GENERAL TECHNICAL FIELD
The invention relates to the supply of a power unit with fuel, and in particular, the management of the fuel phase state.
More specifically, the invention relates to power units comprising a heat engine and an electric machine.
The term "combustion turbine engine" in the present context, machine for converting thermal energy of a mechanical energy working fluid by expanding said working fluid into a turbine.

More particularly, the working fluid may be a flue gas resulting from the chemical reaction of a fuel with air in a combustion chamber after compression of the air in a compressor driven by the turbine through a first rotary shaft.

Thus, the thermal turbine engines, such as included in the present context include turbo single or double flow, turboprop engines, turboshaft engines or gas turbines, among others.

In the following description, the terms "upstream" and "downstream" are defined relative to the normal flow direction of the working fluid in the turbine engine.

The fuel feeding internal combustion engines turbine may include impurities, particularly water in suspension. At normal temperatures the presence of traces of water in the fuel is not very problematic. However, when temperatures are low, this water can freeze. The resulting ice particles may eventually block the passage of the fuel, including agglomerating at the input of filters typically used to prevent the passage of other solid impurities. Accordingly, it should avoid icing in the fuel system.

STATE OF THE ART

A first solution against the gel fuel is to add additives, costly, toxic and binding. This solution is deliberately excluded.

A second solution is, as shown in US 20120240593, to recover the heat generated by an electronic circuit, in this case a power conversion electronics (GCU for "Generator Control Unit"), to warm the fuel and keep the latter freezes. A heat exchanger allows the heat transfer.

The GCU functions as a radiator.

In an Old document, the gestion du transfert de chaleur between the GCU and the filter if fait par contrôle du débit de fluide or by ajout d'un radiateur électrique supporters supplémentaire here Permet d'une part of the heat will generate supplémentaire et en de solliciter mandate the GCU, are here to tour chauffe mandate.

Nevertheless, there is a risk, not mentioned in the document cited above, the fuel receives too much energy and to reach its vaporization temperature. Indeed, some embedded electronic operate for very short periods, implying a higher power. In addition, the voltage used, often on the order of a few tens of volts, causes very high amperage, resulting in significant heat generation.

This vaporization phenomenon must imperatively be avoided.

PRESENTATION DE L'INVENTION

The invention aims to remedy the aforementioned drawbacks by providing an assembly comprising:

A fuel supply circuit configured to supply a heat engine fuel turbine,

An electronic module,

An energy source to supply the electronic module into electricity,

A heat exchanger positioned to allow a flow of heat from the electronic module to the fuel supply circuit,

the assembly being characterized in that the electronic module comprises a phase change material (PCM), configured to change state when its temperature reaches a predetermined temperature of phase change.

With PCM, the temperature rise is better distributed over time, which can limit temperature peaks and thus avoid reaching the gasoline vaporization temperature.

In addition, the PCM material protects the electronics module of the temperature peaks that can damage it.

The PCM material and serves to distribute the flow of heat in an optimized way between the electronic module and the fuel.

In order to prevent the fuel to vaporize the phase-change material of the phase change temperature is selected so as to be

lower than said fuel vaporization temperature which circulates in the fuel supply circuit.

The invention may include the following characteristics, taken alone or in combination:

- said predetermined temperature of phase change is less than the fuel vaporization temperature,

- the electronic module is an electronic power module, configured to convert the energy supplied by the energy source,

- the phase change temperature is less than 150 ° C, preferably below 140 ° C.

- the electronic module comprises the following:

a base substrate forming a support,

electronic components positioned on the support, and wherein the heat exchanger is located, relative to the base substrate on the side opposite to the components,

- the electronic components are encapsulated in the phase change material PCM,

- PCM phase change material is integrated into the base substrate,

- the electronic module comprises a cold plate, and wherein the phase change material is integrated with the cold plate.

- the cold plate is positioned between the base substrate and the heat exchanger,

- the heat exchanger is integrated in the cold plate,

The invention also provides a motor group comprising:

A combustion turbine engine,

An assembly as previously described,

wherein the fuel feed circuit is configured to supply the engine.

The energy source is preferably an electric machine operable as a motor or a generator and wherein the electric machine is mechanically coupled to a rotating shaft of the engine.

The invention also provides a fuel heating process using a set or a power unit as described above, wherein the fuel is heated in the heat exchanger of the fuel supply circuit by heat from the electronic module via the PCM phase change material.

The invention provides also the use of PCM phase change material to control heat transfer between on the one hand an electronic module in which heat when energized, and on the other hand a turbine for fuel gas, through a heat exchanger.

PRESENTATION DES FIGURES

Other features, objects and advantages of the invention will become apparent from the following description, which is purely illustrative and not restrictive, and must be read with the accompanying drawings, wherein:

- Figure 1 illustrates schematically a power electronics module and a heat exchanger motor unit, shown without PCM material for clarity,

- Figure 2 is similar to Figure 1, but with three PCM integration variants, and with an addition of a cold plate,

- Figure 3 shows temperature curves related to the use of phase-change material,

- Figure 4 schematically illustrates an aircraft with an engine having two engines and two electric motor-generators,

- Figure 5 illustrates more specifically the engine group.

DETAILED DESCRIPTION

Referring to Figure 1, it defines an assembly comprising a fuel supply circuit 15, an electronic module 14 and an energy source 13 that provides energy, typically electricity to the module 14.

The power supply circuit in carburantl5 is operable to power a heat engine fuel turbine. Of particular embodiments will be detailed later.

The electronic module 14 generally comprises at least one electronic circuit on which are interconnected electronic components adapted to process electrical signals (information or energy).

Therefore, when approached by the energy source 13, the module 14 generates heat. So that this heat is transmitted to the fuel supply circuit 15, a heat exchanger 16 is provided. Typically, the heat exchanger 16 is positioned between the electronic module 14 and the fuel supply circuit 15a, 15b.

The heat exchanger 16 makes it possible to optimize the heat flow between the module 14 and the power supply circuit 15. It may take different forms such as a plate heat exchanger, fin, or simply in the form of pipes branching favoring heat exchange.

The electronic module 14 comprises in one embodiment a base substrate 100 forming medium having fixed electronic components 110, such as bipolar transistors insulated gate, diodes, capacitors, inductors, etc. As shown in Figure 1, these components 110 may require

transmitters 112, doors 114, a collector 116 and son links 118, for example.

Different layers of materials, such as a brazed joint 102, a copper flange 104, another insulating substrate 106, for example ceramic to realize the interconnections between the semiconductor and with external circuits on the copper flange 104 , are conventionally provided for the operation of the electronic module.

To better regulate the transfer of energy, the electronic module 14 includes a phase change material PCM referenced to "Phase-change material". Figure 2 shows various detailed embodiments thereafter.

PCM materials change state, generally in the solid state to the liquid state, since their melting temperature is reached. As there are also materials which PCM phase change from a solid or liquid state to a gaseous state, more generally speaking the phase change temperature Tm.

This temperature Tf is a characteristic of the PCM material.

In certain flight phases of an aircraft, the electric power demand of an electrical system can be very high at times that do not exceed a few tens of seconds or even a minute. In these conditions where significant heat dissipation is required, but that is cyclical or transient, using PCM material provides better thermal management as close to 110 critical electronic components such as the static components, capacitors, self, etc.

Indeed reaching its melting temperature, thus passing from the solid state to the liquid state the phase-change material will absorb an amount of heat while remaining at the same temperature (sufficient time that the entire material changed state ) and a thermal transfer will then take place between the electronic components 110 within the electronics module 14 and the PCM material. This absorption is related to the enthalpy change of state of the PCM material, also known as latent heat, which corresponds to the energy to be received by a unit mass of the material to change state.

The PCM will then absorb the peak temperature.

Indeed, one of the main problems of the development of electronic on board aircraft is that of the temperature resistance of 110 electronic components including those brazed / welded or on the substrate 100. In fact the thermomechanical stresses between the component 110 and the substrate 100 may in some cases cause delamination of the solder or solder the component on the substrate, which can destroy the component. Such PCM uses are already known, as in US 20130147050.

The PCM also enables gains in sizing and occupied volume. In fact, the electronic components 110 such as transistors, capacitors, inductors, may be sized not on a maximum peak temperature but a lower temperature averaged.

Therefore, the PCM material has a primary role, which is to absorb the heat to prevent the electronic module 14 to exceed a critical temperature. 3 illustrates the absorption as a function of time: the curve CO is the temperature rise of the electronic module 14 in the absence of phase-change material, the Ci to C18 curves represent the temperature rise of the electronic module 14 in the presence PCM material for different thermal resistances between the PCM material and the substrate 100, the areas C23 to C27 represent the rise in temperature of the PCM material (associated with the curves C13 to C17). It is noted that the phase change temperature Tm of the PCM material is slightly less than 120 ° C.

However, as previously stated, the electronic module 14 also has the function of heating fuel. Now it turns out that power peaks can generate excessive heat and the management of heat transfer is problematic.

Therefore, the PCM material, which has absorbed the heat peak, gradually returns to the heat exchanger 16a, 16b. Thus, the PCM material enables averaging the heat transfer between the electronic module 14 and the fuel.

Thus, the said fuel vaporization risks are largely reduced.

The integration of a phase-change material in such heat exchange architecture between the electronic module 14 and the fuel circuit 15 makes it possible to a thermal barrier which, by spreading in time the heat and protects the fuel vaporization, while protecting the module 14 from overheating. Furthermore, unlike conventional uses of PCM materials whose goal is simply to absorb heat during a relatively short time interval, the PCM material is here used as a radiator, from the stored energy via the electronic module 14 .

So that this function is satisfied, selecting a phase-change material whose phase change temperature Tm is lower than the fuel vaporization temperature Tv.

the following fuels are known, with their typical temperature vaporization start Tv indicated in brackets cast (180 ° C), JP8 and JP8 + 100 (170 ° C), Jetal (170 ° C), JP5 (200 ° C), F76 (200 ° C), TS1 (160 ° C) and RT (160 ° C).

For these fuels, a temperature Tf below 150 ° C, preferably 140 ° C, more preferably less than or equal to 130 ° C is suitable. Complementarily, the temperature Tf is higher than 120 ° C, to prevent the change of state is completely

performed while the electronic module 14 has not yet reached temperatures might jeopardize its operation.

There are also known the following fuels with their vaporization temperature Tv in parentheses: JetB and JP4 (80 ° C), and AvGas AutGas (60 ° C).

For these fuels, Tm temperature below 50 ° C is suitable.

The integration of PCM materials in the electronic module can be performed in different ways, as shown in Figure 2, which show three variants, not necessarily exclusive of each other.

In a first variant, the electronic components 110 are encapsulated in the PCM material 1. For this, a specific matrix comprising phase-change material is used. This alternative requires that electronic components 110 are sealed.

In a second variant, the PCM2 material may be integrated in the substrate 100. In particular familiar with document US2013 / 0147050 which discloses such integration in the substrate 100. A specific volume must then be provided in the substrate 100.

In a third alternative, a cold plate 120 is provided against the substrate 110 on the side opposite to the electronic components 110. The cold plate 120 is positioned between the heat exchanger 16 and the base substrate 100. The cold plate 120 has the function of promoting the cooling of the electronic module 14. the PCM3 material is then integrated with the cold plate 120.

These three variants can be combined without difficulty.

Various types of exchangers have been previously described. Depending on the type of exchanger, the relative positioning of the fuel system and the base substrate and / or the cold plate can be adapted. In particular, the heat exchanger can be accommodated in the base substrate 100 or in the cold plate 120. The heat exchanger can then take the form of a fluid circuit, such as a branch pipe, arranged in the plate. The circulation of the fluid is then preferably enforced by a dedicated pump.

The phase-change material may include salt hydrates, paraffins, and / or alcohols.

The advantage of PCM material also lies in the mass gain and volume compared to other technologies.

In a particular embodiment, the electronic module 14 is a power module, configured to convert the energy supplied by the energy source. It is therefore particularly subject to temperature increases, especially for very short time during which he is sought.

In this embodiment, the electronic components 110 may in particular be power semiconductors.

Now a more comprehensive architecture within the framework of a helicopter will be described. However, the invention is implemented on any aircraft comprising electronics generates heat, regardless of the number of motor or type.

4 illustrates an aircraft 1 in rotary wing, more specifically a helicopter having a main rotor 2 and an anti-torque tail rotor 3 coupled to a motor unit 4 for their actuation. The motor group 4 illustrated comprises a first heat engine 5a and a second 5b engine. These heat engines 5a, 5b are thermal turbine engines and more

specifically turbine whose power take-off shafts 6 are both connected to a main gearbox 7 for actuating the main rotor 2 and tail rotor 3.

The motor unit 4 is illustrated in greater detail in Figure 5. Each engine 5a, 5b comprises a compressor 8, a combustion chamber 9, a first turbine 10 connected by a rotary shaft 11 to the compressor 8 and a second turbine 12 or free turbine, coupled to the power take-off shaft 6. the compressor assembly 8, combustion chamber 9, the first turbine 10 and rotary shaft 11 is also known as the "gas generator". The rotary shaft 11 of each gas generator is mechanically coupled to the power source 13a, 13b, which is specifically an electric machine 13a, 13b generally in the form of a generator-motor, electrically connected to the electrical module 14a , 14b, which is here a power electronics module, which is more specifically a power converter connected also electrically to an electrical storage device 20 and to an electrical network of the aircraft 1. This electric storage device 20 can e.g. be a battery, although other electrical storage devices (eg. ex. fuel cells or flywheels) are also conceivable.

The electric machines 13a, 13b serve as the start of combustion engines 5a, 5b corresponding to the power generation after the startup. In the first case, the electric machine 13a, 13b operating in motor mode, and the electronic power module 14a, 14b ensures its electrical supply from the electrical network of the aircraft and / or the electrical storage device 20. in the second case, the electric machine 13a, 13b operates in generator mode, and the electronic power module 14a, 14b adjusts the generated current to a voltage and amperage

suitable for supplying the electrical network of the aircraft and / or the electrical storage device 20.

In addition, however, each electric machine 13a, 13b can also serve to maintain the engine 5a, 5b corresponding to the standby mode, even during the flight of the aircraft 1, by rotating the rotary shaft 11, with the chamber 9 burning off at a reduced speed Nveille, which may be, e.g., between 5 and 20% of a rated speed NI of the rotary shaft 11. Indeed, it is known that the maintenance of a combustion engine turbine in standby mode on a multi-engine aircraft saves fuel by cruising flight and accelerate its eventual restart.

The power supplied by the motor unit 4 may vary substantially along the flight stage of the aircraft 1. Thus, the power required for the cruising speed is normally substantially less than the maximum continuous power of the drive unit 4, and even less compared with its maximum take-off power. Or, the motor unit 4 is dimensioned according to the latter, it is substantially oversized with respect to the power required for the cruising regime. Accordingly, cruise, with the two heat engines 5a, 5b in operation, they could end up far from their optimum operating speed, which would result in a relatively high specific fuel consumption. In principle, with a drive unit comprising a plurality of combustion engines, it is possible to maintain the cruising speed with at least one of these off heat engines. With other combustion engines running on a diet so close to their optimum speed, the specific fuel consumption can be reduced. To enable such a mode of operation of a motor group, ensuring the immediate start off the engine, it has been proposed in GB 2967132 to maintain this engine off in standby mode.

In the power unit 4 illustrated in Figure 5, the first heat engine 5a is turned off while the aircraft 1 cruising speed, while the second 5b engine provides the power to the main rotor 2 and tail rotor 3 through the main gearbox 7. the electric machine 13b associated with the second engine 5b simultaneously ensures the supply to the electric network of the aircraft 1 through its electronic power module 14b and feeding of the machine electrical 13a through its electronic 14a. In order to ensure starting of the first engine emergency 5a, particularly in the event of failure of the second heat 5b engine, the first engine 5a is kept in standby mode by actuating the rotary shaft 11 by the corresponding electric machine 13a , supplied through its electronic power module 14a.

For supplying heat engines 5a, 5b fuel, each of which is associated with fuel supply circuits 15a, 15b, with the heat exchanger 16a, 16b and, in addition, a fuel filter 17a, 17b located downstream of the heat exchanger 16a, 16b in the direction of the flow of fuel to the engine 5a, 5b.

As illustrated in Figure 3, each heat exchanger 16a, 16b is adjacent to a base 14a of the power electronic module, 14b (e.g., a cold plate 21) corresponding, in a housing 22 which can be sealed and the common electronic power module 14a, 14b and the heat exchanger 16a, 16b corresponding, so that the fuel flowing through the heat exchanger 16a or 16b to be heated by the heat generated by the operation of the electronic power module 14a, 14b, and 14a simultaneously contribute to the cooling of the power electronics module, 14b to enable it to function in an optimum temperature range. Typically, each electronic power module 14a, 14b can handle a power Pe of the order of 100 kW with heat losses of less than 10%, thus resulting in a heating power Ph, e.g., less than 10 kW or even less than 1 kW.

However, each power electronics module 14a, 14b can have a normal operating mode and a degraded electrical efficiency operating mode can be implemented to generate additional heat for heating fuel. This degraded performance mode of operation may be obtained for example by imposing semiconductor 14a of the power electronic module, 14b a higher cutting frequency than that which would normally be applied according to usual electrical design criteria.

Each fuel supply circuit 15a, 15b may also include a bypass line 18a, 18b of the heat exchanger 16a, 16b and a three-way valve 19a, 19b for controlling the flow of fuel by heat exchanger 16a, 16b or the bypass line 18a, 18b.

For heating the fuel supplied to an internal combustion engines 5a, 5b during start thereof at low temperature prior to lighting the combustion chamber 9, the latter is directed through the heat exchanger 16a, 16b corresponding in wherein it is heated by the heat generated by the operation of the electronic power module 14a, 14b through which the electric machine 13a, 13b is electrically energized to rotate the rotary shaft 11 of the engine 5a, 5b. If the heat generated by the power electronics 14a of module 14b in normal operation is insufficient to allow a quick start without risk of clogging of the fuel filter 17a, 17b by particles of water ice, a fashion degraded electrical performance operation of the electronic power module 14a, 14b may be implemented to increase the heat generation in this module, and transmitting, through the heat exchanger 16a, 16b, to the fuel.

For against, it is not necessary to heat the fuel to one or the other heat engines 5a, 5b, or to cool the electronic power module 14a, 14b associated with the three-way valve 19a, 19b can direct the fuel through the bypass pipe 18a, 18b corresponding.

claims
1. An assembly comprising:
A fuel supply circuit (15, 15a, 15b) configured to supply a heat engine fuel turbine,

An electronic module (14, 14a, 14b),

A power source (13, 13a, 13b) for supplying the electronic module (14, 14a, 14b) into electricity,

A heat exchanger (16, 16a, 16b) positioned to allow a flow of heat from the electronic module (14, 14a, 14b) to the fuel supply circuit (15, 15a, 15b),

the assembly being characterized in that the electronic module (14, 14a, 14b) comprises a phase change material (PCM), configured to change state when its temperature reaches a predetermined temperature phase change (Tf).

2. Assembly according to the preceding claim wherein said predetermined temperature of phase change (Tf) is less than the fuel vaporization temperature (Tg).

3. An assembly according to any preceding claim, wherein the electronic module (14, 14a, 14b) is an electronic power module, configured to convert the energy supplied by the energy source (13, 13a, 13b ).

4. An assembly according to any preceding claim, wherein the phase change temperature (Tm) is less than 150 ° C, preferably below 140 ° C.

5. An assembly according to any preceding claim, wherein the electronic module (14, 14a, 14b) comprises the following elements:

- a base substrate (100) forming a support,

- the electronic components (110) positioned on the support, and wherein the heat exchanger (16, 16a, 16b) is located, relative to the base substrate (100) on the side opposite to the components (110).

6. The assembly of claim 5, wherein the electronic components (110) are encapsulated in the phase change material (PCM).

7. An assembly according to claim 5 or 6, wherein the phase change material (PCM) is integrated to the base substrate (100).

8. An assembly according to claim 5 or 6 or 7, wherein the electronic module (14, 14a, 14b) comprises a cold plate (120) and wherein the phase change material (PCM) is integrated with the cold plate.

9. Motor unit (4) comprising:

A combustion turbine engine (5a, 5b)

An assembly according to any one of the preceding claims,

wherein the fuel supply circuit (15, 15a, 15b) is configured to supply the heat engine (5a, 5b).

10. Motor unit (4) according to the preceding claim, wherein the energy source is an electrical machine (13, 13a, 13b) being operable as a motor or a generator and wherein the electric machine is mechanically coupled to a rotating shaft the engine.

11. Fuel heating method using an assembly according to any one of claims 1 to 8 or a power unit according to any one of claims 9 to 10, wherein the fuel is heated in the heat exchanger (16, 16a, 16b) of the fuel supply circuit (15, 15a, 15b) by heat from the electronic module (14) through the phase change material (PCM).