IMPROVED HEAT EXCHANGER DEVICE FOR AN AIRCRAFT TURBOCHARGER

Description

Technical Field

[0001] This paper concerns a heat exchanger device for an aircraft turbomachine, such as a turboprop or turbojet engine. It also concerns a turbomachine incorporating such a heat exchanger device. Previous technique

[0002] Heat exchangers, or heat exchangers, are used in aircraft turbomachinery to meet various needs, for example hot air / gas exchangers recovering hot gases from the nozzle outlet to heat the air entering the combustion chamber, so-called "intercooler" air / air exchangers to cool the hot inter-compressor air with ambient air, nozzle exchangers for heating cryogenic fuel, or exchangers for cooling with ambient air the air taken from the inter-compressor and intended to be routed to the cabin air conditioning system.

[0003] There figure 1 This schematically represents a front and cross-sectional view of a prior art cross-flow heat exchanger 1', comprising a first flow 10, referred to as the "hot flow," and a second flow 20, referred to as the "cold flow." Indeed, it is well known that heat exchangers used for the above applications involve a hot fluid at high temperature, generally a compressible fluid in a gaseous state with a temperature ranging from 400°C to 1000°C, and a cold fluid at a lower temperature, generally between -150°C and 400°C.

[0004] Typically, heat exchangers include inlet and / or outlet manifolds of a heat exchanger body 30, ensuring the distribution of hot and cold fluids to and / or from the heat exchanger body. Thus, the hot stream 10 comprises, from upstream to downstream (depending on the direction of hot fluid flow), an upstream hot fluid manifold 12, channels of the heat exchanger body 30, and a downstream hot fluid manifold 14. The upstream hot fluid manifold 12 is configured to collect a first fluid, referred to as the "hot fluid," from a separate portion of the turbomachine (not shown). For example, the upstream hot fluid manifold 12 can draw hot gases from the low-pressure turbine outlet and convey them to the heat exchanger body 30, through which the cold fluid also circulates.

[0005] It is thus understood that the upstream hot fluid manifold 12 extends between a first upstream end 12a which collects the hot fluid at high temperature, and a second downstream end 12b attached to the heat exchanger body 30, through which the hot fluid is injected into the channel(s) of the heat exchanger body 30. The downstream hot fluid manifold 14 also extends between a first upstream end 14a attached to the heat exchanger body 30 and through which the hot fluid which has circulated in the heat exchanger body 30 is recovered, and a downstream end 14b communicating with a separate portion (not shown) of the turbomachine.

[0006] Similarly, the cold stream 20 comprises, from upstream to downstream (according to the direction of flow of the cold fluid), an upstream cold fluid manifold 22, channels of the heat exchanger body 30, and a downstream cold fluid manifold 24. The upstream cold fluid manifold 22 is configured to collect a second fluid, called "cold fluid", in a separate portion of the turbomachine (not shown), for example in the secondary air flow channel.

[0007] It is thus understood that the upstream cold fluid manifold 22 extends between a first upstream end 22a allowing the collection of the cold fluid at low temperature, and a second downstream end 22b fixed to the heat exchanger body 30, through which the cold fluid is injected into the channel(s) of the heat exchanger body 30. The downstream cold fluid manifold 24 also extends between a first upstream end 24a fixed to the heat exchanger body 30 and through which the cold fluid having circulated in the heat exchanger body 30 is recovered, and a downstream end 24b communicating with a separate portion (not shown) of the turbomachine.

[0008] The heat exchanger body 30 (or heat exchanger core) is the component in which the actual heat exchange takes place between the hot fluid and the cold fluid. It follows that the heat exchanger body 30 comprises one or more channels through which the hot fluid flows, and one or more channels through which the cold fluid flows, with heat transfer between these two fluids occurring through the walls of these different channels. In the case of a cross-flow heat exchanger, the channels through which the cold fluid flows are perpendicular to the channels through which the hot fluid flows, and these different channels may be superimposed on one another.

[0009] DE 10 2005 022389 A1 and EP 3 531 057 A1 describe other examples of heat exchangers according to the preamble of claim 1.

[0010] However, these heat exchangers are subjected to significant thermal stresses. Thermal expansion / contraction of the body (or core) of the heat exchanger 30 and the manifolds occurs with each engine cycle, with significant thermal transients linked in particular to engine starts and stops. These stresses lead in particular to significant constraints at the junctions between the manifolds 12, 14, 22, 24 and the heat exchanger body 30. In the case of the cross-flow heat exchanger 1' in particular, four junction zones a, b, c, d exist between the downstream ends 12b, 22b of the upstream hot and cold fluid manifold 12, 22 and the heat exchanger body 30, and between the upstream ends 14a, 24a of the downstream hot and cold fluid manifold 14, 24 and the heat exchanger body 30. In the case of heat exchangers with rectangular cross-section manifolds, these junction zones between the ends of the manifolds and the heat exchanger body are straight lines of contact.

[0011] These stresses can lead, through repeated thermal cycles, to the formation of cracks in the heat exchanger / manifold assembly, particularly in the junction zones a, b, c, and d. These so-called thermal fatigue cracks can themselves cause leaks and lead to a fracture of the assembly, which significantly reduces the heat exchanger's lifespan. The mechanical properties of the manifold walls can also be damaged when the temperature of the hot fluid circulating in the manifold exceeds the wall's permissible temperature (for example, 100 K for a stainless steel wall, or 500 K for an aluminum wall).

[0012] Conversely, it should be noted that the walls of the heat exchanger body 30 are less affected. Indeed, since the heat exchange between the hot fluid and the cold fluid takes place mainly within the heat exchanger body 30, the temperature of the walls within the heat exchanger body lies between that of the hot fluid and that of the cold fluid.

[0013] A known solution involves adding flexible sections or bellows to the manifolds, allowing for the expansion and contraction of the manifold / heat exchanger assembly. This reduces stress on the assembly's supports and, consequently, the risk of heat exchanger deformation. However, this type of device is difficult to implement in terms of operability and maintenance, is expensive, and does not adequately address the aforementioned problem of cracking, particularly at the junctions between the manifolds and the heat exchanger body.

[0014] There is therefore a need for a heat exchanger device that can limit, or even eliminate, the problems related to thermal fatigue on the one hand, and to the mechanical strength of the collectors on the other. Description of the invention

[0015] The present disclosure relates to a heat exchanger device for an aircraft turbomachine, the heat exchanger device as defined in claim 1 comprising a heat exchanger body, an upstream hot fluid manifold fixed to the heat exchanger body and configured to collect a first fluid at a first temperature and to bring it to the heat exchanger body, an upstream cold fluid manifold fixed to the heat exchanger body and configured to collect a second fluid at a second temperature lower than the first temperature and to bring it to the heat exchanger body, the upstream hot fluid manifold at least comprising a double wall forming a peripheral cavity surrounding a main cavity configured to receive a main flow of the first fluid, the peripheral cavity being configured to receive a secondary flow of the first fluid or of the second fluid.

[0016] In this description, the terms "upstream" and "downstream" are defined in relation to the direction of fluid flow in the different streams of the heat exchanger device, namely the "hot" and "cold" streams. More precisely, the first fluid flows through the heat exchanger device in its direction of flow, from upstream to downstream, first in the upstream hot fluid manifold, then in the heat exchanger body, and finally in the downstream hot fluid manifold defined later. Similarly, the second fluid flows from upstream to downstream, first in the upstream cold fluid manifold, then in the heat exchanger body, and finally in the downstream cold fluid manifold defined later.

[0017] In this description, it is understood that the double wall of the upstream hot fluid manifold comprises two walls relatively close to each other, without being in contact. The resulting gap between the two walls of this double wall forms a peripheral cavity surrounding the main cavity. It should be noted that the main cavity allows the first fluid collected in the turbomachine to be conveyed to the heat exchanger body via a main flow.

[0018] Furthermore, a fraction of the first or second fluid may flow into the peripheral cavity, this fraction forming a secondary flow around the periphery of the main flow. Consequently, the first high-temperature fluid flowing into the main cavity is not separated from the ambient-temperature outside of the manifold by a single wall, but by a double wall: the peripheral cavity and the secondary flow within this peripheral cavity.

[0019] This configuration reduces heat transfer by distributing it between the two walls of the collector and in the secondary flow, thus limiting the risk of cracks appearing in these walls, particularly at the junction between the upstream hot fluid collector and the heat exchanger body.

[0020] In some embodiments, the device includes a downstream cold fluid manifold attached to the heat exchanger body and configured to collect the second fluid from the heat exchanger body, the upstream hot fluid manifold being configured to take a fraction of the second fluid flowing into the upstream cold fluid manifold, and to bring said fraction to the downstream cold fluid manifold via the peripheral cavity.

[0021] In this configuration, while the majority of the second fluid flows from upstream to downstream through the upstream cold fluid manifold, the heat exchanger body, and then the downstream cold fluid manifold, a smaller fraction of the second fluid does not flow through the heat exchanger body but is diverted to the upstream hot fluid manifold, specifically into the peripheral cavity formed by the double wall of said upstream hot fluid manifold. After flowing through the peripheral cavity, this fraction of the second fluid is then reinjected into the downstream cold fluid manifold, downstream of the heat exchanger body.

[0022] This flow of the second fluid, cooler than the first, into the peripheral cavity allows for localized cooling of the wall on the side of the first fluid, particularly at the junctions between the manifold and the heat exchanger body, as these junctions are subject to significant thermal stress. Consequently, during turbomachine operation, the upstream hot fluid manifold experiences less temperature variation, which reduces or even eliminates crack formation and improves its mechanical strength. Thus, the double wall itself acts as a heat exchanger, heating this portion of the second fluid while simultaneously cooling the wall of the upstream hot fluid manifold.

[0023] In some embodiments, the peripheral cavity includes at least one inlet section opening into a main cavity of the upstream cold fluid manifold, the inlet section being configured to take the fraction of the second fluid and being disposed at a first junction between the upstream cold fluid manifold, the upstream hot fluid manifold and the heat exchanger body.

[0024] It is understood that the inlet section can be an opening formed in the junction between the upstream cold fluid manifold, the upstream hot fluid manifold, and the heat exchanger body, allowing fluidic communication between the main cavity of the upstream cold fluid manifold and the peripheral cavity of the upstream hot fluid manifold. Thus, depending on the dimensions of the inlet section, a small fraction of the second fluid flowing in the upstream cold fluid manifold can enter the peripheral cavity of the upstream hot fluid manifold through this inlet section. Positioning the inlet section at this junction increases heat exchange between the second fluid and the wall of the upstream hot fluid manifold at this point, thereby reducing the risk of cracking at this junction.

[0025] In some embodiments, the peripheral cavity includes at least one outlet section opening into a main cavity of the downstream cold fluid manifold, the outlet section being configured to inject into the downstream cold fluid manifold the fraction of the second fluid flowing into the peripheral cavity, and being disposed at a second junction between the downstream cold fluid manifold, the upstream hot fluid manifold and the heat exchanger body.

[0026] Similar to the inlet section, the outlet section can be an opening formed in the junction between the upstream hot fluid manifold, the downstream cold fluid manifold, and the heat exchanger body. This opening allows fluidic communication between the main cavity of the downstream cold fluid manifold and the peripheral cavity of the upstream hot fluid manifold. Thus, the portion of the second fluid introduced through the inlet section and flowing into the peripheral cavity can be reinjected into the downstream cold fluid manifold via the outlet section. Positioning the outlet section at this junction increases heat exchange between the second fluid and the wall of the upstream hot fluid manifold at this point, thereby reducing the risk of cracking at this junction.

[0027] In some embodiments, the upstream and downstream hot fluid manifolds, and the upstream and downstream cold fluid manifolds have a rectangular cross-section.

[0028] In this configuration, the first junction (and the second junction) between the upstream cold fluid manifold (and the downstream cold fluid manifold), the upstream hot fluid manifold and the heat exchanger body is a linear junction, the inlet section and the outlet section extending linearly over at least part of these junctions.

[0029] Alternatively, the upstream and downstream hot fluid manifolds, and the upstream and downstream cold fluid manifolds have a circular cross-section, the first and second junction extending in an arc of a circle, the inlet and outlet sections extending over an angular sector between 20° and 180°.

[0030] The inlet and outlet sections are preferably identical. Furthermore, the shape of the collectors is not limited; other geometric shapes (for example, elliptical) can be considered.

[0031] In some embodiments, the upstream hot fluid collector includes fins extending longitudinally in the direction of flow of the first fluid in the main cavity, and extending from one of the two walls of the double wall to the other of the two walls, inside the peripheral cavity.

[0032] It is understood that the fins are walls extending vertically from one of the two walls of the double wall, in other words, perpendicular to it, towards the other wall, but without contacting it. The fins also extend longitudinally, that is, from upstream to downstream. It should be noted that these fins preferably extend from the inner wall of the double wall. These fins, positioned in the peripheral cavity and thus immersed in the portion of the second fluid flowing into said cavity, improve heat transfer by increasing the surface area for exchange with the second fluid, and thereby further reduce the wall temperature of the upstream hot fluid manifold.

[0033] In some embodiments, the fins extend longitudinally along part of the length of the upstream hot fluid manifold, and extend along the entire height of a space separating the two walls of the double wall.

[0034] Unlike the previous configuration, the fins extend across the entire height of the space between the two walls of the double wall, remaining in contact with both walls. This configuration further improves heat transfer by increasing the exchange surface area with the second fluid, thus further reducing the wall temperature of the upstream hot fluid manifold.

[0035] In some embodiments, a wall of the downstream hot fluid manifold and the downstream cold fluid manifold include a flexible portion configured to allow longitudinal deformation of the downstream hot fluid manifold and the downstream cold fluid manifold. The flexible portion may be a bellows that can be extended or retracted like the accordion section of a straw, thus absorbing the expansion of the manifolds.

[0036] The flexible sections allow for the expansion and contraction of the entire manifold / heat exchanger assembly. In addition to the advantages provided by the double wall, these flexible sections reduce stress on the supports of this assembly, and consequently minimize the risk of deformation.

[0037] In some embodiments, the upstream hot fluid manifold includes an intermediate wall disposed in the peripheral cavity, separating the fraction of the second fluid taken from the upstream cold fluid manifold into an internal secondary flow and an external secondary flow.

[0038] In other words, the intermediate wall divides the peripheral cavity into two cavities, through which the internal secondary flow and the external secondary flow circulate, respectively. Similarly, the fraction of the second fluid drawn from the upstream cold fluid manifold is divided into two flows, namely the internal secondary flow and the external secondary flow.

[0039] It is therefore understood that the internal secondary flow occurs between the inner wall separating the peripheral cavity from the main cavity of the upstream hot fluid manifold, and the intermediate wall. Similarly, the external secondary flow occurs between the outer wall separating the peripheral cavity from the outside of the upstream hot fluid manifold, and the intermediate wall. Separating the fraction of the second fluid extracted improves the temperature homogenization of the walls of the upstream hot fluid manifold and better distributes heat transfer.

[0040] In some embodiments, the fraction of the second fluid taken from the upstream cold fluid manifold is between 0.5 and 5% of the flow rate of the second fluid flowing in the upstream cold fluid manifold.

[0041] These values ​​make it possible to obtain the effects mentioned above, of cooling the temperature of the walls of the upstream hot fluid collector, while limiting the impact on the main flow of the second fluid used for heat transfers with the first fluid in the exchanger body.

[0042] In some embodiments, the device includes a downstream hot fluid manifold attached to the heat exchanger body, configured to collect the first fluid from the heat exchanger body, comprising a double wall forming a peripheral cavity, and configured to take a fraction of the second fluid flowing in the upstream cold fluid manifold, and to bring said fraction to the downstream cold fluid manifold via the peripheral cavity.

[0043] In this configuration, the upstream hot fluid manifold and the downstream hot fluid manifold each have a double wall, and a portion of the second fluid is diverted to flow into the cavity of each manifold. Preferably, this portion of the second fluid is diverted into the peripheral cavity of the downstream hot fluid manifold via an inlet section and reinjected into the downstream cold fluid manifold via an outlet section. The technical effects described above with reference to the upstream hot fluid manifold can thus also be achieved for the downstream hot fluid manifold.

[0044] It should be noted that the fraction of the second fluid drawn off and diverted into the peripheral cavity of the downstream hot fluid manifold may differ from the fraction of the second fluid drawn off and diverted into the peripheral cavity of the upstream hot fluid manifold, in order to adapt this quantity of second fluid drawn off to the temperature of the walls of the downstream hot fluid manifold. Indeed, since the downstream hot fluid manifold is downstream of the heat exchanger body, the first fluid flowing into the downstream hot fluid manifold, downstream of the heat exchanger body, necessarily has a lower temperature than its temperature when it passed through the upstream hot fluid manifold.

[0045] In some embodiments, the upstream hot fluid manifold is configured to take a fraction of the first fluid at an upstream end of the upstream hot fluid manifold, and to bring said fraction to the heat exchanger body at a downstream end of the upstream hot fluid manifold via the peripheral cavity.

[0046] In this configuration, unlike the embodiments described above, the first fluid flows simultaneously in the main cavity and the peripheral cavity, in the same direction. In other words, the first fluid is separated into a central main flow and a peripheral secondary flow. This configuration allows for a more gradual variation in wall temperature, thus reducing thermal gradients. In particular, having a peripheral flow within the double wall, with a lower flow rate than the main flow, results in a lower heat transfer coefficient and therefore a lower thermal gradient within the walls.

[0047] It should be noted that the upstream cold fluid manifold, the downstream hot fluid manifold, and the downstream cold fluid manifold can also be equipped with a similar double wall, allowing the respective flows to be separated into a central main flow and a peripheral secondary flow.

[0048] In some embodiments, the double wall comprises an inner wall delimiting the main cavity, and an outer wall arranged around the inner wall, with an interval between the inner wall and the outer wall being between 1 and 10 mm.

[0049] This presentation also relates to an aircraft turbomachine comprising a heat exchanger device according to any of the preceding embodiments. Brief description of the drawings

[0050] The invention and its advantages will be better understood upon reading the detailed description below of various embodiments of the invention, given by way of non-limiting examples. This description refers to the accompanying figure pages, on which: [ Fig. 1 ] There figure 1 schematically represents a front and cross-sectional view of a prior art cross-flow heat exchanger, [ Fig. 2 ] There figure 2 schematically represents a perspective view of a cross-flow heat exchange device according to a first embodiment, [ Fig. 3 ] There figure 3 schematically represents a front and cross-sectional view of the heat exchange device of the figure 2 , [ Fig. 4 ] There figure 4 schematically represents a front and cross-sectional view of a cross-flow heat exchanger according to a second embodiment, [ Fig. 5 ] There figure 5 schematically represents a front and cross-sectional view of a cross-flow heat exchanger according to a third embodiment, [ Fig. 6 ] There figure 6 schematically represents a front and cross-sectional view of a cross-flow heat exchanger according to a fourth embodiment, [ Fig. 7 ] There figure 7 schematically represents a front and cross-sectional view of a cross-flow heat exchange device according to a fifth embodiment, [ Fig. 8 ] There figure 8 schematically represents a front and cross-sectional view of a cross-flow heat exchange device according to a sixth embodiment. Description of the implementation methods

[0051] In the following discussion, the terms "upstream" and "downstream" are defined in relation to the direction of fluid flow in the different streams of the heat exchanger device, i.e. the "hot" and "cold" streams.

[0052] It should also be noted that for the sake of clarity and understanding, the heat exchanger devices according to the different embodiments are represented schematically, the details of the actual structure of such a device, for example the arrangement of the internal channels of the exchanger body 30, not being represented.

[0053] There figure 2 represents a perspective view of a heat exchanger device 1 according to a first embodiment, of the cross-flow type, and the figure 3 The diagram schematically represents a front and cross-sectional view of this device, comprising a first current 10, referred to as the "hot current," and a second current 20, referred to as the "cold current." Furthermore, according to this embodiment and also the following ones, the collectors 12, 14, 22, and 24 are conduits with a rectangular cross-section. It should be noted, however, that the invention is not limited to collectors with a rectangular cross-section and also applies to other shapes, such as circular or elliptical ones.

[0054] It should also be noted that the invention is not limited to cross-flow heat exchanger devices, but also applies to other types of exchangers such as co-current or counter-current exchangers. Furthermore, apart from the double wall described below, the other elements of the heat exchanger device 1 are identical to the heat exchanger device 1' described previously with reference to the figure 1 , and will not be repeated.

[0055] According to the present embodiment, the upstream hot fluid collector 12 comprises a double wall 120. More specifically, the double wall 120 comprises an inner wall 121, and an outer wall 122 surrounding the inner wall 121.

[0056] The inner wall 121 defines a main cavity 125 through which a main flow of a first fluid, referred to as the "hot fluid" in the following description, circulates from the upstream end 12a of the upstream hot fluid manifold 12 to the downstream end 12b, so as to bring said hot fluid into the heat exchanger body 30. The outer wall 122 is arranged around the inner wall 121, spaced from it by a distance, for example, between 1 and 10 mm. A peripheral cavity 16, surrounding the main cavity 125, is thus formed between the inner wall 121 and the outer wall 122 of the double wall 120.

[0057] Furthermore, at the downstream end 12b fixed to the heat exchanger body 30, and at the linear junction "a" between the upstream hot fluid manifold 12, the upstream cold manifold 22, and the heat exchanger body 30, the upstream hot fluid manifold 12 includes an inlet section 16e, putting the peripheral cavity 16 into fluidic communication with the main cavity 225 of the upstream cold fluid manifold 22, in which the second fluid, called "cold fluid" in the rest of the description, circulates.

[0058] Furthermore, at the downstream end 12b fixed to the heat exchanger body 30, and at the linear junction "b" between the upstream hot fluid manifold 12, the downstream cold fluid manifold 24, and the heat exchanger body 30, the upstream hot fluid manifold 12 includes an outlet section 16s, connecting the peripheral cavity 16 with the main cavity 245 of the downstream cold fluid manifold 24, in which the cold fluid flows downstream of the heat exchanger body 30. It should also be noted that the peripheral cavity 16 is closed at the upstream end 12a of the upstream hot fluid manifold 12.

[0059] Preferably, the inlet section 16e is sized so that a portion P1 comprising between 0.5 and 5% of the main flow of the cold fluid stream 20 flowing in the upstream cold fluid manifold 22 is collected in the peripheral cavity 16. Therefore, during its flow in the upstream cold fluid manifold 22, a portion P1 (represented by an arrow on the figure 3 ) of the cold fluid does not enter the exchanger body 30, but is diverted into the peripheral cavity 16.

[0060] The enlarged image at the bottom of the figure 3 The diagram schematically represents the path (shown by arrows) of this portion P1 of the cold fluid in the peripheral cavity 16. Although this figure is shown in plan view, and the arrows indicate a longitudinal flow of the cold fluid in the peripheral cavity 16, it is understood that the cold fluid does not flow only longitudinally between the ends 12a and 12b in one direction and then the other, but also flows around the main cavity 125, given the shape of the peripheral cavity 16, which is particularly visible on the diagram. figure 2 , at the end of the upstream hot fluid manifold 12. Thus, the portion P1 of the cold fluid diffuses into at least part of the peripheral cavity 16, and is then reinjected into the downstream cold fluid manifold 24, via the outlet section 16s.

[0061] It should be noted that the flow of portion P1 of the cold fluid, in particular its extraction via the inlet section 16e until its reinjection into the downstream cold fluid collector 24 via the outlet section 16s, can be achieved by the interplay of pressure and temperature differences existing between the inlet section 16e and the outlet section 16s.

[0062] Furthermore, in this example, the downstream hot fluid manifold 14 also includes a double wall 140, comprising an inner wall 141 and an outer wall 142 forming between them a peripheral cavity 16. The peripheral cavity 16 is in fluidic communication with the main cavity 225 of the upstream cold fluid manifold 22 via an inlet section 16e, and with the main cavity 245 of the downstream cold fluid manifold 24 via an outlet section 16s.

[0063] The inlet section 16e is disposed at the upstream end 14a fixed to the heat exchanger body 30, at the linear junction "c" between the downstream hot fluid manifold 14, the upstream cold manifold 22, and the heat exchanger body 30, and the outlet section 16s is disposed at the upstream end 14a fixed to the heat exchanger body 30, at the linear junction "d" between the downstream hot fluid manifold 14, the downstream cold manifold 24, and the heat exchanger body 30.

[0064] Therefore, in this example, a portion P2 (represented by an arrow on the figure 3 ) of the cold fluid, which may also be between 0.5 and 5% of the main flow of the cold fluid, is taken and diverted into the peripheral cavity 16 of the downstream hot fluid manifold 14, in the same way as the upstream hot fluid manifold 12. It should be noted that the inlet section 16e and the outlet section 16s of the downstream hot fluid manifold 14 may be identical to the inlet section 16e and the outlet section 16s of the upstream hot fluid manifold 12, or different from it.

[0065] In an example application of the heat exchanger device 1, a hot fluid, in particular the hot gases exiting the low-pressure turbine, at a temperature of 1000°C can be collected at the inlet of the hot stream 10, and a cold fluid, flowing for example in the secondary air flow duct, at a temperature of 100°C can be collected at the outlet of the cold stream 20. In this case, the double walls 120, 140 of the hot fluid collectors allow the average temperature of their walls to be reduced by approximately 300 to 500°C, this range depending on the heat exchange properties of each of the two fluids (hot and cold) in contact with the walls. Thus, the walls of the hot fluid collectors are subjected to a narrower temperature range during a given operation of the turbomachine engine due to the reduction in the wall temperature of the hot fluid collectors 12, 14.

[0066] In particular, without a double wall, the hot fluid manifolds can experience a temperature variation ranging from 20°C (ambient temperature before engine start) to 1000°C (temperature reached during engine operation). With double walls, this range can be reduced to [20°C-500°C], assuming a maximum temperature drop of 500°C for the inner wall 121, 141 due to heat exchange with the cold fluid in the peripheral cavity 16. This reduces thermal stresses in the hot fluid manifolds, especially in the most sensitive areas of the junctions a, b, c, and d, and decreases the risk of manifold deformation and leakage at these junctions.

[0067] There figure 4 schematically represents a heat exchanger device 1 according to a second embodiment. This heat exchanger device 1 differs from the heat exchanger device according to the first embodiment in that the upstream hot fluid manifold 12 comprises a plurality of fins 30 arranged in the peripheral cavity 16.

[0068] As illustrated in the image at the bottom left of the figure 4 Representing a section of the upstream hot fluid manifold 12 in a cross-sectional plane AA, the fins 30 are walls extending vertically from and relative to the inner wall 121, for example, perpendicularly to it, in the direction of the outer wall 122, but without contacting it. The fins 30 also extend longitudinally, that is, from upstream to downstream, between the upstream end 12a and the downstream end 12b, over at least part of the length of the upstream hot fluid manifold 12. The fins 30 are preferably distributed at regular intervals around a central axis of the manifold.

[0069] These fins 30 are arranged in the peripheral cavity 16, immersed in the fraction of cold fluid flowing into said cavity, thus increasing the surface area for heat exchange with the cold fluid and consequently the heat transfer. It should be noted that the downstream hot fluid manifold 14, which in this example comprises a double wall 140, can also include similar fins 30 in its peripheral cavity.

[0070] There figure 5 schematically represents a heat exchanger device 1 according to a third embodiment. As illustrated in the image at the bottom left of the figure 5 representing a section of the upstream hot fluid manifold 12 in a cutting plane AA, this heat exchanger device 1 differs from the heat exchanger device according to the second embodiment in that the fins 30 extend over the entire height of the space separating the inner wall 121 and the outer wall 122.

[0071] In this configuration, the fins 30 extend longitudinally over only part of the length of the upstream hot fluid manifold 12 between the upstream end 12a and the downstream end 12b, and not over its entire length, in order to allow the fraction of cold fluid taken through the inlet section 16e to flow into the peripheral cavity 16 and to the outlet section 16s.

[0072] There figure 6 This schematically represents a heat exchanger device 1 according to a fourth embodiment. This heat exchanger device 1 differs from the heat exchanger device according to the first embodiment in that the downstream hot fluid manifold 14 and the downstream cold fluid manifold 24 comprise flexible portions 40. In this example, the flexible portions 40 are bellows arranged on a section of the manifolds 14, 24, and allowing longitudinal deformation of the latter by extending or contracting so as to absorb the expansion of the manifolds.

[0073] There figure 7 schematically represents a heat exchanger device 1 according to a fifth embodiment. This heat exchanger device 1 differs from the heat exchanger device according to the first embodiment in that the upstream hot fluid manifold 12 includes an intermediate wall 123 disposed in the peripheral cavity 16, and separating the fraction of cold fluid taken from the upstream cold fluid manifold 22 into two fractions P11 and P12, resulting in an external secondary flow and an internal secondary flow in the peripheral cavity 16.

[0074] More specifically, the intermediate wall 123 divides the peripheral cavity 16 into an external peripheral cavity 161 in which the external secondary flow circulates, i.e. the portion of cold fluid P11, and an internal peripheral cavity 162 in which the internal secondary flow circulates, i.e. the portion of cold fluid P12. To achieve this, the intermediate wall 123 extends around the internal wall 121 and transversely to it so as to close the internal peripheral cavity 162 at one of its ends.In other words, the end 123b of the intermediate wall 123 on the side of the downstream end 12b of the collector 12 is disposed between the inner wall 121 and the outer wall 122 so as to divide the inlet section 16e and the outlet section 16s in two, and the end 123a of the intermediate wall 123 closer to the upstream end 12a of the collector 12 is in contact with the inner wall 121 by being fixed to it, so as to close the internal peripheral cavity 162 at this end 123a.

[0075] In this example, the downstream hot fluid collector 14 also includes an intermediate wall 143 similar to the intermediate wall 123, arranged between the inner wall 141 and the outer wall 142, and separating the fraction P2 of cold fluid taken into two portions P21 and P22.

[0076] There figure 8This schematically represents a heat exchanger device 1 according to a sixth embodiment. In this embodiment, unlike the previous embodiments, the peripheral cavity 16 is not closed at the upstream end 12a of the upstream hot fluid manifold 12, but is open. Furthermore, at the downstream end 12b, the peripheral cavity 16 does not open into the main cavity 225 of the upstream cold fluid manifold 22, but opens into the main cavity 125 of the upstream hot fluid manifold 12, opposite the heat exchanger body 30. Thus, according to this embodiment, a portion P1 of the main hot flow 10 is diverted into the peripheral cavity 16 at the upstream end 12a, and flows along the peripheral cavity 16, in the same direction of flow as the main flow in the main cavity 125, to the downstream end 12b.

[0077] This portion P1 of the main hot stream 10 then flows into the heat exchanger body 30. In this example, the downstream hot fluid manifold 14 also includes a double wall 140 similar to the double wall 120 of the upstream hot fluid manifold 12, including in particular an inner wall 141 and an outer wall 142. A portion P1 of the main hot stream 10 exiting the heat exchanger body 30 can thus be diverted into the double wall 140 of the downstream hot fluid manifold 14.

[0078] In this example as well, the upstream cold fluid manifold 22 comprises a double wall 220 having an inner wall 221 and an outer wall 222, and the downstream cold fluid manifold 24 comprises a double wall 240 having an inner wall 241 and an outer wall 242. Thus, in the same way as for the double walls of the upstream and downstream hot fluid manifolds, a portion P2 of the main cold stream 20 can be taken at the upstream end of the upstream cold fluid manifold 22, flow along its peripheral cavity to the heat exchanger body 30, and then be reinjected into the peripheral cavity of the downstream cold fluid manifold 24.

[0079] It should be noted that, unlike the previous embodiments in which the double-walled manifolds are fixed to the heat exchanger body 30 via their inner wall 121, 141, the manifolds of the heat exchanger device 1 according to the sixth embodiment are fixed to the heat exchanger body 30 via their outer wall 122, 142, 222, 242. Thus, while in the previous embodiments the peripheral cavity 16 of the upstream hot fluid manifold 12 opens into the main cavity 225 of the upstream cold fluid manifold 22, the peripheral cavity 16 of the upstream hot fluid manifold 12 according to the sixth embodiment opens onto the heat exchanger body 30.

[0080] It should also be noted that in the various embodiments one to six previously described, the exchanger body 30 and the various collectors comprising the heat exchanger device 1 can be separate parts assembled and fixed together by welding or brazing for example, or be manufactured as a single unit, by additive manufacturing for example.

[0081] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

1. A heat exchanger device (1) for aircraft turbomachine, comprising a heat exchanger body (30), an upstream hot-fluid header (12) attached to the heat exchanger body (30) and configured to collect a first fluid at a first temperature and to feed it to the heat exchanger body (30), an upstream cold-fluid header (22) attached to the heat exchanger body (30) and configured to collect a second fluid at a second temperature lower than the first temperature and to feed it to the heat exchanger body (30), at least the upstream hot-fluid header (12) comprising a double wall (120) forming a peripheral cavity (16) surrounding a main cavity (125) configured to receive a main flow of the first fluid, characterized in that the peripheral cavity (16) is configured to receive a secondary flow formed by a fraction of the first fluid or of the second fluid.

2. The device (1) according to claim 1, comprising a downstream cold-fluid header (24) attached to the heat exchanger body (30) and configured to collect the second fluid flowing from the heat exchanger body (30), the fraction being a fraction of the second fluid flowing into the upstream cold-fluid header (22), the upstream hot-fluid header (12) being configured to collect said fraction of the second fluid, and to feed said fraction to the downstream cold-fluid header (24) by means of the peripheral cavity (16).

3. The device (1) according to claim 2, wherein the peripheral cavity (16) comprises at least one inlet section (16e) opening in a main cavity (225) of the upstream cold-fluid header (22), the inlet section (16e) being configured to collect the fraction of the second fluid and being arranged at a first junction (a) between the upstream cold-fluid header (22), the upstream hot-fluid header (12) and the heat exchanger body (30).

4. The device (1) according to claim 2 or 3, wherein the peripheral cavity (16) comprises at least one outlet section (16s) opening in a main cavity (245) of the downstream cold-fluid header (24), the outlet section (16s) being configured to inject the fraction of the second fluid flowing into the peripheral cavity (16) into the downstream cold-fluid header (24), and being arranged at a second junction (b) between the downstream cold-fluid header (24), the upstream hot-fluid header (12) and the heat exchanger body (30).

5. The device (1) according to any one of claims 1 to 4, wherein the upstream hot-fluid header (12) comprises fins (30) extending on the one hand longitudinally in a direction of flow of the first fluid in the main cavity (125), and extending on the other hand from one of the two walls of the double wall (120) to the other of the two walls, inside the peripheral cavity (16).

6. The device (1) according to claim 5, wherein the fins (30) extend on the one hand longitudinally over a portion of a length of the upstream hot-fluid header (12), and extend on the other hand over the entire height of a space separating the two walls (121, 122) of the double wall (120).

7. The device (1) according to any one of claims 1 to 4, wherein the upstream hot-fluid header (12) comprises an intermediate wall (123) arranged in the peripheral cavity (16), and separating the fraction of the second fluid collected in the upstream cold-fluid header (22) into a secondary internal flow (162) and a secondary external flow (161).

8. The device (1) according to any one of claims 1 to 7, wherein the fraction of the second fluid collected in the upstream cold-fluid header (22) is between 0.5 and 5% of the flow rate of the second fluid flowing into the upstream cold-fluid header (22).

9. The device (1) according to any one of claims 1 to 8, comprising a downstream hot-fluid header (14) attached to the heat exchanger body (30), configured to collect the first fluid flowing from the heat exchanger body (30), comprising a double wall (140) forming a peripheral cavity (16), and configured to collect a fraction of the second fluid flowing into the upstream cold-fluid header (22), and to feed said fraction to the downstream cold-fluid header (24) by means of said peripheral cavity (16).

10. The device (1) according to claim 1, wherein the fraction is a fraction of the first fluid, the upstream hot-fluid header (12) being configured to collect said fraction of the first fluid at an upstream end (12a) of the upstream hot-fluid header (12), and to feed said fraction to the heat exchanger body (30) at a downstream end (12b) of the upstream hot-fluid header (12) by means of the peripheral cavity (16).

11. The device (1) according to any one of claims 1 to 10, wherein the double wall (120) comprises an internal wall (121) delimiting the main cavity (125), and an external wall (122) arranged around the internal wall (121), a gap between the internal wall (121) and the external wall (122) being between 1 and 10 mm.

12. An aircraft turbomachine comprising a heat exchanger device (1) according to any one of the preceding claims.