RETRACTABLE AIR-OIL HEAT EXCHANGER FOR AIRCRAFT ENGINE SYSTEM

Description

Technical field

[0001] The invention relates to the field of dual-flow aircraft propulsion systems. The invention relates more specifically to a heat exchanger intended to cool a hot fluid, such as oil circulating in a lubrication circuit of the propulsion system, with cold air from a secondary flow of the propulsion system. State of the prior art

[0002] Document EP 2 336 525 A1 describes an air-oil heat exchanger known as "ACOC", from the English "Air Cooled Oil Cooler". This exchanger extends radially in a secondary vein of the propulsion unit so as to be crossed by the secondary flow of cold air and thus cool the oil used to lubricate parts of the engine of this propulsion unit.

[0003] Such an exchanger forms an aerodynamic discontinuity in the secondary vein, which results in singular pressure losses in all phases of flight.

[0004] Document US 2017 / 0159490 A1 describes a heat exchanger housed in an internal nacelle structure which includes a scoop system intended to convey a fraction of the secondary flow to the exchanger.

[0005] Such a scoop system makes it possible to reduce singular pressure losses during take-off but nevertheless generates significant singular pressure losses during cruise. Documents US8534043B2 and US8776952B2 disclose other heat exchangers according to the state of the art. Statement of the invention

[0006] The invention aims to provide a propulsion unit nacelle having an exchanger capable of efficiently cooling a fluid using the secondary flow while limiting singular pressure losses.

[0007] To this end, the invention relates to a nacelle for a dual-flow aircraft propulsion unit, comprising an internal structure, an external structure and a heat exchanger, the internal structure and the external structure radially delimiting between them a flow duct for a first fluid intended to form a secondary flow, the exchanger comprising an external cover and a transfer module, the transfer module comprising a circulation circuit for a second fluid, the exchanger being connected to one of the internal structure and the external structure so as to be able to transmit heat from the second fluid to the first fluid.

[0008] According to the invention, this nacelle comprises an actuator configured to move the outer cover and the transfer module of the exchanger between: a retracted position in which the transfer module is received in a housing of the internal or external structure to which the exchanger is connected and in which the external cover closes an opening of this housing so as to reconstitute a delimitation surface of the flow duct, a deployed position in which the transfer module extends into the flow duct so as to be able to be crossed by a fraction of the secondary flow and thus transmit heat from the second fluid to the first fluid.

[0009] Such a nacelle allows the exchanger transfer module to be exposed to the first fluid when there is a need to cool the second fluid and only in this case.

[0010] When such cooling is not necessary, its retraction makes it possible to limit or even cancel the singular pressure losses that it is likely to generate. The reduction or cancellation of singular pressure losses results on the one hand from the retraction as such of the exchanger and on the other hand from the geometry of the external cover since it is designed to reconstitute the delimitation surface of the flow duct.

[0011] In other words, in the retracted position, the exchanger is arranged to avoid the creation of a shape accident in the flow duct likely to disturb the secondary flow circulating in this duct.

[0012] The aerodynamic continuity of the flow duct results more particularly from the fact that the outer cover reconstitutes the delimitation surface of the flow duct, that is to say from the fact that this outer cover is flush with the parts of said delimitation surface adjacent to the part of this surface which is constituted by the outer cover itself. Such a configuration of the outer cover makes it possible in particular to limit or prevent the introduction of a part of the first fluid into the housing of the transfer module.

[0013] This results in a significant reduction in singular load losses and an overall improvement in the performance of the propulsion system in all phases of flight including take-off and cruise phases.

[0014] Preferably, the actuator is configured to move the outer cover and the transfer module of the exchanger between the retracted position and the deployed position by radial translation.

[0015] In one embodiment, the exchanger comprises an inner wall, the transfer module extending radially between the inner wall and the outer cover, the inner wall of the exchanger being configured to close said opening of the housing of the internal or external structure to which the exchanger is connected so as to reconstitute said delimiting surface of the flow duct when the exchanger is in the deployed position.

[0016] The exchanger in the deployed position obviously introduces an aerodynamic discontinuity within the flow duct since the outer cover and the transfer module extend radially in the flow duct.

[0017] However, the resulting singular pressure losses are reduced given the configuration of the inner wall which, in the same way as the outer cover in the deployed position, is flush with the adjacent parts of the delimiting surface and prevents or limits the introduction of part of the first fluid into the housing of the transfer module.

[0018] The geometry of the outer cover and / or the inner wall of the exchanger is preferably configured to define, with the internal or external structure to which the exchanger is connected, a delimiting surface of the flow duct having a curvature, at least in a median longitudinal plane of the nacelle.

[0019] Thus, the outer cover of the exchanger may comprise a surface having, in a median longitudinal plane, a single or double curvature.

[0020] Similarly, the inner wall of the exchanger may comprise a surface having, in a median longitudinal plane, a single or double curvature.

[0021] In one embodiment, the exchanger comprises a member for connecting the circulation circuit of the second fluid, this member being configured to connect this circulation circuit to a lubrication circuit of the propulsion unit.

[0022] The nacelle preferably comprises a member for detecting and / or evaluating at least one parameter such as the temperature of the second fluid and a control module connected on the one hand to this member and on the other hand to the actuator so as to be able to move the outer cover and the transfer module as a function of the at least one parameter.

[0023] In one embodiment, the outer cover of the exchanger may comprise a cavity configured to circulate a portion of said second fluid in this outer cover.

[0024] The presence of such a cavity in the outer cover makes it possible to increase the total heat exchange surface.

[0025] This cavity can for example be connected to said circuit of the transfer module to form a common circuit with it.

[0026] Preferably, the cavity of the outer cover may be configured to perform a heat exchange between the first and second fluids when the exchanger is in the retracted position.

[0027] The invention also covers a propulsion assembly for an aircraft, this propulsion assembly comprising a nacelle as defined above, as well as an aircraft comprising such a propulsion assembly.

[0028] The invention also relates to a method of manufacturing a nacelle as defined above.

[0029] According to the invention, this method comprises a step of additive manufacturing of the outer cover of the exchanger.

[0030] Additive manufacturing of the outer cover makes it possible to optimize its geometry relative to the opening of the housing of the exchanger transfer module, so as to reduce discontinuities between this outer cover and the internal or external structure of the nacelle to which the exchanger is connected when it is in the retracted position.

[0031] Preferably, this method also includes a step of additive manufacturing of the inner wall of the exchanger.

[0032] Additive manufacturing of the inner wall makes it possible to optimize its geometry relative to the opening of the housing of the exchanger transfer module, so as to reduce discontinuities between this inner wall and the internal or external structure of the nacelle to which the exchanger is connected when it is in the deployed position.

[0033] Of course, the invention also covers a method of additive manufacturing of all or part of the exchanger, including for example a step of additive manufacturing of the outer cover, the inner wall and the transfer module.

[0034] Other advantages and characteristics of the invention will appear on reading the detailed, non-limiting description which follows. Brief description of the drawings

[0035] The following detailed description refers to the attached drawings in which: [ Fig. 1] is a schematic half-view in axial section of an aircraft propulsion unit according to a first embodiment of the invention, comprising a heat exchanger connected to an internal structure of the propulsion unit, the exchanger being in the retracted position; [ Fig. 2 ] is a half-view schematic in axial section of the propulsion assembly of the figure 1 , the heat exchanger being in the deployed position; [ Fig. 3 ] is a schematic half-view in axial section of an aircraft propulsion unit according to a second embodiment of the invention, comprising a heat exchanger connected to an external structure of the propulsion unit, the exchanger being in the retracted position; [ Fig. 4 ] is a half-view schematic in axial section of the propulsion assembly of the figure 3 , the heat exchanger being in the deployed position. Detailed description of embodiments

[0036] He is represented at the figure 1an aircraft propulsion unit 1 comprising a turbomachine 2 shrouded by a nacelle 3. In this example, the turbomachine 2 is a twin-spool, twin-flow turbojet.

[0037] Subsequently, the terms “upstream” and “downstream” are defined in relation to a direction D1 of flow of gases through the propulsion unit 1 when the latter is propelled.

[0038] The turbojet 2 has a longitudinal central axis A1 around which its various components extend, in this case, from upstream to downstream, a fan 4, a low-pressure compressor 5, a high-pressure compressor 6, a combustion chamber 7, a high-pressure turbine 8 and a low-pressure turbine 9. The compressors 5 and 6, the combustion chamber 7 and the turbines 8 and 9 form a gas generator.

[0039] During operation of the turbojet 2, an air flow 10 enters the propulsion unit 1 through an air inlet upstream of the nacelle 3 and passes through the fan 4. Downstream of the fan 4, a portion of this air flow 10 enters the gas generator, into a space 11A called the “primary vein”, so as to form a primary flow 10A passing through the gas generator. Another portion of the air flow 10 continues its trajectory in a duct 11B surrounding the gas generator so as to form a secondary flow 10B. The duct 11B is called the “secondary vein”.

[0040] The nacelle 3 more precisely comprises an internal structure 21 forming an internal fairing of the gas generator and an external structure 22 forming an external fairing of the propulsion unit 1. The internal structure 21 and the external structure 22 of the nacelle 3 radially delimit between them said secondary vein 11B.

[0041] Such an architecture thus makes it possible to generate a double flow comprising on the one hand the primary flow 10A reaching a relatively high temperature in the primary vein 11A and, on the other hand, the secondary flow 10B whose temperature remains relatively low within the secondary vein 11B.

[0042] In a manner known per se, the turbojet engine 2 comprises a lubrication circuit (not shown) in which a fluid such as oil is circulated in order to cool and / or lubricate mechanical components (not shown) of the turbojet engine 2.

[0043] The invention relates more specifically to a heat exchanger 25 making it possible in this example to cool the oil circulating in the lubrication circuit.

[0044] Unless otherwise indicated, the following description relates to the method of carrying out the figures 1 And 2 .

[0045] The exchanger 25 is configured to be able to be placed in a retracted position, illustrated in figure 1 , or in a deployed position, shown in figure 2 .

[0046] Generally, the exchanger 25 comprises an outer cover 26, an inner wall 27 and a transfer module 28 extending radially between the outer cover 26 and the inner wall 27.

[0047] In this example, the outer cover 26 and the inner wall 27 each form a solid structure having a continuous surface.

[0048] The transfer module 28 comprises a circulation circuit (not shown) to which the lubrication circuit of the turbojet 2 is connected so that the cooling and / or lubricating oil, more generally forming a heat transfer fluid, circulates in the circuit of the transfer module 28.

[0049] The connection of the circulation circuit to the lubrication circuit is in this example made by a connection member (not shown) comprising flexible pipes.

[0050] In this example, the exchanger 25 is connected to the internal structure 21 of the nacelle 3. In the embodiment of the figures 3 And 4 , the exchanger 25 is connected to the external structure 22.

[0051] The propulsion assembly 1 comprises an actuator (not shown) such as a cylinder configured to move the exchanger from the retracted position ( figure 1 ) to the deployed position ( figure 2 ) and vice versa.

[0052] The internal structure 21 comprises a housing 31 having an opening opening into the secondary vein 11B.

[0053] In the retracted position of the figure 1, the transfer module 28 is received in the housing 31 of the internal structure 21 and the external cover 26 closes the opening of the housing 31, thus preventing or limiting an introduction of a part of the secondary flow 10B within the housing 31.

[0054] In the retracted position, the outer cover 26 of the exchanger 25 reconstitutes a radially internal delimitation surface 41 of the secondary vein 11B. Under these conditions, the delimitation surface 41 is formed by an external surface 42 of the internal structure 21 of the nacelle 3 and by an external surface 43 of the outer cover 26 of the exchanger 25.

[0055] In the retracted position, the external surface 42 of the internal structure 21 of the nacelle 3 and the external surface 43 of the external cover 26 are flush.

[0056] The exchanger 25 in the retracted position therefore makes it possible to define a relatively smooth secondary vein 11B, tending not to produce any singular pressure loss.

[0057] In the deployed position of the figure 2 , the outer cover 26 as well as the transfer module 28 of the exchanger 25 extend into the secondary vein 11B so that the transfer module 28 can be crossed by a fraction 10C of the secondary flow 10B.

[0058] The inner wall 27 of the exchanger 25 in the deployed position closes the opening of the housing 31, preventing or limiting the introduction of a portion of the secondary flow 10B into the housing 31.

[0059] This position allows a heat exchange to be carried out between the secondary flow 10B and the heat transfer fluid circulating in the circuit of the transfer module 28, which allows this heat transfer fluid to be cooled.

[0060] The exchanger 25 in the deployed position fulfills the function of a conventional air-liquid exchanger, or ACOC exchanger.

[0061] In this example, in the deployed position ( figure 2 ), the inner wall 27 of the exchanger 25 reconstitutes said radially internal delimitation surface 41 of the secondary vein 11B. Under these conditions, the delimitation surface 41 is formed by the external surface 42 of the internal structure 21 of the nacelle 3 and by an internal surface 44 of the inner wall 27 of the exchanger 25.

[0062] The external surface 42 of the internal structure 21 of the nacelle 3 and the internal surface 44 of the internal wall 27 are flush, thus reducing the singular pressure losses when the exchanger 25 is in the deployed position.

[0063] In this example, the outer cover 26, the inner wall 27 and the transfer module 28 form moving parts secured to each other and moved as a unit when the position of the exchanger 25 changes.

[0064] In this respect, the flexible pipes of the connecting member make it possible to maintain a watertight connection between the circulation and lubrication circuits.

[0065] The trajectory of the movement of the moving parts of the exchanger 25 is in this example linear and consists of a radial translation. In other embodiments not shown, this trajectory may be curved and / or comprise one or more phases including a radial translation and / or an axial translation and / or a combination of axial and radial translations.

[0066] In this example, the propulsion unit 1 also comprises a member (not shown) for detecting the temperature of the heat transfer fluid circulating in the lubrication circuit as well as a control module (not shown) connected on the one hand to this detection member and on the other hand to the actuator so as to modify the position of the exchanger 25 as a function of this temperature.

[0067] Typically, if the temperature exceeds a predetermined threshold, the exchanger 25 is placed or maintained in the deployed position and it is placed or maintained in the retracted position otherwise.

[0068] Other parameters can be used to control the position of the exchanger 25, for example a parameter representative of the flight phase or even a flow rate of the secondary flow 10B.

[0069] In this example, the outer cover 26 and the inner wall 27 of the exchanger 25 each have a double curvature, in a median longitudinal plane passing through the exchanger 25.

[0070] The geometry of the outer cover 26 and the inner wall 27 of the exchanger 25 may have any other geometry depending, for example, on the axial position in which the exchanger 25 is placed relative to the other parts of the nacelle 3.

[0071] The outer cover 26 and the inner wall 27 of the exchanger 25 are in this example produced by additive manufacturing, which makes it possible to optimize their geometry and reduce singular pressure losses.

[0072] The above description applies by analogy to the method of carrying out the figures 3 And 4 .

[0073] Unlike the example of the figures 1 And 2, the outer cover 26 of the exchanger 25, when the latter is in the retracted position, or its inner wall 27 when it is in the deployed position, reconstitutes a radially external delimitation surface 51 of the secondary vein 11B.

[0074] In retracted position ( figure 3 ), this delimiting surface 51 is formed by an internal surface 52 of the external structure 22 of the nacelle 3 and by an internal surface 53 of the external cover 26 of the exchanger 25.

[0075] In the deployed position ( figure 4 ), this delimiting surface 51 is formed by the internal surface 52 of the external structure 22 of the nacelle 3 and by an internal surface 54 of the internal wall 27 of the exchanger 25.

Claims

1. A nacelle (3) for a turbofan aircraft propulsion assembly (1), comprising an internal structure (21), an external structure (22) and a heat exchanger (25), the internal structure (21) and the external structure (22) delimiting radially therebetween a conduit (11B) for flowing a first fluid intended to form a secondary flow (10B), the heat exchanger (25) comprising an outer cowl (26) and a transfer module (28), the transfer module (28) including a circuit for circulating a second fluid, the heat exchanger (25) being connected to one of the internal structure (21) and the external structure (22) so as to be able to transmit heat from the second fluid to the first fluid, this nacelle (3) being characterised in that it comprises an actuator configured to displace the outer cowl (26) and the transfer module (28) of the heat exchanger (25) between: - a retracted position in which the transfer module (28) is received in a housing (31) of the internal (21) or external (22) structure to which the heat exchanger (25) is connected and in which the outer cowl (26) seals an opening of this housing (31) so as to reconstitute a delimiting surface (41, 51) of the flow conduit (11B), - a deployed position in which the transfer module (28) extends into the flow conduit (11B) so as to be able to be crossed by a fraction (10C) of the secondary flow (10B) and thus transmit heat from the second fluid to first fluid, the heat exchanger (25) comprising an inner wall (27), the transfer module (28) extending radially between the inner wall (27) and the outer cowl (26), the inner wall (27) of the heat exchanger (25) being configured to seal said opening of the housing (31) of the internal (21) or external (22) structure to which the heat exchanger (25) is connected so as to reconstitute said delimiting surface (41, 51) of the flow conduit (11B) when the heat exchanger (25) is in the deployed position.

2. The nacelle (3) according to claim 1, wherein the actuator is configured to move the outer cowl (26) and the transfer module (28) of the heat exchanger (25) between the retracted position and the deployed position by radial translation.

3. The nacelle (3) according to claim 1 or 2, wherein the outer cowl (26) of the heat exchanger (25) comprises a surface (43, 53) having, in a median longitudinal plane, a single or double curvature.

4. The nacelle (3) according to any one of claims 1 to 3, wherein the heat exchanger (25) comprises a member for coupling the circuit for circulating the second fluid, this member being configured to couple this circulation circuit to a lubrication circuit of the propulsion assembly (1).

5. The nacelle (3) according to any one of claims 1 to 4, comprising a member for detecting and / or evaluating at least one parameter such as the temperature of the second fluid and a control module connected, on the one hand, to this member and, on the other hand, to the actuator so as to be able to displace the outer cowl (26) and the transfer module (28) depending on the at least one parameter.

6. A propulsion assembly (1) for an aircraft, this propulsion assembly (1) comprising a nacelle (3) according to any one of claims 1 to 5.

7. A method for manufacturing a nacelle (3) according to any one of claims 1 to 5, characterised in that it comprises a step of additive manufacturing of the outer cowl (26) of the heat exchanger (25).

8. The method for manufacturing a nacelle (3) according to any one of claims 1 to 5, characterised in that it comprises a step of additive manufacturing of the inner wall (27) of the heat exchanger (25).