Assembly comprising an annular duct and a heat exchanger with an inclined front surface and deflectors, and turbine engine comprising such an assembly

Abstract

The invention relates to an assembly for a turbine engine, in particular for an aircraft, the assembly comprising: - an annular duct with a longitudinal axis in which a first fluid is intended to flow, and - a heat exchanger (3) arranged in the annular duct and having a front surface (11) that is inclined in a main direction (A), relative to the longitudinal axis, the heat exchanger comprising fins (8) extending transversely between two panels (6, 7) arranged facing one another, each of the panels having a thickness that is greater than a thickness of each of the fins. According to the invention, the fins are arranged in several rows transverse to the main direction and a portion of the fins is elongated, forming first deflectors (15) allowing the first fluid entering the heat exchanger to be deflected by the front surface in a direction substantially parallel to a direction of elongation of the fins.

Description

[0001] DESCRIPTION

[0002] TITLE: ASSEMBLY COMPRISING AN ANNULAR VEIN AND A HEAT EXCHANGER WITH AN INCLINED FRONT SURFACE AND DEFLECTORS, AND TURBOMACHINE COMPRISING SUCH AN ASSEMBLY

[0003] Field of invention

[0004] The present invention relates to the general field of aeronautics. It relates in particular to a plate-fin type heat exchanger for a turbomachine, particularly an aircraft.

[0005] Technical background

[0006] The prior art includes documents FR-A1-3132542, US-A1-2008 / 017360 and FR-A1-3118151.

[0007] An aircraft turbomachine and an aircraft comprise various components and / or equipment that must be lubricated and / or cooled for their proper operation. These components and / or equipment may be bearings or gears in the turbomachine or electrical and / or electronic components for electrical systems of the aircraft turbomachine or even systems for conditioning the interior spaces of the aircraft. The heat released by these components and / or equipment, which may be very significant depending on the power of the component and / or equipment, is removed by heat exchange with a cold source available in the turbomachine and / or the aircraft.

[0008] Heat exchange is achieved through one or more heat exchangers installed in the turbomachine or aircraft for various applications. Heat exchangers are increasingly in demand with the increasing need for cooling lubricant fluids, electrical and / or electronic systems (electrical machines, generators, batteries, etc.) of the turbomachine and / or aircraft.

[0009] Plate-fin heat exchangers are known to improve and / or supplement the cooling requirement and are generally arranged in a vein of the turbomachine. These heat exchangers generally comprise two panels which extend in a main direction and fins which extend transversely between the two panels. The heat exchangers further comprise a front surface through which the flow circulating in the vein enters the heat exchanger and a distal surface through which the flow is discharged to the outside. It has been proposed to tilt the heat exchanger relative to the longitudinal axis of the turbomachine so that the flow circulating in the vein is not oriented normal to the front surface of the heat exchanger. The tilting of the exchanger, however, requires a significant deflection of the flow near the exchange surface.This deflection is associated with a significant reduction in speed (significant increase in the passage section) and a significant total pressure loss in the case where the conversion from dynamic pressure to static pressure is only partial due to separations of the flow downstream of the leading edge of the fins. This is all the more important when the density of the air flow considered is low (air at altitude for example) and the mass flow rate of the flow considered is high.

[0010] There is a need to address some or all of the drawbacks as mentioned above.

[0011] Summary of the invention

[0012] The objective of the present invention is to provide a heat exchanger having, on the one hand, an improved frontal surface and, on the other hand, a radial and axial size which is small while reducing pressure losses and avoiding a considerable impact on the mass.

[0013] We achieve this objective in accordance with the invention by means of an assembly for a turbomachine, in particular an aircraft turbomachine, the assembly comprising:

[0014] - an annular vein with a longitudinal axis in which a first fluid is intended to circulate, and

[0015] - a heat exchanger between the first fluid and a second fluid, the heat exchanger being arranged in the annular vein and having a front surface inclined in a main direction relative to the longitudinal axis, the heat exchanger comprising at least two panels arranged opposite each other and a plurality of fins extending transversely between the two panels, the panels each having a thickness which is greater than a thickness of each of the fins, the fins being arranged in several rows transverse to the main direction and a portion of the fins being elongated by forming first deflectors configured so as to allow a deflection of the first fluid entering the heat exchanger by the front surface in a direction substantially parallel to a direction of elongation of the fins. Thus, this solution makes it possible to achieve the aforementioned objective.In particular, by lengthening a portion of the fins so that they have deflectors, the flow of the first fluid is redirected with a significant deflection towards the front surface of the heat exchanger which is inclined and is slowed down significantly before entering the heat exchanger. The installation of the deflectors on the fins provides increased freedom in the arrangement of the fins in the heat exchanger, in terms of the number of fins for example and in the reduction of the pressure drop. The inclination of the heat exchanger reduces the radial and axial dimensions. More precisely, the inclination of the heat exchanger greatly reduces the relative radial dimensions (which are very constrained) of the latter and greatly reduces the axial dimensions of the ducts upstream of the heat exchanger to avoid detachment.In addition, the deflectors limit the separation of the first fluid to ensure the conversion of dynamic pressure into static pressure.

[0016] The set also includes one or more of the following features, taken alone or in combination:

[0017] - the fins each have a thickness between 50 pm and 300 pm.

[0018] - transverse pitch between adjacent fins along the main direction is between 1 mm and 25 mm.

[0019] - the angle of inclination is between 5° and 60° and preferably between 15° and 45°.

[0020] - the heat exchanger is annular and centered on the longitudinal axis or extends over an angular sector around the longitudinal axis.

[0021] - another part of the fins is elongated to form second deflectors configured so as to allow deflection of the first air flow leaving the heat exchanger in a direction substantially parallel to the longitudinal axis.

[0022] - at least one fin out of two is extended with a first deflector or a second deflector.

[0023] - the first deflectors and / or the second deflectors have different lengths.

[0024] - a row of fins arranged near the front surface comprises different profiles arranged along the main direction, the profiles being chosen at least from fins, elongated fins with first deflectors of a first length and elongated fins with first deflectors of a second length.

[0025] - the first and second deflectors have an identical radius of curvature or different radii of curvature.

[0026] - each first deflector or second deflector has a variable radius of curvature between the first edge and the second edge. - the curvature of the first and / or second deflectors is at least partly located at the heart (inside) of the heat exchanger.

[0027] - the first deflectors and / or the second deflectors have a thickness which varies between a first edge and a second edge, the first edge of each first or second deflector defining a leading edge or a trailing edge and the second edge being connected to the rest of the body of the elongated fin.

[0028] - the first and / or second deflectors are configured so that the thickness increases with the deflection and gradually decreases after the majority of the deflection has been achieved.

[0029] -- the direction of elongation of the fins is transverse and preferably perpendicular to the main direction.

[0030] - - the heat exchanger extends at least partly around the longitudinal axis.

[0031] - - the heat exchanger comprises a first end which is disposed at a predetermined distance from the radially inner wall of the flow vein.

[0032] - - the fins without first or second deflectors have an identical length.

[0033] - - each first deflector or second deflector includes a maximum thickness which is a function of the transverse pitch between two fins.

[0034] The invention also relates to a turbomachine with a longitudinal axis X comprising an assembly as mentioned above.

[0035] The invention also relates to an aircraft comprising a turbomachine as presented above.

[0036] Brief description of the figures

[0037] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given as purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

[0038] Figure 1 is a perspective and axial sectional view of a turbomachine vein according to the invention;

[0039] Figure 2 illustrates schematically and in axial section an example of a heat exchanger arranged inclined in a flow vein according to the invention;

[0040] Figure 3 illustrates schematically and in perspective a portion of a plate-fin type heat exchanger according to the invention; Figure 4 is a detailed view of an arrangement of first deflectors of a secondary exchange surface of a heat exchanger according to the invention;

[0041] Figure 5 shows an embodiment of a heat exchanger comprising baffles at the inlet and outlet of a heat exchanger according to the invention;

[0042] Figure 6 shows an example of arrangement of first deflectors at the inlet of the heat exchanger according to the invention;

[0043] Figure 7 is an axial sectional view of one embodiment of the fin arrangement of a heat exchanger according to the invention;

[0044] Figure 8 is an axial sectional view of another embodiment of the fin arrangement of a heat exchanger according to the invention;

[0045] Figure 9 is a perspective view of the fins arranged according to Figure 8.

[0046] Detailed description of the invention

[0047] Figure 1 shows an example of flow path 1 of a turbomachine 2 with longitudinal axis X. The turbomachine 2 can be a turbojet or a turboshaft or even a turboprop.

[0048] The flow path 1 may be a secondary path in which a secondary flow originating from an air flow passing through a fan upstream of the turbomachine circulates. The flow path may also be a tertiary path in which an external primary flow originating from the primary flow which also originates from the air flow passing through the fan circulates. The primary flow and the secondary flow are typically separated by a separation nozzle located downstream of the fan.

[0049] In the present invention, the terms "upstream" and "downstream" are defined in relation to the circulation of gases in the turbomachine and here along the longitudinal axis X and with reference to Figure 1 from left to right.

[0050] The assembly shown in Figure 1 comprises one or more heat exchangers which are mounted in the turbomachine 2 so as to exchange heat between a first fluid and a second fluid. Generally, the second fluid is intended to lubricate and / or cool components and / or equipment of the turbomachine and / or the aircraft. These components and / or equipment may be one or more electrical machines, bearings, an accessory box, electronic / electrical systems, systems for cooling the interior spaces of the aircraft, cryogenic fuel tanks, etc. The heat is dissipated in the first fluid which passes through the heat exchanger.

[0051] As illustrated in Figure 1, the heat exchanger 3 is mounted in the flow stream 1 to cool the first fluid (which is a heat transfer fluid) intended to lubricate and / or cool these members and / or equipment. In particular, the heat exchanger 3 is carried by a radially inner annular wall 4 of the stream 1. The flow stream 1 comprises a radially outer wall 5 coaxial with the radially inner wall 4. The heat exchanger 3 could be carried by the radially outer wall 5. The first fluid, such as an air flow circulating in the flow stream 1, flows in an upstream to downstream direction. Alternatively, the first fluid flows from downstream to upstream.

[0052] The heat exchanger 3 advantageously comprises at least one primary exchange surface and at least one secondary exchange surface. In particular, the heat exchanger 3 is of the plate-fin type. The heat exchanger 3 comprises at least two panels, here a first panel 6 and a second panel 7 which extend in planes which are parallel to each other. These first and second panels 6, 7 form the primary exchange surface. The second panel 7 is arranged opposite the first panel 6. The heat exchanger 3 comprises a plurality of fins 8 which are arranged transversely between the first panel 6 and the second panel 7. The fins 8 form the secondary exchange surface. Advantageously, but not limitingly, the fins 8 extend perpendicular to the first and second panels 6, 7.

[0053] In the installation situation, which is considered in the remainder of the description, the heat exchanger 3 has a main direction A which is inclined relative to the longitudinal axis X. The heat exchanger 3 is also inclined relative to the direction of the air flow entering the flow vein 1. This inclination makes it possible to reduce the axial size of the heat exchanger in the flow vein 1. The inclination of the heat exchanger 3 at an angle of inclination a is between 5° and 60°. Preferably, the angle of inclination a is between 15° and 45°.

[0054] The heat exchanger 3 advantageously comprises a first end 9 and a second end 10 which are opposite in the main direction A. In the present example, the first end 9 is arranged at a distance D1 from the radially inner wall 4 and the second end 10 is connected to the radially inner wall 4. Advantageously, the predetermined distance D1 is between 10 mm and 250 mm. Preferably, the predetermined distance D1 is between 30 mm and 100 mm. In this way, the air flow can circulate above (radially outside) the heat exchanger. Alternatively, the heat exchanger could occupy the entire height of the vein.

[0055] The second end 10 may be connected to the radially inner wall 4 while providing a gap or may be connected without a gap. However, the connection distance of the second end 10 may be minimal in order to avoid the boundary layer. The connection distance will be less than the distance D1.

[0056] Referring to Figure 2, the first and second panels 6, 7 also extend radially. In this case, the fins 8 advantageously extend parallel or substantially parallel (plus or minus 10°) to the circumferential direction, around the longitudinal axis X, from the first or second panels. It should be noted that the fins have an elongation direction which depends on the angle of inclination. For example, if the angle of inclination of the main direction of the heat exchanger is equal to 90°, then the direction of elongation will be parallel to the longitudinal axis.

[0057] Advantageously, the fins 8 are arranged in several rows which are parallel to the main direction A. The fins 8 of each row are spaced from each other and arranged parallel to each other along the main direction A.

[0058] In the embodiment of Figure 2, the fins 8 of a row are discontinuous and arranged in a staggered manner relative to the fins 8 of the adjacent rows in a transverse direction B. In other words, the fins 8 are discontinuous and have staggered pitches. Of course, the fins 8 can be arranged differently without hindering the circulation of the first fluid between them.

[0059] The heat exchanger 3 comprises, for example, a front surface 11 through which the first fluid enters the heat exchanger 3. Due to the inclination of the heat exchanger 3, the front surface 11 is transverse or partially transverse to the longitudinal axis X. For example, the normal to the front surface may have a transverse component and a component parallel to the longitudinal axis X. The front surface 11 is inclined along the main direction A. Furthermore, the section of the front surface 11 is larger with the inclination of the heat exchanger 3, which allows a slowing down of the air flow entering the heat exchanger 3. The heat exchanger 3 comprises, for example, a distal surface 12 through which the first fluid is evacuated therefrom. In particular, the spaces (which determine transverse pitches P) between the fins 8 open into the front surface 11 and also into the distal surface 12.

[0060] On the other hand, covers (not shown) are arranged at the first end 9 and the second end 10.

[0061] Each fin 8 has a leading edge 8a and a trailing edge 8b opposite in the transverse direction B to the main direction A. The fins 8 have a length in the direction of elongation (parallel to the transverse direction B) which is measured between the leading edge 8a and the trailing edge 8b. Each fin 8 comprises a first surface 8c and a second surface 8d which are connected by the leading edge 8a and the trailing edge 8b. Here each fin 8 has a generally rectangular shape. The fins 8 are advantageously thin and flat.

[0062] In the present application, a thin fin is a fin whose thickness e1 is between 50 μm and 300 μm. The thickness e1 of the fins 8 is measured between the first surface 8c and the second surface 8d opposite transversely. The thickness of each fin 8 is for example constant along the entire height of the fin 8 measured between two panels 6, 7.

[0063] The transverse pitch P between adjacent fins 8 along the main direction A is between 1 mm and 25 mm. Preferably, the transverse pitch P is between 1 mm and 5 mm. With this example of transverse pitch, the fins 8 are considered to be arranged “tightly” in the heat exchanger 3. This makes it possible to arrange a high number of fins 8 in the heat exchanger 3 and to increase the heat exchange surface, in particular by taking into account the fins equipped with deflectors. Such an exchanger with a tight transverse pitch P also makes it easier to manufacture, reduces the manufacturing costs of the heat exchanger 3 and provides great flexibility in the arrangement of the fins and the deflectors. The fins are in fact extended to form the deflectors. The latter, being small in size, are advantageous in terms of mass and size.

[0064] With reference to Figure 3, the two panels, here the first panel 6 and the second panel 7, advantageously each comprise a thickness e2 which is greater than a thickness e1 (see Figure 7) of each of the fins. The thickness e2 of each first and second panel 6, 7 is measured on an internal surface 13a and an external surface 13b opposite transversely (here in the circumferential direction). The thickness of each panel 6, 7 may be 1.5 to 4 times greater than that of a fin 8. This thickness e2 of the panels 6, 7 ensures sealing.

[0065] Advantageously, but not limitatively, the distance D2 between two panels 6, 7; i.e. the height of a fin 8, is between 2 mm and 20 mm, and preferably between 7 mm and 15 mm or between 2 mm and 5 mm.

[0066] The heat exchanger 3 extends at least partly around the longitudinal axis X. In the present embodiment, the heat exchanger 3 is annular (360°) and centered on the longitudinal axis X. Alternatively, the heat exchanger 3 extends over an angular sector around the longitudinal axis X. In this case, the heat exchanger 3 comprises several panels 6, 7 which are arranged in radial planes around the longitudinal axis X and fins 8 which extend between two panels 6, 7. The direction of elongation of the fins 8 extends transversely to the main direction A. The distance D2 is measured in the circumferential direction or around the longitudinal axis X.

[0067] As can be seen in Figures 2 and 3, a portion of the fins 8 is elongated / extended by forming first deflectors 15 configured so as to allow a deflection of the first fluid entering the heat exchanger 3 in a direction parallel to the direction of elongation of the fins 8. In other words, the leading edges of this portion of fins are modified. The first deflectors 15 being in the extension of the fins 8, these also contribute to the heat exchange. The first deflectors 15 having the same transverse pitch P as those of the fins 8, this implies that very long deflectors are not necessary. In other words, the transverse pitch P is proportional to the level of the deflectors and the fins 8 to the order of 1. For example, by dividing the transverse pitch by ten, the length of the deflector will be divided by ten (the same ratio is maintained).

[0068] The fins 8 equipped with a deflector are referred to as “elongated fins 8'” in the remainder of the description. Furthermore, these elongated fins 8' have, for example, a length different from the other fins 8. Advantageously, but not limitingly, the fins 8 without first deflectors 15 have an identical length.

[0069] Advantageously, the first deflectors 15 extend across the front surface 11 of the heat exchanger 3. In other words, the first deflectors 15 are arranged at least partly outside the heat exchanger 3. The elongated fins 8' are arranged in the first row of fins 8, that is to say the one which is close to the front surface 11. The air flow thus undergoes a first modification of its direction at the inlet of the heat exchanger 3. The air flow circulates in the transverse direction B perpendicular to the main direction A in the heat exchanger 3. This inlet deflection is associated with a significant slowdown. The first deflectors 15 are also configured so as to define a divergent path for guiding the first towards the front surface 11 opening inside the heat exchanger 3.The deflection due to the first deflectors 15 and the slowdown due to the inclination are then correlated and the slowdown obtained is greater with this combination.

[0070] The first deflectors 15 are spaced apart from each other so as to form a passage 16 or airflow path which opens into the front surface 11. Each first deflector 15 comprises an elongated body between a first edge 15a and a second edge 15b. The first edge 15a forms the leading edge of the fins 8 which are elongated. Each first deflector 15 has a length L1 (measured between the first edge 15a and the second edge 15b) which is less than the length L2 of the non-elongated fins.

[0071] With reference to Figure 4, the body of each first deflector 15 has a relatively constant thickness between the first edge 15a and the second edge 15b. The thickness e1 at the second edge 15b is identical to the thickness of the rest of the fin 8. The first edge 15a has a tapered tip (while being rectilinear). The thickness of each first edge 15a is for example less than or equal to 0.5 mm. Such a shape of the first deflectors 15 makes it possible to reduce the aerodynamic losses due to the introduction of the deflectors into the first fluid, here the air flow. All the first edges 15a (or tapered tips) are oriented in the same direction.

[0072] Advantageously, but not limitatively, each first deflector 15 comprises a first flank 15c and a second flank 15d which are connected by a first surface 15e and a second surface 15f. The first and second surfaces 15e, 15f are connected to the first edge 15a and to the second edge 15b. Each first surface 15e is oriented towards the front surface 11 of the heat exchanger. Likewise, each first edge 15a is oriented upstream. The air flow which arrives parallel to the longitudinal axis X is deflected at the first deflectors 15 to be directed towards the front surface 11 so as to open into the core of the heat exchanger 3.

[0073] The first curved, concave surface 15e extends between a first end 15e1 and a second end 15e2. The second curved, convex surface 15f extends between a first end 15f1 and a second end 15f2. The first ends 15e1, 15f1 are connected to the first edge 15a and the second ends 15e2, 15f2 are connected to the second edge 15b.

[0074] Advantageously, the first surface 15e has a convex curved shape and the second surface has a concave curved shape. According to another advantageous, but not limiting, characteristic, the body of the first deflectors 15 has at least one radius of curvature. The radius of curvature can be equal to 1 times the transverse pitch P to 20 times the transverse pitch P. Preferably, the radius of curvature can be between 1 and 7 times the transverse pitch P. For example, the smaller the transverse pitch P, the smaller the radius of curvature will be.

[0075] The curvature of the first surface 15e and the second surface 15f may be the same or different. Advantageously, the curvatures of a first deflector 15 are different so as to provide converging or diverging paths.

[0076] According to another embodiment, the first deflectors 15 have different radii of curvature. More precisely, a row of fins, the one close to the front surface 11, may comprise elongated fins 8', each with a first deflector 15 having a first radius of curvature, and elongated fins, each with a first deflector 15 having a second radius of curvature. Of course, arrangements of extended fins with first deflectors 15 that have more than two independently different radii of curvature are conceivable. The first deflectors 15 with the different curvatures may be arranged alternately. This would reduce the pressure losses in the area where the passage section of the front surface 11 is still small and therefore the speeds are still high.

[0077] According to an embodiment illustrated in Figure 5, the heat exchanger 3 comprises second deflectors 17 which are arranged at the outlet (distal surface 12) of the heat exchanger 3. In this case, another part of the fins 8 is elongated, forming second deflectors 17 configured so as to allow a deflection of the first fluid (here the air flow) leaving the heat exchanger in a direction substantially parallel to the longitudinal axis. Here, it is the trailing edges of the elongated fins 8' which are modified. In this way, the air flow undergoes two deflections, one at the inlet of the heat exchanger and one at the outlet thereof. This configuration makes it possible to achieve, in addition to the deflection, a significant acceleration of the air flow evacuating from the heat exchanger 3.The second deflectors 17 are also configured to define a converging path for guiding the first fluid exiting the heat exchanger 3. The flow of the air stream is less sensitive to detachments when it is accelerated.

[0078] These second deflectors 17 have the same configurations as those of the first deflectors 15, namely thickness, curved surfaces and radii of curvature. However, the first edge 17a' is oriented downstream. The second surface 15f is oriented towards the distal surface of the second panel. The air flow which passes through the heat exchanger 3 is evacuated by passages formed between the fins and which open into the distal surface and onto the second deflectors 17 which, by their shapes and configurations, direct the air flow in a direction substantially parallel to the longitudinal axis X while slowing it down.

[0079] According to another embodiment illustrated in Figure 6, the first and / or second deflectors 15, 17 may have different arrangements. In this case, at least one fin 8 out of two is elongated with a first deflector 15. Alternatively, one fin out of three is elongated with a first deflector 15. Not all the fins 8, in particular those located near the front surface 11, will necessarily be elongated / extended. This configuration makes it possible to adapt to an arrangement where the transverse pitch P between the fins 8 is more or less narrow. As a variant or in addition, at least one fin 8 out of two is elongated with a second deflector 17.

[0080] Still in Figure 6, we see that there are first deflectors 15 which have different lengths. The elongated fins 8' comprise at least two different lengths, one longer and one shorter. In this example, there are three fin profiles which are arranged successively along the main direction A. Advantageously, these profiles are arranged in the first row which is close to the front surface 11. In particular, there is a fin 8 alternating with two elongated fins 8', i.e. an elongated fin with a first deflector 15 of a first length L11 which and an elongated fin 8' with a first deflector 15 of a second length L12. The first length L11 is greater than the second length L12. The elongated fin 8' with the first deflector 15 of a first length L1 extends outside the heat exchanger 3 and passes through the front surface 11.The elongated fin 8' with the first deflector 15 of a second length L12 extends inside the heat exchanger 3 and downstream of the front surface 11 in the direction of flow of the air flow. Other configurations are possible with several fin profiles, for example between two and four different fin profiles and with different lengths of first deflectors. This configuration can also apply to the elongated fins 8' with the second deflectors 17.

[0081] The arrangement of first and / or second deflectors 15, 17 with different lengths makes it possible to control the speed of the first fluid and the pressure losses at the front surface 11. Indeed, the first fluid, here the air flow, arrives with a high speed at the first edges 15a and is then slowed down in contact with the first deflectors 15. The air flow passes through an “enlarged passage 18” which is formed between two first deflectors 15 of greater lengths, which makes it possible to reduce the pressure losses. The first edge 15a of the first deflector 15 of shorter length being placed downstream of the first edges 15a of the first deflectors 15 of greater length, this makes it possible to create this enlarged passage. Once the air flow is slowed down, there is a tightening of the elongated fins 8' to ensure greater deflection over a short distance.

[0082] According to another embodiment illustrated in Figure 7, the heat exchanger 3 comprises an alternation, along the circumferential direction, of elongated fins 8' with first deflectors 15 of different profiles. In particular, the row of fins which is located close to the front surface 11 comprises elongated fins with a first deflector 15 having a first length L11 and a first radius of curvature (which are called long elongated fins) and elongated fins with a first deflector 15 having a second length L12 and at least a second radius of curvature (which are called long elongated fins). This arrangement is reproduced along the circumferential direction. The second length L12 is greater than the first length L11.The first deflector 15 with the first length L11 makes it possible to further increase the deflection and reduce the pressure drop by being arranged downstream of the second deflectors with the second length L12. The ratio between the first length L11 and the second length L12 (L12 / L11) can be between 1, 2 and 4. Similarly, the first radius of curvature is greater than the second radius of curvature. Alternatively, the first radius of curvature and the second radius of curvature can be identical. The curvatures of the deflectors 15 (with the lengths L11 and L12) are preferably located at least partly at the heart of the heat exchanger, i.e. downstream of the front surface 11. We understand that the second edge 15b can be outside or inside (downstream of the front surface 11) of the heat exchanger.

[0083] Advantageously, but not limited to, the first deflector 15 of the elongated fins comprises a variation in the radii of curvature between the first edge 15a and the second edge 15b. In the case of the embodiment of Figure 7, the first radius of curvature follows the following pattern: large radius of curvature Rc1 at the first edge of the first deflector 15, small radius of curvature Rc2 near the first edge of the adjacent first deflector, then large radius of curvature Rc3 towards the second edge of the first deflector. In other words, the radius of curvature decreases, increases, then decreases from the first edge 15a to the second edge 15 of the longest first deflector 15. For example, the small radius of curvature Rc2 is less than 0.7 * Rc1 and / or the small radius of curvature Rc2 is less than 0.7 * Rc3. The small radius of curvature Rc2 can be even smaller than 0.4*Rc2 and / or the small radius of curvature Rc2 is smaller than 0.4*Rc3.This configuration can also be applied to the 8' extended fins with the second deflectors 17.

[0084] Figures 8 and 9 illustrate another embodiment of the first deflectors 15. Each first deflector 15 has a thickness e3 which varies between the first edge 15a and the second edge 15b. The variation in thickness makes it possible to better control the variation in the flow section at the front surface 11 of the heat exchanger 3 and to control the slowing down of the first fluid relatively independently of the variation in the orientation of the first fluid. Each first deflector 15 is configured so that the thickness e3 increases with the deflection and then gradually decreases after the majority of the deflection has been achieved. By the expression "most of the deflection" we mean that between 75% and 99% of the change in orientation of the first fluid has been achieved. By the term gradually we mean that the change in value is substantially linear and that there are no abrupt changes in the thickness value.A target flow section (the usual spacing of the fins at the heart of the exchanger downstream of the deflection) is then obtained. For example, the progressive reduction in thickness presents a variation of the order of 0.5 mm to 2 mm towards a thin thickness of the order of 0.2 mm to 4 mm. The thickness and / or the variation in thickness depends on the target flow section presenting for example an opening angle of the order of 5° to 20°.

[0085] Due to the small transverse pitch P between the fins 8, a length L3, measured between a straight line D3 transverse to the direction of elongation of the fin and passing through a thickness e3max (described below) and the second edge 15b of the deflector 15, is relatively short (of the order of 1 mm -10 mm) before having a thin fin again. The increases in mass and pressure loss associated with a greater thickness are therefore minimal.

[0086] In particular, in Figure 8, all the first deflectors 15 are identical. Each first deflector 15 comprises a maximum thickness e3max which is a function of the transverse pitch P between two fins 8. The maximum thickness e3max is for example between 0.5 and 0.10 times the transverse pitch P. The thickness of the first deflector increases from the first edge 15a to this maximum thickness e3max and decreases from the maximum thickness to the second edge 15b making the junction with the rest of the body of the elongated fin 8'. The thickness at the first edge 15a is different from the thickness at the second edge 15b. More precisely, the thickness at the second edge 15b is greater than the thickness at the first edge 15a. This configuration can also apply to the elongated fins with the second deflectors 17.

[0087] We also see in Figure 8 that the curvatures of the deflectors 15 are preferably located at least partly in the heart of the heat exchanger, i.e. downstream of the front surface 11. Here, the second edge 15b is inside (downstream of the front surface 11) of the heat exchanger. Of course, the second edge 15b could be outside the heat exchanger.

[0088] Figure 9 differs from Figure 8 in that the first deflectors 15 have different lengths. In particular, there is an alternation of first deflectors having a first length L11 with first deflectors having a second length L12. This configuration makes it possible to reduce the pressure losses in the zone 18 where the passage section is small, and the velocities of the first fluid are still high. This configuration can also be applied to the elongated fins with the second deflectors 17.

[0089] Advantageously, the heat exchanger 3 is produced using an additive manufacturing process. This makes it possible to produce complex shapes. The material of the heat exchanger 3 is metallic and advantageously, but not limited to, includes aluminum. Aluminum has good thermal conductivity.

[0090] The heat exchanger 3 may comprise one or more channels (not shown) which are arranged in the thickness of the first panel and / or second panels and in which the second fluid circulates to carry out the heat transfer with the air flow which circulates through the heat exchanger 3.

[0091] In this way, such a heat exchanger 3 with deflectors 15, 17 equipping certain elongated fins in particular at the level of the front surface 11 ensures an increase in the front surface 11, a significant slowing down of the flow and a reduction in the size given that the transverse pitch P between the fins 8 is relatively very small (of the order of a micron) compared to the distance between the panels 6, 7. Furthermore, a better distribution of the first fluid is obtained inside the heat exchanger 3 which improves the overall performance thereof.

Claims

CLAIMS 1. Assembly for a turbomachine (2), in particular for an aircraft, the assembly comprising: - an annular vein (1) with a longitudinal axis (X) in which a first fluid is intended to circulate, and - a heat exchanger (3) between the first fluid and a second fluid, the heat exchanger (3) being arranged in the annular vein (1) and having a front surface (11) inclined in a main direction (A) relative to the longitudinal axis, the heat exchanger comprising at least two panels (6, 7) arranged opposite each other and a plurality of fins (8) extending transversely between the two panels (6, 7), the panels (6, 7) each having a thickness (e2) which is greater than a thickness (e1) of each of the fins (8),characterized in that the fins (8) are arranged in several rows transverse to the main direction (A) and in that a part of the fins is elongated by forming first deflectors (15) configured so as to allow a deflection of the first fluid entering the heat exchanger (3) by the front surface (11) in a direction substantially parallel to a direction of elongation of the fins (8)., 2. Assembly according to claim 1, characterized in that the fins (8) each have a thickness (e1) of between 50 pm and 300 pm.

3. Assembly according to any one of the main claims, characterized in that a transverse pitch (P) between adjacent fins (8) in the main direction (A) is between 1 mm and 25 mm.

4. Assembly according to any one of the preceding claims, characterized in that the angle of inclination (a) is between 5° and 60° and preferably between 15° and 45°.

5. Assembly according to one of the preceding claims, characterized in that the heat exchanger (3) is annular and centered on the longitudinal axis (X) or extends over an angular sector around the longitudinal axis (X).

6. Assembly according to any one of the preceding claims, characterized in that another part of the fins (8) is elongated, forming second deflectors. (17) configured so as to allow a deflection of the first air flow leaving the heat exchanger (3) in a direction substantially parallel to the longitudinal axis (X).

7. Assembly according to one of the preceding claims, characterized in that at least one fin (8) out of two is elongated with a first deflector (15) or a second deflector (17).

8. Assembly according to one of the preceding claims, characterized in that the first deflectors (15) and / or the second deflectors (17) have different lengths.

9. Assembly according to any one of the preceding claims, characterized in that a row of fins (8) arranged near the front surface (11) comprises different profiles arranged in the main direction (A), the profiles being chosen at least from fins (8), elongated fins (8') with first deflectors of a first length (L11) and elongated fins (8') with first deflectors (15) of a second length L12).

10. Assembly according to one of the preceding claims, characterized in that the first and second deflectors (15, 17) have an identical radius of curvature or different radii of curvature.

11. Assembly according to any one of the preceding claims, characterized in that each first deflector (15) or second deflector (17) has a variable radius of curvature between the first edge (15a) and the second edge (15b).

12. Assembly according to any one of claims 10 and 11, characterized in that the curvature of the first and / or second deflectors are located at least partly at the heart of the heat exchanger (3).

13. Assembly according to any one of the preceding claims, characterized in that the first deflectors (15) and / or the second deflectors (17) have a thickness (e1, e3) which varies between a first edge (15a) and a second edge (15b), the first edge (15a) of each first or second deflector (15, 17) defining a leading edge (8a) or a trailing edge (8b) and the second edge (8b) being connected to the rest of the body of the elongated fin (8').

14. Assembly according to the preceding claim, characterized in that the first and / or second deflectors (15, 17) are configured so that the thickness (e3) increases with the deflection and gradually decreases after the majority of the deflection has been carried out.

15. Turbomachine (1) with longitudinal axis (X) characterized in that it comprises an assembly according to any one of the preceding claims.

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