FR2862724A1 - Hydraulic fluid cooling device for aircraft, has heat exchanger installed outside fuel tank, and control valve to control circulation of fuel in upstream line and returning of heated fuel to fuel tank - Google Patents

Abstract

The device (4) has a heat exchanger (38) installed outside a fuel tank (30) and traversed by an upstream line (34) and a hydraulic fluid line (24) so that heat is transferred from the hydraulic fluid to fuel circulating in the line. The circulation of the fuel in the line and returning of heated fuel to the tank is controlled by a control valve (40) that is controlled by a valve control unit (42). The valve control unit (42) receives information provided by detection units (44, 46, 48, 49) which detects temperature of the fuel inside the fuel tank (30), level of the fuel inside the tank, operation state of a fuel pump (32), and temperature of the hydraulic fluid at output of the heat exchanger (38), respectively. Independent claims are also included for the following: (a) an aircraft equipped with a hydraulic fluid cooling device (b) a method for cooling hydraulic fluid circulating in a hydraulic fluid line of a hydraulic circuit of an aircraft.

Description

2862724 2

  2. It comprises, in a manner known per se, a hydraulic fluid reservoir 10, one or more hydraulic pumps 12, and pipelines 14, 16, 18, 20.

  The operating principle of such a circuit will be briefly recalled, in a particular case where the circuit supplies a single consumer 22, it being understood that a circuit feeding several consumers 22 operates according to a similar principle.

  The hydraulic pump 12 is a high-pressure pump which pumps or draws hydraulic fluid from the tank 10 through a first pipe called fluid suction pipe 14. The hydraulic fluid is then sent, under high pressure, to a consumer 22 through a second pipe called fluid supply pipe 16. The consumption of energy by said consumer 22 results in a decrease in the pressure of the hydraulic fluid, which is at low pressure at the consumer outlet, in a third pipe called fluid return line 18, through which it is returned to the hydraulic fluid reservoir 10.

  The hydraulic fluid circuit generally comprises an additional pipe, called drainage pipe 20, associated with the hydraulic pump. This makes it possible to send back directly to the reservoir 10 a portion of the hydraulic fluid coming from the hydraulic pump 12 and corresponding to the internal leaks of this pump 12. It is conventionally estimated that about 10% to 15% of the power SP 21972 Total VD available to the pumps is lost due to the existence of these internal leaks, and this fraction of power is transformed into heat. This results in a heating of the hydraulic fluid circulating in the drainage pipe 20 towards the hydraulic fluid reservoir 10.

  Hydraulic fluid consumers can also heat up said hydraulic fluid, but to a lesser degree than the pumps.

  Such heating of the hydraulic fluid has adverse repercussions for the operation of the hydraulic circuit. Indeed, it results from these heating degradation of the hydraulic fluid, and therefore a decrease in its performance. In particular, a heating of the fluid can induce an increase in the acidity of said fluid, which can cause deterioration of consumer devices of said hydraulic fluid. It can also result from these heating a degradation of the hydraulic circuit seals, and as a result of external leaks of the hydraulic circuit.

  It is therefore necessary to maintain the hydraulic fluid, flowing in such a hydraulic circuit for supplying one or more consumers, below a so-called stability temperature of said hydraulic fluid.

  A first solution is to use the natural ability of the hydraulic circuit to dissipate heat by natural or forced convection with ambient air around the pipes. This first solution is satisfactory for aircraft SP 21972 / VD whose hydraulic power requirements are low enough for such heat dissipation by the fluid supply lines completely or almost totally dissipates the heating of the hydraulic fluid. The dissipation is all the more effective as the supply lines are long. But for aircraft that are compact with respect to the hydraulic power installed, that is to say that have a short length of supply lines in comparison with the available hydraulic power, the natural heat dissipation remains insufficient.

  A second solution for improving the cooling of the hydraulic fluid is to complete the hydraulic circuit by a heat exchanger placed inside a fuel tank of the aircraft. The hydraulic fluid passes through this heat exchanger, is then cooled, and its heat is transferred to the fuel contained in the fuel tank accommodating the heat exchanger. This second solution could be used on old aircraft, but it is no longer acceptable since the entry into force of new safety regulations, which require minimizing all thermal transfers to fuel.

  A first condition required by the regulations is to limit the generation of fuel vapor inside each fuel tank. This condition is achieved if the fuel temperature remains below its flammability temperature TF. Or with the second SP 21972 / VD.

  solution of the prior art, in the presence of a heat exchanger inside the fuel tank, the risk exists that the heat exchanger is at least partially out of the fuel when the fuel level is low. In this case excessive local heating of the fuel surface may occur, and an excessive amount of fuel vapor may be generated. Consequently, this second solution does not fulfill the first regulatory condition.

  A second condition required by the regulations requires that the temperature Tm of the fuel at the engine inlet does not exceed a maximum value. But the second solution does not control the temperature of the fuel at the engine inlet, and therefore this second solution does not meet the second regulatory requirement.

  SUMMARY OF THE INVENTION There is therefore a need for a device for cooling a hydraulic fluid circulating inside an aircraft to supply energy to consumers such as hydraulic actuators, which does not encounter the technical problems of the devices. which have been recalled above.

  According to a first aspect of the invention, the device for cooling a hydraulic fluid flowing in a hydraulic circuit of an aircraft comprises: at least one fuel tank, SP 21972 / VD '; at least one fuel pump per whereby fuel is withdrawn from said fuel tank, - at least one heat exchanger installed outside said fuel tank, which is traversed by both said hydraulic fluid and said fuel, so that thermal transfer is effected from said hydraulic fluid to said fuel, and - at least one fuel line, through which the fuel passes through said heat exchanger, and is returned to said fuel tank.

  According to a second aspect, the invention also relates to an aircraft equipped with such a device for cooling a hydraulic fluid.

  According to a third aspect of the invention, the method of cooling a hydraulic fluid flowing in a hydraulic circuit of an aircraft, is characterized in that said hydraulic fluid passes into at least one heat exchanger of a hydraulic fluid cooling device comprising: - at least. a fuel tank, at least one fuel pump, through which fuel is withdrawn from said fuel tank; at least one heat exchanger installed outside said fuel tank, which is traversed at both by said hydraulic fluid and by said fuel, so that a thermal transfer SP 21972 / VD is effected from said hydraulic fluid to said fuel, and - at least one fuel pipe, through which the fuel passes through said heat exchanger, then is returned to said fuel tank.

  According to a fourth aspect of the invention, said cooling method is applied to the cooling of a hydraulic fluid coming from a drainage pipe of a hydraulic pump of a hydraulic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

  Other features and advantages of the invention will appear on reading the following detailed description of particular embodiments of the invention, with reference to the appended drawings, in which: FIG. 1, already described, illustrates a consumer hydraulic supply circuit, as well as its operating principle; FIG. 2 illustrates a hydraulic fluid cooling device according to the invention, as well as its principle of operation; FIG. 3A illustrates a first variant of a first preferred embodiment of the cooling device for hydraulic fluid according to the invention; FIG. 3B is similar to FIG. 3A for a second variant of the first preferred embodiment of the cooling device for hydraulic fluid according to the invention; SP 21972 / VD - Figure 4 illustrates a second preferred embodiment of the cooling device for hydraulic fluid according to the invention.

  DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS On the right-hand part of FIG. 2 is schematically represented a hydraulic fluid pipe, indicated by 24, in which hydraulic fluid circulates to be cooled. Said hydraulic fluid pipe 24 may be one of the pipes of a hydraulic fluid circuit 2 as mentioned above with reference to FIG. 1, namely a hydraulic fluid suction pipe 14, or a hydraulic fluid supply pipe 16, or a drainage pipe 20 of a hydraulic pump 12. It is particularly advantageous to cool fluid from a drainage pipe of a hydraulic pump, since it is usually when the hydraulic fluid has, in the absence of cooling, the highest temperature when returning to the hydraulic fluid reservoir.

  On the left part of Figure 2 is schematically shown a hydraulic fluid cooling device according to the invention, identified by the reference numeral 4. Fuel is taken from a fuel tank 30, by means of at least one pump of fuel 32, then it circulates and returns to the fuel tank 30 via at least one fuel line 34, 36. In the illustrated example, the fuel pump SP 21972 / VD is located at the tank, but could also be located outside the tank. When several fuel pumps 32 are present, inside or outside the fuel tank 30, they are installed in a parallel connection.

  Between said at least one fuel pump 32 and the fuel tank 30, said fuel 36 passes through at least one heat exchanger 38, which is also traversed by said hydraulic fluid 24 to be cooled. Within this heat exchanger 38 is therefore a thermal transfer of the hydraulic fluid to the fuel, which allows to cool said hydraulic fluid. The fuel, meanwhile, comes out heated heat exchanger 38.

  The portion of the fuel line 34, 36 that is located between the fuel tank 30 and the heat exchanger 38 is called the upstream pipe and is part of the fuel between the fuel indicated in the figures by the mark 34. fuel 34, 36 which is the heat exchanger 38 and the tank 30 is called fuel return pipe and is indicated in the figures by the reference 36.

  The fuel flow in said upstream pipe 34 is controlled by control means 40, 42, 44, 46, 48, 49 of said circulation, which comprise a control valve 40 controlled by a valve control unit 42. Said unit valve control 42 receives information from one or more detection means 44, 46, 48, 49 of parameters, according to which it modulates SP 21972 / VD the opening and closing of said control valve 40. Said control means 42, 44, 46, 48, 49 may comprise means for detecting the fuel temperature 44 inside the fuel tank 30, and / or fuel level detection means 46 inside. of the fuel tank 30, and / or means for detecting the operating state 48 of said at least one fuel pump 32, and or means for detecting the temperature of the hydraulic fluid at the outlet of the heat exchanger. heat 38.

  Thus the control valve 40 can be closed if the fuel temperature inside the fuel tank 30 is too high, or if the fuel level inside the fuel tank 30 is too low. Indeed, the temperature of the fuel in the fuel tank 30 increases especially as its volume, measured by the fuel level in the fuel tank 30, is low. The control valve 40 can also be closed in the event of failure or malfunction of the at least one fuel pump 32.

  The hydraulic fluid cooling device 4 according to the invention has the advantage that the exchanger is located outside the fuel tank 30, on a pipe dedicated to cooling, the supply is controlled, this pipe being the fuel line 34, 36.

  With a. heat exchanger 38 located outside the fuel tank 30, the risk of SP 21972 / VD generating excess fuel vapor in the fuel tank 30 by local heating of the fuel surface is eliminated. Thus the first regulatory condition mentioned above is fulfilled.

  In addition, by the control means 40, 42, 44, 46, 48, 49 of the fuel circulation in said fuel line 34, 36, the return of heated fuel to the fuel tank 30 can be interrupted.

  The interruption of fuel flow through the heat exchanger 38 can be controlled when the temperature TR of the fuel within the fuel tank reaches or exceeds a predetermined value.

  The value of the temperature TR can be set according to the desired temperature TM at the motor inlet. Thus, the second regulatory condition mentioned above is fulfilled.

  The fact that the heated fuel returns to the fuel tank 30 after having passed through the heat exchanger 38, and that it is not conducted directly to an engine of the aircraft after having been heated, makes it possible to guarantee that the fuel which is led to said engine comes directly from the fuel tank 30. Thus, the temperature TM of the fuel at the inlet of said engine is known and controlled.

  Furthermore, the interruption of the flow of fuel through the heat exchanger 38 can be controlled when the temperature TH of the hydraulic fluid SP 21972 / VD becomes equal to or less than a predetermined value. This predetermined value corresponds for example to a viscosity value of the hydraulic fluid above which the desired performance of the hydraulic fluid is not reached.

  It is considered that the amount of fuel heated through its passage through the heat exchanger 38 is again cooled when said fuel returns to the fuel tank 30, by dissipation of its heat in the fuel tank 30, said dissipation resulting from the mixing this amount of fuel with the large amount of fuel contained in the fuel tank 30. In addition it is possible to provide the initial mass of fuel inside said fuel tank 30 so that the fuel level remains sufficient to ensure that this phenomenon of dissipation actually occurs.

  The fuel tank can itself be cooled by forced convection with the external aerodynamic flow when it is placed in a wing of the aircraft.

  The cooling device according to the invention is even more advantageous when the fuel tank is a nanny-type tank. It is recalled that a reservoir type nanny or feedtank is a tank that serves to directly feed a motor of the aircraft, via a fuel pump. Such a nurse-type tank is maintained filled by fuel transfer from other tanks of the aircraft during the greatest possible duration of the flight, until the said other tanks are exhausted. To cool hydraulic fluid, fuel is taken from a reservoir type nurse before passing through a heat exchanger, also traversed by the hydraulic fluid to be cooled, and returned to said reservoir type nanny. This fuel is then cooled in a high capacity cold source which is regularly renewed, this source being said nurse type tank. As a result, the risk of a significant increase in the temperature of fuel or fuel vapors in the fuel tank 30 is avoided. As a result, the two regulatory conditions mentioned above are even better met when the tank is a nanny type tank.

  A preferred embodiment of the hydraulic fluid cooling device 4 according to the invention is shown in Figures 3A and 3B. To simplify FIGS. 3A and 3B, the control means 42, 44, 46, 48, 49 for controlling the opening / closing of the control valve 40 have not been represented, but they are implicitly contained in a analogous to Figure 2.

  According to this preferred embodiment, part of an existing fuel circuit on the aircraft is used, namely a part of a fuel supply circuit of at least one engine of the aircraft. Thus, fuel is drawn SP 21972 / VD into the fuel tank 30 by means of a fuel pump 32 or a set of fuel pumps 32 installed in parallel in said fuel tank 30, to then feed at least a motor (not shown) of the aircraft by means of a fuel supply pipe 50.

  For this preferred embodiment, the upstream pipe 34 is a pipe mounted in shunt of said fuel supply pipe 50. The bifurcation point of the fuel supply pipe 50 to the upstream pipe 34 is marked 51.

  As a result, the same fuel pump 32, or the same set of fuel pumps 32, if any, makes it possible to draw fuel into the fuel tank 30, both to supply said engine of the aircraft, and to circulate fuel through the heat exchanger 38.

  As previously indicated with reference to FIG. 2, said fuel return line 36 is a channel dedicated to cooling, which returns the heated fuel to the fuel tank 30.

  The fuel that serves to cool the hydraulic fluid thus flows successively in the fuel tank 30, then in the fuel supply pipe 50 to the bifurcation 51, then in the upstream pipe 34, then in the heat exchanger 38, and finally in the fuel return line 36, before returning to the fuel tank 30.

  An advantage of this embodiment, bypassing the fuel line 34, 36 with respect to the fuel supply line 50, is that it allows better control of the temperature of the fuel. fuel for supplying said engine, since this temperature is substantially equal to the temperature of the fuel in the fuel tank 30. It should be noted that said temperature could not be controlled if the heat exchanger 38 was installed directly on a pipe d fuel supply 50 of an engine of the aircraft, upstream of said engine, because then the fuel would arrive warmed to the input of said engine.

  According to a first variant illustrated in FIG. 3A, of this first preferred embodiment of the cooling device 4 according to the invention, the bifurcation 51 towards the fuel line 34, 36 is situated upstream of said valve 52 of the motor circuit.

  According to a second variant, illustrated in Figure 3B, of this first preferred embodiment of the cooling device according to the invention, the bifurcation 51 to the fuel line 34, 36 is located downstream of said valve 52 of the motor circuit.

  Preferably, a non-return device is installed on the fuel return line, between the heat exchanger 38 and the fuel tank 30. This non-return device 60 may be a calibrated check valve. A calibrated check valve means a valve that opens SP 21972 / VD only if there is a pressure difference between the upstream and downstream of said valve which is sufficient to let the fluid. It prevents a flow of fuel from the fuel tank 30 to the heat exchanger 38 when said at least one fuel pump 32 is not active. In such a case, this non-return device 60 has the advantage of preventing fuel coming from the fuel tank 30 from escaping through a leak that would exist on the upstream pipe 34 or on the fuel return pipe 36 for example at the level of the heat exchanger 38. In a similar way, always when said at least one fuel pump 32 is not active, this antiretour device 60 makes it possible to prevent fuel heated by its passage through the heat exchanger 38 is sent into said engine of the aircraft through the fuel return line 34 and then through the fuel supply line 50.

  A second preferred embodiment of the hydraulic fluid cooling device according to the invention is particularly suitable for an aircraft comprising several engines, each engine being associated with a nipple-type fuel tank of its own type, and which feeds it with fuel. This second embodiment is illustrated with reference to FIG. 4 for a four-engine type aircraft.

  An aircraft wing 100 is shown schematically. It carries two motors 150A, 150B SP 21972 / VD, each associated with a 30A, 30B nurse type fuel tank in which fuel is drawn by means of a fuel pump or a set of parallel mounted fuel pumps. 32A, 32B, to be conducted to said engine 150A, 150B via a fuel supply line 50A, 50B. The fuel supply of said engine 150A, 150B may be modulated or interrupted by means of a motor circuit valve 52A, 52B installed on said fuel supply line 50A, 50B. The other wing of the aircraft, not shown for the sake of simplification, similarly carries two 150C, 150D, two 30C, 30D, or fuel pumps or associated fuel pump assemblies. 32C, 32D, associated lines 50C, 50D, and associated motor circuit valves 52C, 52D.

  Each of the motors 150A, 150B, 150C, 150D is also associated with a heat exchanger 38A, 38B, 38C, 38D, installed on a fuel line 34A, 36A, 34B, 36B, 34C, 36C, 34D, 36D mounted as a bypass. the fuel supply line 50A, 50B, 50C, 50D from a bifurcation 51A, 51B, 51C, 51D. More specifically, the heat exchanger 38A, 38B, 38C, 38D is installed between an upstream line 34A, 34B, 34C, 34D and a fuel return line 36A, 36B, 36C, 36D. The fuel, heated by its passage through said heat exchanger 38A, 38B, 38C, 38D, is returned to the fuel tank 30A, 30B, 30C, 30D of SP 21972 / VD type nanny associated with said engine 150A, 150B, 150C , 150D. Also present are means for controlling the circulation of fuel in the fuel line 34A, 36A, 34B, 36B, 34C, 36C, 34D, 36D, comprising in particular a control valve 40A, 40B, 40C, 40D installed on said line. upstream 34A, 34B, 34C, 34D between the bifurcation 51A, 51B, 51C, 51D and the heat exchanger 38A, 38B, 38C, 38D. The opening and closing of the control valves 40A, 40B, 40C, 40D are controlled according to different parameters such as the temperature of the fuel in each fuel tank 30A, 30B, 30C, 30D, and / or the fuel level in each tank 30A 30B, 30C, 30D, and / or the operating state of each at least one associated fuel pump 32A, 32B, 32C, 32D.

  One or more connecting pipe (s) 70 connects (s) between them the fuel supply lines 50A, 50B, 50C, 50D of different engines 150A, 150B, 150C, 150D successive. This (these) connecting pipe (s) 70 meets (s) each fuel supply pipe 50A, 50B, 50C, 50D at an intersection 71A, 71B, 71C, 71D downstream of each of the fuel pumps 32A, 32B, 32C, 32D and upstream of the corresponding motor circuit valve 52A, 52B, 52C, 52D. Intermediate valves 80AB, 80BC, 80CD are installed on said linkage pipe (s) 70. This (these) connecting pipe (s) 70 allows (the) cross-feeding of one of the engines from of SP 21972 / VD fuel tanks 30 type feedback dedicated to other engines.

  In a manner known per se, these intermediate valves 80AB, 80BC, 80CD, when open, allow to continue to supply the motors 150A, 150B, 150C, 150D, even when the fuel pump 32A, 32B, 32C, 32D associated with said engine 150A, 150B, 150C, 150D is inoperative, or when the reservoir type of nurse associated with said engine 150A, 150B, 150C, 150D is empty.

  For example, if the fuel pump 32A associated with the engine 150A is out of order, the intermediate valve 80AB is then open, and the fuel that then supplies the engine 150A does not come from the tank 30A, but from another tank (not shown ), by means of one of the connecting pipe (s) 70. In this case, it is preferred to close the control valve 40A, and to suppress the heat transfer at the heat exchanger 38A, so that there is no fuel that returns to the tank 30A whose at least one pump 32A has failed. Indeed, if fuel returned to said fuel tank 30A, it could no longer be removed, which would have the effect of reducing the remaining flight time of the aircraft. In addition, if the fuel tank 30A were still full, returning fuel to this tank would result in unwanted fuel overflow. Consequently, these two disadvantages are avoided because of the presence of the control valves 40A, 40B, 40C, SP 21972 / VD 40D. The heat transfer that does not take place at the heat exchanger 38A can be compensated by thermal transfers occurring at the other heat exchangers 38B and / or 38C and / or 38D.

  The cooling of the hydraulic fluid is then performed in degraded mode, since the total cooling power is lower.

  The hydraulic fluid cooling device which has just been described is not limited to the exemplary embodiments presented. One could consider other equivalent embodiments and within the scope of the skilled person of the cooling device according to the invention.

  For example, it could be envisaged that the pump 32, or the set of pumps 32, is not located inside the tank but outside the tank, on a first part of the upstream pipe 34.

SP 21972 / VD

Claims (21)

  1. Cooling device (4) for a hydraulic fluid flowing in a hydraulic circuit (2) of an aircraft, characterized in that it comprises: at least one fuel tank (30, 30A, 30B), at least one fuel pump (32, 32A, 32B) through which fuel is withdrawn from said fuel tank (30, 30A, 30B), at least one heat exchanger (38, 38A, 38B) installed outside said fuel tank (30, 30A, 30B), which is traversed by both said hydraulic fluid and said fuel, so that heat transfer from said hydraulic fluid to said fuel, and at least one fuel line (34, 36, 34A, 36A, 34B, 36B) through which the fuel passes through said heat exchanger (38, 38A, 38B) and is returned to said fuel tank (30). , 30A, 30B).   2. Cooling device (4) according to claim 1, characterized in that it further comprises control means (40, 40A, 40B, 42, 42A, 42B, 44, 46, 48, 49) of the circulation fuel in said fuel line (34, 36, 34A, 36A, 34B, 36B), upstream of said heat exchanger (38, 38A, 38B).   SP 21972 / VD Cooling device (4) according to claim 2, characterized in that said control means (40, 40A, 40B, 42, 42A, 42B, 44, 46, 48, 49) comprise a control valve (40, 40A, 40B) located upstream of the heat exchanger (38, 38A, 38B) on said fuel line (34, 36, 34A, 36A, 34B, 36B), and controlled by a valve control unit (42). , 42A, 42B).   4. Cooling device (4) according to claim 2 or 3, characterized in that said control means (40, 40A, 40B, 42, 42A, 42B, 44, 46, 48, 49) comprise means for measuring the fuel temperature (44) in the fuel tank (30, 30A, 30B).   Cooling device (4) according to one of claims 2 to 4, characterized in that said control means (40, 40A, 40B, 42, 42A, 42B, 44, 46, 48, 49) comprise means for measuring the fuel level (46) in the fuel tank (30, 30A, 30B).   6. Cooling device (4) according to any one of claims 2 to 5 characterized in that said control means (40, 40A, 40B, 42, 42A, 42B, 44, 46, 48, 49) comprise means for detecting the operating state (48) of said fuel pump (32, 32A, 32B).   Cooling device (4) according to one of claims 2 to 6, characterized in that said control means (40, 40A, 40B, 42, 42A, 42B, 44, 46, 48, 49) comprise means for SP 21972 / VD detecting the temperature of the hydraulic fluid at the outlet of the heat exchanger (38, 38A, 38B).   8. Cooling device (4) according to any one of claims 1 to 7, characterized in that it further comprises at least one antiretour means (60) disposed on said fuel pipe (34, 36, 34A, 36A , 34B, 36B), between said heat exchanger (38, 38A, 38B) and said fuel tank (30, 30A, 30B).   9. Cooling device (4) according to any one of claims 1 to 8, characterized in that said fuel tank (30, 30A, 30B) is a supply tank of a motor (150A, 150B) of the aircraft and said fuel pump (32, 32A, 32B) is a fuel pump of said engine (150A, 150B) which sends fuel to said engine (150A, 150B) via a fuel line fuel supply (50, 50A, 50B), and in that said fuel line (34, 36, 34A, 36A, 34B, 36B) is connected bypass of said fuel supply line (50, 50A, 50B). ) of said motor (150A, 150B).   10. Cooling device (4) according to claim 9, characterized in that said fuel line (34, 36, 34A, 36A, 34B, 36B) is derived from a bifurcation (51, 51A, 51B) of the pipe of the fuel supply (50, 50A, 50B), said bifurcation (51, 51A, 51B) being located upstream of a motor circuit valve (52, 52A, 52B) of said fuel supply line (50, 50A, 50B); , 5P 21972 / VD 50A, 50B), which interrupts the fuel supply of the corresponding engine (150A, 150B).   11. Cooling device (4) according to claim 9, characterized in that said fuel line (34, 36, 34A, 36A, 34B, 36B) is derived from a bifurcation (51, 51A, 51B) of the pipe of the fuel supply (50, 50A, 50B), said bifurcation (51, 51A, 51B) being located downstream of a motor circuit valve (52, 52A, 52B) of said fuel supply line (50, 50A, 50B); , 50A, 50B), which interrupts the fuel supply of the corresponding engine (150A, 150B).   12. Cooling device (4) according to any one of claims 1 to 11, the aircraft being of the type comprising several engines (150A, 150B) each associated with a fuel tank (30, 30A, 30B) and a fuel pump (32, 32A, 32B), device (4) characterized in that it comprises as many heat exchangers (38, 38A, 38B) that the aircraft comprises motors (150A, 150B).   13. Cooling device (4) according to claim 12, said aircraft comprising a plurality of motor circuits each comprising a fuel tank (30A, 30B) nanny type. associated with one of the motors (150A, 150B), a supply pump (32A, 32B) of said engine (150A, 150B), by means of which fuel is drawn from said fuel tank (30A, 30B) then sent to said engine (150A, 150B) via a fuel supply line (50A, 50B), device (4) SP 21972 / VD characterized in that it comprises, associated with each engine ( 150A, 150B) of the aircraft: - a heat exchanger (38A, 38B) installed outside said fuel tank (30A, 30B) and traversed by both said fuel and said hydraulic fluid (24A, 150B); ), so that a thermal transfer is effected from said hydraulic fluid to said fuel, and - a fuel line (34, 36, 34A, 36A, 34B, 36B) through which the fuel passes through said heat exchanger. heat (38A, 38B), then returned to said fuel tank (30A, 30B), which is shunt-connected to said channel fuel supply (50A, 50B).   Aircraft, characterized in that it is equipped with a hydraulic fluid cooling device (4) according to any one of the Claims 1 to 13.   15. A method of cooling a hydraulic fluid circulating in a hydraulic fluid line (24) of a hydraulic circuit (2) of an aircraft, characterized in that said hydraulic fluid (24) is passed through at least one a heat exchanger (38, 38A, 38B) of a hydraulic fluid cooler (4) comprising: - at least one fuel tank (30, 30A, 30B), - at least one fuel pump (32, 32A, 32B), through which fuel is SP 21972 / VD taken from said fuel tank (30, 30A, 30B), at least one heat exchanger (38, 38A, 38B) installed at the outside said fuel tank (30, 30A, 30B), which is traversed by both said hydraulic fluid and said fuel, so that thermal transfer from said hydraulic fluid to said fuel, and at least one fuel line (34, 36, 34A, 36A, 34B, 36B) through which the fuel crosses said heat exchanger (38, 38A, 38B) and is returned to said fuel tank (30, 30A, 30B).   16. A method of cooling according to claim 15, characterized in that the heat exchange is interrupted when the temperature of the fuel in said fuel tank (30, 30A, 30B) reaches or becomes higher than a predetermined maximum fuel temperature.   Cooling method according to claim 15 or 16, characterized in that the heat exchange is interrupted when the fuel level in said fuel tank (30, 30A, 30B) reaches or falls below a predetermined minimum level of fuel, or when the fuel level in said fuel tank (30, 30A, 30B) reaches or becomes greater than a predetermined maximum level of fuel.   18. The method of cooling according to any one of claims 15 to 17, characterized in that the heat exchange is interrupted in case of SP 21972 / VD malfunction of said fuel pump (32, 32A, 32B).   19. Cooling method according to any one of claims 15 to 18, characterized in that the heat exchange is interrupted when the temperature of the hydraulic fluid at the outlet of the heat exchanger (38, 38A, 38B) reaches or becomes less than a predetermined minimum temperature of hydraulic fluid.   20. Cooling method according to any one of claims 15 to 19, characterized in that said cooling is carried out in degraded mode when a heat transfer between said hydraulic fluid and fuel is interrupted at one of the exchangers. of heat (38, 38A, 38B), and at least one further heat transfer between said hydraulic fluid and fuel continues at another heat exchanger (38, 38A, 38B).   21. Application of the method of cooling a hydraulic fluid circulating in a hydraulic circuit (2) of an aircraft according to any one of claims 15 to 20, characterized in that said hydraulic fluid comes from a drainage pipe ( 20) of a hydraulic pump (32) of said hydraulic circuit (2). SP 21972 / VD