Fuel oil heat exchanger

Abstract

A turbine engine heat exchanger (50) for exchanging heat between a first fluid (60) and a second fluid (62), the heat exchanger (50) comprising: a reference axis (58); a network (100) of tubular meshes, comprising a plurality of meshes, each mesh being formed in sequence along the reference direction (58) with at least two curvilinear branches referred to as front branches, a junction where the two front branches meet, and at least two curvilinear branches referred to as rear branches, the branches branching from the junction; wherein the meshes are stacked in staggered rows. The invention also relates to a turbine engine comprising the heat exchanger, and a manufacturing method for manufacturing the heat exchanger.

Description

Technical Field

[0001] The invention relates to the field of turbine heat exchangers. More precisely, the invention proposes an oil / fuel heat exchanger for a turbine. The invention also relates to an axial flow turbine, in particular a turbojet. The invention also proposes a process for manufacturing a heat exchanger. Background Art

[0002] Document US 2018 / 0057942 A1 discloses an oil / fuel heat exchanger for an aircraft and manufactured by additive manufacturing. The heat exchanger comprises a set of straight parallel channels formed between two manifolds. The fuel flows through these channels and is heated by the oil, which flows through a cavity defined by a guide wall and a cylindrical wall. The known heat exchanger does not allow a homogeneous distribution of the fuel flowing through the channels. This means that the heat exchange capacity cannot be fully utilized in all areas of the cavity.

[0003] Another example of a heat exchanger is given in US document 9,976,815 B1, which comprises a non-linear network of tubes arranged in parallel. This prior art heat exchanger does not allow two homogeneous distributions.

[0004] Finally, document US 2018 / 0187984 A1 describes a heat exchanger comprising a so-called helical icosahedron structure, i.e. a minimum surface area that varies periodically threefold. This heat exchanger has the disadvantage that the surfaces in contact with the two fluids are identical, which is not always advantageous for the heat exchanger, especially when the two fluids involved have different flow rates. In order to compensate for this inherent difference in the flow, it is necessary to add fins to the helical icosahedron structure to form an obstacle that slows down one of the fluids. However, fins are difficult to integrate into the so-called helical icosahedron. This design also requires a special manufacturing process, in this case LBM (Laser Beam Machining). Summary of the invention

[0005] Technical issues

[0006] The object of the present invention is to solve at least one of the problems of the prior art. The object of the present invention is to optimize the heat exchange, the pressure drop and the operation of the turbine. The present invention also serves to provide a simple and compact solution.

[0007] Technical Solution

[0008] The invention relates to a heat exchanger between a first fluid and a second fluid, in particular a turbine heat exchanger, the heat exchanger comprising: a reference direction; and a network of tubes, the tubes defining an inner channel for the first fluid, the mesh network comprising a plurality of meshes, each mesh being formed in sequence along the reference direction with at least two curvilinear branches called front branches, a confluence where the two front branches meet, and at least two curvilinear branches called rear branches, the rear branches branching from the confluence;

[0009] The multiple meshes include at least a first mesh, a second mesh and a third mesh, and at least one front branch of the first mesh is connected to at least one rear branch of the second mesh, and at least another front branch of the first mesh is connected to at least one rear branch of the third mesh.

[0010] According to a preferred embodiment, the heat exchanger comprises one or more of the following technical features (in any possible combination):

[0011] 5 to 40 meshes are stacked along the reference direction;

[0012] 200 to 3000 mesh bodies;

[0013] The thickness of the walls forming the branches and confluences is 0.4 to 0.8 mm;

[0014] For a given web body, the number of anterior branches differs from the number of subsequent branches;

[0015] For a given mesh body, the number of anterior branches equals the number of posterior branches;

[0016] The number of front branches of the first mesh body is different from the number of front branches of the second mesh body, and / or the number of rear branches of the first mesh body is different from the number of rear branches of the second mesh body;

[0017] The number of branches of each mesh body is 4, 6, 8, 10 or 12;

[0018] At least one of the mesh bodies supports at least one internal or external fin;

[0019] The tubular mesh network is disposed between the inlet partition and the outlet partition. The tubular mesh network opens into the apertures of the inlet partition and the outlet partition. The tubular mesh network directs the first fluid from an inlet manifold to an outlet manifold, the inlet manifold being partially defined by the inlet partition and the outlet manifold being partially defined by the outlet partition;

[0020] a body having a side wall, an inner surface of the wall defining a cavity in which a second fluid flows;

[0021] The side wall of the heat exchanger body is generally cylindrical, preferably with a diameter of 7 to 25 cm and a height of 10 to 60 cm, with the axis of the cylinder aligned in the reference direction;

[0022] a bypass channel for the first fluid to bypass the tubular mesh network, the bypass channel being arranged in a central position of the heat exchanger and being substantially aligned in the reference direction. The network is thereby arranged in an annular space around the bypass;

[0023] The diameter of the bypass channel is preferably 30% to 60% of the diameter of the body;

[0024] The heat exchanger is parallel and / or counter-current. Thus, the main flow directions of the two fluids are parallel and have the same direction or parallel and opposite directions;

[0025] an inner surface of the side wall and / or at least one guide element which guides the second fluid in the first part of the cavity in a flow direction substantially parallel to the reference direction and at least over a majority of the height of the body;

[0026] The guide member further guides the second fluid in another portion of the cavity in a direction opposite to the reference direction over at least a majority of the height of the body;

[0027] The guide element comprises at least one partition wall extending partially and from the inlet partition in a plane parallel to the reference direction;

[0028] The heat exchanger is made of aluminum;

[0029] The heat exchanger is manufactured in a single component. Thus, all mesh networks, collectors, bypasses and the heat exchanger body are manufactured as one component, manufactured together during a single manufacturing operation.

[0030] The heat exchanger is adapted to receive fuel as a first fluid and oil as a second fluid;

[0031] A bypass for the second fluid is integrated in the heat exchanger;

[0032] a drain and / or thermostatic type valve is arranged in the bypass channel for the first fluid or in the bypass for the second fluid;

[0033] The distribution of mesh in the heat exchanger is not necessarily homogeneous. Thus, the number of meshes may be denser radially inwardly or radially outwardly. The mesh density may be higher axially near the fluid inlet to facilitate a very chaotic flow of the fluid as it enters the heat exchanger. Also, the mesh diameter may vary inversely with the mesh density along the flow direction, for example according to successive mesh stages.

[0034] The invention also relates to an aircraft turbojet engine comprising a bearing and in particular a transmission for driving a fan and a heat exchanger as described above.

[0035] The invention also relates to a process for manufacturing a heat exchanger according to the invention, the process comprising the following steps:

[0036] (a) Design of heat exchanger;

[0037] (b) The heat exchanger is fabricated by additive manufacturing along the printing direction parallel to the reference direction.

[0038] The invention may alternatively be defined by a heat exchanger in which at least one mesh has only one of its front branches connected to a rear branch of a second mesh.

[0039] The present invention may alternatively be defined by a heat exchanger wherein a plurality of meshes comprise mesh stages arranged sequentially according to a reference direction, wherein each junction of the meshes of a given stage is offset relative to the junction of an adjacent stage along a direction perpendicular to the reference direction (optionally offset in staggered rows).

[0040] Advantages provided

[0041] In terms of heat exchange, the proposed solution is a compact, lightweight and efficient one. The special structure of the tubular mesh network allows the fluid to be redistributed over all the meshes, which ensures that all areas of the heat exchanger, even the farthest areas (radially), have optimal heat exchange. This solution makes it possible to reduce the size and therefore the weight of the heat exchanger while maintaining the same efficiency. The shape of the curved tubes and the repetition of the cross areas between the tubes promote turbulence and therefore improve heat transfer. In addition, the tubular mesh network forms a self-supporting structure, which improves the design of the components and eliminates the need for any additional mechanical supports in the heat exchanger. The presence of a central bypass avoids the risk of blockage when the heat exchanger is operated in extremely cold conditions. Finally, the heat exchanger is a single component, eliminating the risk of leakage while ensuring very good resistance to stresses. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 shows a turbine according to the invention;

[0043] Figure 2 A heat exchanger according to the present invention is shown;

[0044] Figure 3 A first mesh variation is shown, having four branches arranged in a plane;

[0045] Figure 4 A second mesh variation is shown, having four branches arranged in two secant planes;

[0046] Figure 5 A third mesh variation is shown, called an asymmetric structure with five branches;

[0047] Figure 6 The fourth mesh variation example is shown, with six branches that are rotationally symmetric;

[0048] Figure 7 The fifth mesh variation example is shown, with six mirror-symmetrical branches;

[0049] Figure 8 The sixth mesh variation example is shown, with eight mirror-symmetrical branches;

[0050] Fig. 9 Different alternative embodiments for the junction are shown. DETAILED DESCRIPTION

[0051] Figure 1 A simplified representation of an axial turbine or turbojet or turbine engine 2 is shown. The turbojet engine 2 comprises a first low-pressure compressor 4 and a second high-pressure compressor 6, a combustion chamber 8 and one or more turbines 10. During operation, the mechanical power of the turbine 10 transmitted to a rotor 12 drives the two compressors 4 and 6. The latter comprises a plurality of rows of rotor blades associated with rows of stator blades. The rotation of the rotor around its axis of rotation 14 can thus generate an air flow and gradually compress it to the inlet of the combustion chamber 8.

[0052] A fan 16 is coupled to the rotor 12 and generates an air flow that is divided into a primary flow 18 and a secondary flow 20 along the machine through an annular duct (partially shown) before merging with the primary flow at the turbine outlet.

[0053] A speed change mechanism (eg, reduction gearbox 22) can reduce the rotational speed of the low pressure compressor and / or fan relative to the associated turbine. The secondary flow can be accelerated to produce the thrust response required to allow the aircraft to fly.

[0054] The rotor 12 comprises a drive shaft 24 mounted on a housing via two bearings 26 .

[0055] In order to lubricate the rotating parts of the turbojet 2, a lubrication system 30 is provided. This circuit 30 comprises pipes 32 to transport oil to components of the turbojet, such as the gearbox 22 and the bearings 26. For this purpose, the circuit 30 comprises a pump 34 to move the oil in the circuit 30 and in the tank 36. The oil return lines of the components and their associated discharge pumps are not shown.

[0056] Figure 1 Also shown is a fuel system 40 having pipes 42, a low-pressure pump 44, a high-pressure pump 48 and a tank 46, for example mounted in a wing.

[0057] The oil that lubricates the bearings 22, 26 and 27 is heated and must be cooled. For this purpose, a Fuel Cooled Oil Cooler exchanger (FCOC 50) is provided to regulate the oil temperature in the circuit 32. Using fuel stored in the wing, which is cold at high flight altitudes, allows the oil to cool.

[0058] Figure 2 A heat exchanger according to the invention is shown.

[0059] The heat exchanger 50 comprises a heat exchanger matrix, which comprises a network of tubular meshes 100 arranged between an inlet partition 70 and an outlet partition 72. The flow path formed by the network of tubular meshes 100 is open outward through the partitions 70, 72. The network of tubular meshes 100 guides a first fluid 60 (e.g., fuel) from an inlet manifold 96 to an outlet manifold 98. The network of tubular meshes 100 comprises several levels of staggered meshes. Each mesh comprises branches in the form of curved tubes branching out from a confluence. The network 100 has a set of channels that separate and merge together while ensuring redistribution of the fluid between them. By evolving radially and / or circumferentially relative to the center of the heat exchanger, a given fluid particle can thus reach from one mesh to another. The network 100 may have symmetry (or not).

[0060] The heat exchanger 50 may include a body having a side wall 82, the side wall surrounding the network 100, the two walls 70, 72 and the inner surface portion of the side wall 82 defining a cavity 84, in which the second fluid 62 (e.g., oil) flows. The side wall 82 of the heat exchanger 50 may have a generally cylindrical shape, preferably with a diameter of 7 to 25 cm and a height of preferably 10 to 60 cm, with the cylindrical axis aligned with the reference direction 58.

[0061] The heat exchanger 50 may include a bypass channel 86 for the first fluid 60 to bypass the network 100, the bypass channel 86 being formed at a central position of the heat exchanger 50, the bypass channel 86 being substantially aligned with the reference direction 58. The diameter of the bypass channel 86 may be 30% to 60% of the body diameter. The presence of the bypass channel 86 may strengthen the structure and facilitate maintenance of the tubular mesh network 100.

[0062] The heat exchanger 50 can be parallel (i.e. the first and second fluids flow in the same direction) and / or countercurrent (they flow in opposite directions). In the example shown, there is parallel flow in one portion of the heat exchanger and countercurrent flow in another portion of the heat exchanger. For this purpose, a guide element 88 is provided to guide the second fluid 62 into a portion of the cavity 84 in a flow direction substantially parallel to the reference direction 58. Furthermore, the guide element 88 guides the second fluid 62 into another portion of the cavity over at least a majority of the height of the body in a direction opposite to the reference direction 58. The guide element 88 may include at least one partition wall extending in a plane parallel to the reference direction 58 and arranged between the two partitions 70, 72. Figure 2 The guide element 88 in allows a return flow of the second fluid 62 .

[0063] The bypass channel 86 for the first fluid may include a valve 74, which is of exhaust and / or thermostatic type. Also, the heat exchanger may include a bypass 92 for the second fluid, which is integrated into the body of the heat exchanger 50. Figure 2 In the example of the embodiment of the present invention, the bypass 92 is formed in the lower part of the partition wall serving as the guide element 88. Alternatively, the bypass channel 92 can be manufactured in a module which is integrated with the wall 82 of the heat exchanger body 50, which module can be integrated with the wall of the heat exchanger 50. A valve 94 of the exhaust and / or thermostatic type can be installed in the bypass channel 92.

[0064] Figure 3 Another embodiment of the present invention is represented in which a mesh 103 used as a basic pattern for a tubular mesh network 100 comprises four branches arranged in a plane, the four branches comprising two front branches 103.1, a junction 103.2 and two rear branches 103.3 in sequence along the orientation 58. The basic pattern can be stacked to form a flat or curved plate of a tube (not shown). The upper mesh 103 ( Figure 3 The top and bottom of the right side) can be relative to the lower level 103 mesh body ( Figure 3 The second structure allows for a better three-dimensional redistribution of the fluid.

[0065] Figure 4 An embodiment is shown in which the mesh body 104 has four branches, wherein two rear branches are arranged in a plane that is secant relative to the front branches.

[0066] Figure 5 An embodiment of a mesh 105 is shown, with the mesh 105 having five branches, including two rear branches and three front branches. The construction is asymmetrical.

[0067] Figure 6 Another embodiment of a mesh body 106 having six branches with a rotationally symmetrical structure is shown. The front branches or the rear branches may be evenly distributed with an angle of about 120 degrees between the planes where the branches are located.

[0068] Figure 7 An embodiment of a mesh body 107 having six branches with a mirror-symmetrical structure is shown. The front branches or the rear branches may be evenly distributed, with an angle of about 120 degrees between the planes where the branches are located.

[0069] Figure 8 An embodiment of a mesh body 108 having eight branches with a mirror-symmetrical structure is shown. The front branches or the rear branches can be evenly distributed with an angle of about 90 degrees between the planes where the branches are located.

[0070] These different mesh displays are given as examples. A person skilled in the art will adjust the number of branches and their orientation, the number of meshes, their relative orientation as required and in particular as a function of the flow rate or the desired compactness of the heat exchanger.

[0071] Fig. 9 A mesh 109.1 with a junction as an intermediate tube is shown. In this configuration, the cross section of the internal channel is approximately equal to half of the sum of the channel cross sections of each branch. This configuration achieves a pressure drop, which is desirable for slowing down the flow rate.

[0072] Alternatively, the meshes 109.2 and 109.3 can be designed in such a way that the rear branch is directly connected to the front branch, forming a compartment at the junction 103.2. The compartment improves the mechanical strength of the assembly. The junction of the mesh 109.2 includes a rounded portion for improving the structural strength. For example, a teardrop shape (visible in a plane parallel to the reference direction) can be helpful for realization by additive manufacturing, because it is not necessary to provide reinforcement during the manufacturing process.

[0073] The mesh 109.3 has a junction that includes sharp angles to prevent fluid stagnation and reduce pressure drop. For example, sharp angles such as triangles or pentagons (visible in a plane parallel to the reference direction) are helpful for implementation by additive manufacturing because they are not necessary for providing reinforcement during manufacturing. The cross-section of the branch can be circular. Other cross-sectional shapes (square, triangle, rectangle, ellipse) can control turbulence and / or optimize the strength of the tubular mesh network 100. Fig. 9 The three exemplary junctions can be combined with Figures 3 to 8 Combinations of mesh variations showing various numbers or arrangements of branches.

[0074] Also, the meshes 103, 104, 105, 105, 106, 107, 108, 109.1, 109.2, 109.3 can be stacked in any suitable arrangement, including along directions associated with cylindrical coordinates or Cartesian coordinates.

[0075] The structures of the mesh bodies 103, 104, 104, 105, 106, 106, 107, 108, 109.1, 109.2, and 109.3 as described above with respect to the number of branches and regulations are not limited to the examples given in the accompanying drawings.

[0076] The complexity of the mesh network structure is not obtainable by conventional manufacturing means and is therefore achieved according to the invention by additive manufacturing with powders (which can be titanium or aluminum). The thickness of the layer can be 20 μm to 50 μm, which can form a tube thickness that forms a mesh of about 0.4 to 0.6 mm and a partition / wall of 0.60 mm. In the invention based on a process (not shown), two steps are performed:

[0077] (a) Designing a heat exchanger 50;

[0078] (b) The heat exchanger 50 is manufactured by additive manufacturing along a printing direction, which is parallel to the reference direction 58.

[0079] With additive manufacturing, complex shaped flow paths can be planned that intersect through the matrix.

[0080] Also, the present invention is not limited to use in oil / fuel heat exchange.

Claims

1. A heat exchanger (50) between a first fluid (60) and a second fluid (62), the heat exchanger (50) comprising: Reference direction (58); and A network (100) of tubes defining an inner passage for a first fluid (60), the network (100) comprising a plurality of meshes (103, 104, 104, 105, 106, 106, 107, 108, 109.1, 109.2, 109.3), each of the meshes (103, 104, 105, 105, 106, 107, 108, 109.1, 109.2, 109.3) being formed in sequence according to a reference direction (58) with at least two curvilinear branches referred to as front branches (103.1), a junction (103.2) where the two front branches (103.1) meet, and at least two curvilinear branches referred to as rear branches (103.3), the rear branches branching from the junction (103.2); in The plurality of meshes (103, 104, 105, 105, 106, 107, 107, 108, 109.1, 109.2, 109.3) include at least one first mesh (103, 104, 104, 105, 106, 107, 108, 109.1, 109.2, 109.3) having a first front branch and a second front branch (103.1), at least one second mesh (103, 104) having at least one rear branch (103.3), , 104, 105, 106, 107, 108, 109.1, 109.2, 109.3) and at least one third mesh (103, 104, 105, 106, 107, 108, 109.1, 109.2, 109.3) different from the second mesh (103, 104, 105, 105, 106, 107, 108, 109.1, 109.2, 109.3) and having at least one rear branch (103.3), wherein the first front branch (103.1) of the first mesh (103, 104, 105, 105, 106, 107, 108, 109.1, 109.2, 109.3) is only connected to a corresponding one of at least one rear branch (103.3) of the second mesh (103, 104, 108, 109.1, 109.2, 109.3), and the second front branch (103.1) of the first mesh (103, 104, 105, 105, 106, 107, 108, 109.1, 109.2, 109.3) is only connected to a corresponding one of at least one rear branch (103.3) of the third mesh (103, 104, 105, 105, 106, 107, 108, 109.1, 109.2, 109.3), The heat exchanger (50) further comprises a body having a cylindrical side wall (82) defining a cavity (84), wherein the second fluid (62) flows in the cavity, and the cylindrical axis is aligned with the reference direction (58), and the heat exchanger (50) is a parallel flow and / or counter-flow.

2. The heat exchanger (50) as claimed in claim 1, wherein the heat exchanger (50) comprises a stacked structure of 5 to 40 mesh bodies (103, 104, 105, 105, 106, 107, 107, 108, 109.1, 109.2, 109.3) arranged sequentially along a reference direction (58).

3. The heat exchanger (50) according to claim 1, wherein the heat exchanger (50) comprises 200 to 3000 mesh bodies (103, 104, 105, 106, 107, 108, 109.1, 109.2, 109.3).

4. The heat exchanger (50) of claim 1, wherein the branches (103.1, 103.3) and the junction (103.2) are formed by a wall having a thickness of 0.4 to 0.8 mm.

5. The heat exchanger (50) according to claim 1, wherein at least one of the mesh bodies comprises a plurality of front branches (103.1), and the number of the front branches is different from the number of the rear branches (103.3).

6. The heat exchanger (50) according to claim 1, wherein the number of branches of each mesh body (103, 104, 105, 105, 106, 107, 107, 108, 109.1, 109.2, 109.3) is 6.

7. The heat exchanger (50) of claim 1, wherein at least one of the meshes (103, 104, 105, 105, 106, 107, 108, 109.1, 109.2, 109.3) supports at least one internal or external fin.

8. The heat exchanger (50) of claim 1, wherein the network of tubular mesh (100) is disposed between the inlet manifold (96) and the outlet manifold (98).

9. The heat exchanger (50) of claim 1, wherein the side wall (82) has a diameter of 7 to 25 cm and a height of 10 to 60 cm.

10. The heat exchanger (50) of claim 1, wherein the heat exchanger (50) comprises a bypass channel (86) for the first fluid (60) allowing it to bypass the network (100), the bypass channel (86) being arranged in a central position of the heat exchanger (50) and aligned with the reference direction (58).

11. The heat exchanger (50) of claim 10, wherein the diameter of the bypass channel (86) is 30% to 60% of the side wall diameter.

12. The heat exchanger (50) of claim 1, wherein the first and second fluids have respective general flow directions, and the general flow direction of the first fluid is parallel to the general flow direction of the second fluid.

13. The heat exchanger (50) of claim 1, wherein the at least one guide element (88) and the side wall (82) guide the second fluid (62) in the first portion of the cavity (84) in a flow direction substantially parallel to the reference direction (58) over at least half the height of the body.

14. The heat exchanger (50) of claim 13, wherein the guide member (88) and the side wall further guide the second fluid (62) in the second portion of the cavity in a flow direction opposite to the reference direction (58).

15. The heat exchanger (50) of claim 14 in combination with claim 8, wherein the guide element is a partition wall extending from an inlet partition (70) defining the inlet manifold, the partition wall extending along a plane parallel to the reference direction (58).

16. The heat exchanger (50) of claim 1, wherein the heat exchanger (50) is a one-piece component fabricated from aluminum.

17. The heat exchanger (50) of claim 1, wherein a bypass (92) for the second fluid is integrated in the heat exchanger (50).

18. The heat exchanger (50) as claimed in claim 1, wherein the heat exchanger (50) comprises a valve (74) of the thermostatic type arranged in the bypass channel (86) for the first fluid or in the bypass for the second fluid.

19. An aircraft turbojet engine (2) comprising a bearing (26) and a transmission (22) driving a fan (16), further comprising at least one heat exchanger (50) according to any one of claims 1 to 18, wherein the first fluid (60) is a fuel and the second fluid (62) is an oil.

20. A method for manufacturing a heat exchanger (50) according to claim 1, the method comprising the following steps: (a) designing a heat exchanger (50); (b) Manufacturing the heat exchanger (50) by additive manufacturing along a printing direction parallel to the reference direction (58).

21. A method as claimed in claim 20, wherein it comprises in step (b) manufacturing successive layers parallel to each other, the successive layers being visible in a plane perpendicular to the plane of the layers, the mesh being manufactured to have a water drop profile or a pentagonal profile.

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