AIR-OIL HEAT EXCHANGER WITH A BYPASS FOR A TURBOMACH

Description

Domain

[0001] The invention relates to the field of turbomachine heat exchangers. More specifically, the invention proposes an air / oil heat exchanger for an axial turbomachine. Prior art

[0002] In a turbomachine (turbojet), it is generally necessary to cool the oil in the lubrication circuit. For this purpose, it is known to place one or more heat exchangers in the secondary flow, i.e. downstream of the fan.

[0003] However, the arrangement of a heat exchanger in the secondary circuit penalizes the performance and overall efficiency of the turbomachine. Indeed, the thrust force generated by the fan is partly slowed down by the bulky exchanger. In addition, aerodynamic disturbances of the secondary flow can occur, leading to vibrations and noise pollution.

[0004] Published patent document EP 3 674 531 A1 discloses an air-oil heat exchanger arranged in the secondary flow stream of a turbomachine. Such a heat exchanger generates significant disturbances to the secondary flow having a speed too high for aerodynamic or thrust losses to be negligible.

[0005] Published patent document US 2021 / 0108597 A1 discloses a turbomachine comprising a heat exchanger positioned in a fan duct.

[0006] The state of the art therefore presents disadvantages relating to performance penalties. To which is added the constraint linked to the fragility of the heat exchanger. Indeed, it cannot be placed in a tertiary flow vein radially between the primary flow and the secondary flow. However, the risk of debris and foreign bodies passing into the tertiary flow vein is high, which can damage the heat exchanger. Summary of the invention Technical problem

[0007] The invention aims to propose a heat exchanger that minimizes the aerodynamic losses induced by the presence of the exchanger in the air flow stream. Also, the invention also aims to improve the heat exchange in order to guarantee efficient cooling in a restricted space without hindering the efficiency of the turbomachine. Technical solution

[0008] The invention relates to a heat exchanger for an annular air stream of an axial turbomachine, comprising a heat exchange zone with oil passages and heat exchange surfaces forming a heat exchange passage for the air, said heat exchange zone being radially delimited by an upper wall and by a lower wall, the oil passages extending radially and axially between said upper wall and lower wall, said heat exchange zone having a profile facing the air flow and included in a plane perpendicular to said air flow, said profile of the heat exchange zone being in the shape of an arc of a circle so as to be able to be arranged in the annular air stream, remarkable in that the heat exchanger further comprises a wall with a profile in the shape of an arc of a circle parallel to, and radially at a distance from, the heat exchange zone so as to form,between said wall and said heat exchange zone, a bypass passage for air, parallel to the heat exchange passage.,

[0009] According to an advantageous embodiment of the invention, the bypass passage, outside the radial and / or lateral limits of said bypass passage, is free of material.

[0010] According to an advantageous embodiment of the invention, the radial limits of the bypass passage have an arc-shaped profile and the lateral limits are perpendicular to said radial limits.

[0011] According to an advantageous embodiment of the invention, the bypass passage extends radially over a height of between 10% and 20% of a cumulative radial height of said bypass passage and of the heat exchange zone.

[0012] According to an advantageous embodiment of the invention, the bypass passage extends longitudinally over a total extent of the heat exchanger.

[0013] According to an advantageous embodiment of the invention, the wall comprises at least one upstream or downstream end a fixing flange so as to be able to be fixed to an upstream or downstream casing of the annular air stream.

[0014] According to an advantageous embodiment of the invention, the wall is an inner wall radially inside the heat exchange zone, so as to form a radially inner guide wall for the annular air stream.

[0015] According to an advantageous embodiment of the invention, the exchanger further comprises an outer wall radially and adjacent to the heat exchange zone.

[0016] According to an advantageous embodiment of the invention, the outer wall comprises at least one upstream or downstream end a fixing flange so as to be able to be fixed to an upstream or downstream casing of the annular air stream.

[0017] According to an advantageous embodiment of the invention, the wall is located radially outside the heat exchange zone, so as to form a radially external guide wall for the annular air stream.

[0018] According to an advantageous embodiment of the invention, the exchanger further comprises an inner wall radially and adjacent to the heat exchange zone.

[0019] According to an advantageous embodiment of the invention, the inner wall comprises at least one upstream or downstream or circumferential end, a fixing flange so as to be able to be fixed to an upstream or downstream casing of the annular air stream.

[0020] According to an advantageous embodiment of the invention, the heat exchange zone has a divergent longitudinal section following the flow of air.

[0021] According to an advantageous embodiment of the invention, the heat exchange zone has a cross-section to the air flow, said cross-section increases along said air flow.

[0022] According to an advantageous embodiment of the invention, the air bypass passage has a constant radial height over the entire extent of the heat exchanger following the air flow.

[0023] According to an advantageous embodiment of the invention, the exchanger comprises several angular sectors, each angular sector comprising an oil inlet and an oil outlet, said oil inlet and / or said oil outlet is integrally formed in the inner wall, and at least one of the sectors comprises a passage for short-circuiting said sector, extending fluidically between the oil inlet and the oil outlet along the inner wall. Advantages of the invention

[0024] The invention is particularly advantageous in that it allows efficient heat exchange to be guaranteed in a reduced footprint while avoiding hindering the engine's performance, which results in energy efficiency and optimized thrust which advantageously allows carbon dioxide emissions to be reduced.

[0025] In addition, the positioning of the exchanger in the tertiary flow vein including a bypass passage for the air ensures reliable operation of the exchanger in the turbomachine. Description of the drawings

[0026] [ Fig. 1 ] is a partial perspective view of the exchanger according to a first embodiment; [ Fig.2 ] illustrates a sectional view of the exchanger according to a second embodiment; [ Fig.3 ] represents oil paths in the exchanger according to a third embodiment; [ Fig. 3a] illustrates a perspective view from below of the oil paths according to the third embodiment; [ Fig.4 ] represents an oil path in the exchanger according to a fourth embodiment; [ Fig.5 ] illustrates a sectional view of the exchanger arranged in the annular air stream and according to the second embodiment; [ Fig.6 ] represents an enlarged portion “A” of the heat exchange zone of the [ Fig.2 ]. Detailed description

[0027] In the following description, the terms "internal" and "external" refer to a position relative to the axis of rotation of a turbomachine. The axial direction corresponds to the direction along the axis of rotation of the turbomachine. The radial direction is perpendicular to the axis of rotation. Upstream and downstream refer to the direction of flow of a stream in the turbomachine.

[0028] The figures show the elements schematically and are not drawn to scale. In particular, some dimensions are enlarged to make the figures easier to read.

[0029] There [ Fig. 1 ] illustrates a partial perspective view of a heat exchanger 2 according to a first embodiment. It should be noted that a perspective view of the heat exchanger 2 is supposed to have an arcuate profile, however the [ Fig. 1 ] has been greatly simplified to make it easier to understand.

[0030] The heat exchanger 2 is of the air / oil type, configured to be mounted in an annular air stream of an axial turbomachine. Preferably, the axial turbomachine is a three-flow turbomachine, and the annular air stream is preferably a tertiary flow annular stream.

[0031] With reference to the [ Fig. 1], the exchanger 2 comprises a heat exchange zone 3 having oil passages 4 and heat exchange surfaces 6 forming a heat exchange passage for the air flow F.

[0032] Preferably, the exchanger 2 is a single-piece part obtained by additive manufacturing, and more preferably obtained by laser fusion on an aluminum powder bed. For this purpose, the oil passages 4 are formed by tubular channels allowing the circulation of oil and the exchange surfaces 6 are preferably formed by thin walls or plates, and advantageously, each plate delimits two exchange surfaces 6.

[0033] The heat exchange zone 3 is radially delimited by an upper wall 12 and by a lower wall 9, the oil passages extend radially and axially between said upper wall 12 and lower wall 9.

[0034] Indeed, the heat exchanger 2 of the present invention is of the “ACOC” type, an acronym for the English expression “Air-Cooled Oil Cooler”, the latter being different from a “SACOC” surface air-oil exchanger, in which the oil remains in the lower and upper walls and does not pass radially through the exchanger.

[0035] Advantageously, the heat exchange zone 3 has a profile opposite the air flow and included in a plane perpendicular to said air flow, said profile of the heat exchange zone 3 being in an arc of a circle allowing the exchanger 2 to be able to be arranged in the annular air stream, in particular thanks to a wall 8 of the exchanger 2, called the inner wall 8 and which is situated radially inside the heat exchange zone 3, so as to form a radially inner guide wall 8 of the annular air stream.

[0036] The inner wall 8 makes it possible to form a bypass passage for the air 10 which is parallel to the heat exchange passage between the inner wall 8 and the heat exchange zone 3.

[0037] In this configuration, the exchanger 2 comprises an outer wall 12 radially and adjacent to the heat exchange zone 3, said outer wall 12 comprises at least one upstream or downstream end a fixing flange 15 so as to be able to be fixed to an upstream or downstream casing of the annular air stream, the casing is preferably a casing external to the air flow F having the upstream and downstream parts fixed to the exchanger 2.

[0038] The air bypass passage 10 is delimited radially by two radial limits having an arcuate profile and consisting of the inner wall 8 and a radial wall 9, the latter being the lower radial delimitation of the heat exchange zone 3.

[0039] The air bypass passage 10 is free of material between its two radial limits 8, 9 and / or its two lateral limits 11, one of which is not illustrated in the [ Fig. 1 ] due to the cut made. The two lateral limits 11 are mainly perpendicular to the radial limits 8, 9, thus forming the by-pass passage for the air 10 having a cross-section to the air flow F and which is rectangular curved following the arc of a circle profile.

[0040] The air bypass passage 10 is commonly called the air bypass 10, and may also be called a "FOD" bypass, an acronym for the English expression "Foreign Object Debris". Indeed, the air bypass 10 extends longitudinally over a total extent of the exchanger 2, its main role is to allow the passage of debris contained in the air flow F through the annular vein of the turbomachine. The debris or "FOD" may for example be birds, hail, hailstones or any other object that can obstruct or damage the exchanger.

[0041] In parallel with the air bypass 10, a protective grid can be placed on a front face of the exchanger 2 to further protect the oil passages 4 and the exchange surfaces 6, without hindering their heat exchange capacity.

[0042] The air bypass 10 extends radially over a height h of between 10% and 20% of a cumulative radial height H of said bypass passage and of the heat exchange zone. Preferably, the height of the air bypass 10 extends radially to a maximum of 15% of the cumulative radial height H.

[0043] The radial height h of the air bypass 10 is constant over the entire extent of the exchanger 2 following the air flow F. Indeed, the height h does not change at all following the air flow because it is not desired to modify the speed of the latter, only the passage of debris is expected from the air bypass 10. However, the height h may present a small variation of at most 1% of the value h, which may be relative to the manufacturing precision.

[0044] Advantageously, the constancy of the height h makes it possible to limit the difference in pressure losses between the air bypass 10 and the heat exchange zone 3. However, the radial height h of the air bypass 10 may vary slightly in order to compensate for possible pressure losses which may be caused by aerodynamic disturbances downstream of the exchanger 2. In this respect, the air bypass 10 may have a convergent and / or divergent longitudinal section.

[0045] According to the first embodiment illustrated in the [ Fig. 1 ], the heat exchange zone 3 is radially delimited by a radially internal face 14 belonging to the radial wall 9, and a radially external face 16 belonging to the external wall 12.

[0046] Preferably, the exchanger 2 comprises an oil inlet and an oil outlet on the radially internal face 14.

[0047] The oil passages 4 comprise several paths between an oil inlet and an oil outlet, said paths extending radially outwardly to the radially internal face 14, and which are distributed along the arcuate profile of the heat exchange zone 3.

[0048] The heat exchange zone 3 may comprise a circumferential divergence in its downstream part, i.e. the circumferential section of the heat exchange zone 3 increases from upstream to downstream, allowing the oil passages 4 to be distributed circumferentially in the exchanger 2 between the oil inlet and the oil outlet while avoiding passing through the air bypass.

[0049] There [ Fig.2 ] illustrates a sectional view of the exchanger 2 according to a second embodiment, schematically illustrating the oil paths.

[0050] Indeed, the second embodiment consists in positioning the air bypass 10 in a radially high position so that said air bypass 10 is adjacent to the external casing of the turbomachine. Whereas the first embodiment consists in positioning the air bypass 10, having the same geometric configuration as that described previously, as being adjacent to an internal casing of the turbomachine.

[0051] In this regard, and with reference to the [ Fig.2 ], the exchanger 2 comprises an outer wall 12' located radially outside the heat exchange zone 3, so as to form a radially external guide wall for the annular air stream.

[0052] Similar to the outer wall 12 of the [ Fig. 1 ], the outer wall 12' of the [ Fig.2 ] may also include a fixing flange for fixing the exchanger to an external casing of the turbomachine.

[0053] In this configuration, the air bypass 10 is delimited radially by two radial limits consisting of the outer wall 12' and a radial wall 9' radially delimiting the heat exchange zone 3 externally. For this purpose, the radial height h of the air bypass 10 is between the radial wall 9' and the outer wall 12.

[0054] The exchanger 2 further comprises an inner wall 8', arranged radially internally and adjacent to the heat exchange zone 3. For this purpose, the inner wall 8' comprises at least one upstream or downstream or circumferential end, a fixing flange so as to be able to be fixed to an upstream or downstream casing of the annular air stream, said casing is preferably a casing internal to the air flow having the upstream and downstream parts fixed to the exchanger 2.

[0055] In this configuration, the exchanger 2 is configured to be an integral part of the internal and external casings of the turbomachine and to ensure aerodynamic continuity of the annular air stream.

[0056] Advantageously, the exchanger 2 can be manufactured and adapted according to the architecture of the turbomachine in which it will be mounted in order to anticipate the radial part of the annular air stream which includes the greatest risk of impact with the “FOD” debris so that the air bypass 10 is arranged there.

[0057] There [ Fig.2 ] also illustrates the heat exchange zone 3 as being radially delimited by a radially internal face 14' belonging to the internal wall 8', and a radially external face 16' belonging to the radial wall 9'.

[0058] Preferably, the exchanger 2 comprises an oil inlet 18 and an oil outlet 20 on the radially inner face 14'. However, the exchanger 2 may comprise the oil inlet and outlet 18, 20 on the radially outer face 16'.

[0059] The oil passages 4 comprise several paths 22 between the oil inlet 18 and the oil outlet 20 and which are distributed along the arcuate profile of the heat exchange zone 3. The exchanger 2 can comprise a single oil path as it can comprise several paths of up to 10 oil paths.

[0060] Each of the paths 22 comprises at least one forward portion 26 and at least one return portion 28, the terms "forward" and "return" corresponding to the main radial flow direction of the oil in the oil passages 4. In this regard, the forward portion 26 corresponds to a portion of the oil path 22 in which the oil flows radially from bottom to top. Similarly, the return portion 28 corresponds to a portion of the oil path 22 in which the oil flows radially from top to bottom.

[0061] The two forward 26 and return 28 portions are offset along the arcuate profile of the heat exchange zone 3, and extend radially between the radially inner face 14' and the radially outer face 16' of the heat exchange zone. In addition, each of the paths 22 comprises at least one connection portion 30 connecting the at least one forward portion 26 to the at least one return portion 28.

[0062] Advantageously, as can be seen on the [ Fig.2 ], the circumferential offset along the arcuate profile of the heat exchange zone 3 provided by the connection portion 30 between the forward portion 26 and the return portion 28 makes it possible to circumferentially increase the path of the oil in the exchanger. For this purpose, the air flow is perpendicular to the path of the oil, and the heat exchange is maximized.

[0063] The radially inner face 14' further comprises a distributor 32 fluidly disposed between the oil inlet 18 and the paths 22 and extending along the arcuate profile, and a manifold 34 fluidly disposed between the paths 22 and the oil outlet 20 and extending along the arcuate profile.

[0064] The oil inlet 18 is at one end of the distributor 32 following the arcuate profile and having a transverse passage section of said arcuate profile which gradually decreases along the latter from the oil inlet 18 to an opposite end of the distributor 32.

[0065] Similarly, the oil outlet 20 is at one end of the manifold 34 following the arcuate profile and having a transverse passage section of said arcuate profile which gradually decreases along the latter from the oil outlet 20 to an opposite end of the manifold 34.

[0066] Preferably, the distributor 32 and the collector 34 are side by side along an axial extent of the radially internal face 14' of the heat exchange zone 3.

[0067] The present invention presents two different variants concerning the oil paths. The third and fourth embodiments which will be described concern variants of the oil path, it being understood that each of these third and fourth embodiments can be applied either to the first mode or to the second mode. Indeed, it is possible to choose a high or low radial position of the air bypass and at the same time define the embodiment of the desired oil path.

[0068] There [ Fig.3 ] illustrates the oil paths 22 as described previously, in the exchanger according to the third embodiment, and in which, each of the forward 26, return 28 and connection 30 portions of each of the paths 22 extend over a total axial length of the heat exchange zone.

[0069] Each path 22 comprises several parallel oil passages 4 distributed over the total axial length of the heat exchange zone. More precisely, the oil passages 4 extend axially over the majority of the axial length of the heat exchange surfaces. Preferably, the number of oil passages 4 is between 5 and 30 oil passages 4, and more preferably, between 10 and 25 oil passages 4.

[0070] There [ Fig. 3a ] illustrates a perspective view from below of the oil paths of the [ Fig.3 ] which are according to the third embodiment of the invention.

[0071] For this purpose, the distributor 32 makes it possible to supply the oil passages 4 which are included in the forward portions 26, and the connection between the distributor 32 and said forward portions 26 is made by means of an oil inlet passage 33.

[0072] Preferably, each oil inlet passage 33 is an integral part of the oil passages 4, and comprises a passage section transverse to the air flow F and which gradually decreases along the latter.

[0073] Advantageously, the reduction in the cross-section of the oil inlet passage 33 makes it possible to reduce pressure losses.

[0074] Similarly, the collector 34 allows the oil leaving the oil passages 4 which are included in the return portions 28 to be recovered by means of an oil outlet passage 35.

[0075] There [ Fig.4 ] represents an oil path 22' in the exchanger according to a fourth embodiment. Preferably, the exchanger comprises a plurality of oil paths similar to the oil path 22'.

[0076] The oil path 22' comprises several oil passages 4' which are formed by parallel tubular channels and forming a forward portion 26' and a return portion 28'. Each of the forward 26' and return 28' portions forms an oil flow profile which is doubly bent with a first radial portion 36, a second axial portion 38 and a third radial portion 40.

[0077] The exchanger according to the fourth embodiment may comprise a plurality of oil paths 22'. In this regard, each oil path 22' may be directly connected to the distributor 32' and the manifold 34' as well as to the oil inlet passages 33' and the oil outlet passages 35' which are identical to those described previously for the third embodiment.

[0078] In the direction of oil flow, i.e. from the oil inlet passage 33 to the oil outlet passage 35, the forward portions 26' and the return portions 28' are connected to each other via a connection portion 30'. Specifically, said connection portion 30' makes it possible to connect two third radial portions 40, each belonging to the forward portion 26' and the other to the return portion 28'.

[0079] Similarly and in the same direction of oil flow, the return parts 28' are connected to the forward parts 26' by means of the connection portion (not shown in the [ Fig.4 ]). Specifically, said connection portion makes it possible to connect two first radial parts 36, each belonging to the return part 28' and the other to the outward part 26'.

[0080] There [ Fig.4] illustrates a single return portion 28', however, each oil path 22' may comprise several return portions 28' and several forward portions 26'. Preferably, the oil path 22' comprises two forward portions 26' and two return portions 28'.

[0081] The second axial portions of the forward 26' and return 28' portions have opposite flow directions. For this purpose, the second axial portion 38 of the return portion 28' comprises the oil which is in a first axial flow direction opposite to the second axial portion 38 of the forward portion 26', the flow direction of the latter being particularly opposite to the air flow F.

[0082] In this configuration, the heat exchange between the oil passages 4' and the air is partly carried out in counter-flow. Advantageously, this allows a more efficient heat exchange by convection between the oil passages 4' and the air flow F, this concretely allows to minimize the length of the oil path in the oil passages 4' of the exchanger, which allows to reduce the size and the weight of the exchanger in the turbomachine.

[0083] Preferably, the fourth embodiment of the invention is used in the case where the total axial extent of the heat exchange zone is greater than the total radial extent of the latter. Advantageously, this makes it possible to maximize the heat exchange in counter-current with the air flow.

[0084] The exchanger of the invention has a heat exchange zone which is preferably divergent in the radial direction and in the direction of air flow.

[0085] Advantageously, the divergence of the heat exchange zone makes it possible to limit pressure losses within the exchanger and to improve the heat exchange between the air and the oil flowing through the 4' oil passages.

[0086] There [ Fig.5 ] illustrates a sectional view of the exchanger 2 according to the second embodiment, the exchanger 2 being arranged in the annular air stream.

[0087] The 4' oil passages illustrated in the [ Fig.5 ] belong to the fourth embodiment of the invention. However, the divergence of the exchanger 2 is not limited to this latter mode in particular, and the oil passages 4 illustrated in Figures 3 and 3a representing the third embodiment can also be used in the [ Fig.5 ].

[0088] With reference to the [ Fig.5], the total radial height Z of the heat exchange zone 3 increases from upstream to forward, and the axial air passage comprises air channels 5 delimited by the heat exchange surfaces 6 and having passage sections increasing from upstream to downstream in correspondence with the total radial height Z of the heat exchange zone 3.

[0089] The total radial height Z of the heat exchange zone 3 and / or the sections of the air channels 5 increase from upstream to downstream over at least 70% of a total axial extent of said heat exchange zone 3. Preferably, the sections of the air channels 5 increase from upstream to downstream over the entire total axial extent of the heat exchange zone 3.

[0090] The increase in the total radial height Z of the heat exchange zone 3 and / or the increase in the sections of the air channels 5 is monotonous and / or at least 30%. Preferably, the increase in the sections of the air channels 5 is monotonous and at least 50%.

[0091] Preferably, the exchanger 2 comprises several angular sectors, each angular sector comprising the oil inlet 18 and the oil outlet, said oil inlet and / or said oil outlet is integrally formed in the inner wall, and at least one of the sectors comprises a short-circuiting passage (not shown) of said sector, also called an oil bypass, extending fluidically between the oil inlet 18 and the oil outlet along the inner wall.

[0092] Advantageously, the oil bypass ensures the cold operation of the exchanger 2, in particular at temperatures around -40°C. In fact, cold oil has a high viscosity which is not suitable for allowing it to pass into the exchanger 2, the oil therefore passes into the oil bypass until it reaches a suitable viscosity.

[0093] In this regard, another circuit called defrosting circuit (not shown) can be arranged near or in contact with the oil bypass, and can also be in contact with the oil passages 4', the defrosting circuit can ensure the heating of the oil included in the exchanger 2.

[0094] The oil bypass comprises a normally closed valve capable of opening in the presence of a pressure difference between the oil inlet 18 and the oil outlet, greater than or equal to a limit value. The valve can also open when the viscosity of the oil is too high compared to a previously identified threshold.

[0095] There [ Fig.6 ] represents an enlarged portion A of the heat exchange zone identified in the [ Fig.2 ].

[0096] The enlarged portion A is slightly in perspective to facilitate its description and shows the oil passages 4 according to the third embodiment of the invention or the oil passages 4' according to the fourth embodiment.

[0097] The air channels 5 are delimited by the exchange surfaces 6 and the forward portion 26, 26' or the return portion 28, 28'. The sections of the air channels 5 have a polygonal and preferably pentagonal shape. More preferably, each air channel 5 is delimited by four plates having four exchange surfaces 6 and a forward portion 26, 26' or a return portion 28, 28' and two exchange surfaces 6 out of the four belonging to transverse plates integrally formed with the oil passages 4, 4' of the forward portions 26, 26' or the return portions 28, 28'.

[0098] For this purpose, the oil passages 4, 4' may be formed by a material recess in a plate or panel, and the forward and return portions may be included in a radial panel.

[0099] The air channels 5 between each pair of neighboring forward portions 26, 26' and return portions 28, 28' form at least two radial rows 42, 44 of nested polygons, preferably pentagons. The number of radial rows 42, 44 may depend on the circumferential distance between the forward portion 26, 26' and the return portion 28, 28'.

[0100] The heat exchange zone further comprises edge plates 7 having the exchange surfaces 6, in fact, the edge plates 7 are similar to the plates having the exchange surfaces 6 of the heat exchange zone.

[0101] Advantageously, the edge plates 7 make it possible to guarantee a heat exchange at the edges of the heat exchange zone while generating a constant pressure drop relative to the rest of said heat exchange zone, this makes it possible to minimize the aerodynamic disturbances of the air flow in the annular vein.

[0102] The exchanger of the invention and according to any of the embodiments previously described, can extend continuously over 360° in a section of the annular air stream around the longitudinal axis of the turbomachine. Preferably, the exchanger extends discontinuously over 360° around the longitudinal axis by being subdivided into several angular segments and each exchanger can provide a heat exchange function between the air and the oil which can be different from one segment to another.

[0103] Indeed, each can combine the cooling of several functions or oil circuits of the turbomachine, and this depending on different parameters linked to the need for oil cooling, ie inlet temperatures, flow rates, required outlet temperature or air conditions, the different circuits can be put in thermal contact or insulated.

[0104] In this regard, the exchanger can ensure the cooling of the oil used in several components of the aircraft, including an engine, a gearbox, an engine generator and any electronic component requiring cooling.

[0105] Advantageously, the exchanger and in particular the oil passages can withstand a low oil temperature of up to -54°C, and at the same time withstand a high oil temperature of up to 180°C with a flow rate of up to 30,000 1 / h.

[0106] It should be noted that the invention is not limited to the examples described in the figures. The teachings of the present invention may in particular be applicable to another type of turbomachine.

[0107] Each technical characteristic of each illustrated example is applicable to the other examples. In particular, the combination of the third or fourth embodiment with the first or second embodiment.

Claims

1. Heat exchanger (2) for an annular air vein of an axial turbomachine, comprising a heat exchange zone (3) with oil passages (4) and heat exchange surfaces (6) forming a heat exchange passage for the air, said heat exchange zone (3) being radially delimited by an upper wall (12, 9') and by a lower wall (9, 8'), the oil passages (4) extending radially and axially between said upper wall (12, 9') and lower wall (9, 8'), said heat exchange zone (3) having a profile facing the air flow (F) and included in a plane perpendicular to said air flow (F), said profile of the heat exchange zone (3) being in an arc shape so as to be able to be disposed in the annular air vein, characterized in that the heat exchanger (2) further comprises a wall (8, 12') with an arc-shaped profile parallel to, and radially spaced from the heat exchange zone (3) so as to form, between said wall (8, 12') and said heat exchange zone (3), a bypass passage for the air (10), parallel to the heat exchange passage.

2. Heat exchanger (2) according to claim 1, wherein the bypass passage (10), outside the radial (8, 9, 9', 12') and / or lateral (11) limits of said bypass passage (10), is free of material.

3. Heat exchanger (2) according to claim 2, wherein the radial limits (8, 9, 9', 12') of the bypass passage (10) have an arc-shaped profile and the lateral limits (11) are perpendicular to said radial limits.

4. Heat exchanger (2) according to any one of claims 1 to 3, wherein the bypass passage (10) extends radially over a height (h) between 10% and 20% of a cumulative radial height (H) of said bypass passage (10) and the heat exchange zone (3).

5. Heat exchanger (2) according to any one of claims 1 to 4, wherein the bypass passage (10) extends longitudinally over the entire length of the heat exchanger (2).

6. Heat exchanger (2) according to any one of claims 1 to 5, wherein the wall (8, 12') comprises at least one upstream or downstream end a fixing flange (15) so as to be able to be fixed to an upstream or downstream casing of the annular air vein.

7. Heat exchanger (2) according to any one of claims 1 to 6, wherein the wall (8) is an inner wall radially inside the heat exchange zone (3), so as to form a radially internal guiding wall (8) of the annular air vein, and preferably said heat exchanger (2) further comprises an outer wall (12) radially adjacent to the heat exchange zone (3).

8. Heat exchanger (2) according to claim 7, wherein the outer wall (12) comprises at least one upstream or downstream end a fixing flange (15) so as to be able to be fixed to an upstream or downstream casing of the annular air vein.

9. Heat exchanger (2) according to any one of claims 1 to 6, wherein the wall (12') is located radially outside the heat exchange zone (3), so as to form a radially external guiding wall (12') of the annular air vein.

10. Heat exchanger (2) according to claim 9, further comprising an inner wall (8') radially adjacent to the heat exchange zone (3).

11. Heat exchanger (2) according to claim 10, wherein the inner wall (8') comprises at least one upstream or downstream or circumferential end, a fixing flange so as to be able to be fixed to an upstream or downstream casing of the annular air vein.

12. Heat exchanger (2) according to any one of claims 1 to 11, wherein the heat exchange zone has a divergent longitudinal section following an air flow (F).

13. Heat exchanger (2) according to any one of claims 1 to 12, wherein the heat exchange zone has a cross-section to the air flow, said cross-section increasing along said air flow.

14. Heat exchanger (2) according to any one of claims 1 to 13, wherein the bypass passage (10) for the air has a constant radial height (h) over the entire length of the heat exchanger following the air flow (F).

15. Heat exchanger (2) according to any one of claims 1 to 14, wherein said heat exchanger comprises several angular sectors, each angular sector comprising an oil inlet (18) and an oil outlet (20), said oil inlet (18) and / or said oil outlet (20) being integrally formed in the inner wall (8, 8'), and at least one of the sectors comprises a short-circuit passage of said sector, extending fluidically between the oil inlet and the oil outlet along the inner wall (8, 8').