HEAT EXCHANGER SYSTEM FOR AN AIRCRAFT TURBOMACHINE AND ASSEMBLY COMPRISING SUCH A SYSTEM

Abstract

The invention relates to a heat exchanger system (1) for an aircraft turbomachine comprising: - a heat exchanger (10) having a front face (12) and a rear face (13), respectively, for the inlet and outlet of a gas flow (F), and an annular core (15) interposed between the front and rear faces and provided with heat exchange surfaces (16), - a diffuser (30) located upstream of said annular core and comprising an upstream face (30a) for the inlet of the gas flow, a downstream face (30b) for the outlet of the gas flow corresponding to the front face (12), an inner annular wall (31) and an outer annular wall (32), characterized in that the outer annular wall diverges radially from the inner annular wall between the upstream and downstream faces, and in that the diffuser comprises a plurality of interposed annular walls (33) extending around each other between the inner and outer annular walls,These intercalated walls extend axially from the upstream face to the heat exchange surfaces and divide an annular space supplying the exchanger into several coaxial annular passages (35) for the flow of said gas flux (F) and for supplying the flow paths (18). Figure for the abbreviation: Fig. 5,

Description

Title of the invention: HEAT EXCHANGER SYSTEM FOR AN AIRCRAFT TURBOMACHINE AND A SET CONTAINING SUCH A SYSTEM Technical field of the invention

[0001] The invention relates to the technical field of heat exchanger systems for an aircraft turbomachine as well as to that of assemblies comprising such heat exchanger systems. Technical background

[0002] An aircraft turbomachine and an aircraft comprise various components and / or equipment that must be lubricated and / or cooled for their proper operation. These components and / or equipment may include bearings or gears in the turbomachine, electrical and / or electronic components for the aircraft turbomachine's electrical systems, or even systems for conditioning the aircraft's interior spaces. The heat generated by these components and / or equipment, which can be very significant depending on the power of the component and / or equipment, is dissipated by heat exchange with a cold source available in the turbomachine and / or the aircraft.

[0003] Heat exchange is achieved using one or more heat exchangers installed in the turbomachine or aircraft for various applications. Depending on the application, the heat exchangers generally use either two gases, or a gas stream and a fluid, which can be the turbomachine's fuel or lubricating oil (the main applications), ambient air, air from the turbomachine's secondary flow, or air from the turbomachine's primary flow. Heat exchange occurs between the gas stream and the fluid for cooling and / or heating.

[0004] The cooling requirements for lubricant fluids, electrical and / or electronic systems (electrical machines, generators, batteries, etc.) are constantly increasing due to the rising rotational speeds and power levels involved in meeting the specification trends for turbomachinery and the electrification of future aircraft. This implies that heat exchangers will be subjected to increasing demands.

[0005] Fuel / oil heat exchangers, commonly known by their English acronym FCOC for "Fuel Cooled Oil Cooler", are well-known. These FCOC heat exchangers can have a dual function: heating the fuel before combustion in the turbomachine's combustion chamber and cooling it. The oil is heated by the turbomachine's heat dissipation. However, FCOC heat exchangers are insufficient to absorb all the heat dissipation because the fuel temperature is limited due to safety constraints. Additional cooling is achieved by air-to-oil heat exchangers, known by the acronym ACOC for "Air-Cooled Oil Cooler," particularly surface-type heat exchangers, known by the acronym SACOC for "Surface Air-Cooled Oil Cooler." Surface heat exchangers are generally arranged in the turbomachine's secondary intake and use the secondary airflow to cool the oil circulating within the turbomachine. These heat exchangers consist of a metallic surface component with integrated oil channels.The secondary airflow is guided along fins on this surface area, which serve to increase the contact area with the secondary airflow and to extract heat.

[0006] Also known are heat exchangers for turbomachinery comprising at least two stages or paths separated by a transverse plate and allowing the circulation of a first fluid and a second fluid. The first and second fluids circulate alternately in each stage. In other words, when the first fluid circulates in the first stage, the second fluid circulates in the second stage, and vice versa. In such exchangers, the heat exchange between the first and second fluids takes place in specially designed exchange zones. These exchange zones allow the transfer of thermal energy from the first fluid to the second fluid or vice versa. These heat exchangers typically have a general annular shape, which allows their integration into a conventional turbomachinery flow path.

[0007] However, in twin-spool turbomachinery, the geometry of the runners varies along the longitudinal axis of the turbomachine. Depending on the runner section in which the heat exchanger is implemented, the runner passage area upstream or downstream of the heat exchanger can be significantly reduced or significantly increased compared to the runner passage area at which the heat exchanger is located.

[0008] The prior art has proposed a heat exchanger system comprising a heat exchanger and a diffuser to improve the distribution of the gas flow at the inlet or outlet of the heat exchanger.

[0009] According to a first configuration, the diffuser is located upstream of the heat exchanger and the cross-section of the flow stream in which the exchanger system is situated is convergent. The heat exchanger comprises a front face for the gas flow inlet and a rear face for the gas flow outlet. The diffuser comprises an upstream face The inlet face of the gas flow and the outlet face of the gas flow also form the front face of the heat exchanger. Thus, the cross-sectional area of ​​the gas flow decreases from the upstream face of the diffuser at least to the rear face of the heat exchanger. As the cross-sectional area of ​​the gas flow decreases from the diffuser to the heat exchanger, the gas flow velocity increases due to flow restriction (Venturi effect). This configuration therefore does not pose any problems with heat exchange efficiency because there is little pressure drop (due to form drag) as a result of the flow acceleration.

[0010] According to a second configuration, the diffuser is located downstream of the heat exchanger, and the cross-section of the gas stream in which the diffuser is located is divergent; that is, the cross-section of the gas stream at the diffuser is significantly reduced compared to the cross-section of the gas stream at the heat exchanger. In this configuration, the upstream face of the diffuser corresponds to the rear face of the heat exchanger. The position of the diffuser relative to the heat exchanger prevents the diffuser from playing a role in distributing the gas flow within the heat exchanger. Indeed, since the heat exchanger is located upstream of the diffuser in the direction of gas flow, it is the heat exchanger that acts as the gas distributor for the diffuser.

[0011] According to a third configuration illustrated in [Fig. 2], the diffuser 30' is located in The upstream section of the 10' heat exchanger and the cross-sectional area through which the gas flow passes immediately before entering the heat exchanger are divergent. This is the configuration of interest in the present application. However, the 1' heat exchanger system in this third configuration raises two issues. First, since the cross-sectional area of ​​the upstream section of the 10' heat exchanger is very small compared to the frontal area of ​​the exchanger, it is necessary to make the profile of the upstream section of the 10' heat exchanger highly divergent and therefore increase the cross-sectional area of ​​the section over a short axial length to obtain a cross-sectional area suitable for the dimensions of the front face of the 10' heat exchanger.Secondly, as the increase in the cross-section of the vein occurs over a short axial length, a separation and recirculation of the gas flow is observed, which significantly increases the pressure drop and disrupts the distribution of the gas flow through the heat exchanger.

[0012] This poor distribution of gas flow can lead to a reduction in thermal performance, an increase in pressure losses within the annular core of the exchanger and, in some cases, an increase in thermal stresses. This is due to the increased temperature gradients within the heat exchanger at the macroscopic scale. Indeed, when the front face of the exchanger is oriented approximately (perpendicularly or at a slight angle) perpendicular to the average flow direction, the difficulty lies in the fact that a significant increase in the cross-sectional area requires a substantial cross-sectional length to achieve a small angle α ([Fig. 2]), i.e., less than 10°. If the angle α is too large, the flow separates, creating a recirculation zone that results in a high pressure drop and very poor heat exchanger supply.

[0013] The invention provides a heat exchanger system for an aircraft turbomachine in which the diffuser improves the distribution of the gas flow in a heat exchanger located downstream of said diffuser, the gas flow passage cross-section being divergent from the diffuser to the heat exchanger. Summary of the invention

[0014] The invention proposes for this purpose a heat exchanger system for an aircraft turbomachine comprising:

[0015] - a heat exchanger extending around a longitudinal axis and comprising:

[0016] > a front face for the inlet of a gas flow and a rear face for the outlet of a flow gas, and

[0017] > an annular heat transfer core interposed between the front and rear faces and equipped with a plurality of heat exchange surfaces, said exchange surfaces being arranged so as to form a plurality of gas flow paths from the front face to the rear face, and

[0018] - a diffuser located upstream of said annular core and comprising:

[0019] > an upstream face for the inlet of the gas flow into the diffuser and a downstream outlet face of the gas flow from the diffuser, the downstream face being defined by the front face of the heat exchanger,

[0020] > an inner annular wall and an outer annular wall located radially external relative to the inner annular wall,

[0021] characterized in that the outer annular wall diverges radially from the inner annular wall between the upstream and downstream faces, and in that the diffuser comprises a plurality of intercalated annular walls extending around each other between the inner and outer annular walls, these intercalated walls extending axially from the upstream face to the heat exchange surfaces and dividing an annular supply space of the exchanger, delimited by the inner annular wall and the outer annular wall, into several coaxial annular passages for the flow of said gas stream and for supplying the flow paths.

[0022] The invention thus overcomes the aforementioned drawbacks of the prior art. The heat exchanger system allows for improved gas flow distribution, reduced pressure losses, and significant axial compactness.

[0023] Indeed, since the outer annular wall diverges radially from the inner annular wall between the upstream and downstream faces, the diffuser's aerodynamic profile adapts better to the profile of the duct section into which the system is intended to be integrated. This avoids the recirculation and turbulence that would have been generated by the gas flow bypassing the system. Thus, the lubrication and / or cooling of the turbomachine's electrical and / or electronic components can be carried out without significantly reducing the gas flow velocity in the duct.

[0024] Furthermore, the coaxial annular passages maintain a substantially axial flow direction along the longitudinal axis and prevent recirculation and turbulence phenomena that would occur inside the diffuser due to the radial divergence of the outer annular wall relative to the inner annular wall. The coaxial annular passages thus significantly reduce pressure losses, maintain optimal gas flow to the heat exchanger, and reduce thermal gradients within the heat exchanger. This therefore substantially improves the thermal performance of the heat exchanger.

[0025] According to various features of the invention which may be taken together or separately: • the inner annular wall, the intercalated walls and the outer annular wall are curved; • the inner annular wall, the intercalated walls and the outer annular wall comprise, respectively, two radially inclined portions, said radially inclined portions consisting of a distal portion of the front face of the heat exchanger and a proximal portion of the front face of the heat exchanger, the proximal portion of the front face of the heat exchanger having a higher inclination than the distal portion of the front face of the exchanger; • the inner and outer annular walls have concavities in opposite directions, the intercalated walls having, respectively, a concavity in the same direction as that of the inner and outer annular walls which is radially closest to the intercalated wall considered; • each of the coaxial annular passages defines a sector of cone angle, said sectors of cone angle being identical; Each of the coaxial annular passages defines an annular section S(x) between the upstream face of the diffuser and the downstream face of the diffuser, the annular section S(x) increasing from the upstream face of the diffuser to the downstream face of the diffuser; the coaxial annular passage formed between the outer annular wall and the intercalary wall closest to the outer annular wall on the one hand and / or the coaxial annular passage formed between the inner annular wall and the intercalary wall closest to the inner annular wall on the other hand have, at the level of the downstream face of the diffuser, first passage sections that are smaller than the second passage sections of the other annular passages; the thickness of the inner annular wall and / or the outer annular wall and / or the intercalated walls decreases axially from the upstream face of the diffuser to the downstream face of the diffuser; the diffuser further includes at least one longitudinal reinforcing element connecting the intercalated walls to each other; the diffuser comprises a plurality of longitudinal reinforcement elements connecting the intercalated walls to each other, the longitudinal reinforcement elements being two by two successively and angularly spaced at an angle between 3° and 20°, particularly between 3° and 7°, preferably equal to 5°; the outer annular wall comprises an inner outer annular wall and an outer outer annular wall separated from the inner outer annular wall by a space, the inner outer annular wall having a concavity oriented outwards and the outer outer annular wall having a concavity oriented inwards; the heat exchanger is chosen from a gas-gas type turbine exchanger, an air-oil exchanger, a turbine blade cooling exchanger and an air-nitrogen exchanger; the heat exchanger system is manufactured by additive metal powder bed manufacturing; the heat exchanger and the diffuser are made from a single piece; The inner annular wall, the intercalated walls, and the outer annular wall comprise, respectively, two radially inclined portions, said radially inclined portions consisting of a distal portion of the front face of the heat exchanger and a proximal portion of the front face of the heat exchanger, the proximal portion of the front face of the heat exchanger having a shallower inclination than the portion distal of the front face of the exchanger such that the proximal portion of the front face of the heat exchanger is slightly inclined with respect to the direction of extension of the flow paths and that the distal portion of the front face of the heat exchanger is inclined with respect to the direction of extension of the flow paths at an angle (0) between 10° and 65°, preferably between 20° and 40°.

[0026] The invention also relates to an assembly comprising an exchanger system as previously described, and an annular vein with a longitudinal axis in which the gas flow is intended to circulate, the heat exchanger extending around the longitudinal axis on an internal annular wall of the annular vein.

[0027] Advantageously, the annular vein comprises an external annular wall radially spaced from the internal annular wall, the internal annular wall being separated from the external annular wall at a first zone located at the heat exchanger by a distance, and at a second zone located upstream of the diffuser in the direction of flow of the first fluid by a distance, a ratio dl / d2 being between 1.2 and 10, preferably between 2 and 4. Brief description of the figures

[0028] Other objects, features and advantages of the invention will become more apparent in the following description, made with reference to the accompanying figures, in which:

[0029] - Fig. 1 is an axial cross-sectional view of a turbomachine for an aircraft to which the present invention applies,

[0030] - [Fig. 2] is a perspective view of a heat exchanger system according to earlier art,

[0031] - [Fig. 3] is a perspective view of a heat exchanger,

[0032] - [Fig. 4] is a cross-sectional view of an assembly according to an embodiment of the present invention,

[0033] - [Fig.5] is a perspective view of the assembly illustrated in [Fig.4],

[0034] - [Fig. 6] is a cross-sectional side view of a heat exchanger system according to an embodiment of the invention,

[0035] - Fig. 7 is a perspective view of the heat exchanger system illustrated in Fig. 7. [Fig.6]

[0036] - [Fig. 8a] is a cross-sectional side view of a heat exchanger system according to an embodiment of the invention,

[0037] - [Fig. 8b] is a cross-sectional side view of a heat exchanger system according to an embodiment of the invention,

[0038] - Figure 9 is a comparison of the flow velocity in a system of heat exchanger for a constant cross-sectional variation (left figure) and for a variable cross-sectional variation (right figure),

[0039] - the [Fig. 10] illustrates a variation in the cross-section of a coaxial annular passage of diffuser,

[0040] - [Fig. 1 1] is a perspective view of a heat exchanger system according to an alternative implementation,

[0041] - [Fig. 12] is a schematic side view of a heat exchanger system according to one embodiment of the invention,

[0042] - [Fig. 13] is a cross-sectional side view of a heat exchanger system according to an embodiment of the invention,

[0043] - [Fig. 14] is a cross-sectional side view of a heat exchanger system according to another embodiment of the invention. Detailed description of the invention

[0044] Figure 1 shows an axial cross-sectional view of a turbomachine with longitudinal axis X to which the invention applies. The turbomachine shown is a twin-flow turbomachine intended for mounting on an aircraft. Of course, the invention is not limited to this type of turbomachine.

[0045] In the present invention, the terms "upstream" and "downstream" are defined with respect to the gas flow in the turbomachine, here along the longitudinal axis X and with reference to [Fig. 1] from left to right. Similarly, a turbomachine generally consists of several modules that are manufactured independently of each other and then assembled together to facilitate its assembly, disassembly, and maintenance.

[0046] The twin-flow turbomachine 100 comprises an assembly including an annular duct 2 with longitudinal axis X in which a gas flow F is intended to circulate, and a heat exchanger 10 between the gas flow F and a secondary fluid. The secondary fluid is intended to cool and / or lubricate components and / or equipment of the turbomachine. The gas flow is typically an air flow F.

[0047] Generally, the turbomachine 100 comprises a gas generator 101 upstream of which a fan 102 is mounted. The gas generator 101 comprises a gas compressor assembly (here including a low-pressure compressor 103a and a high-pressure compressor 103b), a combustion chamber 104, and a turbine assembly (here including a high-pressure turbine 105a and a low-pressure turbine 105b). Conventionally, the turbomachine 100 comprises a low-pressure shaft 106 that connects the low-pressure compressor 103a and the low-pressure turbine 105b to form a low-pressure casing, and a high-pressure shaft 107 that connects the The high-pressure compressor 103b and the high-pressure turbine 105a form a high-pressure unit. The low-pressure shaft 106, centered on the longitudinal axis, drives a fan shaft 108. A speed reducer 109 can be interposed, as shown here, between the fan shaft 108 and the low-pressure shaft 106. Rotating guide bearings 110 also allow the low-pressure shaft 106 and the fan shaft 108 to be guided in rotation relative to a fixed structure of the turbomachine 100.

[0048] The fan 102 is enclosed by a fan housing 111. The fan housing 111 carries a first nacelle section 112a. The latter is annular, centered on the longitudinal axis X and extends radially outside the fan housing 111. The first part of the nacelle 112a is connected to an aircraft tail assembly or to an aircraft wing directly or via a pylon.The gas flow F entering the blower 102 is divided into a primary airflow Fl, which flows through the gas generator 101 in a primary channel 113, and a secondary airflow F2, which flows in a secondary channel 2 around the gas generator 101. The primary channel 113 and the secondary channel 2 are separated by an intermediate casing 114, or inter-channel casing. The intermediate casing 114 is extended downstream by a second nacelle section 112b. The secondary airflow F2 is ejected by a secondary nozzle 115 terminating the first part of the nacelle 112a, while the primary airflow is ejected outside the turbomachine 100 via an ejection nozzle 116 located downstream of the gas generator 101. The ejection nozzle 116 is carried by the second part of the nacelle 112b.

[0049] The guide bearings 110 and the speed reducer 109 in this example configuration of the turbomachine 100 must be lubricated and / or cooled to ensure the performance of the turbomachine. The power generated by these bearings is dissipated in the secondary fluid, which is a heat transfer fluid from a fluid supply source installed in the turbomachine 100. This secondary fluid lubricates and / or cools various components and / or equipment of the turbomachine 100. Of course, other equipment of the turbomachine or the aircraft has significant thermal energy to transfer, such as heat that must be extracted and removed from its environment. This equipment and / or equipment may include one or more electrical machines, an accessory drive, electronic / electrical systems, aircraft interior cooling systems, cryogenic fuel tanks, etc.

[0050] With reference to Figures 3, 4 and 5, the invention relates to a heat exchanger system 1 for an aircraft turbomachine. The turbomachine may, as previously indicated, be the twin-flow turbomachine 100 illustrated in [Fig. 1]. However, the invention is not limited to such a turbomachine.

[0051] The heat exchanger system 1 comprises a heat exchanger 10 and a diffuser 30.

[0052] As illustrated in Figures 4 and 5, the heat exchanger 10 extends around the longitudinal axis X of the turbomachine. The heat exchanger 10 cools the heat transfer fluid used to lubricate and / or cool the components and / or equipment of the turbomachine 100. As described below, its precise location in the turbomachine 100 depends on the function to be performed. It comprises a front face 12 for the inlet of the gas flow F, a rear face 13 for the outlet of the gas flow F, and an annular heat transfer core 15 interposed between the front face 12 and the rear face 13, respectively, for the inlet and outlet of the gas flow F ([Fig. 3]). The annular core 15 is provided with a plurality of heat exchange surfaces 16 which are arranged to form a plurality of flow paths 18 of the gas flux F from the front face 12 to the rear face 13. On the perspective view of [Fig.3], however, it is not possible to view the entire rear face 13.

[0053] A heat exchange surface 16 may consist of a plate, a tube, or a fin. In the latter case, the heat exchange surface 16 also allows for better direction of the gas flow F.

[0054] The gas flow paths 18 can also be called "stages" because they are superimposed. The paths 18 allow the gas flow F and the heat transfer fluid intended to lubricate and / or cool these components and / or equipment to circulate, thus enabling heat exchange between them. In the example illustrated in [Fig. 3], there are three such paths 18. However, the annular core 15 can have between two and several dozen gas flow paths 18. Each path 18 is separated from the path 18 above and / or below by a heat exchange surface 16 in the form of a plate. Preferably, each of the heat exchange surfaces 16 separating two consecutive gas flow paths 8 is sealed.There are various ways to arrange the heat exchange surfaces 16 to achieve, or even optimize, the heat exchange between the gas flow F and the heat transfer fluid, which are well known to those skilled in the art. The annular core 15 thus allows the transfer of thermal energy from one of the fluids between the gas flow F and the heat transfer fluid to the other of the fluids between the gas flow F and the heat transfer fluid.

[0055] The heat exchanger 10 used in the heat exchanger system 1 according to the invention may be of the air / oil heat exchanger (ACOC) type, in particular a surface heat exchanger known by the acronym SACOC. That being said, the heat exchanger 10 may also be selected from a gas-gas turbine heat exchanger, a turbine blade cooling heat exchanger, and an air-nitrogen heat exchanger.

[0056] The heat exchanger 10 can be mounted in the secondary flow 2 of the turbomachine 100 and supported by an annular wall 3. This is the annular wall 3 radially internal to the intermediate casing 114 and the second nacelle section 112b. The heat exchanger 10 could be supported by an annular wall 4 of the fan casing 111. The heat exchanger 10 could be mounted upstream or downstream of the arm of the intermediate casing 114. Alternatively, the heat exchanger 10 is arranged in the primary stream 113. In this case, the heat exchanger 10 is supported by an annular wall (radially internal) of the intermediate casing 114 or an annular wall of an inner casing 120. The heat exchanger 10 could also be mounted in a third stream in the case of a triple-flow turbomachine (not shown).

[0057] As illustrated in Figures 4 and 5, the diffuser 30 is located upstream of the annular heat transfer core 15 along the direction of the gas flow F. More precisely, the diffuser 30 is located upstream of the heat exchanger 10. The diffuser 30's role is to distribute the gas flow F more efficiently within the heat exchanger 10. We will discuss this in more detail later.

[0058] The diffuser 30 comprises an upstream face 30a for the inlet of the gas flow F into the diffuser 30 and a downstream face 30b for the outlet of the gas flow F from the diffuser 30. The downstream face 30b corresponds to the front face 12 of the heat exchanger 10; that is, the downstream face 30b of the diffuser 30 coincides with the front face 12 of the heat exchanger 10. There is therefore no discontinuity between the diffuser 30 and the heat exchanger 10, so that once the gas flow F has entered the diffuser 30, it is forced to pass through the heat exchanger 10, in particular through the annular core 15, to exit the heat exchanger system 1 according to the invention. This is illustrated by the two lower flow lines in [Fig. 4]. The diffuser 30 and the heat exchanger 10 thus form a sealed unit. Advantageously, the diffuser 30 and the heat exchanger 10 are manufactured as a single piece.In this regard, as will be seen later, the diffuser 30 and the heat exchanger 10 can therefore be manufactured by additive manufacturing as a single piece. The diffuser 30 can also be fixed to the heat exchanger 10 so that the downstream face 30b and the front face 12 coincide.

[0059] The diffuser 30 further comprises an inner annular wall 31 and an outer annular wall 32 located radially external to the inner wall 31. In the illustrated embodiment, the inner annular wall 31 of the diffuser 30 is formed within the radially internal annular wall 3 of the intermediate housing 114, which carries the heat exchanger 10. In the embodiment illustrated in [Fig. 3], the outer annular wall 32 is located radially external to the inner annular wall 31 and separated from the annular wall 4 of the blower housing 111. Incidentally, a portion of the gas flow F may not enter the heat exchanger system 1, and thus pass between the outer annular wall 32 of the diffuser 30 and annular wall 4 of blower housing 111, as indicated by the upper flow line on [Fig.4].

[0060] That being said, the outer annular wall 32 of the diffuser 30 can be formed in the annular wall 4 of the blower housing 111 when, for example, the heat exchanger 10 extends over the entire height of the stream 2, that is to say over the distance between the annular wall 3 of the intermediate housing 114 and the annular wall 4 of the blower housing 111. In this case, the downstream face 30b of the diffuser 30 also extends over the entire height of the stream 2. Under these conditions, the entire gas flow F that enters the stream also enters the diffuser 30 of the system 1. The entire gas flow F is therefore involved in the heat exchanges that occur in the annular core 15 of the heat exchanger 10.

[0061] In this configuration, as in the previous one, the heat exchanger system 1 may, in addition to the heat exchanger 10 and the diffuser 30, include a grid (not shown) to prevent foreign bodies from entering the system 1. The grid is thus intended to prevent foreign bodies from reaching and damaging the heat exchanger 10. In this respect, the grid is preferably located at the inlet of the system 1, for example, at the upstream face 30a of the inlet of the gas flow F from the diffuser. The grid may be formed directly into the upstream face 30a, attached to the upstream face 30a, or fixed to the upstream face 30a.

[0062] As also visible in Figures 4 and 5, the aerodynamic profile of the annular wall 4 of the vein 2 is not rectilinear over the entire illustrated vein section. It can be seen that this aerodynamic profile exhibits a curvature around the heat exchanger 10. In this case, and preferably, the outer annular wall 32 comprises an inner outer annular wall 320 and an outer outer annular wall 322 separated from the inner outer annular wall 320 by a gap 324. The inner outer annular wall 320 has a concavity oriented outwards from the diffuser, and the outer outer annular wall 322 has a concavity oriented inwards from the diffuser. Such a configuration improves the topology of the gas flow F around the exchanger 10 from an aerodynamic point of view.

[0063] In certain applications, such as the recirculating cycle, the maximum radius at the turbine outlet is small (e.g., 60 mm) compared to the external radius of a conventional heat exchanger (e.g., 200 mm). In this case, it is possible to use asymmetric diffusers such as the one illustrated in Figures 6 and 7. Thus, variations in shape and dimensions are possible while remaining within the inventive concept underlying the present invention. Preferably, in this embodiment, the radius of curvature around the longitudinal axis X is preferably between 100 millimeters and 1 meter.

[0064] In this regard, according to a first aspect of the invention, the heat exchanger system 1 is characterized in that the outer annular wall 32 diverges radially from the inner annular wall 31 between the upstream face 30a and the downstream face 30b of the diffuser. In other words, a cross-section S(x), separating the outer annular wall 32 and the inner annular wall 31, increases in the direction of the gas flow F. Thus, the aerodynamic profile of the diffuser 30 adapts better to the profile of the section 2 into which the system 1 according to the invention is intended to be integrated, which reduces the force wrench induced by the pressure field acting on the system 1 in the section 2 and avoids the recirculation and turbulence phenomenon TU that would have been generated by the gas flow F if it bypassed the system 1.Indeed, this element is seen as an obstacle to the flow of gas F in channel 2 from the perspective of the gas flow F, because it is oriented perpendicular to the average flow direction. Thus, the lubrication and / or cooling of the electrical and / or electronic components of the turbomachine can be carried out without significantly reducing the flow velocity of the gas F in channel 2.

[0065] According to a second aspect of the invention, the heat exchanger system 1 is characterized in that the diffuser 30 comprises a plurality of intercalated annular walls 33 extending around each other between the inner annular walls 31 and outer annular walls 32. These intercalated walls 33 extend axially from the upstream face 30a to the heat exchange surfaces 16 and divide an annular supply space of the exchanger 10, delimited by the inner annular wall 31 and the outer annular wall 32, into several coaxial annular passages 35 for the flow of the gas flux F and for supplying the flow paths 18. Thus, we maintain a substantially axial flow direction along the longitudinal axis X and we avoid the phenomenon of recirculation and turbulence TU which would occur inside the diffuser 30 because of the radial divergence of the outer annular wall 32 with respect to the inner annular wall 31 ([Fig.2]). The coaxial annular passages 35 significantly reduce pressure losses, maintain optimal gas flow to the heat exchanger 10, and reduce thermal gradients within the heat exchanger 10. This therefore substantially improves the thermal performance of said heat exchanger 10.

[0066] In a preferred embodiment, the interlayer walls 33 have a thickness between 0.3 mm and 1 mm. In this regard, it is advantageous for the thickness of the inner annular wall 31 and / or the outer annular wall 32 and / or the interlayer walls 33 to decrease axially from the upstream face 30a of the diffuser to the downstream face 30b of the diffuser; in other words, for the thickness of the inner annular wall 31 and outer annular wall 32 and / or the interlayer walls 33 to be more The pressure drop is low near the front face 12 of the heat exchanger 10 / downstream face of the diffuser 30 compared to the upstream face 30a of the diffuser. This allows for better control of the gas flow F in the diffuser 30 and further reduces pressure losses at the inlet of the heat exchanger 10.

[0067] In a preferred embodiment, the number of interlayer walls 33 is between 1 and 10, and preferably between 1 and 4, which allows for maintaining an appropriate flow velocity. In a preferred embodiment, the distance separating the upstream face 30a and the downstream face 30b of the diffuser is between 40 mm and 150 mm. In one embodiment, the ratio R of the cross-sectional area of ​​the heat exchanger system 1 between the upstream face 30a of the diffuser 30 and the downstream face 30b of the diffuser 30 is between 1.2 and 10, preferably between 2 and 4. Increasing the cross-sectional area reduces the flow velocity F. These embodiments can be combined.

[0068] In the embodiments illustrated in Figures 8a and 8b, the inner annular wall 31, the intercalated walls 33, and the outer annular wall 32 converge to form a circle of convergence located upstream of the diffuser 30 along the direction of gas flow F. Indeed, since the outer annular wall 32 diverges radially from the inner annular wall 31 between the upstream face 30a and the downstream face 30b, the outer annular wall 32 is inclined relative to the inner annular wall 31. In the cross-sectional plane of Figures 8a and 8b, only one point C of the circle of convergence, intersected by the cross-sectional plane of Figures 8a and 8b, is visible in said figures. The circle of convergence extends inside the channel 2 around the longitudinal axis X. Each point C of the circle of convergence corresponds to the vertex of a conical opening angle.Figures 8a and 8b illustrate an angular sector ai with vertex C of said conical opening angle.

[0069] At this stage, it should be specified that, in each plane of section, it is more precisely the lines crossing the distal and proximal annular borders of each of the inner annular walls 31 and outer annular walls 32 and of the intercalated walls 33 that converge at point C of the circle of convergence. For example, and as illustrated in [Fig. 8a], the inner annular wall 31 has a first proximal annular border 31a and a first distal annular border 31b, while the outer annular wall 32 has a second proximal annular border 32a and a second distal annular border 32b. Line DI, passing through the first proximal annular borders 31a and distal annular borders 31b in the plane of section [Fig.8a], passes through point C. Similarly, line D2, passing through the second proximal annular borders 32a and distal annular borders 32b in the plane of section [Fig.8a], passes through point C. Lines DI and D2 therefore intersect at point C.The same applies to the intercalated walls 33.

[0070] In the embodiment illustrated in [Fig. 8a], the inner annular wall 31, the intercalated walls 33, and the outer annular wall 32 are curved, which allows for axial modulation of the flow velocity. This implementation is not, however, limited to the embodiment of [Fig. 8a] since it can be implemented in all variants of the shape and dimensions of the diffuser 30 used in the system according to the invention, without prejudice to the inventive concept underlying the present invention.

[0071] Advantageously, the inner annular walls 31 and outer annular walls 32 have concavities in opposite directions, and the intercalated walls 33 have, respectively, a concavity of the same orientation, that is to say, of the same direction, as that of said inner annular walls 31 and outer annular walls 32 which is radially closest to the intercalated wall 33 under consideration. In other words, the intercalated walls 33 have, respectively, a concavity in the same direction as that of said inner annular walls 31 and outer annular walls 32 which is located on the same side as said intercalated wall 33 with respect to an imaginary annular wall dividing the conical opening angle into two equal opening angles. In the cross-sectional plane of Figures 8a and 8b, only a section B of this imaginary annular wall is visible. Thus, on [Fig.[8a], although their curvatures differ, the walls 32, 33 located radially external with respect to the imaginary annular wall all have the same orientation. The same is true for the walls 31, 33 located radially internal with respect to the imaginary annular wall.

[0072] Preferably, the angular sector ai is between 20° and 90°. Indeed, although the choice of the opening angle ai depends on the aerodynamic profile of the section of the channel 2 in which the heat exchanger system 1 according to the invention is intended to be placed, the aforementioned preferred range allows for an increase rate R of the cross-section of the heat exchanger system 1 between the upstream face 30a of the diffuser 30 and the downstream face 30b of the diffuser 30 of between 1.2 and 10, and preferably between 2 and 4. This achieves a compromise between the standard dimensions of a heat exchanger and the need to maintain a substantially axial flow direction inside the diffuser 30. When this increase rate R is greater than 10, high pressure losses are likely to occur in the system 1, even when adjusting the inclination of the walls 31, 32, 33 along each of them.

[0073] In this regard, and very advantageously, the inclination of each or some of the inner annular walls 31, outer annular walls 32, and intermediate walls 33 can vary along said wall(s). The inclination of the wall concerned can advantageously be adapted in this way in order to minimize pressure losses in the diffuser 30 and therefore in the system 1 according to the invention.

[0074] More specifically, and as illustrated in the example of [Fig. 8a], the intercalated walls 33 and the outer annular wall 32 comprise, respectively, two radially inclined portions, said radially inclined portions consisting of a distal portion of the front face 12 of the heat exchanger 10 and a proximal portion of the front face 12 of the heat exchanger 10, the proximal portion of the front face 12 of the heat exchanger 10 having a greater inclination than the distal portion. Thus, the inclination of a wall 31, 32, 33 is greater near the front face 12 of the heat exchanger 10 compared to the inclination of the same wall 31, 32, 33 near the upstream face 30a of the diffuser 30.For example, in the case of the inner annular wall 31, the inclination of said inner annular wall 31 between the first proximal annular border 31a and a bottom of the concavity is less than the inclination of the same inner annular wall 31 between the bottom of the concavity and the first distal annular border 31b in the plane of section considered.

[0075] Advantageously, each of the annular passages 35 defines a sector with a cone angle ai, these sectors with cone angles ai being identical. In other words, the intermediate opening angles ai between two radially adjacent walls of the inner annular wall 31, outer annular wall 32, and intermediate walls 33 are identical. For example, the intermediate opening angle ai between the inner annular wall 31 and the intermediate wall 33 radially closest to the inner annular wall 31, and the intermediate opening angle ai between the first wall radially closest to the inner annular wall 31 and the second wall radially closest to said inner annular wall 31 are identical. The same applies to the other walls 33, 32 of the diffuser 30. Consequently, the opening angle ai satisfies the following formula:

[0076] a}=N ■

[0077] Where N is a natural number, corresponding to the number of coaxial annular passages 35 of the diffuser 30. In the embodiment example of [Fig.8a], the number N is equal to 7.

[0078] In practice, it is advantageous for the annular cross-section S(x) of each of the coaxial annular passages 35 to increase from the upstream face 30a of the diffuser to the downstream face 30b of the diffuser as illustrated in Figure 10. In this respect, the annular cross-section can satisfy the following condition d^x), particularly near the face __ downstream 30b of the diffuser, and therefore of the heat exchanger 10. This further reduces the pressure losses that could occur in the annular core 15. That being said, it is possible to deviate from this condition locally to ensure tangency with the vein 2 at the upstream face 30a of the diffuser 30 and / or at the interface between the diffuser 30 and the annular heart 15, particularly in the case where the diffuser 30 extends over the entire height of the vein 2.

[0079] With reference to [Fig. 13], it may also be advantageous for the coaxial annular passage 35 formed between the outer annular wall 32 and the intercalated wall 33 closest to the outer annular wall 32, and / or the coaxial annular passage 35 formed between the inner annular wall 31 and the intercalated wall 33 closest to the inner annular wall 31, to have, at the downstream face 30b of the diffuser, first passage cross-sections hO that are smaller than the second passage cross-sections hl of the other annular passages 35. In other words, the condition hO < hl is satisfied in this particular embodiment. This allows for better control of the upstream flow boundary layer absorption in the extreme annular passages 35. Indeed, the flow boundary layer can be absorbed in the most extreme annular passages 35.

[0080] The embodiment illustrated in [Fig. 8b] is similar to that illustrated in [Fig. 8a]. However, it differs in the curvature of the inner annular walls 31, outer annular walls 32, and intercalated walls 33. In this embodiment, the walls have less pronounced curvatures than those illustrated in [Fig. 8a]. For example, it is possible to reduce the curvature of the walls when the expected pressure losses in the heat exchanger are lower. Indeed, the greater the pressure losses in the heat exchanger, the more one can significantly increase the cross-sectional area of ​​the diffusers near the heat exchanger without causing recirculation. Thus, in configuration 8a, there is relatively low permeability of the heat exchanger, while in configuration 8b, there is relatively high permeability of the heat exchanger. This depends on the nature of the exchanger, the geometry of the exchanger, or the flow velocity F of the gas flow.

[0081] According to an embodiment illustrated in [Fig. 14], the inner annular wall 31, the intercalated walls 33, and the outer annular wall 32 comprise, respectively, two radially inclined portions, said radially inclined portions consisting of a distal portion of the front face 12 of the heat exchanger 10 and a proximal portion of the front face 12 of the heat exchanger 10. As illustrated in [Fig. 14], the proximal portion of the front face 12 of the heat exchanger 10 has a shallower inclination than the distal portion of the front face 12 of the exchanger 10. More specifically, the proximal portion of the front face 12 of the heat exchanger 10 is slightly inclined with respect to the direction of extension of the flow paths 18, while the distal portion of the front face 12 of the heat exchanger 10, i.e.The portion through which the gas flow F enters the diffuser 30 is more inclined relative to the direction of extension of the flow paths 18 than the proximal portion. In particular, the distal portion of the face. The front of the heat exchanger 10, 12, is inclined at an angle θ between 10° and 65°, preferably between 20° and 40°, relative to the direction of the flow paths 18. This configuration is particularly advantageous because it gives the diffuser 30 a deflecting function. In other words, the diffuser 30 diverts the gas flow F. Thus, not only does the cross-sectional area of ​​the gas flow F increase more and more rapidly, but the average direction of the flow also changes.

[0082] Figure 9 compares the flow velocity for a heat exchanger system 1 (left figure) in which the change in cross-section is substantially constant and for a heat exchanger system 2 (right figure) in which the change in cross-section increases significantly near the heat exchanger 10. These figures illustrate the advantage of "accelerating" the increase in cross-section near the exchanger rather than a purely linear increase.

[0083] According to a particular embodiment illustrated in [Fig. 11], the diffuser 30 further comprises at least one longitudinal reinforcing element 36 connecting the interlayer walls 33 to each other. This ensures good mechanical strength of the diffuser 30 and allows it to be manufactured within tolerances. In a particular implementation, the diffuser 30 comprises a plurality of longitudinal reinforcing elements 36 connecting the interlayer walls 33 to each other, the longitudinal reinforcing elements 36 being arranged in pairs successively and angularly spaced at an angle between 3° and 20°, particularly between 3° and 7°, preferably 5°. In certain applications, this is advantageous for meeting very tight tolerances.

[0084] Advantageously, the system 1 according to the invention can be manufactured by metal additive manufacturing on a powder bed. In this case, and as mentioned previously, the diffuser 30 and the heat exchanger 10 can be manufactured as a single piece. The manufacturing of the heat exchanger 10 and the diffuser 30 can be carried out in the orientation illustrated in [Fig. 12], that is, starting with the rear face 13 of the exchanger 10 and ending with the upstream face 30b of the diffuser 30. The proposed orientation for this metal additive manufacturing on a powder bed is vertical, i.e., along the Z-axis, so that the assembly can be manufactured without support structures.

[0085] The invention also relates to an assembly E comprising a heat exchanger system 1 as previously described and an annular channel 2 with longitudinal axis X in which the gas flow F is intended to circulate, the heat exchanger 10 extending around the longitudinal axis X on an internal annular wall 3 of the annular channel 2. An embodiment is illustrated in Figures 4 and 5.

[0086] In a particular embodiment, the heat exchanger system 1 can extend over the entire height of the vein 2, that is, between the inner annular wall 3 of the vein and the outer annular wall 4 of the vein, said annular walls 3 and 4 not being included. In the case mentioned above, the inner annular wall 3 of the vein 2 corresponds to the annular wall 3 of the intermediate casing 114, while the outer annular wall 4 of the vein corresponds to the wall 4 of the blower casing 111. The heat exchanger system 1 can also extend over only a portion of the height of the vein 2. When the assembly E operates in this way, it is referred to as a bypass.

[0087] In this case, it is then preferable that system 1 extend over an appropriate height so that the mass flow rate F of total gas passing through the vein 2 is between 5% and 95%, and even more preferably between 35% and 65%.

[0088] More specifically, and as illustrated in Figures 4 and 5, the inner annular wall 3 is separated from the outer annular wall 4 at a first zone ZI located at the heat exchanger 10 by a distance dl, and at a second zone Z2 located upstream of the diffuser 30 in the flow direction of the first fluid F by a distance d2. Advantageously, a ratio R = dl / d2 is between 1.2 and 10, preferably between 2 and 4, which makes it possible to obtain a mass flow rate F of total gas passing through the vein 2 between 5% and 95% and which makes it possible to achieve an efficient bypass of a heat exchanger of conventional dimensions.

[0089] The configurations shown in the cited figures are only possible examples, by no means limiting, of the invention which on the contrary encompasses variants of forms and designs within the reach of a person skilled in the art.

Claims

Demands

1. A heat exchanger system (1) for an aircraft turbomachine comprising: - a heat exchanger (10) extending about a longitudinal axis (X) and having: > a front face (12) for the inlet of a gas flow (F) and a rear face (13) for the outlet of a gas flow (F), and > an annular heat transfer core (15) interposed between the front (12) and rear (13) faces and provided with a plurality of heat exchange surfaces (16), said heat exchange surfaces (16) being arranged to form a plurality of flow paths (18) for the gas flow (F) from the front face (12) to the rear face (13), and - a diffuser (30) located upstream of said annular core (15) and comprising: > an upstream face (30a) for the inlet of the gas flow into the diffuser (30) and a downstream face (30b) of the outlet of the gas flow from the diffuser (30), the downstream face (30b) being defined by the front face (12) of the heat exchanger (10),> an inner annular wall (31) and an outer annular wall (32) located radially external with respect to the inner annular wall (31), characterized in that the outer annular wall (32) diverges radially from the inner annular wall (31) between the upstream (30a) and downstream (30b) faces, and in that the diffuser (30) comprises a plurality of intercalated annular walls (33) extending around each other between the inner (31) and outer (32) annular walls, these intercalated walls (33) extending axially from the upstream face (30a) to the heat exchange surfaces (16) and dividing an annular supply space of the exchanger (10), delimited by the inner annular wall (31) and the outer annular wall (32), into several coaxial annular passages (35) for the flow of said gas flux (F) and for supplying the paths (18) of flow.,

2. Exchanger system (1) according to claim 1, wherein the inner annular wall (31), the intercalated walls (33) and the outer annular wall (32) are curved.

3. Heat exchanger system (1) according to claim 2, wherein the inner annular wall (31), the intercalated walls (33) and the outer annular wall (32) comprise, respectively, two radially inclined portions, said radially inclined portions consisting of a distal portion of the front face (12) of the heat exchanger (10) and a proximal portion of the front face (12) of the heat exchanger (10), the proximal portion of the front face (12) of the heat exchanger (10) having a higher inclination than the distal portion of the front face (12) of the exchanger (10).

4. Exchanger system (1) according to any one of claims 2 or 3, wherein the inner annular walls (31) and outer annular walls (32) have concavities in opposite directions, the intercalated walls (33) having, respectively, a concavity in the same direction as that of the inner annular walls (31) and outer annular walls (32) which is radially closest to the intercalated wall (33) considered.

5. Exchanger system (1) according to any one of claims 1 to 4, wherein each of the coaxial annular passages (35) defines a cone angle sector (ai), said cone angle sectors (¾) being identical.

6. Exchanger system (1) according to any one of claims 1 to 5, wherein each of the coaxial annular passages (35) defines an annular section S(x) from the upstream face (30a) of the diffuser to the downstream face (30b) of the diffuser, the annular section S(x) increasing from the upstream face (30a) of the diffuser to the downstream face (30b) of the diffuser.

7. Exchanger system (1) according to any one of claims 1 to 4, wherein the coaxial annular passage (35) formed between the outer annular wall (32) and the intercalated wall (33) closest to the outer annular wall (32) on the one hand and / or the coaxial annular passage (35) formed between the inner annular wall (31) and the intercalated wall (33) closest to the inner annular wall (31) on the other hand have, at the downstream face (30b) of the diffuser, first passage sections (h0) smaller than second passage sections (hl) of the other annular passages (35).

8. Heat exchanger system (1) according to any one of claims 1 to 7, wherein the thickness of the inner annular wall (31) and / or the outer annular wall (32) and / or the intercalated walls (33) decreases axially from the upstream face (30a) of the diffuser to the downstream face (30b) of the diffuser.

9. Exchanger system (1) according to any one of claims 1 to 8, wherein the diffuser (30) further comprises at least one longitudinal reinforcing element (36) connecting the intercalated walls (33) to each other.

10. Exchanger system (1) according to claim 9, wherein the diffuser (30) comprises a plurality of longitudinal reinforcing elements (36) connecting the intercalated walls (33) to each other, the longitudinal reinforcing elements (36) being two by two successively and angularly spaced at an angle between 3° and 20°, particularly between 3° and 7°, preferably equal to 5°.

11. Exchanger system (1) according to any one of claims 1 to 10, wherein the outer annular wall (32) comprises an inner outer annular wall (320) and an outer annular wall (322) separated from the inner outer annular wall (320) by a space (324), the inner outer annular wall (320) having an outwardly oriented concavity and the outer annular wall (322) having an inwardly oriented concavity.

12. Exchanger system (1) according to any one of claims 1 to 11, wherein the heat exchanger (10) is selected from a gas-gas turbine exchanger, an air-oil exchanger, a turbine blade cooling exchanger and an air-nitrogen exchanger.

13. Exchanger system (1) according to any one of claims 1 to 12 manufactured by powder bed metal additive manufacturing.

14. Exchanger system (1) according to any one of claims 1 to 13, wherein the heat exchanger (10) and the diffuser (30) are made of a single piece.

15. A heat exchanger system (1) according to claim 2, wherein the inner annular wall (31), the intercalated walls (33), and the outer annular wall (32) comprise, respectively, two radially inclined portions, said radially inclined portions consisting of a distal portion of the front face (12) of the heat exchanger (10) and a proximal portion of the front face (12) of the heat exchanger (10), the proximal portion of the front face (12) of the heat exchanger (10) having a lower inclination that the distal portion of the front face (12) of the exchanger (10) such that the proximal portion of the front face (12) of the heat exchanger (10) is slightly inclined with respect to the direction of extension of the flow paths (18) and that the distal portion of the front face (12) of the heat exchanger (10) is inclined with respect to the direction of extension of the flow paths (18) at an angle (0) between 10° and 65°, preferably between 20° and 40°.

16. Assembly (E) comprising: - a heat exchanger system (1) according to any one of claims 1 to 15, - an annular vein (2) with longitudinal axis (X) in which the gas flow (F) is intended to circulate, the heat exchanger (10) extending at least in part around the longitudinal axis (X) on an internal annular wall (3) of the annular vein (2).

17. Assembly (E) according to claim 16, wherein the annular vein (2) comprises an external annular wall (4) radially spaced from the internal annular wall (3), the internal annular wall (3) being separated from the external annular wall (4) at a first zone (Z1) located at the heat exchanger (10) by a distance (d1), and at a second zone (Z2) located upstream of the diffuser (30) in the flow direction of the first fluid (F) by a distance (d2), a ratio (R) d1 / d2 being between 1.2 and 10, preferably between 2 and 4.

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