 20 as the row or each row of orifices 22, as is the case in [Fig.1].
[0066] 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 [Fig.1].
[0067] Each of the channels 24 can be in fluidic communication with only one of the orifices 20 of each row or several orifices 20 of the or each row, and can be in fluidic communication with orifices 20 of several rows.
[0068] In the case of [Fig.1] for example, each of the channels 24 can be in fluidic communication with one of the orifices 20 of the row.
[0069] The channels 24 have an axial length L5 which preferably represents between 30 and 100% of the chord C of the blades 14.
[0070] The section 18 further includes an annular slot 26 which is formed in the thickness of the housing 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.
[0071] The slot 26 extends continuously over 360° all around the housing 12. It can be seen in [Fig.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.
[0072] 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.
[0073] 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.
[0074] 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
[0075] El is, for example, on the order of 1mm
[0076] The compressor 10 further comprises a ferrule 32 which is housed in the slot 26 and which includes 34 lights passing through in a radial direction.
[0077] 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 EL
[0078] The thickness E4 is preferably less than the thickness E3, as illustrated in these figures.
[0079] A preferred embodiment of the ferrule 32 is illustrated in [Fig. 5]. The ferrule 32 is slotted and has an expandable 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.
[0080] The ferrule 32 is rotationally movable in the slot 26 about 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 orifices 22 ([Fig. 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 orifices 22 ([Fig. 2]). In the second position, the openings 34 are radially aligned with the parts 22a, 22b of the orifices 22. In the first position, each of the openings 34 is located between two adjacent orifices 22 in a circumferential direction.
[0081] The elastic deformation capacity of the ferrule 32 allows it to be able to press radially against the external 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.
[0082] As illustrated in Figures 2 to 4, the slots 34 are preferably regularly 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.
[0083] 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 of the or each row is identical to the number of orifices 22 of the or each corresponding row.
[0084] 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.
[0085] As can be seen in [Fig. 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.
[0086] The ferrule 32 and the housing 12 can be made of the same material or of materials having identical behaviors in thermal expansion.
[0087] Although not shown in the drawings, at least some of the orifices 20, 22 or even the lights 34 could be inclined with respect to radial axes.
[0088] Furthermore, although the compressor 10 is described above with a single ferrule 32, the compressor 10 could include a second similar ferrule mounted sliding in another slot at the air outlet ports 20 of the housing 12.
Claims
1. Demands 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 ports (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 ports (22), the ferrule (32) being split and having an extensible diameter so as to be able to press radially against the external wall (30) in operation in order to hermetically close the second parts (22b) of the ports (22) when the ferrule (32) is in its first position.
2. Compressor (10) according to claim 1, wherein 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, wherein 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, wherein 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 capable of moving apart from each other by sliding over each other as the diameter of the ferrule (32) increases.
9. 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).
10. Aircraft turbomachine, comprising a compressor (10) according to any one of the preceding claims.