FR3009024A1 - MOTOR INSTALLATION USING TWO FUELS INCLUDING A FUEL WITH A HIGH TEMPERATURE OF FIGURE - Google Patents

Abstract

The present invention relates to a fuel supply device (1) for a heat engine (2) intended for a rotary wing aircraft (7), said feed device (1) comprising a first and a second tank (10). , 20) respectively containing first and second fuels (11,21) able to feed said engine (2). Said second fuel (21) is heated through a heat exchanger (23) and then passes through a return valve (24) positioned after said heat exchanger (23). Said return valve (24) is driven as a function of the temperature of said second fuel (21) to direct said second fuel (21) to said second reservoir (20) when said temperature of said second fuel (21) is less than or equal to the set temperature Tc and to said heat engine (2) when said temperature of said second fuel (21) is greater than said set temperature Tc.

Description

Power plant using two fuels including a fuel with a high freezing temperature. The present invention is in the field of thermal engines and more particularly the field of devices 5 for supplying fuel to these engines. The present invention relates to a device for supplying fuel to a heat engine. This engine can be powered by a first fuel preferably used only for starting this engine and by a second fuel that has a high freezing temperature. The present invention also relates to a power plant comprising in particular at least one heat engine and at least one such fuel supply device of a heat engine and a rotary wing aircraft equipped with such a power plant. The proper functioning of a heat engine is related to the characteristics of the fuel (s) used. In particular the temperature at which a fuel begins to congeal, that is to say at which this fuel, in the liquid state, begins to solidify, has direct effects on the operation of the engine. Indeed, below a certain temperature that may be called "freezing temperature", in any fuel in the liquid state, we can see solid particles of this fuel appear when it begins to congeal. These particles can then clog the filters of this engine, increase pressure losses, disrupting its operation or even causing it to stop.

In addition, the viscosity of a fuel decreases with its temperature. In fact, the high viscosities, which can also be problematic for a heat engine, are therefore encountered at low temperatures.

The field of operation of a heat engine, such as its start or its cruising flight for example, is therefore limited to low temperatures, particularly by this freezing temperature. Low temperatures mean temperatures below 0 ° C. On the other hand, it can be noted that a high temperature of the fuel when it is injected into the combustion chamber makes it possible to reduce the consumption of the heat engine. US2011 / 0114068 discloses a heat engine that can be powered by two fuels using the same pipe and the same injector. A first fuel is used to start the engine while the second fuel is substituted for the first fuel when the engine is sufficiently hot. The first fuel is more volatile than the second fuel and thus facilitates the starting of the engine, especially at low temperatures. Similarly, there is known on some turboshaft engines, a motor / fuel oil exchanger mainly to cool the oil thus ensuring proper lubrication of the engine. Secondarily, this heat exchanger makes it possible to heat the fuel slightly and, consequently, to obtain a reduction in consumption. In addition, the document US2012 / 0260666 describes a system for the combustion of two fuels, and more particularly gases such as natural gas and synthesis gas. Two lines respectively direct the two fuels to the combustion chamber of this system while a third pipe allows to inject one of the two fuels in the combustion chamber through a set of openings. This system thus makes it possible to reduce the emissions of carbon monoxide (Cox) from nitrogen oxide (NOx). Also known is US7712451 which discloses a multiple injector and multiple fuel system for an internal combustion engine. The injectors are placed firstly at the inlet of the combustion chamber and secondly directly inside the combustion chamber. This system uses more particularly two different fuels, which can be on the one hand an alternative fuel such as ethanol, hydrogen or natural gas and on the other hand a fossil fuel such as diesel or gasoline . Each injector can inject one or the other of the two fuels and then allow to obtain a mixture of these two fuels in the combustion chamber to reduce the noise and slamming of the engine and improve its performance . In addition, in the particular case of rotary wing aircraft, the operating conditions may vary during a flight, the temperature decreasing for example with the altitude of the aircraft. The environment in which an aircraft operates can also be diversified, especially in terms of temperature. In order to avoid the appearance of problems related to these diverse and changing conditions, regulations may require the use of fuels with a very low freezing temperature, for example below -40 ° C in order to ensure safe flights. on high temperature ranges.

On the other hand, such regulation is not compatible with an efficient and economical use of alternative fuels, such as biofuels or fuels made from coal or natural gas.

Biofuels are termed "ecological" fuels, such as fuels obtained for example from biomass. The production yield of these biofuels can be related to their freezing temperatures. Indeed, these yields are high when the biomass rate converted into biofuel is high. Such yields can be obtained especially for high freezing temperatures, for example of the order of 0 ° C. Similarly, alternative fuels based on coal or natural gas can have high production yields when their freezing temperature is high, for example of the order of 0 ° C. On the other hand, good cold characteristics, ie at low temperatures, are obtained at low yield prices, and therefore for high production costs of these alternative fuels. Therefore, such alternative fuels are little used and almost exclusively for test flights and very limited temperature ranges while they have advantageous production costs.

In addition, the freezing temperature of these alternative fuels can be lowered by adding additives to expand their use cold, that is to say at low temperatures. On the other hand, the addition of these additives increases the cost of these alternative fuels and entails the cost of qualifying fuel / expensive additive mixtures. The present invention therefore aims to provide a fuel supply device for a heat engine to overcome the limitations mentioned above and to allow the use of alternative fuels having a high freezing temperature, including biofuels or fuels based on coal or natural gas. According to the invention, a fuel supply device of a heat engine comprises two segregated tanks, two feed pumps and two supply lines. A first tank contains a first fuel and a second tank contains a second fuel. The first and second tanks are in communication with a power supply unit of the engine through respectively first and second supply lines. The first feed pump is positioned between the first tank and the first supply line while the second feed pump is positioned between the second tank and the second supply line. Thus, each fuel is able to supply a power supply box, the power supply unit for injecting fuel into the engine. The first and second supply lines can be connected directly to the supply box. Preferably, the first and second supply lines meet to form a final pipe, this final pipe supplying the supply box. This device is remarkable in that a heat exchanger is interposed between the second feed pump and the second feed pipe. The second fuel thus passes through the heat exchanger leaving the second feed pump for heating the second fuel before reaching the second supply line. Thus, the power supply unit of the heat engine can be supplied on the one hand directly by the first fuel via the first feed pump and the first feed pipe and on the other hand by the second fuel pump. fuel via the second feed pump and the second feed line, which second fuel can be heated through the heat exchanger. The first fuel supplying the power supply directly must allow the operation of the engine regardless of the temperature conditions. This first fuel may have a very low freezing temperature, for example less than or equal to -40 ° C., and may constitute a starting fuel enabling the engine to start under very low temperature conditions. The second fuel can be heated by passing through the heat exchanger before supplying the power supply box 20 and, consequently, the heat engine. This second fuel can then have a setting temperature higher than the first fuel, for example greater than or equal to 0 ° C, the heat exchanger allowing the second fuel to reach a temperature above this freezing temperature. Preferably, the heat exchanger uses a portion of the thermal energy available as a result of the operation of the heat engine. The second fuel makes it possible, once it has reached a sufficient temperature, that is to say above its freezing temperature, to feed the feed box and, consequently, the heat engine without risk of malfunction of this engine. This second fuel then replaces the first fuel to supply the engine. The second fuel may be an alternative fuel, such as a biofuel obtained from biomass, for example from algae. The second fuel may also be an alternative fuel based on coal or natural gas. The use of this second fuel advantageously makes it possible to reduce, on the one hand, the polluting emissions and, on the other hand, the overall carbon balance of this heat engine during its operation. Carbon balance is the carbon dioxide (CO2) emissions released during the complete cycle of the second fuel, that is to say from its production until its combustion in the engine. In addition, through the use of the heat exchanger, no additive is added to this second fuel. In this way, the cost of this second fuel is not increased and its efficiency is not decreased. Thus, the fuel supply device of a heat engine according to the invention allows the use of a second fuel to supply this heat engine at a reasonable cost and with a carbon balance of this second fuel advantageous, a first fuel ensuring the start of this engine regardless of the temperature conditions. The heat exchanger of the fuel supply device of a heat engine according to the invention may be for example an air / fuel exchanger using the air flowing around the heat engine. This air is in fact heated by the heat generated by the heat engine during its operation and can then heat the second fuel flowing in this heat exchanger.

The heat exchanger may also be an air / fuel exchanger using the exhaust gases released by the engine during operation. These exhaust gases resulting from the combustion of the fuel in the thermal engine are indeed very hot, the temperature of the exhaust gases being, for example, of the order of 700 ° C. in the case of a turbine engine of one engine. rotary wing aircraft. These exhaust gases can then heat the second fuel in this exchanger. An intermediate fluid may also be used, the exhaust gas heating this intermediate fluid and this intermediate fluid heating the second fuel. In addition, the heat exchanger may be an oil / fuel exchanger using oil circulating in a mechanical gearbox driven by the engine. This oil is heated during operation of this mechanical gearbox and can then heat the second fuel in this heat exchanger. Advantageously, the heat exchanger can use, as in all the examples mentioned above, free and available thermal energy. Indeed, this thermal energy is released during operation of the engine or the mechanical gearbox and is not used. The heat exchanger can also use electric resistors to heat the second fuel. Such a heat exchanger requires a source of electrical power, but may allow the second fuel to be heated while the engine is stationary. As a result, the second fuel being heated even when the engine is off may possibly be used to start this engine.

The thermal power of the heat exchanger must be sufficient to raise the temperature of the second fuel from the minimum operating temperature, typically -40 ° C, to a temperature above 0 ° C which may correspond, for example, to setting temperature of this second fuel, the second fuel having a high production efficiency, as mentioned above. This thermal power required is for example of the order of 5 kW for a turbine engine with a power of about 500 kW. This thermal power is widely available on a rotary wing aircraft regardless of the second fuel heater described above. The choice of the heat exchanger used in the fuel supply device of a heat engine according to the invention depends in particular on the heat flux emitted by the thermal source chosen. Advantageously, the higher the heat flux, the smaller the heat exchanger and the lower the mass. This choice also depends on the installation constraints and more particularly the volumes available near these 20 sources. Finally, in the case where the fuel supply device of a heat engine is installed on board a rotary wing aircraft, this choice also depends on the structure of this aircraft and the definition of its "fire zones". . Indeed, a fire zone is an area in which the propagation of a fire must be contained for a fixed period of time and the fuel can circulate on board such an aircraft only in such fire zones. The heat exchanger must therefore be located in a fire zone of the aircraft. According to a first embodiment of the invention, the supply device comprises an inlet pipe and an outlet pipe of the heat exchanger as well as a return pipe opening into the second tank and a return valve. . The inlet pipe is interposed between the second feed pump and the heat exchanger while the outlet pipe is interposed between the heat exchanger and the second supply pipe. The return valve is positioned at one end of the outlet line, between this outlet line and the second supply line, and is connected to a return line. This return valve directs the second fuel leaving the heat exchanger to the second supply line and, consequently, to the heat engine or to the return line and, consequently, to the second tank. This return valve is controlled according to the temperature of the second fuel to direct the second fuel to the return line when the temperature of the second fuel is less than or equal to a set temperature Tc and to the second supply line when the temperature of the second fuel is higher than this set temperature Tc. Thus, when the second fuel is at a temperature less than or equal to the set temperature Tc, it is directed to the tank, then goes back into the heat exchanger to be heated again in order to reach a higher temperature at this setpoint temperature Tc. On the other hand, when the second fuel is at a temperature higher than this setpoint temperature Tc, it is then directed towards the second supply pipe and, consequently, towards the heat engine. In this way, if the set temperature Tc is, for example, greater than or equal to this setting temperature of the second fuel, this second fuel is sent to the heat engine only when its temperature is higher than its freezing temperature, thereby eliminating any risk of obstruction filters of this engine by solidified particles of the second fuel. The engine can then be powered only by the second fuel, the second fuel replacing the first fuel. Advantageously, the first feed pump can then be stopped when the return valve directs the second fuel to the engine, the first fuel no longer supplying the engine.

Preferably, the set temperature Tc is equal to the setting temperature of the second fuel, to which is added a safety margin making it possible to take into account, on the one hand, the viscosity dispersions specific to the second fuel and on the other hand dispersions and uncertainties related to measurements of the temperature of this second fuel. This safety margin also ensures that the second fuel is injected into the engine with a temperature above this freezing temperature. This safety margin makes it possible to take into account the circulation of the second fuel in the various pipes to the engine and the cooling that it can undergo. This safety margin can for example be of the order of 10 ° C. According to a second embodiment of the invention, the supply device comprises, in addition to the first embodiment, a bypass line and a bypass valve. This bypass valve is positioned on the inlet line between the second feed pump and the heat exchanger. The bypass line is connected to the bypass valve and opens into the outlet line. This bypass valve directs the second fuel leaving the second feed pump to the heat exchanger or to the branch line. Such a bypass valve is controlled according to the temperature of the second fuel to direct the second fuel from the second feed pump to the heat exchanger when the temperature of the second fuel is less than or equal to the set temperature Tc and directly to the outlet line via the bypass line when the temperature of the second fuel is higher than this set temperature Tc. Thus, if the second fuel is at a temperature less than or equal to the set temperature Tc, it is directed to the heat exchanger to be heated. On the other hand, if the second fuel is at a temperature higher than the set temperature Tc, it is then directed to the second supply pipe via the outlet pipe and the bypass pipe and, consequently, to the heat engine. In this way, this second fuel does not circulate in the heat exchanger when its temperature is higher than the set temperature Tc. Advantageously, this second fuel does not undergo the pressure drops associated with the crossing of this heat exchanger. Consequently, the suction capacities of the heat engine may be sufficient to draw the second fuel in the second tank to the power supply housing of the heat engine, the return valve of course directing the second fuel to the second fuel pipe. supply and, consequently, to the engine. Advantageously, the second feed pump can then be stopped.

According to a third embodiment of the invention, the feed device comprises, in addition to the second embodiment, a feed valve positioned at a junction of the first and second feed lines, between the first and second lines. feeding and final driving. The feed valve is driven according to the temperature of the second fuel to direct the first fuel from the first supply line to the final line and, consequently, to the feed box when the temperature of the second fuel is less than or equal to the set temperature Tc. The feed valve also directs the second fuel from the second feed line to the final pipe and, consequently, to the feed box when the temperature of the second fuel is higher than the set temperature Tc. According to this third embodiment, the suction capabilities of the heat engine may be sufficient to suck the first fuel in the first tank to the power supply of this engine without the use of a dedicated pump. In this case, the first feed pump can be formed to this heat engine. In addition, each valve, ie the return valve, the bypass valve and / or the supply valve, may be a thermostatic valve automatically directing the second fuel as a function of its temperature to one of the outlets of this valve. Each valve can also be driven by a computer that includes the supply device, the computer being coupled to at least one measuring instrument of the supply device. Such a measuring instrument makes it possible to measure the temperature of the second fuel in the feed device.

For example, a first measuring instrument can measure the temperature of the second fuel at the outlet of the heat exchanger to drive the return valve and a second measuring instrument can measure the temperature of the second fuel at the outlet of the second pump. supply to control the bypass valve. The supply valve can be controlled jointly by the first and second measuring instruments or by a third measuring instrument measuring the temperature of the second fuel in the second supply line. This computer can also control the stopping of the first and second feed pumps according to the temperature measurements of the second fuel and the control of the valves of the fuel supply device of a heat engine. The present invention also relates to a power plant comprising: at least one heat engine, a feed box for each heat engine, the feed box for injecting the fuel into the heat engine, mechanical gearbox driven by each heat engine, - a feed device as previously described to supply fuel to at least one engine. In addition, the present invention relates to a rotary wing aircraft comprising at least one main rotor provided with a plurality of blades and possibly a rear rotor. This aircraft comprises a power plant as mentioned above, this power plant driving each rotor of the aircraft through the mechanical gearbox. The present invention also relates to a fuel supply method for a heat engine, this thermal engine being able to be fed via a feed box by a first fuel and a second fuel, the first fuel being stored in a first tank and the second fuel being stored in a second tank. During this method of supplying a fuel to a heat engine, the first fuel is pumped into the first tank to direct it to a first supply line, the second fuel is pumped into the second tank for directed to a heat exchanger, the second fuel is circulated in the heat exchanger to heat the second fuel, the second fuel is directed to a second supply line and the feed box is energized and following, the engine 20 thermal by the first fuel or by the second fuel. Thus, the power supply unit of the heat engine can be supplied on the one hand directly by the first fuel and secondly by the second fuel, the second fuel passing through the heat exchanger to be heated. The first fuel must allow the operation of the engine regardless of the temperature conditions while the second fuel must be heated before supplying the engine when its temperature is below its freezing temperature. The second fuel allows, once it has reached a sufficient temperature to feed the power supply and, consequently, the engine, this second fuel then substituting for the first fuel.

Preferably, the heat exchanger uses a portion of the thermal energy available following the operation of the heat engine. In addition, it is possible, at the outlet of the heat exchanger, to circulate the second fuel in a return valve. Then, through the return valve, the second fuel can be directed to the second tank when the temperature of the second fuel is less than or equal to a set temperature Tc. The second fuel can then pass through the heat exchanger again, through the second feed pump to be heated. By cons, can be directed through the return valve the second fuel to the engine when the temperature of the second fuel is higher than the set temperature Tc. Indeed, the temperature of the second fuel then being at a temperature sufficient to supply the engine, it is then directed to the second supply line and, consequently, to the engine. In addition, it is possible, after pumping the second fuel, to circulate this second fuel in a bypass valve. Then, by means of the bypass valve, the second fuel can be directed to the exchanger when the temperature of the second fuel is less than or equal to the set temperature Tc and to the return valve when the temperature of the second fuel is greater than the temperature. setpoint temperature Tc.

Thus, when the second fuel is at a temperature higher than the set temperature Tc, it does not circulate in the heat exchanger and is directed directly to the second supply line via the return valve and, consequently, to the thermal motor. The second fuel then undergoes less pressure drop before reaching the power supply. On the other hand, if the second fuel is at a temperature less than or equal to the set temperature Tc, it is directed towards the heat exchanger in order to be heated.

Finally, before supplying the heat engine, it is possible to circulate the first and second fuels in a feed valve. Then, it is possible to direct towards the heat engine, thanks to this supply valve, the first fuel when the temperature of the second fuel is lower than or equal to the set temperature Tc or the second fuel when its temperature is higher than the temperature. setpoint Tc. The invention and its advantages will appear in more detail in the context of the description which follows with exemplary embodiments given by way of illustration with reference to the appended figures which represent: FIG. 1, an aircraft equipped with a power plant comprising a fuel supply device of a heat engine according to the invention, and - Figures 2 to 4, three power plants comprising three embodiments of this fuel supply device of a heat engine. The elements present in several separate figures are assigned a single reference.

FIG. 1 represents an aircraft 7 with rotary wing, comprising a power plant 50 and a main rotor 8 provided with a plurality of blades and a rear rotor 9. This power plant 50 comprises - a heat engine 2, - a housing of supply 3 connected to the heat engine 2, the supply box 3 for injecting fuel into the engine 2, - a mechanical gearbox 6 driven by the engine 2 and driving the main rotor 8 and the rear rotor 9 - A fuel supply device 1 of the engine 2. This power plant 50 rotates the main rotor 8 and the rear rotor 9 via the mechanical gearbox 6. Figures 2 to 4 show three motor installations 50 provided with different embodiments of the fuel supply device 1 of the engine 2.

In a common manner, each fuel supply device 1 of the engine 2 comprises: - two tanks 10,20, a first tank 10 containing a first fuel 11 and a second tank 20 containing a second fuel 21, - two pumps 12,22 supply, - two supply lines 16,26, - a final pipe 5, - a heat exchanger 23, - an inlet pipe 27 and an outlet pipe 28 and - a return valve 24. The first fuel 11 is directed from the first tank 10 to the first supply line 16 via the first feed pump 12. The second fuel 21 is directed from the second tank 20 to the heat exchanger 23 via of the second feed pump 22. The second fuel 21 enters the heat exchanger 23 through the inlet pipe 27 and leaves the heat exchanger 23 through the outlet pipe 28 after having been heated through this exchanger 10 tea Next, the second fuel can be directed to the second supply line 26. The first supply line 16 and the second supply line 26 meet before the feed box 3 to form the final line. supplying this power supply unit and consequently the heat engine 2. Thus, the power supply unit 3 of the heat engine 2 can be fed by this final pipe 5 on the one hand directly by the first fuel 11 and on the other hand by the second fuel 21 previously heated through the heat exchanger 23. The first fuel 11 has a very low freezing temperature, for example less than or equal to -40 ° C and is a starting fuel of the engine 2. This first fuel 11 allows the operation of the engine 2 for temperatures down to -40 ° C. The second fuel 21 has a higher freezing temperature than the first fuel 11, for example of the order of 0 ° C. The second fuel 21 may be a biofuel obtained for example from biomass such as algae, its use to reduce on the one hand the polluting emissions and on the other hand the global carbon footprint of the engine during its operation. The second fuel 21 may also be an alternative fuel based on coal or natural gas.

The second fuel 21 may, once it has reached a temperature above its freezing temperature, be used to supply the heat engine 2 without risk of freezing and, consequently, thus eliminating any risk of obstruction of the filters of this heat engine 2 by solidified particles of the second fuel 21. The second fuel 21 is then substituted for the first fuel 11 for supplying the heat engine 2. The feed device 1 comprises a return valve 24 and a return pipe 29. This return valve 24 is positioned at one end of the outlet pipe 28 and makes it possible to direct the second fuel 21 coming out of the heat exchanger 23 according to the temperature of this second fuel 21. Thus, when the temperature of the second fuel 21 is less than or equal to a set temperature Tc, the second fuel 21 is directed to the return line 29 and when the temperature of the second fuel 21 is higher below this setpoint temperature Tc, the second fuel 21 is directed to the second supply line 26 and, consequently, to the heat engine 2. The return line 29 allows a return of the second fuel 21 to the second tank 20 to return to the heat exchanger 23 to be heated again. In this way, the set temperature Tc being greater than the setting temperature of the second fuel 21, the second fuel 21 is directed to the engine 2 only when its temperature is above its freezing temperature. The heat engine 2 is then powered only by the second fuel 21, the first feed pump 12 can then be stopped to stop the supply of the engine 2 by the first fuel 11. According to a first embodiment of the invention shown in FIG. 2, this return valve 24 is a thermostatic valve which automatically directs, depending on the temperature of the second fuel 21, the second fuel 21 to the second supply line 26 or to the return line 29.

The second embodiment of the invention shown in FIG. 3 is a variant of the first embodiment comprising, in addition to the return valve 24, a bypass valve 25 and a bypass line 30. This bypass valve 25 is positioned on the inlet line 27, between the second feed pump 22 and the heat exchanger 23. The bypass line 30 is positioned between this bypass valve 25 and the outlet line 28. This bypass valve 25 allows to direct the second fuel 21 leaving the second feed pump 22 according to the temperature of the second fuel 21. Thus, when the temperature of the second fuel 21 is less than or equal to the set temperature Tc, the second fuel 21 is directed to the heat exchanger 23 and when the temperature of the second fuel 21 is higher than this set temperature Tc, the second fuel 21 is directed to the control pipe. bypass 30 and, consequently, to the return valve 24. The temperature of the second fuel 21 being greater than this setpoint temperature Tc, the return valve 24 makes it possible to direct the second fuel 21 towards the second supply pipe 26 and as a result to the heat engine 2.

In this way, the set temperature Tc being greater than the setting temperature of the second fuel 21, the second fuel 21 is directed to the heat exchanger 23 only when its temperature is less than or equal to its freezing temperature to be heated. On the other hand, if the temperature of the second fuel 21 is higher than its freezing temperature, the second fuel 21 is then directed towards the outlet pipe 28 via the bypass line 30 and, consequently, to the heat engine 2. When the second fuel 21 fuel 21 does not circulate in the heat exchanger 23, it does not undergo the pressure drops related to the crossing of the heat exchanger 23. Consequently, the suction capacity of the engine 2 may be sufficient to allow the stopping the second feed pump 22. According to this second embodiment, the feed device 1 also comprises a computer 33 and two measuring instruments 34, 35. These measuring instruments 34, 35 make it possible to measure the temperature of the second fuel 21 in the feed device 1, a first measuring instrument 34 measuring this temperature at the outlet of the heat exchanger 23 and a second measuring instrument 35 measuring this temperature at the output of the second feed pump 22. The computer 33 is coupled to the measuring instruments 34,35 and can thus drive the return valves 24 and bypass 25 to direct the second fuel 21. This calculator can also control the shutdown of the feed pumps 12,22. The third embodiment of the invention shown in FIG. 4 is a variant of the second embodiment comprising, in addition to the return valves 24 and the bypass valves 25, a supply valve 31. This supply valve 31 is positioned at a junction of the first and second supply lines 16,26 and allows to direct the first fuel 11 or the second fuel 21 to the final pipe 5 and, consequently, to the engine 2 according to the temperature of this second fuel 21. Thus, when the temperature of the second fuel 21 is less than or equal to the set temperature Tc, the first fuel 11, coming from the first supply line 16, is directed to the heat engine 2 via the final pipe 5 and the power supply box 3. On the other hand, when the temperature of the second fuel 21 is higher than this set temperature Tc, the second fuel 21, coming from the second supply line entation 26, is directed to the heat engine 2 via the final pipe 5 and the supply box 3. According to this third embodiment, the feed device 1 also comprises a computer 33 and three measuring instruments 34,35, 36, a first measuring instrument 34 measuring the temperature of the second fuel 21 at the outlet of the heat exchanger 23, a second measuring instrument 35 measuring this temperature at the outlet of the second feed pump 22 and a third measuring instrument 36 measuring the temperature in the second supply line 26. The computer 33 is coupled to the measuring instruments 34,36 and can thus control the return valves 24 and supply 31 and the stoppage of the feed pumps 12,22 . For this third embodiment, the suction capacity of the heat engine 2 may allow to suck the first fuel 11 into the first tank 10 without the use of a dedicated pump. In this case, the first feed pump 12 can be formed by the heat engine 2. In addition, the heat exchanger 23 uses a portion of the thermal energy available as a result of the operation of the heat engine 2.

According to the first and second embodiments respectively shown in Figures 2 and 3, the heat exchanger 23 is an air / fuel exchanger using the air flowing around the engine 2. This air is heated by the heat released by the engine 2 during its operation and directed to the heat exchanger 23 by the first transfer line 32. This air can then heat the second fuel 21 when it passes through the heat exchanger 23. According to the third embodiment shown in FIG. 4, the heat exchanger 23 is an oil / fuel exchanger using oil circulating in the mechanical gearbox 6 driven by the engine 2. This oil is heated during operation of this mechanical gearbox 6 and directed to the heat exchanger 23 through the second transfer line 38. This air can then heat the second fuel 21 in this heat exchanger 23. Advantageously, these two types of heat exchanger 23 use free thermal energy available. Indeed, this thermal energy is released during operation of the heat engine 2 or that of the mechanical gearbox 6 and is not used. In addition, the heat exchanger 23 may also be an air / fuel exchanger using the exhaust gas released by the heat engine 2 during its operation.

In addition, the heat exchanger 23 can also use electric resistors to heat the second fuel. This heat exchanger 23 then requires a source of electrical energy.

Naturally, the present invention is subject to many variations as to its implementation. Although several embodiments have been described, it is well understood that it is not conceivable to exhaustively identify all the possible modes. It is of course conceivable to replace a means described by equivalent means without departing from the scope of the present invention.

Claims (24)

REVENDICATIONS1. Fuel supply device (1) for a heat engine (2), said feeder (1) comprising two reservoirs (10, 20), two feed pumps (12, 22) and two fuel lines (2). supply (16,26), a first reservoir (10) containing a first fuel (11) and a second reservoir (20) containing a second fuel (21), said first and second reservoirs (10,20) being in communication with a power supply unit (3) of said heat engine (2) via respectively first and second supply lines (16,26), a first feed pump (12) being positioned between said first reservoir (10) and said first supply line (16) and a second feed pump (22) being positioned between said second reservoir (10) and said second supply line (16), characterized in that a heat exchanger (23) is interposed between said second feed pump (22) and said second supply line (16) for heating said second fuel (21) before reaching said second supply line (26). 20 2. Feeding device (1) according to claim 1, characterized in that said feed device (1) comprises an outlet pipe (28) interposed between said heat exchanger (23) and said second feed pipe ( 16) and a return valve (24) positioned between said outlet line (28) and said second supply line (26) and connected to a return line (29) opening into said second tank (20) said return valve (24) being driven as a function of the temperature of said second fuel (21) to direct said second fuel (21) to said return line (29) when said temperature of said second fuel (21) is less than or equal to at a set temperature Tc and to said second supply line (26) when said temperature of said second fuel (21) is greater than said set temperature Tc. 3. Feeding device (1) according to claim 2, characterized in that said feed device (1) comprises an inlet pipe (27) interposed between said second feed pump (22) and said heat exchanger (23) and a bypass valve (25) positioned on said inlet line (27) and connected to a branch line (30), said bypass line (30) opening into said outlet line (28). ), said bypass valve (25) being driven as a function of the temperature of said second fuel (21) to direct said second fuel (21) from said second supply pump (22) to said heat exchanger (23) when said temperature of said second fuel (21) is less than or equal to said set temperature Tc and to said bypass line (30) when said temperature of said second fuel (21) is higher than said set temperature Tc. 4. Feeding device (1) according to any one of claims 2 to 3, characterized in that said feed device (1) comprises a feed valve (31) positioned at a junction of said first and second pipes supply valve (16,26), said supply valve (31) being driven according to the temperature of said second fuel (21) to direct said first fuel (11) from said first supply line (16) to said supply box (3) when said temperature of said second fuel (21) is less than or equal to the set temperature Tc and directing said second fuel (21) from said second supply line (26) to said housing supply (3) when said temperature of said second fuel (21) is greater than said set temperature Tc. 5. Feeding device (1) according to any one of claims 2 to 4, characterized in that each valve (24,25,31) may be a thermostatic valve automatically directing said second fuel (21) according to the temperature of said second fuel (21). 6. Feeding device (1) according to any one of claims 2 to 5, characterized in that said feeding device (1) comprises a calculator (33) and at least one measuring instrument (34,35, 36) measuring the temperature of said second fuel (21) in said feeder (1), each valve (24,25,31) being drivable by said calculator (33), said calculator being coupled to each measuring instrument ( 34,35,36). 7. Feeding device (1) according to any one of claims 2 to 6, characterized in that said set temperature Tc is greater than or equal to the setting temperature of said second fuel (21). 8. Feeding device (1) according to any one of claims 1 to 7, characterized in that said second fuel (21) has a setting temperature higher than said first fuel (11). 9. Feeding device (1) according to claim 8, characterized in that said first fuel (11) is a fuel having a freezing temperature of less than or equal to -40 ° C while said second fuel (21) is a fuel having a freezing temperature greater than or equal to 0 ° C. 10. Feeding device (1) according to any one of claims 1 to 9, characterized in that said second fuel (21) is a biofuel. 10 11. Power plant (50) comprising: - at least one heat engine (2), - a feed box (3) for each heat engine (2), said feed box (3) for injecting the fuel in said engine (2), - a mechanical gearbox (6) driven by each engine (2), characterized in that said powerplant (50) comprises at least one feed device (1) for feeding at least one heat engine (2), said feed device (1) being according to any one of claims 1 to 10. 12. Powerplant (50) according to claim 11, characterized in that said heat exchanger (23) uses oil flowing in said mechanical gearbox (6) for heating said second fuel (21). 25 13. Powerplant (50) according to claim 11, characterized in that said heat exchanger (23) uses air flowing around at least one heat engine (2) for heating said second fuel (21). 14. Powerplant (50) according to claim 11, characterized in that said heat exchanger (23) uses exhaust gas from at least one heat engine (2) for heating said second fuel (21). 15. Powerplant (50) according to claim 14, characterized in that said heat exchanger (23) uses an intermediate fluid heated by said exhaust gas of at least one heat engine (2) for heating said second fuel ( 21). 16. Powerplant (50) according to claim 11, characterized in that said heat exchanger (23) uses electric resistors to heat said second fuel (21). 17. Powerplant (50) according to any one of claims 11 to 16, characterized in that said first feed pump (12) can be formed by said engine (2). 20 18. Aircraft (7) with rotary wing, comprising at least one main rotor (8) provided with a plurality of blades, characterized in that said aircraft (7) comprises a power plant (50) according to any one of the claims 11 to 17, said power plant (50) rotating each main rotor (8) through said mechanical gearbox (6). 19. A method of supplying fuel to a heat engine (2), said heat engine (2) being powered by a first fuel (11) and a second fuel (21), said first fuel (11) being stored in a first tank (10) and said second fuel (21) being stored in a second tank (20), during which said first fuel (11) is pumped into said first tank (10) to direct it to a first line 10 (16) is pumped said second fuel (21) into said second tank (20) to direct it to a heat exchanger (23), said second fuel (21) is circulated in said heat exchanger (23). ) for heating said second fuel (21), directing said second fuel (21) to a second supply line (26) and - supplying said engine (2) with said first fuel (11) or said second fuel (21). 20. A method of supplying fuel to a heat engine (2) according to claim 19, characterized in that - at the output of said heat exchanger (23), said second fuel (21) is circulated in a return valve. (24), said second fuel (21) is directed through said return valve (24) to said second reservoir (10) when the temperature of said second fuel (21) is less than or equal to a set temperature Tc and to said heat engine (2) when said temperature of said second fuel (21) is greater than said set temperature Tc. 21. A method of supplying fuel to a heat engine (2) according to claim 20, characterized in that - before supplying said engine (2), said first and second fuels are circulated (11,21). in a supply valve (31), said first fuel (11) coming from said first supply line (16) to said engine (2) is directed by said supply valve (31) when said temperature of said second fuel (21) is less than or equal to said set temperature Tc and said second fuel (21) from said second supply line (26) is directed to said engine (2) when said temperature of said second fuel (21) is reached. ) is greater than said set temperature Tc. 22. A method of supplying fuel to a thermal engine (2) according to any one of claims 20 to 21, characterized in that after pumping, said second fuel (21) is circulated in a bypass valve ( 25), said second fuel (21) is directed by said bypass valve (25) to said exchanger (23) when the temperature of said second fuel (21) is less than or equal to said set temperature Tc and to said return valve (24) when said temperature of said second fuel (21) is greater than said set temperature Tc. 23. A method of supplying fuel to a heat engine (2) according to claim 22, characterized in that one stops pumping the second fuel (21) when said second fuel (21) is directed to said bypass line (30) via said bypass valve (25), then to said second supply line (26) via said return valve (24). 24. A method of supplying fuel to a heat engine (2) according to any one of claims 20 to 23, characterized in that one stops pumping the first fuel (21) when one directs said second fuel (21) to said second supply line (26) via said return valve (24).