HEAT EXCHANGER WITH AN AIR DIFFUSION SYSTEM AND ASSOCIATED TURBOMACH

Description

Scope of the invention

[0001] The present invention relates to the general field of aeronautics. It relates in particular to a heat exchanger for a turbomachine, especially one used in aircraft. Technical background

[0002] An aircraft turbomachine and an aircraft comprise various components and / or equipment that require lubrication and / or cooling for proper operation. These components and / or equipment may include bearings or gears within 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 substantial depending on the component's power output, is dissipated through heat exchange with a cold source available within 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. Examples of heat exchangers are described in documents WO-A2-2020 / 234525, EP-A2-1898069, and DE-A1-10 2019 119416.

[0004] Depending on the application, heat exchangers generally use a cold source which can be ambient air, air from the secondary flow of the turbomachine, glycol water, a heat transfer fluid of the Novec ® type, hydrofluorocarbons (HFCs), liquefied natural gas (LNG), liquid hydrogen (LH2), etc. and a hot source which can be the turbomachine fuel, oil, air (bleed air) taken from the low pressure or high pressure compressor of the turbomachine, or air from the primary flow of the turbomachine.

[0005] The cooling requirements for lubricants, electrical and / or electronic systems (electrical machines, generators, batteries, etc.) are constantly increasing due to the rising rotational speeds and power levels required to meet turbomachinery specifications and the electrification of future aircraft. This means that heat exchangers will be under increasing stress.

[0006] Furthermore, the new turbomachine and aircraft architectures using alternative fuels ((LH2), (LNG)) which are stored in liquid form at low temperature (typically 23K for LH2) to limit the volume of tanks and the mass added to the aircraft generates the need to heat them before use, i.e. the use of heat exchangers.

[0007] Fuel-cooled oil coolers (FCOCs) are commonly known. These FCOCs can serve a dual purpose: preheating the fuel before combustion in the turbomachine's combustion chamber and cooling the oil heated by the turbomachine's heat dissipation. However, FCOCs alone cannot absorb all heat loss because the fuel temperature is limited for safety reasons. Additional cooling is achieved using air-cooled oil coolers (ACOCs), particularly surface-type ACOCs.Surface heat exchangers are typically arranged in the secondary flow of the turbomachine and utilize the secondary airflow to cool the oil circulating within the turbomachine. These heat exchangers consist of a metallic surface component through which oil flows via machined channels. The secondary airflow is guided along fins mounted on this surface component, which increase the contact area with the secondary airflow and extract heat.

[0008] One of the problems observed in heat exchangers for the various applications mentioned above is the generation of additional pressure losses on the air (or gas) side, as they disrupt the flow. This has the effect of increasing the specific fuel consumption (SFC) of the turbomachine and negatively impacting its performance.

[0009] The examples of heat exchangers described in patents FR-B1-3096444 and FR-B1-3096409 (also published under number WO-A1-2020 / 234525) in the name of the applicant, were proposed to improve their performance, particularly aerothermal performance. One of these heat exchangers is shown in the figure 1It comprises a deceleration wall Pr for the airflow entering the fins A1 and an acceleration wall Pa for the airflow exiting the fins. To achieve significant deceleration, the ratio between the cross-sectional area hi at the inlet of the deceleration wall Pr and the height he of the fins A1, and the ratio between the outlet cross-sectional area hs of the acceleration walls Pa and the height he of the fins A1, must both be high. However, with such a deceleration wall Pr, a risk of separation may occur in zone B if the air entering the heat exchanger is poorly distributed. A risk of boundary layer separation could also occur at the external surfaces of the deceleration and acceleration walls that are in direct contact with the airflow F2 bypassing the heat exchanger (the airflow F2 being at high Mach (approximately 0.5 to 0.8 in cruise)), particularly in zones A and C.All these risks of detachment can increase the total pressure drop. Furthermore, excessive length of the deceleration and acceleration walls, for example to ensure homogeneous flow, could impact the size of the heat exchanger. Summary of the invention

[0010] The objective of the present invention is to provide a heat exchanger enabling better optimization of aerothermal performance while reducing pressure losses and avoiding significant impact on mass.

[0011] We achieve this objective in accordance with the invention by means of a heat exchanger for a turbomachine, particularly an aircraft turbomachine, with a longitudinal axis, the heat exchanger comprising: a support wall extending in a first direction, a plurality of fins each rising in a second direction from an external surface of the support wall, the fins being intended to be swept by an airflow in the first direction, a first profiled wall disposed upstream of the fins and configured to guide and slow down the airflow entering the heat exchanger, a second profiled wall disposed downstream of the fins and configured to accelerate the airflow exiting the heat exchanger, and a profiled panel covering the fins, the profiled panel extending in the first direction between the first wall and the second wall to which it is fixed, the heat exchanger comprising an air diffusion system including an air intake device configured to slow down the airflow in a third direction,The device comprises several separate air intake openings arranged upstream of the fins in the first direction and distributed in the third direction.

[0012] Thus, this solution achieves the aforementioned objective. In particular, by installing a first upstream wall and an air intake device for a diffusion system with multiple openings acting as air intakes at the heat exchanger inlet, the airflow is slowed down twice. This is achieved by varying the cross-sectional area, firstly in the second direction (radially), and secondly in the azimuthal direction. Slowing the flow velocity at the heat exchanger inlet minimizes (or even eliminates) pressure drop and can even generate thrust during certain phases of aircraft flight. This phenomenon is known as the "Meredith Effect" and significantly improves the aerothermal performance of the heat exchanger. Indeed, the second downstream wall and the thermal energy related to the airflow further accelerate the airflow exiting the heat exchanger.The pressure drop decreases until it disappears at a practical speed, beyond which the heat exchanger contributes to propulsion. The Meredith effect is a physical phenomenon whereby the drag caused by a heat exchanger heating the air is compensated by a suitable design of the heat exchanger channel (divergent / exchanger / convergent device) capable of generating more useful thrust. The Meredith effect becomes increasingly significant as the aircraft speed increases. In order to achieve zero drag and potentially generate thrust from the heat exchanger during certain phases of flight, the drag factor must be greater than 6. This heat exchanger offers high aerodynamic performance and high drag within a limited footprint, thus meeting the requirements for drag factor and the Meredith effect.

[0013] The heat exchanger also includes one or more of the following features, taken alone or in combination: The first wall has a first end forming an air inlet with the supporting wall, the air inlet device being located upstream of the plane in which the air inlet is defined. The first wall has a first end connected to the supporting wall, the air inlet device being located downstream of the plane in which the first end is defined, the air inlet openings being formed in the first wall and arranged at a predetermined distance from the first end of the first wall. The diffusion system includes an air exhaust device configured to accelerate the airflow in the third direction, the exhaust device having several distinct air exhaust openings arranged downstream of the fins along the first direction and distributed along the third direction. The second wall has a first end forming an air outlet with the supporting wall, the air exhaust device being located downstream of the plane in which the air outlet is defined. The second wall has a first end connected to the supporting wall, the air exhaust device being located upstream of the plane in which the first end is defined, the inlet openings being formed in the second wall and arranged at a predetermined distance from the first end of the second wall. The number of air inlet openings of the air inlet device and / or the air exhaust device is between 1 and 100.The intake and / or exhaust device comprises several rows of openings, each row comprising openings aligned along the third direction, and the openings in the rows aligned along the first direction or exhibiting an angular offset. The heat exchanger includes a flow control device, the control device comprising a movable gate arranged within an opening, the movable gate moving within the opening along the first and / or second direction so as to vary the cross-section of the opening. The heat exchanger is annular or extends over an angular sector.

[0014] The invention also relates to a longitudinal axis turbomachine comprising a blower, an annular casing which is centered on the longitudinal axis and which surrounds the blower, and a heat exchanger as above.

[0015] The turbomachine also includes one or more of the following features, taken alone or in combination: The turbomachine includes a nacelle arranged radially outside the annular casing, around which external dynamic air is intended to circulate. The heat exchanger is also arranged radially outside the nacelle, and a portion of the external dynamic air forms the airflow sweeping over the fins. Alternatively, the heat exchanger may be arranged radially inside the annular casing, through which an airflow is intended to circulate, with a portion of the airflow forming the airflow sweeping over the fins. The nacelle or annular casing includes an annular wall with a recess in which the heat exchanger is installed, the fins having a height greater than or equal to the height of the recess. The recess is annular or extends over an angular sector around the longitudinal axis. The bulkheads of the inlet and exhaust devices extend outside the recess.

[0016] The invention further relates to an aircraft comprising a turbomachine as mentioned above. Brief description of the figures

[0017] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent upon reading the detailed explanatory description that follows, of embodiments of the invention given by way of purely illustrative and non-limiting examples, with reference to the accompanying schematic drawings in which: There figure 1 is a schematic axial cross-sectional view of a heat exchanger according to the prior art; The figure 2 is an axial cross-sectional view of an example of a turbomachine to which the invention applies; The figure 3 is a schematic and axial cross-sectional view of a heat exchanger arranged outside a turbomachine and equipped with an air diffusion system according to the invention; The figure 4is a perspective view of an example of a heat exchanger mounted on an aircraft turbomachine and equipped with an upstream air intake device and a downstream exhaust arrangement according to the invention; The figure 5 is a radial cross-sectional view of the heat exchanger of the figure 4 ; There figure 6 illustrates another embodiment of a heat exchanger equipped with an air diffusion system according to the invention; The figure 7 illustrates schematically, and following a radial cross-sectional view, another example of the embodiment of a heat exchanger according to the invention; The figure 8 is an axial and schematic cross-sectional view of another embodiment of a heat exchanger according to the invention; The figure 9 is a radial cross-sectional view of the heat exchanger of the figure 8 ; There Figure 10 illustrates, following a radial and partial cross-section, another embodiment of a heat exchanger according to the invention; The figure 11illustrates, in radial section, another embodiment of the heat exchanger according to the invention; The figure 12 illustrates another example of the implementation of a heat exchanger equipped with an air flow control device according to the invention; The figure 13 represents a schematic and axial cross-sectional view of an example of a semi-buried heat exchanger according to the invention; The figure 14 represents a schematic and axial cross-sectional view of an example of a buried heat exchanger according to the invention; The figure 15 represents another embodiment of a heat exchanger arranged in a secondary flow of a turbomachine according to the invention. Detailed description of the invention

[0018] There figure 1 represents a prior art heat exchanger and has been described previously.

[0019] There figure 2The figure 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.

[0020] In the present invention, the terms "upstream" and "downstream" are defined with respect to the gas flow in the turbomachine and here along the longitudinal axis X and with reference to the figure 2 From left to right. Similarly, a turbomachine generally consists of several modules that are manufactured independently of each other and then assembled together in such a way as to facilitate its assembly, disassembly and maintenance.

[0021] The double-flow turbomachine 1 generally comprises a gas generator or gas turbine engine 2, upstream of which is mounted a fan or fan module 3. The gas generator 2 includes a gas compressor assembly (here comprising a low-pressure compressor 4a and a high-pressure compressor 4b), a combustion chamber 5, and a turbine assembly (here comprising a high-pressure turbine 6a and a low-pressure turbine 6b). Typically, the turbomachine 1 includes a low-pressure shaft 7 that connects the low-pressure compressor 4a and the low-pressure turbine 6b to form a low-pressure casing, and a high-pressure shaft 8 that connects the high-pressure compressor 4b and the high-pressure turbine 6a to form a high-pressure casing. The low-pressure shaft 7, centered on the longitudinal axis, drives a fan shaft 9. A speed reducer 10 can be interposed, as shown here, between the fan shaft 9 and the low-pressure shaft 7.Rotating guide bearings 11 also allow the low pressure shaft 7, the high pressure shaft 8 and the blower shaft 9 to be guided in rotation relative to a fixed structure of the turbomachine.

[0022] The fan 3 is enclosed by a fan casing 12. The fan casing 12 is supported by a nacelle 13. The latter is annular, centered on the longitudinal axis and extends radially outside the fan casing 12. The nacelle 13 is connected to an aircraft tail assembly or to an aircraft wing directly or via a pylon. The airflow F entering the fan 3 is divided into a primary airflow F1 which flows through the gas generator 2 in a primary channel 14 and a secondary airflow F2 which flows in a secondary channel 15 around the gas generator 2. The secondary airflow F2 is ejected by a secondary nozzle 16 ending the nacelle 13 while the primary airflow F1 is ejected outside the turbomachine 1 via an ejection nozzle 17 located downstream of the gas generator 2.

[0023] The guide bearings 11 and the speed reducer 10 in this example of turbomachine 1 configuration must be lubricated and / or cooled to ensure the turbomachine's performance. The power generated by these bearings is dissipated into a fluid from a fluid supply source installed in the turbomachine, which lubricates and / or cools various components and / or equipment within the turbomachine. Of course, other equipment in the turbomachine or 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, generators, batteries, an accessory drive, electronic / electrical systems, aircraft interior cooling systems, etc.The heat exchanger system is also applicable of course to all cold and hot sources (ambient air, primary or secondary air from the turbomachine, Novec ®< , HFC, LNG, LH2, etc.).

[0024] For this purpose, the turbomachine 1 includes a heat exchange system 20 which cools the fluid used to lubricate and / or cool its components and / or equipment. In this example, the fluid is an oil and the cold source used to cool the oil is the airflow circulating in or around the turbomachine 1.

[0025] With reference to figures 3 and 4The heat exchange system 20 includes a heat exchanger 21 which is mounted outside the turbomachine 1. The heat exchanger 21 is in particular supported by the nacelle 13. The heat exchanger 21 is arranged radially outside the nacelle 13. An external dynamic airflow (or ram air) F3 circulates around the nacelle 13 and at least part of this air is intended to pass through the heat exchanger 21.

[0026] The heat exchanger 21 has a support wall 22 extending along a first longitudinal direction L. We use the term "direction" to describe the heat exchanger 21 in particular. In the installed configuration, the first direction L is parallel to the longitudinal axis X of the turbomachine 1. In this example, the support wall 22 is annular and centered on the longitudinal axis X. More precisely, the support wall 22 is formed from a portion of the wall 18 of the nacelle 13.

[0027] The heat exchanger 21 also includes a plurality of fins 23, each extending from an external surface 24 of the support wall 22 along a second direction R. This second direction R is perpendicular to the first longitudinal direction L. The second direction R is parallel to a radial axis Z extending from the longitudinal axis L of the turbomachine 1. The fins 23 also extend along the first direction L. Advantageously, each fin 23 is continuous and straight. Each fin 23 is generally flat. These fins are arranged parallel to each other along a third direction C. This third direction is parallel to a circumferential direction around the longitudinal axis X in the installation configuration. The fins 23 are designed to be swept by the external dynamic airflow F3 along the first direction L.Alternatively, the fins 23 are discontinuous and placed in a staggered pattern (with offset steps) along the first direction or along the third direction, or are corrugated along the radial or longitudinal direction.

[0028] Each fin 23 has a leading edge 23a and a trailing edge 23b, which are opposed along the first direction L. Each fin 23 also includes a first longitudinal edge 23c and a second longitudinal edge 23d, which are opposed along the second direction R. The first longitudinal edge 23c is connected to the support wall 22. This wall is also connected to the leading edge 23a and the trailing edge 23b, as is the second longitudinal edge 23d. Advantageously, each fin 23 in this example has a generally rectangular shape. Alternatively, the fins 23 may have a trapezoidal shape or any other shape.

[0029] Each fin 23 has a height he measured between the first longitudinal edge 23c and the second longitudinal edge 23d. The height he of the fins 23 is between 5 mm and 20 mm. Each fin 23 also has a length L1 along the longitudinal direction L. The length L1 is measured between the leading edge 23a and the trailing edge 23b of each fin 23. The length L1 is between 5 cm and 20 cm.

[0030] The heat exchanger 21 includes a first profiled wall 25 arranged upstream of the fins 23 (following the direction of airflow along the external surface 24 or the first direction L). The first wall 25 is configured to orient and guide the airflow F3a (portion of the external dynamic airflow F3) entering the heat exchanger 21. This first wall 25 is also configured to slow down the airflow F3a entering the heat exchanger 21. The first wall 25 has a diverging profile.

[0031] The first wall 25 is inclined with respect to the first direction L in an axial plane. In particular, the first wall 25 extends between a first end 25a and a second end 25b substantially along the first direction L. The first end 25a forms, upstream, with the support wall 22, an air inlet 25aa which has a predetermined first height hi along the second direction R. The first height hi is less than the radial height he of the fins 23. The second end 25b covers the leading edge 23a of the fins 23. The first wall 25 also extends along the third direction, and in this case, the first end 25a is annular. In particular, the first wall 25 has a shape of revolution about the longitudinal axis X.

[0032] The heat exchanger 21 is also provided with a second profiled wall 26 positioned downstream of the fins 23 to reduce recirculation phenomena occurring downstream of the fins 23. The second profiled wall 26 is also configured to accelerate the flow exiting the heat exchanger 21. The second wall 26 has essentially the same configuration as the first wall 25. However, it has a convergent profile. The second wall 26 also extends between a first end 26a and a second end 26b along the first direction L. The first end 26a, downstream, forms an air outlet 26aa with the support wall 22, which has a second predetermined height hs along the second direction. The second height hs is less than the height he of the fins 23. The second end 26b covers the trailing edge 23b of the fins 23.

[0033] The ratio between the first height hi and the second height hs is between 0.5 and 1.

[0034] The heat exchanger 21 includes a profiled panel 27 covering the fins 23. The panel 27 is specifically connected to the second longitudinal edge 23d of each fin 23. In this way, the panel 27 guides and controls the airflow F3a within the heat exchanger 21. The fins 23 are thus arranged radially between the support wall 22 and the profiled panel 27. The profiled panel 27 extends along the first longitudinal direction L. The panel 27 also extends along the third direction C. In this example, the panel 27 is substantially cylindrical and centered on the longitudinal axis X of the turbomachine when installed in the turbomachine 1. The panel 27 extends radially outward from the support wall 22.

[0035] Panel 27 extends between an upstream edge 27a and a downstream edge 27b along the first longitudinal direction L. Panel 27 has a length (measured between the upstream edge 27a and the downstream edge 27b) that is substantially equal to the length L1 of the fins. The upstream edge 27a of panel 27 is connected to the second end 25b of the first panel 25. The downstream edge 27b is connected to the second end 26b of the second wall 26. Panel 27 extends along the first direction L between the first panel 25 and the second panel 26.

[0036] With reference to the figure 4 , panel 27 has an external surface 28 having a surface continuity with an external surface 29 of the first wall 25. The external surface 28 also has a surface continuity with an external surface 30 of the second wall 26.

[0037] The heat exchanger 21 can be equipped with support elements (not shown) allowing the first wall 25 and / or the second wall 26 to be fixed to the support wall 22. These support elements are placed at a distance from the fins 23, upstream of the fins 23, and / or downstream of the fins 23.

[0038] On the figure 4The heat exchanger 21 includes an air diffusion system. The diffusion system includes an air inlet device 35 configured to slow down the airflow entering the exchanger along the third direction C. The air inlet device 35 has several separate air inlet openings 36 arranged upstream of the fins 23 along the first direction. Advantageously, the openings 36 are distributed along the third direction C and around the longitudinal axis X. These openings 36 are formed by partitions 37 which are spaced apart from each other and distributed around the third direction C. Each air intake opening 36 is delimited along the third direction by two partitions 37 spaced along the third direction C. In other words, the intake openings 36 extend over an angular sector α (alpha) between 1 and 360°.The openings 36 (and the partitions 37) are distributed azimuthalally and preferably equidistantly. The partitions 37 extend upstream from the first end 26a of the first wall 25 to the supporting wall 22. In other words, the partitions 37 extend the first wall 25 and are connected to the supporting wall 22.

[0039] Each partition 37 is flat and slightly curved to follow the aerodynamic profile of the first wall 25 and to avoid disturbing the airflow. More specifically, each partition 37 comprises an upstream edge 37a connected to the support wall 22 and a downstream edge 37b connected to the first end 25a of the first wall 25. The downstream edge 37a has a greater height than the upstream edge, which is a vertex (connected to the support wall or the annular wall 18). Each partition 37 also extends between a first lateral edge 37c and a second lateral edge 37d along the third direction C. Each partition has a thin wall thickness of between 0.2 and 2 mm. The partitions have this configuration, and in particular this profile, to minimize disturbance and consequently the corresponding pressure drop. The airflow can circulate below the partition.

[0040] The openings 36 lead into the air inlet 25aa formed by the first end 25a and the support wall 22. The airflow F3a enters through each inlet opening 36 (air intakes), flows under the first wall 25, and then passes through the fins 23. The air entering the heat exchanger 21 is slowed down twice by the openings 36 and the first wall 25. In particular, the airflow F3a entering through the inlet openings 36 occupies part of the circumference of the heat exchanger 21. As we have seen, each opening 36 extends over an angular sector α, and the sum of the angular sectors is defined as αT, which is between 1° and 360° (not the entire circumference (360°)). The airflow F3 which is at the level of the air inlet 25aa of the first wall 25 is distributed over the entire circumference of the first wall 25 (i.e. 360°).This implies a change in the cross-section of the airflow passage between the radial plane passing through 37a (whose angular sectors sum to αT) and the radial plane passing through the air inlet 25aa, which occupies the entire 360° circumference. This change in cross-section corresponds to the ratio 1 / αT. If the ratio is 0.5 (the intake openings 36 occupy 50% of the circumference), there will be a cross-sectional increase ratio of 2 between the air intake cross-section (at level 37a) and the inlet cross-section (at air inlet 25aa), hence a slowing of the flow in the azimuthal direction by a factor of 2. Added to this is the slowing due to the change in cross-section in the radial direction, hence also the concept of "double slowing".

[0041] The number of air inlet openings 36 of the air inlet device 35 is between 1 and 100. This number depends on several factors (type of application, angular sector occupied by the heat exchanger 21, ratio of change of section in the second radial, shape of the heat exchanger (annular, cubic or other), etc...).

[0042] On the figure 5 , the intake device 35 comprises 15 (fifteen) intake openings 36 distributed regularly around the longitudinal axis.

[0043] On the figure 6 , device 35 includes 6 (six) openings 36.

[0044] The heat exchanger diffusion system 21 also includes an air exhaust device 38 located downstream of the fins 23. The air exhaust device 38 has a configuration similar to that of the intake device 35. In particular, the device 38 includes exhaust openings 39 that are regularly distributed around the third direction C (and longitudinal axis X) and are separated by partitions 40. Each partition 40 rises from the external surface 24 along the second direction R. Each partition 40 has an upstream edge 40a connected to the first end 26a of the second wall 26 and a downstream edge 40b connected to the support wall 22. The upstream edge 40a has a greater height than the downstream edge 40b. The downstream edge 40b also has a peak. Each partition 40 also extends between a first lateral edge 40c and a second lateral edge 40d along the third direction.The openings 39 lead into the air outlet 26aa formed by the support wall 22 and the first end 26a of the second wall 26. In this way, the air leaving the fins 23 flows under the second wall 26 and then into the exhaust openings 39 of the device 38. In this embodiment, the number of intake openings 36 and exhaust openings 39 is the same but may be different.

[0045] There figure 7This illustrates an embodiment of a heat exchanger 21. Identical elements and / or elements having the same function as in the previous embodiment are represented by the same reference numerals. This heat exchanger 21 differs from the previous heat exchanger in that it extends over an angular sector along the third direction. The angular sector is less than 360°. For example, the heat exchanger 21 extends over an angular sector between 25° and 120°. The first wall 25, the second wall 26, and the panel 27 have the same width along the third direction. The panel 27 has a width equal to or greater than the distance over which the fins 23 are arranged side by side. In this example, the heat exchanger 21 includes an air inlet device 35 upstream of the first wall 25 and an air outlet device downstream of the second wall 26.Each of the devices 35, 38 here comprises three openings 36, 39 which are separated by delimited by four partitions 37, 40. Of course, the number of intake openings 36 may be different from the number of exhaust openings 39.

[0046] THE figures 8 And 9 illustrate yet another embodiment of the heat exchanger 21. Identical elements and / or elements having the same function in the previous embodiment are represented by the same numerical references. This embodiment differs from the embodiment of the figures 2 to 7in that the air inlet device 35 is located downstream of the plane in which the first end 25a is defined. The first end of the first wall is connected to the support wall 22. Here, each air inlet opening 36 is formed in the first wall 25. In other words, the airflow enters the heat exchanger 21 only through the openings 36 (the heat exchanger is unpartitioned). If the heat exchanger 21 is annular, the first wall 25 is also annular. Alternatively, the heat exchanger 21 and the first wall 25 extend over an angular sector.

[0047] The openings 36 pass transversely through the first wall 25 on both sides and open upstream of the leading edges 23a of the fins 23. Each inlet opening 36 is arranged at a predetermined distance D1 from the first end 25a of the first wall 25. Similarly, the device 38 is located upstream of the plane in which the first end 26a is defined. In this embodiment, the airflow entering through the openings 36 flows in two directions: radially and axially. The airflow can flow below the first wall 25 to the end 25a and then proceed axially towards the fins 23. This generates a double deceleration. According to an advantageous, but not limiting, feature, the heat exchanger includes fixing supports arranged between the first wall 25 and the support wall 22, and downstream of the openings 36.These mounting brackets allow for the mechanical support of the heat exchanger.

[0048] The heat exchanger 21 of this embodiment also includes an exhaust device 38. The second wall 26 is connected to the support wall 22 at its first end 26a. As with the openings 36, the air inlet openings 39 pass transversely through the second wall 26 on both sides and open downstream of the trailing edges 23b of the fins 23. Each exhaust opening 39 is arranged at a predetermined distance D2 from the first end 26a of the second wall 26. Advantageously, the predetermined distance D1, D2 is between 15 and 50 cm. The distances D1, D2 can vary depending on the application of the heat exchanger 21. The airflow escaping from the fins 23 flows towards the openings 36 to exit the heat exchanger.The airflow exiting the fins can flow under the second wall 26 in two directions: radially and axially. The airflow can flow under the second wall 26 to end 26a and then proceed axially towards the openings 39.

[0049] There Figure 10 represents another embodiment of the heat exchanger 21. The heat exchanger 21 is similar to the one illustrated in the figures 8 And 9This heat exchanger 21 includes inlet and outlet devices 35, 38 arranged upstream and downstream of the fins 23. The air inlet openings 36 are formed in the first wall 25, and the outlet openings 39 are formed in the second wall 26. In particular, the devices 35, 38 each comprise several openings 36, 39 that are aligned along the first direction and in the same axial plane. Here, two openings 36a, 36b are aligned along the first direction L. This arrangement forms a first annular row R1 of openings 36a and a second annular row R2 of openings 36b. Such a configuration of the devices improves the flow distribution upstream of the heat exchanger 21, thereby reducing pressure losses. This also applies to the airflow escaping from the heat exchanger 21 at the openings 39.

[0050] There figure 11represents a variant of the previous embodiment in which several openings 36a, 36b are arranged in a staggered pattern. This also applies to the openings 39 of the device 38. In particular, the devices 35, 38 comprise the first annular row R1 of openings 36a, 39a and the second annular row R2 of openings 36b, 39b. The openings 36a, 39a of the first row are angularly offset from the openings 36b, 39b of the second row. The staggered arrangement of the openings 36, 39 allows for uniform flow upstream of the heat exchanger 21. This also applies to the airflow escaping from the heat exchanger 21 at the openings 39.

[0051] There figure 12This represents another embodiment of the heat exchangers presented previously. This heat exchanger 21 includes a flow control device 50 configured to control the flow rate through the heat exchanger 21 according to the aircraft's flight phase. This optimizes the aerothermal performance of the heat exchanger 21. The control device 50 comprises movable gates 51 that move at one or more openings 36, 39. In the case of an annular (360°) heat exchanger 21, the control device 50 cooperates with the exhaust device 39. Movable gates 51 are arranged in the openings 39 and move along the second direction to vary the cross-section of the openings 38. The movable gates 51 can move along the third direction C to vary the cross-section of the openings 39.The movable doors 51 can move along the second direction R and along the third direction C. According to yet another alternative, the movable doors 51 can move along a rotation.

[0052] Alternatively, or in addition, the adjustment device 50 cooperates with the intake device 35 and includes movable doors moving in the openings 36 to vary their section.

[0053] According to yet another alternative, some intake and exhaust openings 36, 39 are devoid of movable doors 51. In this way, the flow can be regulated by completely closing some air intake and exhaust openings and keeping others completely open.

[0054] The movement of the gates 51 is controlled based on the temperature of one of the two fluids (hot source and cold source) at the outlet of the heat exchanger 21 (while knowing its inlet temperature) or on the heat exchanged within the exchanger. For this purpose, the control device 50 is connected to a control unit 100 such as a FADEC (Full Authority Digital Engine Control). Sensors could be placed on the inlet and outlet fluid lines and be electrically connected to the control unit 100.

[0055] There figure 13This represents another embodiment of a heat exchanger 21. This heat exchanger 21 is semi-buried in the nacelle 13. The nacelle 13 includes a recess 42 formed in its annular wall 18. The recess 42 has a bottom surface 42a with a diameter smaller than that of the radially external surface 13a of the nacelle 13. The recess 42 may be annular or extend over an angular sector of the nacelle 13. The fins 23 extend radially outwards from the bottom surface 42a, which serves as the surface of the support wall. Alternatively, the support wall is disposed on the bottom surface 42a. The fins 23 are buried approximately halfway up the height he of the fins 23. The height he of the fins 23 is greater than the height of the recess 42. The height of the recess 42 is measured between the bottom surface 42a and the radially external surface 13a.The fins 23 are covered by the panel 27, which is connected upstream by the first wall 25 and downstream by the second wall 26. The panel 27 is located at a distance from the nacelle wall 18 and radially outside of it. The ratio between the first height hi at the air inlet 25a and the second height hs at the air outlet 26a is between 0.5 and 1. This ratio may vary.

[0056] The heat exchanger 21 includes the inlet and outlet devices 35, 38 arranged upstream of the first wall 25 and downstream of the second wall 36. The devices 35, 38 have the same configuration as the embodiments illustrated in the figures 2 to 7Partitions 37 extend the first wall 25 upstream and are connected to the wall 18 of the nacelle 13. Partitions 40 may extend the second wall downstream. However, the partitions 37 and 40 of the intake and exhaust devices extend outside the recess 42. These partitions 37 and 40 are regularly spaced to form intake and exhaust openings 36 and 39. The airflow F3 enters the heat exchanger 21 through the openings 36 of the air intake device 35 and exits through the openings 39 of the air exhaust device.

[0057] There figure 14This represents another embodiment of a heat exchanger 21 that is embedded in the nacelle 13. In this case, the panel 27 has an external diameter that is substantially equal to the diameter of the radially external surface 13a of the nacelle 13. The external surface 28 of the panel is flush with that of the radially external surface 13a of the nacelle. In this example, the fins 23 are arranged within the thickness of the nacelle, and their height he coincides with the thickness. In other words, the height he of the fins 23 is identical to the height of the recess 42. The partitions of the inlet and outlet devices extend outside the recess. The ratio between the first height hi at the air inlet 25a and the second height hs at the air outlet 26a is between 0.5 and 1. This ratio may vary.

[0058] The first wall 25 is inclined with respect to the longitudinal axis X and flares outwards from downstream to upstream. Conversely, the second wall 26 is inclined with respect to the longitudinal axis and flares outwards from upstream to downstream. The external dynamic airflow F3, which flows along the radially external surface 13a of the nacelle 13, enters through the openings 36 of the intake device 35, then towards the fins 23 arranged in the recess 42, and finally exits through the openings 39 of the exhaust device 38.

[0059] There figure 15This illustrates another embodiment of the heat exchanger 21. In this figure, the heat exchanger 21 is arranged within the blower housing 12, and the fins 23 are swept by the secondary airflow F2. The heat exchanger 21 is annular and is supported by the entire radially internal wall 43 of the blower housing 12. Alternatively, the heat exchanger 21 is arranged on an angular sector of the blower housing 12. According to yet another alternative, the radially internal wall 43 of the blower housing 12 includes a recess 42 in which the heat exchanger 21 is arranged so that the fins 23 are buried or semi-buried. According to yet another alternative, the blower housing 12 includes a radially external wall (radially opposed to the radially internal wall 42) which carries the heat exchanger 21.The secondary airflow F2 enters the heat exchanger 21 through the openings 36 of the air intake device 35 and exits through the openings 39 of the air exhaust device.

Claims

1. A heat exchanger (21) for a turbomachine, in particular an aircraft turbomachine, having a longitudinal axis (X), the heat exchanger (21) comprising: - a support wall (22) extending in a first direction (L), - a plurality of fins (23) each rising in a second direction (R) from an external surface (24) of the support wall (22), the fins (23) being configured to be swept by an air stream (F3a, F2) in the first direction (L), - a first profiled wall (25) arranged upstream of the fins (23) and configured so as to guide and decelerate the air stream (F3a, F2) entering the heat exchanger (21), - a second profiled wall (26) arranged downstream of the fins (23) and configured so as to accelerate the air stream (F3a, F2) leaving the heat exchanger (21), and - a profiled panel (27) covering the fins (23), the profiled panel (27) extending in the first direction (L) between the first wall (25) and the second wall (26) to which it is attached, characterized in that the heat exchanger (21) comprises an air diffusion system comprising an air intake device (35) configured to decelerate the air stream in a third direction (C), the device (35) comprising a plurality of separate air intake openings (36) which are arranged upstream of the fins (23) in the first direction (L) and which are distributed in the third direction (C).

2. The heat exchanger (21) according to the preceding claim, characterized in that the first wall (25) has a first end (25a) forming an air inlet (25aa) with the support wall (22), the air intake device (35) being located upstream of the plane in which the air inlet (25aa) is defined.

3. The heat exchanger (21) according to claim 1, characterized in that the first wall (25) has a first end (25a) connected to the support wall (22), the air intake device (35) being located downstream of the plane in which the first end (25a) is defined, the air intake openings (36) being formed in the first wall (25) and being arranged at a predetermined distance (D1) from the first end (25a) of the first wall (25).

4. The heat exchanger (21) according to any of the preceding claims, characterized in that the diffusion system comprises an air exhaust device (38) configured so as to accelerate the air stream in the third direction, the exhaust device (38) comprising a plurality of separate air exhaust openings (39) which are arranged downstream of the fins (23) in the first direction and which are distributed in the third direction.

5. The heat exchanger (21) according to the preceding claim, characterized in that the second wall (26) has a first end (26a) forming an air outlet (26aa) with the support wall (22), the air exhaust device (38) being located downstream of the plane in which the air outlet (26aa) is defined.

6. The heat exchanger (21) according to claim 4, characterized in that the second wall (26) has a first end (26a) connected to the support wall (22), the air exhaust device (38) being located upstream of the plane in which the first end (26a) is defined, the intake openings (39) being formed in the second wall (26) and being arranged at a predetermined distance (D2) from the first end (26a) of the second wall (26).

7. The heat exchanger (21) according to any one of the preceding claims, characterized in that the number of air intake openings (36, 39) of the air intake device (35) and / or of the air exhaust device (38) is between 1 and 100.

8. The heat exchanger (21) according to any one of the preceding claims, characterized in that the intake device (35) and / or the exhaust device (38) comprise a plurality of rows (R1, R2) of openings (36, 39), each row (R1, R2) comprising openings (36a, 36b, 39a, 39b) which are aligned in the third direction, and the openings (36a, 36b, 39a, 39b) of the rows being aligned in the first direction or having an angular offset.

9. The heat exchanger (21) according to any of the preceding claims, characterized in that it comprises a flow rate adjustment device (50), the adjustment device (50) comprising a movable door (51) which is arranged in an opening (36, 39), the movable door (51) moving in the opening (36, 39) in the first direction and / or in the second direction so as to vary the cross-section of the opening (36, 39).

10. The heat exchanger (21) according to any one of the preceding claims, characterized in that it is annular or extends over an angular sector.

11. A turbomachine (1) of longitudinal axis X comprising a fan (3), an annular casing (12) which is centered on the longitudinal axis (X) and which surrounds the fan (3), and a heat exchanger (21) according to any one of the preceding claims.

12. The turbomachine (1) according to the preceding claim, characterized in that it comprises a nacelle (13) disposed radially outside the annular casing (12) and around which an external dynamic air (F3) is configured to circulate, the heat exchanger (21) being disposed radially outside the nacelle (13) and a portion (F3a) of the external dynamic air (F3) forming the air stream sweeping the fins (23).

13. The turbomachine (1) according to one of claims 11 and 12, characterized in that the heat exchanger (21) is disposed radially inside the annular casing (12) in which an air stream (F2) is configured to circulate, a portion of the air stream forming the air stream sweeping the fins (23).

14. The turbomachine (1) according to one of claims 12 and 13, characterized in that the nacelle (13) or the annular casing (12) comprises an annular wall (18, 43) which comprises a recess (42) in which the heat exchanger (21) is installed, the fins (23) having a height (he) greater than or equal to the height of the recess (42).