Retractable Air-Oil Heat Exchanger for Aircraft Propulsion Assembly

Abstract

The present invention relates to a two - flow aircraft propulsion assembly (1) comprising a retractable heat exchanger (25). The exchanger (25) can be deployed in the secondary channel (11B) of the propulsion assembly (1) so as to cool the fluid flowing in the circuit of the transfer module (28) of the exchanger (25) by means of a secondary flow (10B) flowing in the secondary channel (11B).

Description

Field of the Invention

[0001] The present invention relates to the field of propulsion assemblies for turbofan engine aircrafts.

[0002] More specifically, the present invention relates to a heat exchanger designed to use cold air from the secondary flow of a propulsion system to cool a hot fluid (such as fuel circulating in a lubrication circuit of a propulsion assembly). Prior Art

[0003] Document EP 2 336 525 A1 describes an air-oil heat exchanger called "ACOC" (which stands for "Air Cooled Oil Cooler"). This heat exchanger extends radially in a secondary flow path of a propulsion assembly in order to cross a secondary cold air flow and thus cool the fuel used to lubricate the engine components of the propulsion assembly.

[0004] This heat exchanger creates an aerodynamic discontinuity in the secondary flow path, which results in a singular pressure drop during all flight phases.

[0005] Document US 2017 / 0159490 A1 describes a heat exchanger housed in an internal nacelle structure, said nacelle structure including a gravity-feed cooling system for delivering a portion of the secondary flow to the heat exchanger.

[0006] This gravity-feed cooling system can reduce the singular pressure drop during the takeoff phase, but generates a significant singular pressure drop during the cruise phase. Summary of the Invention

[0007] The present invention aims to provide a propulsion assembly nacelle with a heat exchanger that can effectively cool a fluid using a secondary flow while limiting singular pressure drops.

[0008] To this end, the subject of the present invention relates to a nacelle for a propulsion assembly of a turbofan engine aircraft, which includes an internal structure, an external structure, and a heat exchanger. The internal structure and the external structure radially define a duct therebetween for the flow of a first fluid intended to form a secondary flow. The heat exchanger includes an outer cowl and a transfer module, and the transfer module includes a circuit for circulating a second fluid. The heat exchanger is connected to one of the internal structure and the external structure so as to be able to transfer heat from the second fluid to the first fluid.

[0009] According to the present invention, the nacelle includes an actuator configured to displace the outer cowl and the transfer module of the heat exchanger between:

[0010] - a retracted position, in which the transfer module is received in a housing of the internal or external structure to which the heat exchanger is connected, and in which the outer cowl seals an opening of the housing so as to reconstruct the defining surface of the fluid duct,

[0011] - An extended position, wherein the transfer module extends into the fluid conduit so as to be traversed by a portion of the secondary flow and thereby transfer heat from the second fluid to the first fluid.

[0012] When cooling of the second fluid is required and only in such cases, such nacelle can bring the transfer module of the heat exchanger into contact with the first fluid.

[0013] When such cooling is not required, its contraction can limit or even eliminate the strange pressure drop it may generate. The reduction or elimination of the strange pressure drop is due on the one hand to the same retraction of the heat exchanger and on the other hand to the geometry of the outer cowl, since the latter is designed to reconstruct the bounding surface of the fluid conduit.

[0014] In other words, in the retracted position, the heat exchanger is arranged to avoid creating an incident in the fluid conduit that could disturb the secondary flow circulating in the conduit.

[0015] The aerodynamic continuity of the fluid conduit is more particularly due to the outer cowl reconstructing the bounding surface of the fluid conduit, that is to say, due to the outer cowl being flush with a portion of the bounding surface, the portion of the bounding surface being adjacent to the portion of the surface constituted by the outer cowl itself. Such a configuration of the outer cowl can in particular limit or prevent a portion of the first fluid from being introduced into the housing of the transfer module.

[0016] This results in a significant reduction in the strange pressure drop and overall improvement in the performance of the propulsion system in all flight phases including take-off and cruise phases.

[0017] Preferably, the actuator is configured to move the outer cowl and the transfer module of the heat exchanger between the retracted position and the extended position by radial translation.

[0018] In one embodiment, the heat exchanger includes an inner wall, the transfer module extending radially between the inner wall and the outer cowl, and the inner wall of the heat exchanger is configured to seal the opening of the housing of the internal or external structure to which the heat exchanger is connected so as to reconstruct the bounding surface of the fluid conduit when the heat exchanger is in the extended position.

[0019] Since the outer cowl and the transfer module extend radially into the fluid conduit, the heat exchanger in the extended position naturally introduces an aerodynamic discontinuity into the fluid conduit.

[0020] However, since in the same way as the outer cowl in the extended position, the configuration of the inner wall is flush with the adjacent portion of the bounding surface and prevents or limits the introduction of a portion of the first fluid into the housing of the transfer module, the generated strange pressure drop is reduced.

[0021] The geometry of the outer casing and / or the inner wall of the heat exchanger is preferably configured to define, together with the internal or external structure to which the heat exchanger is connected, a bounding surface of a fluid conduit, the bounding surface having a curvature at least in the longitudinal central plane of the nacelle.

[0022] Thus, the outer casing of the heat exchanger may include a surface having a single curvature or a double curvature along the intermediate longitudinal plane.

[0023] Likewise, the inner wall of the heat exchanger may include a surface having a single curvature or a double curvature along the intermediate longitudinal plane.

[0024] In one embodiment, the heat exchanger includes a member connecting a circuit for circulating a second fluid, the member being configured to connect the circulation circuit to a lubrication circuit of a propulsion assembly.

[0025] The nacelle preferably includes 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 the member and on the other hand to an actuator so as to be able to displace the outer casing and the transmission module according to the at least one parameter.

[0026] In one embodiment, the outer casing of the heat exchanger may include a cavity configured to circulate a portion of the second fluid in the outer casing.

[0027] The presence of such a cavity in the outer casing can increase the total heat exchange surface.

[0028] For example, the cavity may be connected to the circuit of the transmission module so as to form a common circuit therewith.

[0029] Preferably, when the heat exchanger is in the retracted position, the cavity of the outer casing may be configured to effect heat exchange between the first fluid and the second fluid.

[0030] The invention also relates to a propulsion assembly of an aircraft, the propulsion assembly including a nacelle as defined above, and to an aircraft including such a propulsion assembly.

[0031] The invention also relates to a method of manufacturing a heat exchanger of a nacelle as defined above.

[0032] According to the invention, the method includes an additive manufacturing step of the outer casing of the heat exchanger.

[0033] Additive manufacturing of the outer casing can optimize its geometric structure relative to the housing of the transmission module of the heat exchanger so as to reduce the discontinuity between the outer casing and the internal or external structure of the nacelle to which the heat exchanger is connected when the heat exchanger is in the retracted position.

[0034] Preferably, the method further includes an additive manufacturing step of the inner wall of the heat exchanger.

[0035] Additive manufacturing of the inner wall can optimize its geometry relative to the opening of the transfer module housing of the heat exchanger so as to reduce the discontinuity between the inner wall and the internal or external structure of the nacelle to which the heat exchanger is connected when the heat exchanger is in the deployed position.

[0036] Of course, the present invention also relates to a method for additive manufacturing of all or part of a heat exchanger, including, for example, the additive manufacturing steps of an outer cowling, an inner wall, and a transfer module.

[0037] The present invention also relates to a method for manufacturing a nacelle as defined above, which implements this method for manufacturing a heat exchanger.

[0038] Other advantages and features of the present invention will become apparent after reading the following detailed non-limiting description. Description of the Drawings

[0039] The following detailed description relates to the drawings, in which:

[0040] FIG. 1 is a schematic half-view of an axial section of an aircraft propulsion assembly according to a first embodiment of the present invention, the aircraft propulsion assembly including a heat exchanger connected to the internal structure of the propulsion assembly, the heat exchanger being in the retracted position;

[0041] FIG. 2 is a half-view of an axial section of the propulsion assembly of FIG. 1, in which the heat exchanger is in the deployed position;

[0042] FIG. 3 is a schematic half-view of an axial section of an aircraft propulsion assembly according to a second embodiment of the present invention, the aircraft propulsion assembly including a heat exchanger connected to the external structure of the propulsion assembly, the heat exchanger being in the retracted position;

[0043] FIG. 4 is a half-view of an axial section of the propulsion assembly of FIG. 3, in which the heat exchanger is in the deployed position. Detailed Description

[0044] An aircraft propulsion unit 1 is shown in FIG. 1 and includes a turbomachine 2 ducted by a nacelle 3. In the present example, the turbomachine 2 is a turbofan engine and a twin-spool turbojet engine.

[0045] Subsequently, the terms "upstream" and "downstream" are defined relative to the direction D1 of the airflow passing through the propulsion assembly 1 when the propulsion assembly 1 is being propelled.

[0046] The turbojet engine 2 has a longitudinal central axis A1, and different components of the turbojet engine 2 extend near the longitudinal central axis A1. In this case, from upstream to downstream, there are the fan 4, the low-pressure compressor 5, the high-pressure compressor 6, the combustion chamber 7, the high-pressure turbine 8, and the low-pressure turbine 9. The compressors 5 and 6, the combustion chamber 7, and the turbines 8 and 9 form a gas generator.

[0047] During the operation of the turbojet engine 2, the air flow 10 enters the propulsion assembly 1 through the air inlet upstream of the nacelle 3 and passes through the fan 4. Downstream of the fan 4, a part of this air flow 10 penetrates the gas generator in a space 11A called the "main flow path" so as to form a primary flow 10A passing through the gas generator. Another part 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 flow path".

[0048] The nacelle 3 more specifically includes an internal structure 21 forming an inner fairing of the gas generator and an external structure 22 forming an outer fairing of the propulsion assembly 1. The internal structure 21 and the external structure 22 of the nacelle 3 radially define the secondary flow path 11B therebetween.

[0049] Therefore, this architecture can generate a dual flow, which on the one hand includes a primary flow 10A that reaches a relatively high temperature in the primary flow path 11A, and on the other hand includes a secondary flow 10B whose temperature remains relatively low in the secondary flow path 11B.

[0050] In a manner known per se, the turbojet engine 2 includes a lubrication circuit (not shown), for example, a fluid such as fuel circulates therein to cool and / or lubricate mechanical components (not shown) in the turbojet engine 2.

[0051] The present invention more specifically relates to a heat exchanger 25 which can cool the fuel circulating in the lubrication circuit in this example.

[0052] Unless otherwise specified, the following description relates to the embodiments of FIGS. 1 and 2.

[0053] The heat exchanger 25 is configured to be able to be placed in a retracted position as shown in FIG. 1 or an extended position as shown in FIG. 2.

[0054] Generally, the heat exchanger 25 includes an outer casing 26, an inner wall 27, and a transfer module 28 extending radially between the outer casing 26 and the inner wall 27.

[0055] In this example, each of the outer casing 26 and the inner wall 27 forms a solid structure with a continuous surface.

[0056] The transfer module 28 includes a circuit (not shown) in which the lubrication circuit of the turbojet engine 2 is connected so that, more generally, the cooling and / or lubricating oil, which forms the heat transfer fluid, circulates in the circuit of the transfer module 28.

[0057] In the present example, the connection between the circuit and the lubrication circuit is made by a connecting member (not shown) including flexible tubes.

[0058] In the present example, the heat exchanger 25 is connected to the internal structure 21 of the nacelle 3. In the embodiments of FIGS. 3 and 4, the heat exchanger 25 is connected to the external structure 22.

[0059] The propulsion assembly 1 includes an actuator (not shown), such as a cylinder, configured to move the heat exchanger from a retracted position (FIG. 1) to a deployed position (FIG. 2) and vice versa.

[0060] The internal structure 21 includes a housing 31 having an opening leading to the secondary flow path 11B.

[0061] In the retracted position of FIG. 1, the transfer module 28 is received in the housing 31 of the internal structure 21, and the outer cowl 26 seals the opening of the housing 31, thereby preventing or limiting the introduction of a portion of the secondary flow 10B into the housing 31.

[0062] In the retracted position, the outer cowl 26 of the heat exchanger 25 reconfigures the radially inner bounding surface 41 of the secondary flow path 11B. Under these conditions, the bounding surface 41 is formed by the outer surface 42 of the internal structure 21 of the nacelle 3 and by the outer surface 43 of the outer cowl 26 of the heat exchanger 25.

[0063] In the retracted position, the outer surface 42 of the internal structure 21 of the nacelle 3 and the outer surface 43 of the outer cowl 26 are flush.

[0064] Thus, the heat exchanger 25 in the retracted position can define a relatively smooth secondary flow path 11B that tends not to generate a singular pressure drop.

[0065] In the deployed position of FIG. 2, the outer cowl 26 of the heat exchanger 25 and the transfer module 28 extend into the secondary flow path 11B such that the transfer module 28 can be traversed by a small portion 10C of the secondary flow 10B.

[0066] The inner wall 27 of the heat exchanger 25 in the deployed position seals the opening of the housing 31, preventing or limiting the introduction of a portion of the secondary flow 10B into the housing 31.

[0067] This position allows for heat exchange between the secondary flow 10B and the heat transfer fluid circulating in the circuit of the transfer module 28, which can cool the heat transfer fluid.

[0068] The heat exchanger 25 in the deployed position performs the function of a conventional gas-liquid exchanger or an ACOC exchanger.

[0069] In the present example, in the deployed position (Figure 2), the inner wall 27 of the heat exchanger 25 reconstructs the radially inner bounding surface 41 of the secondary flow path 11B. Under these conditions, the bounding surface 41 is formed by the outer surface 42 of the internal structure 21 of the nacelle 3 and by the inner surface 44 of the inner wall 27 of the heat exchanger 25.

[0070] The outer surface 42 of the internal structure 21 of the nacelle 3 and the internal structure 44 of the inner wall 27 are flush, thus reducing the singular pressure drop when the heat exchanger 25 is in the deployed position.

[0071] In the present example, the outer cowling 26, the inner wall 27 and the transmission module 28 form a moving part that is fixed to each other and displaces as a unit when the position of the heat exchanger 25 changes.

[0072] In this regard, the flexible tubes of the connecting members can maintain a sealed connection between the circulation circuit and the lubrication circuit.

[0073] In the present example, the displacement trajectory of the moving part of the heat exchanger 25 is linear and includes a radial translation. In other embodiments not shown, the trajectory may be curved and / or include one or more phases that include a radial translation and / or an axial translation and / or a combination of axial and radial translations.

[0074] In the present example, the propulsion assembly 1 also includes a member (not shown) for detecting the temperature of the heat transfer fluid circulating in the lubrication circuit, and a control module (not shown) that is 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 heat exchanger 25 according to this temperature.

[0075] Generally, if the temperature exceeds a predetermined threshold, the heat exchanger 25 is placed or maintained in the deployed position, and in the contrary case, the heat exchanger 25 is placed or maintained in the retracted position.

[0076] Other parameters can be used to control the position of the heat exchanger 25, such as a parameter representing the flight phase, or even the flow rate of the secondary flow 10B.

[0077] In the present example, along the intermediate longitudinal plane passing through the heat exchanger 25, the outer cowling 26 and the inner wall 27 of the heat exchanger 25 each have a double curvature.

[0078] For example, according to the axial position, the geometries of the outer cowling 26 and the inner wall 27 of the heat exchanger 25 can have any other geometry, and the heat exchanger 25 is placed at the axial position relative to other parts of the nacelle 3.

[0079] In this example, the outer housing 26 and the inner wall 27 of the heat exchanger 25 are produced by additive manufacturing, which can optimize their geometry and reduce the singular pressure drop.

[0080] By analogy, the above description applies to the embodiments of FIGS. 3 and 4.

[0081] Unlike the examples of FIGS. 1 and 2, the outer housing 26 of the heat exchanger 25 (when the heat exchanger is in the retracted position) or its inner wall 27 (when it is in the deployed position) reconstructs the radially outer bounding surface 51 of the secondary flow path 11B.

[0082] In the retracted position (FIG. 3), this bounding surface 51 is formed by the inner surface 52 of the outer structure 22 of the nacelle 3 and by the inner surface 53 of the outer housing 26 of the heat exchanger 25.

[0083] In the deployed position (FIG. 4), this bounding surface 51 is formed by the inner surface 52 of the outer structure 22 of the nacelle 3 and by the inner surface 54 of the inner wall 27 of the heat exchanger 25.

Claims

1. A nacelle (3) of a propulsion assembly (1) of a turbofan aircraft, comprising an internal structure (21), an external structure (22) and a heat exchanger (25), the internal structure (21) and the external structure (22) radially defining therebetween a duct (11B) for the flow of a first fluid that will form a secondary flow (10B), the heat exchanger (25) comprising an outer casing (26) and a transfer module (28), the transfer module (28) comprising 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 transfer heat from the second fluid to the first fluid, characterized in that, The nacelle includes an actuator configured to displace the outer casing (26) of the heat exchanger (25) and the transfer module (28) between the following positions: - A retracted position in which the transfer module (28) is received in the housing (31) of the internal structure (21) or external structure (22) to which the heat exchanger (25) is connected, and the outer casing (26) seals the opening of the housing (31) so as to reconstruct the bounding surfaces (41, 51) of the fluid conduit (11B). - An extended position in which the transfer module (28) extends into the fluid conduit (11B) so as to be traversed by a portion (10C) of the secondary flow (10B) and thereby transfer heat from the second fluid to the first fluid. The heat exchanger (25) includes an inner wall (27), and the transfer module (28) extends radially between the inner wall (28) and the outer casing (26). The inner wall (27) of the heat exchanger (25) is configured to seal the opening of the housing (31) of the internal structure (21) or external structure (22) to which the heat exchanger (25) is connected so as to reconstruct the bounding surfaces (41, 51) of the fluid conduit (11B) when the heat exchanger (25) is in the extended position.

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

3. The engine nacelle (3) according to claim 1 or 2, wherein, The outer casing (26) of the heat exchanger (25) includes surfaces (43, 53) having single or double curvature along a median longitudinal plane.

4. The engine nacelle (3) according to claim 1 or 2, wherein, The heat exchanger (25) includes connection members for connecting the circuit for circulating the second fluid to the lubrication circuit of the propulsion assembly (1).

5. The nacelle (3) according to claim 1 or 2, comprising detection or evaluation means for detecting and / or evaluating at least one parameter, and a control module connected on the one hand to the detection or evaluation means and on the other hand to the actuator so as to be able to displace the outer casing (26) and the transfer module (28) as a function of the at least one parameter.

6. The nacelle (3) according to claim 5, wherein the at least one parameter is the temperature of the second fluid.

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

8. A method for manufacturing a nacelle (3) according to any one of claims 1 to 6, the method comprising a step of additive manufacturing of the outer casing (26) of the heat exchanger (25).

9. A method for manufacturing a nacelle (3) according to any one of claims 1 to 6, the method comprising a step of additive manufacturing of the inner wall (27) of the heat exchanger (23).

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