FR3093765A1 - OPTIMIZED TURBOMACHINE AIR-OIL HEAT EXCHANGER SYSTEM - Google Patents

Abstract

The invention relates to a heat exchanger system (17) for a turbomachine (1) comprising an engine compartment (14) in which oil (H) circulates, this engine compartment (14) comprising a casing (15) delimiting a secondary stream (13) of the turbomachine (1), characterized in that the heat exchanger system (17) comprises a duct (18) which is formed in the engine compartment (14), this duct extending from a suction opening (19) formed at the level of the housing (15) ) to take air (Fp) from the secondary stream (13) to circulate in the duct (18), the duct being delimited by at least one wall (27, 47) separating the air taken (Fp) from the oil (H) to establish a heat exchange between the air taken (Fp) and the oil (H) through said at least one wall (27, 47). Figure for the abstract: Figure 2

Description

OPTIMIZED TURBOMACHINE AIR-OIL HEAT EXCHANGER SYSTEM

The present invention relates to the cooling of oil within a turbomachine, and more particularly to a dual-flow turbomachine equipped with a heat exchanger system between the secondary flow and the oil circulating in the turbomachine.

A turbomachine, such as a turbofan engine 1 with a double body having a longitudinal axis of revolution AX as illustrated in FIG. 1, conventionally comprises a gas generator 2. This gas generator 2 comprises a combustion chamber 3 on either side of which are arranged low pressure 4 and high pressure 6 compressors upstream AM, and high pressure 7 and low pressure 8 turbines downstream AV along the axis AX. the terms “upstream” AM and “downstream” AV are to be considered according to the main direction of gas flow within the turbojet.

The turbojet engine 1 comprises, upstream of the gas generator 2, a fan 9 extending in a radial direction, denoted AY and perpendicular to the axis of revolution AX. The fan 9 is surrounded radially by a fan casing 11 centered on the axis AX. Close downstream of the fan 9, the engine defines a primary stream 12 and a secondary stream 13 separated from each other by an engine compartment 14, commonly called the "core" compartment, delimited in particular by a casing 15 on the side of the secondary stream 13. This secondary stream 13 radially surrounds, along AY, the primary stream 12 while also being delimited in part by a shroud 16 extending the fan casing 11 downstream. The air propelled by the fan is thus divided into a primary flow Fi which crosses the primary stream 12 to supply the gas generator 2, and a secondary flow Fs which is ejected directly downstream.

The low and high pressure turbine and compressor assemblies are each carried by a shaft guided in rotation by bearings housed in enclosures isolating them from the rest of the engine. In addition, such a motor generally comprises one or more gear pinions which are driven in rotation by a mechanical pick-up by means of a bevel gear on the shaft of the low or high pressure assembly and on which come couple equipment from the accessory box or AGB (Accessory GearBox) such as mechanical pumps for hydraulics, electric generators, etc.

Oil ensures the lubrication and cooling of these bearings and pinions, which are metal components subject to wear during their working life. This oil, which then needs to be cooled, conventionally passes through conventional air-oil heat exchangers of the ACOC type (from the English "Air Cooled Oil Cooler") or even of the SACOC type (from the English "Surface Air Cooler Oil Cooled”). These exchangers are generally placed in the secondary stream to take advantage of the secondary flow which is colder than the primary flow, i.e. significantly colder than the oil to be cooled.

The increased performance needs of turbomachines imply the integration of new technologies likely to increase, compared to the current situation, the cooling needs of this oil circulating in its equipment.

However, the air-oil heat exchangers integrated within the secondary stream 13 form singularities seen from the flow, generating so-called “secondary” flows most often in the form of vortex structures which penalize the overall efficiency of the engine.

It follows that the multiplication of these air-oil exchangers within the secondary vein is not an adequate solution to meet the growing needs of oil cooling.

The object of the invention is therefore to propose a substitute or additional air-oil heat exchanger system which improves the aerodynamics of the secondary stream and optimizes heat exchange.

To this end, the subject of the invention is a heat exchanger system of a turbomachine comprising an engine compartment in which oil circulates, this engine compartment comprising a casing delimiting a vein of the turbomachine, characterized in that the system heat exchanger comprises a duct which is formed in the engine compartment, this duct extending from a suction opening formed at the level of the casing to take air from the vein to circulate in the duct, the duct being delimited by at least one wall separating the oil from the bleed air to establish a heat exchange between the bleed air and the oil through said at least one wall.

With this solution, the seat of air-oil heat exchange is isolated within the engine compartment. It follows that the aerodynamics of the vein is less disturbed in comparison with the conventional addition of a heat exchanger providing cooling of the oil via the flow circulating directly in this vein.

The invention also relates to a heat exchanger system thus defined, in which the oil circulates in a pipe which surrounds the conduit along at least a portion of the conduit.

The invention also relates to a heat exchanger system thus defined, in which the oil circulates in a pipe surrounded by the pipe along at least a portion of the pipe.

The invention also relates to a heat exchanger system thus defined, in which the oil is in contact with said at least one wall over the majority of the length of the conduit.

The invention also relates to a heat exchanger system thus defined, in which the heat exchanger system comprises fins which protrude from the said at least one wall by extending into the duct.

The invention also relates to a heat exchanger system thus defined, in which said at least one wall and the fins are formed in one piece, preferably by additive manufacturing.

The invention also relates to a heat exchanger system thus defined, further comprising a radiator which is installed in the duct and in which all or part of the oil circulates.

The invention also relates to a heat exchanger system thus defined, in which the duct extends from the suction opening to an ejection opening formed at the level of the casing to reintroduce the air taken from the flow secondary.

The invention also relates to a dual-flow turbomachine comprising the heat exchanger system thus defined, the air taken from being taken directly from the so-called secondary stream of the turbomachine.

is a block diagram of a turbofan engine in axial section;

is a detail view of Figure 1 illustrating in particular a heat exchanger system according to the invention, in cooperation with a secondary stream and a hydraulic circuit of the turbomachine;

is a perspective radial sectional view of the heat exchanger system of Figure 2;

is a detail view of Figure 1 illustrating the heat exchanger system whose bypass duct is decorated with fins;

is a perspective radial sectional view of the heat exchanger system of Figure 4;

is a detail view of Figure 1 illustrating the heat exchanger system whose branch pipe houses a brick heat exchanger;

is a detail view of Figure 1 illustrating the heat exchanger system whose branch pipe houses a brick heat exchanger while being decorated with fins;

is a perspective, radial sectional view of a variation of the heat exchanger system in a sandwich configuration.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

The basic idea of the invention is to propose a heat exchanger system in a turbomachine as described above, that is to say for example a turbofan engine 1 comprising a secondary stream 13 delimited by a casing 15 from engine compartment 14.

Referring to Figures 2 and 3, the turbine engine 1 is equipped with a heat exchanger system, denoted 17. This heat exchanger system 17 includes a bypass duct 18 arranged in the engine compartment 14. Extending from upstream to downstream from a suction opening 19 as far as an ejection opening 21 formed in the casing 15, this bypass duct 18 is adapted to take off part of the secondary flow Fs, designated by “taken air Fp”. The extracted air Fp rushes into the bypass duct 18 through the suction opening 19 to then be discharged through the ejection opening 21 into the secondary flow Fs which was depleted.

Advantageously, in the downstream extension of the suction opening 19, the bypass duct 18 forms a ramp 22 which moves away radially from the secondary stream 13 with a slight inclination relative to the casing 15. This arrangement makes it possible to efficiently collect the flow of air contiguous to the housing 15, namely to limit the pressure drops likely to reduce the flow rate of the flow of air taken Fp through the suction opening 19. In the same way, upstream of the ejection opening 21, the duct forms a ramp 23 which advances radially towards the casing 15 to straighten the flow withdrawn by orienting it substantially in the overall direction of propagation of the secondary flow Fs in the extension of this ejection opening 21. It is understood here that this reintroduction of air into the secondary stream 13, occurring substantially in the direction of propagation of the secondary flow, limits the introduction of parasitic vortex structures which disperse the energy.

Additionally, the heat exchanger system 17 comprises a pipe 24 delimited, in the example of FIGS. 2 and 3, by a pipe wall 25 which runs along a portion of the bypass duct 18 surrounding it at a distance, in the engine compartment. 14. This pipe 24 is grafted onto a hydraulic circuit 26 of the turbomachine 1, so as to route oil H along the bypass duct 18 in order to then reintroduce it into this hydraulic circuit 26.

The bypass duct 18, in a non-limiting manner with a circular section, is delimited by a duct wall 27 including an internal surface 28 and an external surface 29, seen from the flow of air taken Fp circulating within it. In other words, the inner surface 28 of the duct wall 27 is traversed by the flow of air drawn off Fp, while its outer surface 29 is bathed in the oil H circulating in the pipe 24, also in a non-limiting manner of circular section . More precisely, the pipe 24, in which the oil H circulates, is jointly delimited by the wall of the pipe 25 and the wall of the conduit 27.

The hydraulic circuit 26 comprises in particular an injection pump 31 and a recovery pump 32, making it possible to apply to the oil H a desired direction of circulation within the pipe 24. In practice, during the operating life of the turbomachine 1 equipped with the heat exchanger system 17 according to the invention, the oil H admitted into the pipe 24 under the action of the injection pump 31, has a high temperature since it has just been used at purposes of lubricating a gear or certain equipment, as shown here a rolling bearing 33 which guides in rotation a shaft 34 of axis AX. As this oil progresses in the pipe 24, it is gradually cooled by the conduit wall 27 which constitutes a heat exchange interface, with its internal surface 28 being traversed by the withdrawn flow Fp and its external surface 29 being in contact with the oil H hotter than this sampled flow Fp.

In particular, the heat transfer has a first component of convective exchange between the withdrawn flow Fp and the internal surface 28 of the pipe 18, a second component of convective exchange between the oil H and the external surface 29 of the pipe 18, thus a conductive exchange component within the conduit wall 27 which tends to balance between the two surfaces. Once cooled, this oil H is reinjected under the action of the recovery pump 32 into the hydraulic circuit 26, and more specifically into a tank 36 from which it will again be taken for lubrication purposes.

In the example of FIG. 2, the direction of propagation of the oil within the pipe 24 is opposite to that of the flow of air taken Fp within the bypass duct 18, but it should be noted that a flow in the same direction can be retained without departing from the scope of the invention.

Concretely, the heat exchanger system according to the invention makes it possible to isolate the seat from the air-oil heat exchanges within the engine compartment 14. It follows that the aerodynamics of the secondary stream 13 is less disturbed in comparison with the conventional addition of a heat exchanger providing cooling of the oil via the secondary flow Fs directly in the secondary stream.

In order to increase the heat exchange coefficient, the invention provides in a variant embodiment to enrich the heat exchanger system 17 with a plurality of fins, denoted 38 in the example of Figures 4 and 5. These fins 38 protrude from the inner surface 28 of the conduit wall 27 and extend parallel to the direction of the flow taken Fp along a portion of the conduit 18. The fins, forming an extension of the inner surface 28 within the conduit 18, increase the heat exchange surface, also called "wet surface", between the flow taken Fp and the conduit wall 27.

The integration of the fins 38 within the duct 18 is made possible with a duct wall 27 resulting from the assembly of several segments on each of which part of the fins is attached. Nevertheless, due to the complexity of the shape of the duct 18, the invention advantageously provides for the use of additive manufacturing to manufacture the duct wall 27 in one piece with the fins 38, by way of non-limiting fusion/laser sintering. metal on a powder bed.

Also, in order to increase the heat exchange coefficient according to another variant embodiment, the heat exchanger system 17 includes a brick type exchanger 39, that is to say an ACOC type exchanger also designated as a radiator, integrated within the duct 18. As can be seen in FIG. 6, the radiator 39 is arranged in a central region of the duct 18 and occupies, in a non-limiting manner, the entire passage section of the withdrawn flow Fp along its extent, otherwise said with its periphery which is in continuous contact with the internal surface 28 of the conduit wall 27. This radiator 39 comprises an internal circuit which is in fluid communication with the pipe 24 and which crosses the conduit 18. This internal circuit captures all or part of the oil from pipe 24 and reinjects it into this pipe once it has been exposed to the flow of air drawn off.

According to another embodiment, the invention provides a fins/radiator combination, as illustrated in FIG. 7. In the example of this figure, the dimensions of the radiator 39 are reduced, in other words it does not occupy the whole space available within the duct 18, so that some fins 38 can extend in parallel. It is understood that the invention is not limited to this particular arrangement, and conversely makes it possible to provide discontinuous fins located on either side of the radiator when the latter completely occupies the passage section of the withdrawn flow Fp along its extent.

The heat exchanger system 17 has been explained at this stage with the pipe 24 which surrounds the conduit 18, however any other arrangement is possible without departing from the scope of the invention as long as there is a wall which at least partially delimits the conduit 18, while being in contact with the oil to be cooled so as to form a heat exchange interface.

In this respect, the invention could provide that the pipe 24 extends conversely in the branch pipe 18 crossing the pipe wall 27.

Also, a so-called sandwich arrangement can be retained, as in the example of FIG. 8, with the pipe 24 which splits into a first branch 41 which surrounds the pipe 18, and into a second branch 42 which crosses the wall 25 of on either side so that the branch pipe 18 surrounds this second branch 42. An outer pipe wall 43 can be seen which delimits, together with the pipe wall 27, the first branch 41. This outer pipe wall 43 comprises an inner surface 44 and an outer surface 46, seen from the oil H circulating within the first branch 41. An inner pipe wall 47 defines the second branch 42 and delimits the conduit 18 together with the conduit wall 27. This inner wall of pipe 47 includes an inner surface 48 and an outer surface 49, seen from the oil H flowing within the second branch 42.

With this sandwich arrangement, the withdrawn flow Fp thus propagates between two walls, namely the conduit wall 27 and the inner pipe wall 47 together delimiting the conduit 18, which are each in contact with oil H. As it is understood, the heat exchange potential is thereby increased at iso-withdrawal of air compared to an arrangement with a single wall forming an interface between the air and the oil. In other words, it then becomes possible to reduce the quantity of air bleed necessary to ensure cooling of the oil which is equivalent to that achieved with an arrangement with a single wall forming an interface between the air and the oil. This reduction in the withdrawn flow thus makes it possible to limit the losses in efficiency of the turbine engine, it being understood that the withdrawn flow Fp is generally reintroduced into the secondary stream 13 with a lower speed than that of the secondary flow Fs.

In the case of such a sandwich arrangement, in combination with the addition of fins 38 as illustrated in FIG. 8, these fins 38 are advantageously, and in a non-limiting manner, formed through in the bypass duct 18. More precisely , each fin 38 includes a first end forming a connection point at the inner surface 28 of the conduit wall 27, and a second end forming a connection point at the outer surface 49 of the inner pipe wall 47 With this arrangement, the fins each form a thermal bridge between the oil propagating in the first branch 41 and that propagating in the second branch 42. In other words, the fins 38 add both a convective exchange component by increasing the wetted surface of the two walls delimiting the duct 18, the withdrawn flow Fp propagating at the level of the space defined between two fins, and a conductive exchange component tif between these two walls.

The addition of the radiator 39 also remains applicable, with or without fin, and can in such a case advantageously provide fluid communication between the first and the second branch 41 and 42 by extending into the duct 18, so as to achieve a mixing of the oil and therefore a homogenization of the temperature of the oil between these two ramifications.

In the example of the figures, the walls delimiting the duct and the oil pipe have a generally circular section and are arranged coaxially. It is understood that the invention is not limited to this particular arrangement and in particular allows any type of shape, provided that at least one wall delimiting the duct forms an air-oil heat exchange interface. The duct and the pipe, continuous or having ramifications, can for example have an ovoid, rectangular, triangular, parallelepipedic, conical, prismatic cross-section, or any other shape that a person skilled in the art could consider.

Also, the fins 38 have been presented as extending parallel to the withdrawn flow Fp circulating within the bypass duct 18 so as to essentially increase the heat exchange surface, the air flow propagating between them along their extent. However, other shapes and arrangements of fins can be envisaged without departing from the scope of the invention. In particular, the invention could provide for the formation of fins, for example of the petal type, forming obstacles in the bypass duct 18 in order to increase the heat exchange by turbulence, namely by forcing the withdrawn flow Fp to bypass them. locally.

In practice, the morphology of the bypass duct 18, as well as the arrangement and the dimensioning of the fins 38 and/or of the radiator 39 if applicable, directly condition the flow rate of the air taken Fp. These parameters are thus defined according to the need for heat exchange and the aerodynamic flow conditions of the secondary stream 13. This involves in particular finding a compromise between the exchange surface and the flow section of the sampled air Fp, considering in particular the pressure drops.

Finally, the bypass duct 18 has been described as extending within the engine compartment 14 between a suction opening 19, at the level of which a portion Fp of the secondary flow Fs rushes into this duct 18, and an opening ejection 21 at which this removed portion Fp is reinjected into the secondary vein 13. It is however possible to form the bypass duct 18 free of ejection opening formed at the level of the housing 15, with a view to distributing the flow taken Fp to another module of the turbomachine, or even within the enclosure of the aircraft equipped with the turbomachine. By way of example, the duct 18 could be extended so as to convey the air, at the end of the heat exchanges with the oil taking place in the engine compartment 14, to the cabin of the aircraft in order to renew the air. It is understood here that the heat exchanger system according to the invention could make it possible to provide a flow of heated air within the aircraft, duplicating the extraction of thermal energy from the oil.

In practice, the heat exchanger system is designed to maximize the exchange surface between the oil and the air sampled, in other words that the oil extends over the majority of the length of the conduit 18, at least along half of this duct.

Of course, with regard to pipe 24, the invention is not limited to this designation, which here designates any type of enclosure in which oil is housed, this oil being in contact with a wall delimiting the conduit 18. In particular, the oil can be in motion, as in the example of Figure 2, or even in a stationary state, as in the case of a reservoir. In this respect, it is concretely understood that the heat exchanger system comprises a duct 18 which is advantageously provided in the engine compartment 14 and separating the oil H, housed in the engine compartment, from the air taken Fp to establish an exchange air-oil thermal.

Claims (9)

Heat exchanger system (17) of a turbomachine (1) comprising an engine compartment (14) in which oil (H) circulates, this engine compartment (14) comprising a casing (15) delimiting a vein (13) of the turbomachine (1), characterized in that the heat exchanger system (17) comprises a duct (18) which is provided in the engine compartment (14), this duct extending from an intake opening (19) formed at the level of the casing (15) to take air (Fp) from the vein (13) to circulate in the duct (18), the duct being delimited by at least one wall (27, 47) separating the oil (H) bleed air (Fp) to establish a heat exchange between the bleed air (Fp) and the oil (H) through said at least one wall (27, 47). A heat exchanger system (17) according to claim 1, wherein the oil circulates in a pipe (24) which surrounds the conduit (18) along at least a portion of the conduit (18). A heat exchanger system (17) according to claim 1, wherein the oil circulates in a pipe (24) surrounded by the conduit (18) along at least a portion of the conduit (18). Heat exchanger system (17) according to one of Claims 1 to 3, in which the oil (H) is in contact with the said at least one wall (27, 47) over the majority of the length of the conduit (18) . A heat exchanger system (17) according to claim 1, wherein the heat exchanger system includes fins projecting from said at least one wall (27, 47) extending into the conduit (18). A heat exchanger system (17) according to claim 5, wherein said at least one wall (27, 47) and the fins (38) are integrally formed, preferably by additive manufacturing. Heat exchanger system (17) according to one of the preceding claims, further comprising a radiator (39) which is installed in the conduit (18) and in which all or part of the oil (H) circulates. Heat exchanger system (17) according to one of the preceding claims, in which the duct extends from the suction opening (19) to an ejection opening (21) formed at the level of the casing (15 ) to reintroduce the bleed air (Fp) into the secondary flow (Fs). Dual-flow turbomachine (1) comprising the heat exchanger system (17) according to one of the preceding claims, the bleed air (Fs) coming directly from the so-called secondary stream (13) of the turbomachine (1).