Variable-length finned heat exchanger and corresponding turbine

Abstract

The invention relates to a heat exchanger (1) for a turbine (4), in particular an aircraft turbine, having a longitudinal axis (X), comprising a plurality of fins configured to be swept by a first fluid (2) in a first direction (D1), the fins extending in a second direction between a first panel (23) and a second panel (24), the fins being arranged in a third direction in a plurality of rows (R1, R2, R3), the fins (R1, R2, Rn) of each row (R1, R2, Rn) and are arranged in a staggered manner, the fins of each row (R1, R2, Rn) being parallel to each other and connected to each other. According to the invention, the heat exchanger is annular, centered in said third direction, the heat exchanger having an inner cylindrical surface (25a) defining an inlet (E) and an outer cylindrical surface (25b) defining an outlet (S), the length (L) of the fins decreasing in the heat exchanger radially between the inner and outer cylindrical surfaces along the first direction (D1).

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 the heat exchanger in two different directions. 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] One of the problems observed in this type of heat exchanger applied in turbines is the high pressure drop caused in particular by high shape resistance. It is difficult to significantly increase the number of fins to improve the performance of the turbine. In addition, this type of heat exchanger (especially a heat exchanger with multiple stages) has a difference in the flow circulation velocity between the inlet and outlet of the heat exchanger. The cross-sectional area of ​​the fluid channel can be increased according to the direction of fluid circulation in the heat exchanger. This leads to a decrease in velocity and an approximately linear increase in the hydraulic diameter of the exchange surface. As a result, the exchange coefficient will decrease, and the total exchange coefficient will vary as a function of the distance from the inlet of the heat exchanger, resulting in uneven heat exchange and an imbalance in the convective thermal resistance between the first fluid and the second fluid. The size of the exchanger is usually designed to have an optimal convective 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, have relatively similar temperature / pressure / flow rate conditions and pressure drops, the optimal thermal resistance ratio can be close to 1.

[0007] There is a need to address some or all of the above disadvantages. Summary of the invention

[0008] The object of the present invention is to provide a heat exchanger which enables a better optimization of the aero-thermal performances while reducing the pressure drop and avoiding significant impacts on the mass.

[0009] According to the invention, this object is achieved by a heat exchanger for a turbine, in particular an aircraft turbine, the heat exchanger having a longitudinal axis, the heat exchanger comprising a plurality of fins configured to be swept by a first fluid along a first direction, the fins extending between a first panel and a second panel along a second direction, the fins being arranged in a plurality of rows along a third direction and being staggered, the fins of each row being parallel to each other and connected to each other, the heat exchanger being annular and centered on the longitudinal axis, the heat exchanger having an inner cylindrical surface and an outer cylindrical surface, the inner cylindrical surface defining an inlet of the heat exchanger, the outer cylindrical surface defining an outlet of the heat exchanger, the length of consecutive fins in each row of fins decreasing radially in the heat exchanger along the first direction between the inner cylindrical surface and the outer cylindrical surface.

[0010] Therefore, this solution enables the above-mentioned purposes 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, by varying the exchange coefficient along the radial length of the first fluid side, the total exchange coefficient increases and is relatively uniform along the entire radial length of the heat exchanger. By varying the length of the fins, it is also possible to compensate for changes in the cross section and changes in the flow rate of the first fluid in the heat exchanger. The cross-sectional area of ​​the passage increases with the increase of the radius of the heat exchanger (in the cylindrical coordinate system), resulting in a decrease in velocity. Reducing the fin length will increase the exchange coefficient at constant velocity. The decrease in velocity is compensated by the decrease in the fin length.

[0011] The heat exchanger may further include one or more of the following features, taken alone or in combination:

[0012] The fins of each row are spaced apart by a pitch in a first direction, the pitch having a variation in a second direction.

[0013] The spacing decreases in a first direction from the inner cylindrical surface towards the outer cylindrical surface.

[0014] - Each fin has a height that increases from the inner cylindrical surface to the outer cylindrical surface.

[0015] 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 a third direction, the plurality of stages being separated by passages configured for circulation of a second fluid.

[0016] The heat exchanger comprises covers, each cover closing one end of a passage, the cover extending between the first panel and the second panel.

[0017] The fins are alternately connected by top and bottom walls connected to the first and second panels respectively.

[0018] The heat exchanger is formed as one piece (made in one piece).

[0019] - The length of each fin is defined linearly as a function of the average radial coordinate of the fin and according to the parameter Definition, where L is the length of the fin as a function of the radial position of the fin in a cylindrical coordinate system, 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.

[0020] The heat exchanger comprises an inlet defined in the inner cylindrical surface, through which the first fluid and / or the second fluid enters the heat exchanger, and an outlet defined in the outer cylindrical surface, through which the first fluid and / or the second fluid exits the heat exchanger.

[0021] The heat exchanger comprises an inlet defined in an upstream surface, through which the second fluid enters the heat exchanger, and an outlet defined in an opposite downstream surface along the longitudinal axis, through which the second fluid exits the heat exchanger.

[0022] The invention also relates to a turbine comprising a heat exchanger having any of the aforementioned features, wherein the first panel and the second panel extend along a radial axis perpendicular to the longitudinal axis X on the one hand and are regularly arranged around the longitudinal axis on the other hand, and the fins are arranged between the first panel and the second panel, and the first direction is parallel to the radial axis.

[0023] The invention also relates to an aircraft comprising a turbine as described above.

[0024] 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 using selective fusion on a powder bed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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:

[0026] Figure 1 is a perspective view of a heat exchanger including plates and fins according to the present invention;

[0027] Figure 2 is an axial cross-sectional view of an example of a turbine to which the present invention is applicable;

[0028] Figure 3 is a schematic cross-sectional view of a heat exchanger according to the present invention;

[0029] Figure 4 is a perspective view of an example of a fin arrangement of a heat exchanger according to the present invention;

[0030] Figure 5 According to the present invention Figure 1 A radial cross-sectional view of a heat exchanger; and

[0031] Figure 6 is a side view showing the outer periphery of the heat exchanger according to the present invention. DETAILED DESCRIPTION

[0032] Figure 1 A heat exchanger 1 is shown for 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.

[0033] 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.

[0034] 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. The fan 6 comprises blades 7 surrounded by a fan casing 8. The fan casing 8 carries a nacelle 9. The nacelle is annular, centered on a longitudinal axis X, and is connected to the aircraft.

[0035] The gas generator 5 includes 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 from upstream to downstream. Generally, the turbine 1 includes 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.

[0036] 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.

[0037] 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 and aircraft internal cooling systems) may have to transfer a large amount of thermal energy.

[0038] 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 one or more compressors before passing through a combustion chamber. Heat in the exhaust gas is usually lost.

[0039] Advantageously, but not limitingly, the secondary flow generated by the fan circulates in a secondary duct 19 radially delimited at least by the fan casing 8 and an inter-duct casing 20 surrounding the gas generator. The main flow through the gas generator circulates in a main duct 35 radially delimited at least by the inter-duct casing 20 and an inner casing 36 surrounding the gas generator.

[0040] 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 .

[0041] The heat exchanger may be located in the secondary duct or, alternatively, in the primary duct. 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.

[0042] refer to Figure 1 and Figure 3 , the heat exchanger 1 comprises a primary exchange surface 21 and a secondary exchange surface 22. The primary exchange surface 21 comprises two panels (or plates) referred to as a first panel 23 and a second panel 24 respectively.

[0043] The term “direction” is used in particular to describe the heat exchanger. In the installed condition, a first direction D1 is parallel to a radial axis Z of the turbine 1 .

[0044] refer to Figure 1 and Figure 5 , the annular heat exchanger is centered in the third longitudinal direction D3. In the installed condition, the third direction is centered on the longitudinal axis. The annular shape of the heat exchanger 1 enables it to be better integrated into the turbine 4.

[0045] The heat exchanger 1 has an inner cylindrical surface 25a defining an inner radius Ri and an outer cylindrical surface 25b defining an outer radius Re. The heat exchanger 1 also has an upstream surface 37 (or front surface) and a downstream surface 38 opposite to each other along the longitudinal axis. The upstream surface 37 and the downstream surface 38 are connected by the inner cylindrical surface 25a and the outer cylindrical surface 25b.

[0046] The heat exchanger 1 comprises an inlet E through which the first fluid enters the heat exchanger 1. Advantageously, the inlet E is defined at the inner cylindrical surface 25a. The heat exchanger 1 also comprises at least one outlet S through which the first fluid escapes from the heat exchanger. The outlet S is here defined at the outer cylindrical surface 25b.

[0047] In the diagram showing a portion of two panels 23, 24 and a stage of a heat exchanger Figure 3 , a portion of two panels 23, 24 and a stage of the heat exchanger are superimposed in planes D2, D3. The second panel 24 extends above the first panel 23 along the second direction D2 and is at a distance from the first panel 23 to form a space 27. The second direction D2 is perpendicular to the third direction and the first longitudinal direction D1. The second direction D2 is also parallel to the circumferential direction around the longitudinal axis X of the turbine 1.

[0048] The space 27 formed between the two panels 23 , 24 enables the first fluid 2 to circulate along the first direction D1 . The first fluid 2 can circulate between the inlet E and the outlet S of the heat exchanger 1 .

[0049] The heat exchanger 1 further comprises a plurality of fins 26 extending between the first panel 23 and the second panel 24. The fins 26 form the secondary exchange surface 22. The fins 26 extend transversely to the first panel 23 and the second panel 24. More specifically, the fins 26 extend between the two panels 23, 24 along the second direction D2.

[0050] The fins 26 form channels 31 through which the first fluid 2 flows. The first fluid 2 is configured to pass through the fins 26 and flow between the first panel 23 and the second panel 24 along the first direction D1.

[0051] Figure 4 The fins 26 of the heat exchanger 1 without the panels 23, 24 are shown. The fins 26 are arranged in a plurality of rows R1, R2, ... Rn along the third direction D3. The third direction D3 is perpendicular to the first direction D2 and the second direction D3. The rows of fins 26 are parallel to each other. In this case, the rows R1, R2, Rn of the fins 26 are parallel to the third direction D3.

[0052] Each fin 26 is substantially flat and also extends along the first direction D1. Advantageously, in this example, each fin 23 has a substantially rectangular shape. Alternatively, the fin 23 has a trapezoidal shape or any other shape, or the fin 23 may be inclined relative to the second direction D2.

[0053] The fins 26 each have a leading edge 26a and a trailing edge 26b for the first fluid 2. The leading edge 26a and the trailing edge 26b are opposite to each other in the first direction D1. The leading edge 26a and the trailing edge 26b longitudinally define the fin 26. The leading edge 26a is the edge at which the first fluid 2 first contacts the fin 26. The trailing edge 26b is the edge at which the first fluid 2 contacts the fin 26 last. The leading edge 26a and the trailing edge 26b extend generally along the second direction.

[0054] like Figure 4 As shown, the fins 26 are also staggered. More specifically, the fins 26 are offset in the third direction D3. Advantageously, every other row of fins 26 is located in the same plane parallel to the planes D2, D3. This arrangement makes it possible to improve heat exchange by interrupting and uniformly reforming the thermal boundary layer on the fin surface. The thermal boundary layer is interrupted at the trailing edge of the fin and reformed at the leading edge of the fin.

[0055] Advantageously but not limitingly, the fins 26 of each row are alternately connected to each other by top walls 28 and bottom walls 29. The top walls 28 and bottom walls 29 are generally flat and face each other in the second direction D2. The top walls 28 and bottom walls 29 extend in the first direction D1. Similarly, the fins 26 of adjacent rows in the first longitudinal direction are connected to each other by top walls 28. These top walls 28 and bottom walls 29 have a leading edge 30a connected to the leading edge 26a of the fin 26 and a trailing edge 30b connected to the trailing edge 26b of the fin 26.

[0056] The fins 26 are attached to the first panel 23 and the second panel 24. Advantageously, the attachment is achieved by means of a top wall 28 and a bottom wall 29. The attachment may be achieved by welding or brazing.

[0057] The heat exchanger 1 may be a single-stage heat exchanger or a multi-stage heat exchanger. Figure 2 A single stage is shown. One stage is defined by the fins 26 and the first and second panels 23, 24. In this way, the first fluid 2 circulates through the fins 26 in the channels 31, in the space 25 between the two panels 23, 24, while the second fluid 3 circulates above the first panel 23 and below the second panel 24. In the case of a multi-stage heat exchanger, the various stages will be separated by passages 32 through which the second fluid is configured to circulate. Each passage 32 will be formed between two adjacent panels 23, 24 of different stages.

[0058] Advantageously, each fin 26 has a height H measured in the second direction D2 and a length L measured in the first direction D1 .

[0059] Advantageously, the height H of the fins varies. This variation occurs from the inner cylindrical surface 25a to the outer cylindrical surface 25b. In other words, the height will increase in the radial direction of the heat exchanger. The height of the fins varies linearly with the radius of the heat exchanger (in a cylindrical coordinate system). The top wall 28 of the fin has a flush radial outer surface. With the variation of the height, the flow velocity decreases and the cross-sectional area of ​​the passage increases. This leads to a reduction in the exchange coefficient.

[0060] The length L of the fin 26 varies along the first direction D1. The length L of the fin varies between the inner radius Ri and the outer radius Re of the heat exchanger 1. In particular, the length L of the fin 26 decreases or decreases from the inlet E (inner cylindrical surface) of the heat exchanger to the outlet S (outer cylindrical surface) of the heat exchanger 1. Advantageously, the variation is continuous. In this way, the velocity (and therefore the exchange coefficient) varies continuously. This variation in the length of the fin makes it possible to compensate for the reduction in the exchange coefficient. By varying the length of the fin, it is also possible to compensate for changes in the cross section and changes in the flow rate of the first fluid in the heat exchanger. More precisely, reducing the length of the fin increases the exchange coefficient. This is because there are more fin leading edges in the radial direction and the thermal boundary layer is regenerated.

[0061] The length L of each fin 26 is between 0.5 mm and 150 mm. Advantageously, the length of the fins close to the axis is between 50 mm and 150 mm and the length of the fins remote from the longitudinal axis is between 0.5 mm and 50 mm.

[0062] Each fin 26 in each row of fins is at a distance from the adjacent fin 26 in the first direction D1 and has a specific pitch P. Another advantageous aspect is that the pitch P also varies in the first direction D1. In this example, the variation decreases or decreases in the distance of the pitch from the inlet E of the heat exchanger 1 toward the outlet S of the heat exchanger 1. In other words, the pitch P decreases along the flow of the first fluid 2. By varying the pitch P, the convection thermal resistance is maintained at a relatively constant fluid velocity. In particular, this configuration makes it possible to compensate for the increase in fin length by reducing the fin pitch in the first direction D.

[0063] The pitch P between each fin 26 is between 0.5 mm and 50 mm. Advantageously, the pitch P close to the longitudinal axis of the heat exchanger is between 5 mm and 50 mm, and the pitch away from the longitudinal axis is between 0.5 mm and 5 mm.

[0064] Still reference Figure 4 , the transverse spacing (along the third direction D3) is constant. The transverse spacing is the distance between the fins in each row.

[0065] Figure 5A 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 26 between the two panels 23, 24 is non-uniform. The first panel 23 and the second panel 24 each extend along a radial axis in the turbine. Between each stage is a passage 32 configured for the circulation of a second fluid. Each passage 32 extends between a radially inner end 32a and a radially outer end 32b. The radially inner end 31a of the passage 32 is arranged on the inner radius Ri of the heat exchanger 1. The radially outer end 32b is arranged on the outer cylindrical surface 25b and the outer radius Re of the heat exchanger 1.

[0066] The length L of the fins 26 varies along a first direction D1, which in this case is parallel to the radial axis Z. The length L of the fins 26 increases along the first direction D1 and with the flow of the first fluid 2 (i.e., from the central axis of the heat exchanger 1 toward the position farthest from the center). The spacing P decreases from the heat exchanger inlet toward the heat exchanger 1 outlet. The spacing P1 near the center of the heat exchanger is greater than the spacing P2, and the spacing P2 is greater than the spacing P3 farthest from the center of the heat exchanger (along the radial axis of the heat exchanger).

[0067] In the case of decreasing pitch and increasing fin length as the fin length L increases, the variation in fin length can be defined linearly as a function of the average radial coordinate of the fin and by the parameter Definition. In this ratio, L is the length of the fin as a function of the radial position of the fin in the cylindrical coordinate system, Rmin is the minimum radius of the heat exchanger defined by the inner cylindrical surface 25a, and Rmax is the maximum radius of the heat exchanger defined by the outer cylindrical surface 25b. For example, the parameter λ r It may be between 1.2 and 1.8. r It is the ratio between the length of the fin at the inlet (inner cylindrical surface) and the length of the fin at the outlet (outer cylindrical surface).

[0068] Alternatively, but not limiting, the fins 26 are corrugated and have an offset pitch. When the fins are corrugated, the pitch P of the corrugations decreases as the fin length increases, making it possible to compensate for the decrease in compactness of the heat exchanger by increasing the exchange coefficient. For example, the longitudinal periodicity P l can be reduced linearly as a function of the radial coordinate and by the reduction parameter Definition, where P l is the longitudinal periodicity of the corrugation of the fin as a function of the radial position of the fin in the cylindrical coordinate system. For example, 1.2<λ pl<1.8. The longitudinal periodicity corresponds to the length of the fins and then to the pitch. This is how the pattern repeats along the first direction D1.

[0069] Advantageously, the inlet cross section of the heat exchanger is smaller than the outlet cross section of the heat exchanger. The cross section increases linearly with the distance from the axis of rotation of the heat exchanger. Advantageously, with increasing passage cross section, the velocity of the first fluid 2 decreases.

[0070] Figure 6 1 shows a schematic side view of a heat exchanger 1. The figure shows the outlet S of the heat exchanger 1 through which the first fluid 2 flows. The figure shows the trailing edge 26b of the fin 26. It is also possible to see the covers 33b, which are advantageously mounted on both sides of the fin 26 along the second direction D2. These covers 33b are configured to close at least some of the passages 32 through which the second fluid 2 circulates. More specifically, each cover 33b is arranged at one end of the passage 31 to close the end and the passage 32 at this point. In this example, the cover 33b is arranged at the radially outer end 31b of the passage 32. Each cover 33b includes an outer surface 33bb forming an outer cylindrical surface 25b.

[0071] Advantageously and with reference Figure 5 , a cover 33a is also arranged at the radially inner end 31a of the passage 31. Each cover 33a includes an outer surface 33aa (see Figure 1 ).

[0072] In this way, the second fluid 3 entering the heat exchanger 1 at the radially inner end 31a is directed between the two covers 33a, 33b towards the other outlet. This prevents the first flow from mixing with the second flow.

[0073] Alternatively, the second fluid 3 may be circulated through the heat exchanger 1 axially (along the longitudinal axis) or radially (along the radial axis).

[0074] Each cover 33a, 33b has a width l1 which is the same as the width of the first panel 23 and the second panel 24. The width l1 is measured in the third direction D3. Each cover 33a, 33b also has a height h2 measured between the two panels 23, 24. The radially outer surface of the cover 33b defines the outer radius of the heat exchanger 1, while the radially inner surface of the cover 33a also defines the inner radius of the heat exchanger 1.

[0075] Advantageously, the fins 26, the top wall 28, the first panel 23 and the second panel 24 are formed in one piece (made in one piece or integral). 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 heat exchangers in one piece. In particular, the 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.

[0076] In this additive manufacturing method, the heat exchanger has no top wall 28 and no bottom wall 29. This method enables direct connection of the fins with the first panel 23 and the second panel 24. Additive manufacturing and the absence of these walls means weight savings.

[0077] 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.

[0078] 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.

[0079] Advantageously, the different layers configured to form the heat exchanger are superimposed along a production axis parallel to the third direction D3 .

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) comprising a plurality of fins configured to be swept along a first direction (D1) by a first fluid (2), the fins extending along a second direction (D2) between a first panel (23) and a second panel (24), the fins (26) being arranged in a plurality of rows (R1, R2, Rn) and staggered along a third direction (D3), the fins (26) of each row (R1, R2, Rn) being parallel to each other and connected to each other, characterized in that The heat exchanger (1) is annular and centered in the third direction, and has an inner cylindrical surface (25a) and an outer cylindrical surface (25b), the inner cylindrical surface defining an inlet (E) of the heat exchanger (1), and the outer cylindrical surface defining an outlet (S) of the heat exchanger (1), and the length (L) of the fin (26) radially decreases between the inner cylindrical surface (25a) and the outer cylindrical surface (25b) in the heat exchanger along the first direction (D1).

2. Heat exchanger (1) according to the preceding claim, characterized in that The fins (26) of each row are spaced apart by a pitch (P) in the first direction (D1), and the pitch (P) varies in the second direction (D2).

3. Heat exchanger (1) according to the preceding claim, characterized in that The pitch (P) decreases in the first direction from the inner cylindrical surface (25a) toward the outer cylindrical surface (25b).

4. A heat exchanger (1) according to any one of the preceding claims, characterised in that Each fin (26) has a height (H) that increases from the inner cylindrical surface (25a) toward the outer cylindrical surface (25b).

5. A heat exchanger (1) according to any one of the preceding claims, characterised in that The first panel (23), the second panel (24) and the fins (26) between the first panel and the second panel (23, 24) form a stage, and the heat exchanger (1) includes a plurality of stages arranged around the third direction (D3), the plurality of stages being separated by passages (32) configured for circulation of a second fluid (3).

6. Heat exchanger (1) according to the preceding claim, characterized in that The heat exchanger comprises covers (33a, 33b), each cover closing one end of the passage (32), the covers (33a, 33b) extending between the first panel (23) and the second panel (24).

7. A heat exchanger (1) according to any one of the preceding claims, characterised in that The fins (26) are alternately connected by top walls (28) and bottom walls (29), which are connected to the first and second panels (23, 24), respectively.

8. The heat exchanger (1) according to any one of claims 1 to 6, characterized in that The heat exchanger is formed as a single piece.

9. A turbine having a longitudinal axis X, comprising a heat exchanger (1) according to any one of the preceding claims, wherein the first panel and the second panel (23, 24) extend along a radial axis perpendicular to the longitudinal axis X on the one hand and are regularly arranged around the longitudinal axis on the other hand, the fins (26) are arranged between the first panel and the second panel (23, 24), and the first direction (D1) is parallel to the radial axis (Z).

10. A method for manufacturing a heat exchanger (1), the heat exchanger being a heat exchanger according to any one of claims 1 to 6 and 8, characterized in that The method comprises the step of producing the heat exchanger by additive manufacturing using selective fusion on a powder bed.

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