Variable-height finned heat exchanger and corresponding turbine

Abstract

The invention relates to a heat exchanger (1) for a turbomachine, the heat exchanger having a longitudinal axis (X), the heat exchanger being configured to produce heat exchange between a first fluid (2) and a second fluid (3), the heat exchanger comprising two panels (25, 26) and a plurality of fins (29) extending between the panels, the fins being arranged in rows and staggered along the longitudinal axis, each row of fins is parallel to and connected to each other, and the heat exchanger is annular and centered on the longitudinal axis X. The panel extends radially between an inner cylindrical surface (34a) and an outer cylindrical surface (34b) of the heat exchanger, and the fin has a first exchange surface and a second exchange surface defined in a plane substantially perpendicular to the radial axis and configured to be swept by a first fluid along the longitudinal axis, each row of fins has a height measured between the panels that increases radially between the inner and outer cylindrical surfaces.

Description

Technical Field

[0001] The present invention relates to the general field of aviation. In particular, the present invention relates to a heat exchanger for a turbomachine, in particular for an aircraft. Background Art

[0002] Aircraft turbines and aircraft include various components and / or equipment parts that need to be lubricated and / or cooled for their correct operation, or contain fluids that need to be cooled for the correct operation of the turbine. These components and / or equipment parts and / or fluids may be devices for guiding the rotor in the turbine, electrical and / or electronic components for the electrical system in the turbine of the aircraft, hot exhaust gases from the turbine configured to be introduced upstream of the combustion chamber, or systems for conditioning the interior of the aircraft. The heat released by these components, equipment parts and / or fluids, which may be very high, is discharged by heat exchange in the turbine and / or aircraft.

[0003] Heat exchange is achieved using one or more heat exchangers installed in the turbine or aircraft for various applications. Depending on the application, the heat exchanger usually uses a cold source and a hot source, which can be ambient air, air from the secondary duct of the turbine, etc., and the hot source can be the turbine's fuel, oil, exhaust air collected from the low-pressure compressor or high-pressure compressor of the turbine, or air from the main duct of the turbine.

[0004] The heat exchanger can be a tube heat exchanger, a fin heat exchanger, a plate fin heat exchanger, etc. Plate fin heat exchangers (particularly offset strip fins) are used in turbines due to their low mass. These heat exchangers include multiple rows of fins parallel to each other and multiple rows of fins arranged at staggered or offset intervals. The heat exchanger can be configured in multiple stages. In general, a first fluid (e.g., hot exhaust gas) and a second fluid (e.g., an air flow circulating in a turbine) pass through a heat exchanger. An example of a plate fin heat exchanger is described in patent document FR3077630.

[0005] The prior art also includes the following documents: US-A-3818984, US-A-2792200, US-A1-2021 / 0180886, US-B2-10866030, US-A1-2016 / 0054071, US-A1-2021 / 0222963, US-A1-2012 / 0216543, FR-A1-3097257, US-A-2429508 and US-B2-8601791.

[0006] This type of heat exchanger is difficult to integrate into a turbine because of the number of stages involved and the limited available space included in the turbine.

[0007] Annular heat exchangers have been developed for integration into turbines, but with other types of fin configurations. The arrangement of the fins in these annular heat exchangers results in a high pressure drop, in particular due to the high form drag. It is difficult to significantly increase the number of fins to improve the performance of the turbine. In addition, the different temperatures of the fluids circulating in this type of heat exchanger mean that there are differences in the speed at which the fluids circulate. These speed differences are exacerbated by the differences in hydraulic diameter and hydraulic resistance, which increase with the radius (in cylindrical coordinates) of the heat exchanger. This results in uneven distribution of the flow or fluid in the heat exchanger, which may reduce the hydraulic / aerodynamic performance.

[0008] The size of the heat exchanger is usually designed to have an optimal convection thermal resistance ratio. The optimal thermal resistance ratio depends on the properties of the two fluids, the temperature / pressure / flow rate, and the allowable pressure drop of each fluid. If the fluids have the same properties, with relatively similar temperature / pressure / flow rate conditions and pressure drop, the optimal thermal resistance ratio can be close to 1.

[0009] There is a need to address some or all of the above disadvantages. Summary of the invention

[0010] The object of the present invention is to provide a heat exchanger which makes it possible to optimize the aerodynamic thermal and aerodynamic performances while reducing the pressure drop and avoiding significant effects on the mass.

[0011] According to the invention, this object is achieved by a heat exchanger for a turbomachine, in particular an aircraft turbomachine, the heat exchanger having a longitudinal axis, the heat exchanger being configured to produce a heat exchange between a first fluid and a second fluid, the heat exchanger comprising at least a first panel, a second panel and a plurality of fins extending between the first panel and the second panel, the fins being arranged in a plurality of rows along the longitudinal axis and in a staggered configuration, the fins of each row being parallel to each other and connected to each other,

[0012] The heat exchanger is annular and centered on a longitudinal axis X,

[0013] The first and second panels extend radially between the inner and outer cylindrical surfaces of the heat exchanger, the fins have first and second exchange surfaces, the first and second exchange surfaces are defined in a plane substantially perpendicular to the radial axis of the heat exchanger and are configured to be swept by the first fluid along the longitudinal axis, each row of fins having a height, on the one hand, measured between the first and second panels, and on the other hand, increasing radially between the inner and outer cylindrical surfaces.

[0014] Therefore, this solution enables the above-mentioned objects to be achieved. In particular, by adjusting the size and characteristics of the exchange surface of the first fluid as a function of the distance from the central axis of the heat exchanger, the thermal performance of the heat exchanger is significantly improved. With this configuration, the heat exchanger provides a relatively uniform and improved distribution of the first fluid. Increasing the height of the fins leads to a change in the hydraulic diameter and the exchange surface coefficient. At the fins with a larger height, there will be less resistance to the flow of the first fluid. In addition, the geometrical variation of the exchange surface ensures that the apparent permeability of the heat exchanger remains constant.

[0015] The heat exchanger may further include one or more of the following features, taken alone or in combination:

[0016] - A longitudinal spacing defining the distance between a trailing edge of a first fin of the plurality of fins and a leading edge of an adjacent and consecutive second fin of the plurality of fins is constant.

[0017] - The fins are radially spaced apart by a constant lateral spacing.

[0018] The fins are radially spaced apart by lateral spaces which decrease from the inner cylindrical surface towards the outer cylindrical surface.

[0019] - Each fin has a constant length along the longitudinal axis.

[0020] - Each fin has a length along the longitudinal axis that varies from upstream to downstream.

[0021] The first panel, the second panel and the fins between the first panel and the second panel form a stage, the heat exchanger comprising a plurality of stages separated by passages configured for circulation of the second fluid, the passages opening to the upstream surface and the downstream surface.

[0022] - the first panel, the second panel and the fins between the first panel and the second panel form a stage, the heat exchanger comprising a plurality of stages arranged around the longitudinal axis, the plurality of stages being separated by passages configured for circulation of a second fluid, the passages opening to the inner cylindrical surface and the outer cylindrical surface.

[0023] - The heat exchanger is formed as a single piece.

[0024] The fins are alternately connected by top and bottom walls connected to the first and second panels respectively.

[0025] The heat exchanger comprises an inlet defined in an upstream surface, where the first fluid and / or the second fluid enters the heat exchanger, and an outlet defined in an opposite downstream surface along the longitudinal axis, through which the first fluid and / or the second fluid exits the heat exchanger.

[0026] The heat exchanger comprises an inlet defined in the inner cylindrical surface, through which the second fluid enters the heat exchanger, and an outlet defined in the outer cylindrical surface, through which the second fluid exits the heat exchanger.

[0027] - The increase in fin height is linear.

[0028] -The length of each fin is defined linearly, the length of the fin is determined by the parameter Determine, where s is the lateral space between fins of the same row and is a function of the radial position of the fin in cylindrical coordinates, Rmin is the minimum radius of the heat exchanger defined by the inner cylindrical surface, and Rmax is the maximum radius of the heat exchanger defined by the outer cylindrical surface.

[0029] The invention also relates to a turbomachine comprising a heat exchanger having any of the above characteristics, the first and second panels being regularly arranged around a longitudinal axis, the fins being arranged between the first and second panels.

[0030] The invention also relates to an aircraft comprising a turbine as described above.

[0031] The invention also relates to a method for manufacturing a heat exchanger as described above, said method comprising the step of producing the heat exchanger by additive manufacturing by selective fusion on a powder bed. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be better understood and other objects, details, features and advantages of the invention will become clearer on reading the following detailed description of embodiments of the invention given by way of purely illustrative and non-limiting example, and with reference to the accompanying drawings, in which:

[0033] Figure 1 is a perspective view of a heat exchanger including plates and fins according to the present invention;

[0034] Figure 2 is an axial cross-sectional view of an example of a turbine to which the present invention is applicable;

[0035] Figure 3 is a schematic front view of a stage of a heat exchanger according to the present invention;

[0036] Figure 4 is a perspective view of an example of a fin arrangement of a heat exchanger according to the present invention;

[0037] Figure 5 shows a radial cross-sectional view of an embodiment of a heat exchanger according to the present invention;

[0038] Figure 6is a radial cross-sectional view of another embodiment of a heat exchanger according to the present invention; and

[0039] Figure 7 is a front view of an example of a heat exchanger according to the present invention. DETAILED DESCRIPTION

[0040] Figure 1 There is shown a heat exchanger 1 capable of transferring thermal energy between a first fluid 2 and a second fluid 3. The heat exchanger 1 is configured to be installed in an aircraft turbine 4. Of course, the heat exchanger 1 may be installed in any system where thermal energy transfer is required.

[0041] Figure 2 A turbofan engine 4 with a longitudinal axis X, to which the invention is applicable, is shown in axial cross section. Of course, other types of turbomachines are also contemplated.

[0042] The turbofan engine 4 generally comprises a gas generator or a gas turbine engine 5, upstream of which a fan or a fan module 6 is mounted. In the present invention, the terms "upstream" and "downstream" are defined relative to the circulation of the gases in the turbine, here along the longitudinal axis X and with reference to Figure 2 Defined from left to right.

[0043] The fan 6 comprises blades 7 surrounded by a fan casing 8. The fan casing 8 carries a nacelle 9. The nacelle is annular, centred on a longitudinal axis X, and is connected to the aircraft.

[0044] In a known and non-limiting manner, the gas generator 5 comprises, from upstream to downstream, a low-pressure compressor 10a, a high-pressure compressor 10b, an annular combustion chamber 11, a high-pressure turbine 12a and a low-pressure turbine 12b. Typically, the turbine 1 comprises a low-pressure shaft 13 and a high-pressure shaft 14, the low-pressure shaft connecting the low-pressure compressor 10a and the low-pressure turbine 12a to form a low-pressure body, and the high-pressure shaft connecting the high-pressure compressor 10b and the high-pressure turbine 13a to form a high-pressure body.

[0045] The low-pressure shaft 13 centered on the longitudinal axis drives the fan shaft 15. As here, a speed reducer 16 can be arranged between the fan shaft 15 and the low-pressure shaft 13. Advantageously, a rotary guide bearing 17 can also be used to guide the low-pressure shaft 13, the high-pressure shaft 14 and the fan shaft 15 to rotate relative to the fixed structure of the turbine.

[0046] In this example configuration of the turbine 1, the guide bearing 17 and the reducer 16 must be lubricated and / or cooled to ensure the performance of the turbine. The power generated by these components is dissipated in a fluid from a fluid supply source installed in the turbine, which enables lubrication and / or cooling of various components and / or equipment parts of the turbine. The turbine or other equipment parts of the aircraft (such as motors, generators, batteries, accessory gearboxes, electronic / electrical systems, aircraft internal cooling systems, or even exhaust gases) may have to transfer a large amount of thermal energy.

[0047] The heat exchanger 1 is described in more detail below in the context of being installed in a turbine and in this example enables a first fluid 2 to be cooled by a second fluid 3. In this example, the first fluid 2 comprises gas leaving one or more compressors and the second fluid 3 comprises exhaust gas from a turbine 4 at an injection nozzle 18. The exhaust gas is used, for example, to heat the gas leaving the one or more compressors before passing through the combustion chamber 11. Heat in the exhaust gas is usually lost.

[0048] Alternatively, the first fluid 2 is a secondary flow generated by a fan and the second fluid 3 is a secondary flow through a gas generator.

[0049] Advantageously but not limitingly, the main flow circulates in a primary duct 19 radially delimited by an inner wall 20a of an annular inter-duct casing 20 and an outer wall 21a of an inner casing 21. The secondary flow circulates in a secondary duct 22 radially delimited by at least one inner wall 8a of the fan casing 8 and a wall 20b of the inter-duct casing 20 surrounding the gas generator.

[0050] The terms “radially” or “radial” are defined relative to a radial axis Z extending from and perpendicular to the longitudinal axis L of the turbomachine 1 .

[0051] The heat exchanger 1 may be arranged in the primary duct 19 or alternatively in the secondary duct 22. Alternatively, the heat exchanger may be arranged at the injection nozzle 18. Advantageously, the heat exchanger may be arranged upstream of the combustion chamber or downstream of the combustion chamber.

[0052] refer to Figure 3 , the heat exchanger 1 comprises a primary exchange surface 23 and a secondary exchange surface 24. The primary exchange surface 23 comprises two panels (or plates) referred to as a first panel 25 and a second panel 26 respectively.

[0053] The heat exchanger 1 further comprises a plurality of fins 29 extending between the first panel 25 and the second panel 26. The fins 29 form the secondary exchange surface 24. The fins 29 extend transversely to the first panel 25 and the second panel 26. Advantageously, the fins 29 form channels 30 in which the first fluid 2 circulates. The first fluid 2 is configured to pass / sweep the fins 29 and flow between the first panel 25 and the second panel 26.

[0054] Figure 4 A perspective view of the fins 29 of the heat exchanger 1 is shown without the panels 25, 26. Each fin 29 is substantially flat and extends in a first direction D1.

[0055] The fins 29 each have a leading edge 29a and a trailing edge 29b for the first fluid 2. The leading edge 29a and the trailing edge 29b are opposite to each other in a first direction D1. The leading edge 29a and the trailing edge 29b define the fin 29 longitudinally. The leading edge 29a is the edge at which the first fluid 2 first contacts the fin 29. The trailing edge 29b is the edge at which the first fluid 2 contacts the fin 29 last. The leading edge 29a and the trailing edge 29b extend generally in a second direction D2. Each fin 29 also includes a first exchange surface 29c and a second exchange surface 29d connected to each other by the leading edge 29a and the trailing edge 29b. In the example shown, the first exchange surface 29c and the second exchange surface 29d are opposite to each other in a third direction D3. The third direction D3 is perpendicular to the first direction D2 and the second direction D3.

[0056] Advantageously, in this example, each fin 29 has a substantially rectangular shape. Alternatively, the fin 29 has a trapezoidal shape or any other shape, or the fin 29 may be relatively Figure 4 The planes D1 , D2 in the example shown are inclined.

[0057] The term "direction" is used in particular to describe the heat exchanger. In the installed condition, a first direction D1 is parallel to the longitudinal axis X of the turbomachine 1 .

[0058] The fins 29 are arranged in a plurality of rows R1, R2, ... Rn along the first direction D1. Each row of fins includes a plurality of fins 29. The rows of fins 29 are parallel to each other. In this case, the rows R1, R2, Rn of the fins 29 are parallel to the third direction D3.

[0059] like Figure 4 As shown, the fins 29 are also staggered. More specifically, the fins 29 are offset in the third direction D3. Advantageously, every other row of fins 29 is located in the same plane parallel to the planes D1, D2. This arrangement makes it possible to improve heat exchange by interrupting and uniformly reforming the thermal boundary layer on the surface of the fins 29. The thermal boundary layer is interrupted at the trailing edge of each fin 29 and reformed at the leading edge of each fin 29.

[0060] Advantageously, each fin 29 is spaced apart from the adjacent fin 29 in the first direction D1 and has a specific longitudinal spacing Pl. More specifically, the spacing Pl defines the distance between the trailing edge 29b of the first fin and the leading edge 29a of the adjacent and continuous second fin. Each row of fins is also spaced apart along this longitudinal spacing Pl. Advantageously, the longitudinal spacing Pl is constant.

[0061] Another advantageous feature is that the fins 29 in the same row are spaced apart transversely (along the third direction D3). Thus, a transverse space s is provided between each transverse fin 29. More precisely, the transverse space s defines the distance between the first exchange surface 29d of the first fin 29 and the second exchange surface 29d of the second fin.

[0062] Advantageously but not limitingly, each row of fins 29 is alternately connected to each other by a top wall 31 and a bottom wall 32. The top wall 31 and the bottom wall 32 are generally flat and face each other in the second direction D2. The top wall 31 and the bottom wall 32 extend in the first direction D1. Similarly, the fins 29 of adjacent rows in the first longitudinal direction are connected to each other by the top wall 31. These top walls 31 and the bottom wall 32 have a leading edge 33a connected to the leading edge 29a of the fin 29 and a trailing edge 33b connected to the trailing edge 29b of the fin 29.

[0063] The fins 29 are attached to the first panel 25 and the second panel 26. Advantageously, the attachment is achieved by means of a top wall 31 and a bottom wall 32. The attachment may be achieved by welding or brazing.

[0064] The heat exchanger 1 may be a single-stage heat exchanger or a multi-stage heat exchanger. Figure 2 A single stage is shown. A stage is defined by fins 29 and a first panel 25 and a second panel 26. In this way, the first fluid 2 circulates through the fins 29 in the channels 30, between the two panels 25, 26, while the second fluid 3 circulates above the first panel 25 and below the second panel 26. In the case of a multi-stage heat exchanger 1, the various stages will be separated by passages through which the second fluid is configured to circulate. Each passage will be formed between two adjacent panels 25, 26 of different stages.

[0065] refer to Figure 1 and Figure 5 , the heat exchanger 1 is annular (360°) or in the shape of an angular sector. Advantageously, the heat exchanger 1 is centered in the first longitudinal direction D1. In the installed condition, the first direction D1 is centered on the longitudinal axis X. The annular shape of the heat exchanger 1 enables it to be better integrated and to occupy a smaller overall size in the turbine 4.

[0066] Advantageously, the annular heat exchanger 1 has an inner cylindrical surface 34a defining an inner radius Ri and an outer cylindrical surface 34b defining an outer radius Re. The heat exchanger 1 also has an upstream surface 35 (or front surface) and a downstream surface 36 opposite each other along the longitudinal axis (first direction). The upstream surface 35 and the downstream surface 36 are connected by the inner cylindrical surface 34a and the outer cylindrical surface 34b.

[0067] The heat exchanger 1 comprises an inlet E through which the first fluid 2 enters the heat exchanger 1. The inlet E is defined at the upstream surface 35. The heat exchanger 1 also comprises an outlet S through which the first fluid 2 escapes from the heat exchanger 1. The outlet S is defined at the downstream surface 36. In other words, the first fluid 2 circulates axially along the longitudinal axis from upstream to downstream.

[0068] Advantageously, the heat exchanger 1 comprises a further inlet and a further outlet through which the second fluid 3 enters the heat exchanger.

[0069] The second fluid 3 may flow through the heat exchanger 1 axially (along the longitudinal axis) or radially (along the radial axis).

[0070] The fins are configured to improve the aero-thermal and aerodynamic performance of the annular heat exchanger.

[0071] The height H of the fins 29 varies linearly along the radial axis of the heat exchanger. Advantageously, the height H of each fin is measured between the first 25 and second 26 panels.

[0072] according to Figure 5 In the embodiment shown, the first fluid is perpendicular to Figure 5 Flow in the direction of the plane shown. Lines arranged in the circumferential direction around the longitudinal axis and defining heights H1, H2, etc. represent the trailing edge or leading edge or thickness of the fin along a radial cross section between the first exchange surface 29c and the second exchange surface 29d. The height H of the fin 29 increases linearly from the inner cylindrical surface 34a to the outer cylindrical surface 34b. The height of the fin varies transversely to the flow of the first fluid. The fins 2 in the same row R1, R2, Rn along the radial axis have different heights H1, H2, H3, H4, H5. The first exchange surface 29c and the second exchange surface 29d of the fin 29 are defined in a plane perpendicular to or substantially perpendicular to (+ / - 5°) the radial axis.

[0073] In this example, the fins in the same row extending along the longitudinal axis have the same height. In particular, the fin 29 closest to the longitudinal axis has the smallest height H1 and the fin farthest from the longitudinal axis has the largest height Hn.

[0074] At the outer cylindrical surface 34b, the hydraulic diameter of the heat exchanger is larger. The first fluid can enter the heat exchanger easily and with less resistance at the fins near the outer cylindrical surface 34b than at the fins near the inner cylindrical surface 34a. The flow rate near the inner cylindrical surface is lower. By changing the height, the heat exchange is also improved and the pressure drop is avoided.

[0075] like Figure 5 As can be seen in FIG. 1 , the lateral spacing s between the fins 29 along the radial axis is constant. Figure 5 34a. In other words, the first fluid 2 circulates along the longitudinal axis. For example, the space s is between 5 mm and 100 mm. With a constant lateral space s, the heat exchanger is more "permeable" near the inner cylindrical surface 34a, which means that the first fluid will tend to "pass" through the inner cylindrical surface 34a and have a higher velocity.

[0076] Advantageously, the fins 29 each have a constant predetermined length L. The length L of each fin is measured along the first direction D1 (longitudinal axis) between the leading edge 29a and the trailing edge 29b. For example, the length L of each fin 29 is between 0.5 mm and 150 mm. Advantageously, the length L of the fins can vary linearly.

[0077] according to Figure 6 In an embodiment, the height H of the fins 29 and the lateral spacing s between the fins in the same row are varied. Here, the lateral spacing s1, s2, s3, s4, s5, s6 between each fin 29 along the radial axis decreases or decreases from the inner cylindrical surface 34a to the outer cylindrical surface 34b. Advantageously, the variation of the spacing s is continuous. Here, the spacing increases as the radius of the heat exchanger (i.e., along the radial axis) increases.

[0078] The height H increases linearly from the inner cylindrical surface 34a to the outer cylindrical surface 34b. The fins 29 close to the longitudinal axis have the same height H1. The fins in each row farthest from the longitudinal axis also have the same height H5. As the fin height increases, the permeability of the heat exchanger also increases. The velocity of the first fluid 2 is high, especially near the outer cylindrical surface 34b.

[0079] Advantageously, the transverse spacing s near the longitudinal axis is between 5 mm and 100 mm, and the transverse spacing s between the fins furthest from the longitudinal axis is between 5 mm and 50 mm. Varying the transverse spacing s enables compensation and adjustment for the permeability increase by varying the fin height. The transverse spacing s decreases as the radius of the heat exchanger increases. The second fluid is more evenly distributed.

[0080] exist Figure 6 In this example, the length L of the fin is constant, but it can also vary linearly.

[0081] The longitudinal spacing P1 between each fin 29 is constant. The longitudinal spacing may be between 0.5 mm and 50 mm.

[0082] Figure 7 A radial cross section of a heat exchanger 1 installed in a turbine is shown. The heat exchanger 1 is annular and centered on a longitudinal axis X. The heat exchanger 1 has a plurality of stages arranged around the longitudinal axis X. The pattern formed by the fins 29 between the two panels 25, 26 is non-uniform. The first panel 25 and the second panel 26 each extend radially relative to the longitudinal axis X. The first exchange surface 29c and the second exchange surface 29d of each row of fins 29 are defined in a plane perpendicular to the radial axis. The exchange surfaces 29c, 29d are swept along the longitudinal axis by the first fluid. The channel 30 formed by the fin 29 leads to an upstream surface 35 and a downstream surface 36.

[0083] The length L of the fins 29 also extends axially. Between each stage is a passage 37 arranged for the circulation of a second fluid. Each passage 37 extends between a radially inner end 37a and a radially outer end 37b.

[0084] Advantageously, the radially inner end 37a of the passage 37 opens into the inner cylindrical surface 34a, while the radially outer end 37b opens into the outer cylindrical surface 34b.

[0085] Another advantageous feature is that the passage 37 opens into the upstream surface 35 which can form an inlet for the second fluid 3. The passage 37 also opens into the downstream surface to form an outlet for the second fluid 3.

[0086] The height H of the fins 29 increases along the radial axis (ie, from the central axis of the heat exchanger 1 towards the position furthest from the center). Figure 7 It is shown that the lateral space s is constant.

[0087] The length of each fin 29 can be defined linearly. The variation in length can be a function of the average radial coordinate of the fin and is determined by the parameter where s is the lateral space between the fins 29 and is a function of the radial position of the fins in cylindrical coordinates. Cylindrical coordinates are a known way of locating a given point in space using azimuth, altitude and radius relative to a principal axis (in this case the longitudinal axis).

[0088] For example, the parameter λ r Probably somewhere between 1.2 and 1.8.

[0089] Alternatively, but not limiting, the fins are corrugated and have an offset pitch.

[0090] Advantageously, this makes it possible to have a relatively constant hydraulic diameter over the entire upstream front surface of the heat exchanger for the first fluid 2 in question, with the lateral spacing s decreasing as the fin height H increases: where s is the lateral space between two consecutive fins along the radial axis, H is the fin height, and D H,0 is the average reference hydraulic diameter.

[0091] The first fluid 2 circulates along the longitudinal axis. Advantageously, the first fluid 2 enters the heat exchanger at the upstream front surface 35 and leaves at the downstream surface 36. Similarly, the second fluid 3 circulates along the longitudinal axis and / or along the radial axis.

[0092] Advantageously, the fin 29, the first panel 25 and the second panel 26 are formed in one piece (integral or monolithic). Advantageously, these components are obtained by an additive manufacturing method, in particular by selective melting on a powder bed ("Selective Laser Melting", abbreviated to SLM). This method is particularly suitable for producing annular heat exchangers in one piece. In particular, this method makes it possible to obtain complex shapes and components with good strength and mechanical properties. The principle of additive manufacturing SLM is based on the melting of thin two-dimensional (2D) powder layers (such as metal, plastic or ceramic) using a high-power laser.

[0093] In this additive manufacturing method, the heat exchanger does not have top and bottom walls. This method enables direct connection of the fins to the first and second panels 25, 26. Additive manufacturing and the absence of these walls means weight savings.

[0094] Additive manufacturing is carried out using an SLM device which generally comprises a supply tank containing the powder and a manufacturing support on which the part to be manufactured (in this case, the heat exchanger 1) is produced. The device also comprises a sweeping element which enables a certain amount of powder to be transferred from the supply tank to the manufacturing support, which is mounted so as to be movable in vertical translation Z. The device also comprises an element for generating a laser beam which enables the melting of the powder configured to produce the part, and means (such as a reflector) which allow the laser beam to be directed to the support. A recovery tank enables the recovery of unused or unmelted powder.

[0095] The method involves manufacturing a component by stacking layers of powder from a supply tank and transferring them to a manufacturing support. These powder layers are then melted one by one as a laser beam moves over the surface of each layer. The temperature of the powder is raised to a temperature above the melting temperature of the powder using a laser beam. The molten layers gradually solidify to form a single block.

[0096] Advantageously, the different layers configured to form the heat exchanger are superimposed along a manufacturing axis parallel to the first direction D1 .

Claims

1. A heat exchanger (1) for a turbine (4), in particular an aircraft turbine, the heat exchanger having a longitudinal axis (X), the heat exchanger (1) being annular and centered on the longitudinal axis, the heat exchanger being configured to generate heat exchange between a first fluid (2) and a second fluid (3), the heat exchanger (1) comprising at least a first panel (25), a second panel (26) and a plurality of fins (29) extending between the first panel and the second panel (25, 26), the first panel (25) and the second panel (26) being arranged at an inner cylindrical surface (34a) and an outer cylindrical surface (34b) of the heat exchanger (1). The heat exchanger comprises a heat exchanger having a first surface (29a) and a second surface (29b) extending radially between the first and second surfaces (34b), the fins (29) having a first exchange surface and a second exchange surface (29c, 29d), the first exchange surface and the second exchange surface being defined in a plane substantially perpendicular to the radial axis of the heat exchanger and being configured to be swept along the longitudinal axis by the first fluid (2), the fins (29) of each row (R1, R2, Rn) having a height (H) measured between the first and second panels (25, 26) on the one hand and increasing radially between the inner cylindrical surface (34a) and the outer cylindrical surface (34b) on the other hand, characterized in that The fins (29) are arranged in a plurality of rows (R1, R2, Rn) along the longitudinal axis and in a staggered configuration, the fins (29) in each row (R1, R2, Rn) being parallel to and connected to each other, and a longitudinal spacing (Pl) defining a distance between a trailing edge (29b) of a first fin among the plurality of fins and a leading edge (29a) of an adjacent and continuous second fin among the plurality of fins being constant.

2. The heat exchanger (1) according to claim 1, characterized in that The fins (29) are radially spaced apart by constant lateral spaces (s).

3. The heat exchanger (1) according to claim 1, characterized in that The fins (29) are radially spaced apart by lateral spaces (s) which decrease from the inner cylindrical surface (34a) towards the outer cylindrical surface (34b).

4. A heat exchanger (1) according to any one of the preceding claims, characterised in that Each fin (29) has a constant length (L) along the longitudinal axis.

5. The heat exchanger (1) according to any one of claims 1 to 3, characterized in that Each fin (29) has a length (L) along the longitudinal axis that varies from upstream to downstream.

6. A heat exchanger (1) according to any one of the preceding claims, characterised in that The first panel (25), the second panel (26) and the fins (29) between the first panel and the second panel (23, 24) form a stage, and the heat exchanger (1) includes a plurality of stages, the plurality of stages being separated by passages (37) configured for the circulation of the second fluid (3), the passages (37) opening to an upstream surface (35) and a downstream surface (37).

7. A heat exchanger (1) according to any one of the preceding claims, characterised in that The heat exchanger is formed as a single piece.

8. The heat exchanger (1) according to any one of claims 1 to 6, characterized in that The fins (29) are alternately connected by top walls (31) and bottom walls (32), and the top walls (31) and the bottom walls (32) are connected to the first and second panels (25, 26), respectively.

9. The heat exchanger (1) according to any one of claims 1 to 8, characterized in that The heat exchanger comprises an inlet defined in an upstream surface (35), and an outlet defined in an opposite downstream surface along the longitudinal axis (X), wherein the first fluid and / or the second fluid enters the heat exchanger (1) at the inlet, and the first fluid and / or the second fluid is discharged from the heat exchanger (1) through the outlet.

10. The heat exchanger (1) according to any one of claims 1 to 9, characterized in that The heat exchanger comprises an inlet defined in the inner cylindrical surface (34a), and an outlet defined in the outer cylindrical surface (34b), the second fluid entering the heat exchanger (1) through the inlet, and the second fluid being discharged from the heat exchanger (1) through the outlet.

11. The heat exchanger (1) according to any one of claims 5 to 10, characterized in that The length (L) of the fin (29) is defined linearly and by the parameter Determine, where s is the lateral space (s) between fins (29) of the same row and as a function of the radial position of the fin (29) in cylindrical coordinates, Rmin is the minimum radius of the heat exchanger (1) defined by the inner cylindrical surface (34a), and Rmax is the maximum radius of the heat exchanger (1) defined by the outer cylindrical surface (34b).

12. A turbine having a longitudinal axis X, comprising a heat exchanger according to any one of the preceding claims, the first and second panels (25, 26) being regularly arranged around the longitudinal axis (X), the fins (29) being arranged between the first and second panels (25, 26).

13. A method for manufacturing a heat exchanger, the heat exchanger being the heat exchanger according to any one of claims 1 to 11, characterized in that: The method comprises the step of producing the heat exchanger (1) by additive manufacturing by selective melting on a powder bed.

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