METHOD FOR ADJUSTING A FUEL CELL COOLING SYSTEM

Abstract

Method for adjusting a cooling system (8) of a fuel cell (6) intended to power an electric thruster (3) of an aircraft propulsion unit (1) (2), the cooling system (8) comprising a heat exchanger (9) placed in a channel (10) supplied with air by an inlet (11) and a shut-off device (12) for the inlet (11), the fuel cell (6) having a core (7) placed in the channel (10) downstream of the heat exchanger (9), the method comprising chronologically the steps of: a) measuring the temperature of the core (7) of the fuel cell (6); c) determining the setting of the shut-off device (12) from the temperature of the core (7) measured in step a), so that the temperature of the core (7) remains below a predetermined threshold temperature; d) adjusting the shut-off device (12) according to the setting determined in step c). Figure for the abridged version: 1

Description

Title of the invention: METHOD FOR ADJUSTING A COOLING SYSTEM OF A FUEL CELL Technical field of the invention

[0001] The present invention relates to a method for adjusting a cooling system of a fuel cell. The invention also relates to a propulsion unit comprising a fuel cell cooled by a cooling system which is adjusted by such a method. Technical background

[0002] An aircraft may comprise a propulsion unit equipped with one or more electric thrusters each comprising, for example, a propeller driven by an electric motor.

[0003] The propulsive electrical energy required to power the electric thruster(s) is provided in part or in full by one or more electrical generators (or electrical generators).

[0004] In the remainder of the application, we will focus on the particular case in which the electric generator is a fuel cell better known by the acronym “PAC” or the English term “fuel cell”.

[0005] A fuel cell has the advantage of producing few polluting and noise emissions.

[0006] Such a fuel cell converts the chemical energy contained in a fuel / oxidant pair (for example the hydrogen / oxygen pair) into electrical energy. The fuel cell comprises in particular a core formed by a stack of electrochemical cells.

[0007] The electrochemical reaction of the fuel / oxidant couple produces not only electricity but also heat which is important to evacuate, to allow its operation.

[0008] For this, it is known to cool the core of the fuel cell with a cooling system which notably comprises a cooling circuit in which a heat transfer fluid circulates. To evacuate the thermal energy of the heat transfer fluid into the external environment, the cooling circuit comprises one or more heat exchangers placed in a streamlined vein which is supplied with air by an air inlet (or an air intake).

[0009] The passage of air in the vein generates an aerodynamic drag which significantly penalizes the overall performances of the propulsion unit and the aircraft. Especially since the vein and the heat exchangers generally have large dimensions to meet cooling needs in the most penalizing case, namely when the aircraft is at low speed and low altitude (high temperature), and the fuel cell is operating at full capacity (for example during takeoff).

[0010] To limit aerodynamic drag, it is known to install a flap in the vein, the flap being open when the fuel cell is active and closed when the fuel cell is inactive.

[0011] Engine manufacturers note that such a flap adjustment could be improved.

[0012] Indeed, it is found for example that the flow of air entering the vein is too high when the aircraft is cruising, only a part of this air being necessary to cool the core of the fuel cell. This is explained in particular by the fact that the temperature of the air at altitude is lower than the temperature of the air on the ground.

[0013] Engine manufacturers also note that the temperature of the fuel cell core depends on numerous parameters, including flight conditions (aircraft altitude, aircraft speed, weather, etc.) and its operating regime.

[0014] The objective of the present invention is therefore to provide a simple, effective and economical solution for correctly cooling the core of the fuel cell while minimizing aerodynamic drag. Summary of the invention

[0015] The invention thus proposes a method for adjusting a cooling system of a fuel cell which is intended to supply an electric thruster of an aircraft propulsion unit, the cooling system comprising at least one heat exchanger placed in a vein supplied with air by an inlet and a device for closing the inlet which is movable, the fuel cell comprising a core placed in the vein downstream of the heat exchanger, the core being formed by a stack of electrochemical cells, the method chronologically comprising the steps consisting of: a) measure the temperature of the fuel cell core; c) determining the setting of the shutter device from the core temperature measured in step a), such that the core temperature remains below a predetermined threshold temperature; d) adjusting the sealing device according to the setting determined in step c), so as to adjust the air flow entering the vein.

[0016] Such an adjustment method takes into account the temperature of the core of the fuel cell so as to quickly adapt the flow of air entering the vein according to the cooling needs of the core, and to minimize the aerodynamic drag. produced by the passage of air through the vein throughout a flight (from takeoff to landing), benefiting the overall performance of the propulsion unit and the aircraft (consumption, flight autonomy, etc.).

[0017] The method according to the invention may comprise one or more of the following characteristics and / or steps, taken in isolation from one another or in combination with one another: - the method comprises the step of: (b) measuring the flight altitude of the aircraft and / or measuring the flight speed of the aircraft and / or measuring the air temperature in the vein; the setting of the shutter device being determined in step c) from the core temperature measured in step a), the flight altitude measured in step b) and / or the flight speed measured in step b) and / or the air temperature measured in step b); - step c) includes the sub-steps consisting of: cl) comparing the core temperature measured in step a) with the predetermined threshold temperature; c2) modulating the result of the comparison carried out in sub-step cl) with the flight altitude measured in step b) and / or the flight speed measured in step b) and / or the air temperature measured in step b); - the core temperature is measured in step a) by means of a temperature sensor which is specific to the core of the fuel cell; - the different stages of the process are repeated in a loop via a Proportional Integral Derivative regulator known as PID.

[0018] The present invention also relates to an aircraft propulsion unit comprising an electric thruster powered by a fuel cell which is cooled by a cooling system, the cooling system comprising at least one heat exchanger placed in a stream supplied with air by an inlet and a device for closing the inlet which is movable, the fuel cell comprising a core placed in the stream downstream of the heat exchanger, the core being formed by a stack of electrochemical cells, the cooling system being configured to be adjusted by the adjustment method as described previously.

[0019] The propulsion unit according to the invention may comprise one or more of the following characteristics and / or steps, taken in isolation from one another or in combination with one another: - the closure device is configured to be housed at least partly in an interior compartment in one of its positions, the compartment being defined at least by a conduit delimiting the vein and a fairing of a nacelle; - the shutter device comprises at least one flap movable in translation, the flap being guided by a guide device which is integral with the inlet; - the shutter comprises several slats which are hinged and sealed in relation to each other; - the shutter device comprises a column of rotating movable shutters; - the shutters are adjusted independently of each other or in common or in groups. Brief description of the figures

[0020] The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0021] [Fig-1] [Fig.l] is a schematic view of a propulsion group according to a first embodiment in which a shutter device is in a first position;

[0022] [Fig.2] [Fig.2] is a view similar to [Fig.l] in which the shutter device is in a second position;

[0023] [Fig.3] [Fig.3] is a schematic view of a propulsion unit according to a second embodiment in which a shutter device is in a first position;

[0024] [Fig.4] [Fig.4] is a view similar to [Fig.3] in which the shutter device is in a second position;

[0025] [Fig.5] [Fig.5] is a diagram of a method for adjusting a cooling system according to a first embodiment;

[0026] [Fig.6] [Fig.6] is a diagram of a method of adjusting a cooling system according to a second embodiment. Detailed description of the invention

[0027] Figures 1 to 4 schematically show a propulsion unit 1 of an aircraft 2. The aircraft 2 may be, for example, an airplane or a drone.

[0028] The propulsion unit 1 here comprises an electric thruster 3 comprising a propeller 4 driven directly or indirectly by an electric motor 5. The propeller 4 is rotatable about a longitudinal axis X of the propulsion unit 1. The propeller 4 can be rotated by the electric motor 5 via a speed reducer (for example an epicyclic gear reducer).

[0029] The electric motor 5 is powered directly or indirectly (for example via batteries) by a fuel cell 6 better known by the acronym “PAC” or the English term “fuel cell”. Batteries can be used to store the electrical energy produced by the fuel cell 6. The fuel cell 6 comprises in particular a core 7 formed by one or more stacks of electro chemicals. The core 7 of the fuel cell 6 is commonly called a "stack" in English. The fuel cell 6 may be a hydrogen / oxygen cell, and in other words a cell whose fuel is hydrogen and the oxidant is oxygen.

[0030] The embodiments illustrated in Figures 1 to 4 are in no way limiting; the propulsion unit 1 could, for example, comprise several electric thrusters powered directly or indirectly by a single fuel cell.

[0031] The fuel cell 6 is cooled by a cooling system 8 which comprises one or more heat exchangers 9 placed in a vein 10 supplied with air by an inlet 11 (or an air intake) and a device 12 for closing the inlet 11 which is movable. A vein is understood to mean an air passage delimited by a conduit. The core 7 of the fuel cell 6 is placed in the vein 10 downstream of the heat exchanger(s) 9.

[0032] The heat exchanger(s) 9 allow the thermal energy to be evacuated from the core 7 of the fuel cell 6 into the air which passes through the vein 10.

[0033] As illustrated in Figures 1 to 4, the cooling system 8 here comprises several heat exchangers 9 arranged one behind the other, for example three exchangers. The heat exchangers 9 here form part of a cooling circuit in which a heat transfer fluid circulates by means of a pump. Each heat exchanger 9 comprises two independent paths, namely a first path in which the heat transfer fluid circulates and a second path in which the air from the vein 10 circulates.

[0034] The heat exchangers 9 are for example tube exchangers and / or plate exchangers and / or finned exchangers, a succession of exchangers of the same type or of different types being possible.

[0035] As illustrated in Figures 1 to 4, the vein 10 extends here along an axis which is substantially parallel to the longitudinal axis X. The vein 10 is delimited by a conduit 13 which is placed in a lower housing 14 of a nacelle 15, the electric motor 5 being placed in an upper housing 16 of the nacelle 15.

[0036] By convention in the present application, the terms “upstream” and “downstream” are defined in relation to the direction of circulation of the air around the fairings of the nacelle 15 and in the vein 10, when the propulsion group 1 operates in “propulsor” mode.

[0037] Advantageously, the closure device 12 is configured to be housed at least partly in an interior compartment 17 in one of its positions, the compartment 17 being defined at least by the conduit 13 delimiting the vein 10 and a fairing 18 of the nacelle 15.

[0038] Such a configuration makes it possible to limit aerodynamic disturbances, and thus to reduce aerodynamic drag.

[0039] The closure device 12 may comprise at least one flap 19 movable in translation, hereinafter called sliding shutter 19.

[0040] By way of example, the closure device 12 may comprise a single sliding shutter 19, or even an upper sliding shutter 19 and a lower sliding shutter 19.

[0041] Advantageously, each sliding flap 19 is profiled aerodynamically, and in other words each sliding flap 19 is profiled so as to minimize its drag whatever its position.

[0042] A sliding shutter 19 can be formed from a single element.

[0043] A sliding shutter 19 may comprise several blades 20 which are articulated and sealed relative to each other. The blades 20 may be sealed relative to each other via elastomer seals. Sealing the blades 20 makes it possible in particular to limit air leaks when the flap 19 is in the closed position, so as to reduce aerodynamic drag.

[0044] Advantageously, each sliding shutter 19 is guided by a guide device which is integral with the inlet 11. The guide device may comprise two guides or rails opposite each other in which the lateral ends of the shutter 19 or of the different blades 20 are placed.

[0045] Each sliding shutter 19 can be actuated directly or indirectly by one or more actuators 21. The actuator(s) 21 are for example electric and / or hydraulic and / or mechanical. The actuator(s) 21 can be linked to a sliding shutter 19 via a transmission mechanism. The mechanism can comprise one or more connecting rods, one or more reduction systems, or even a particular kinematic system depending on the installation requirements.

[0046] A sliding shutter 19 can be wound onto a tube (coil or reel) controlled by one or more actuators 21.

[0047] Each sliding shutter 19 is movable in translation between an open position and a closed position.

[0048] The closure device 12 may comprise at least one flap 22 movable in rotation, hereinafter called pivoting flap 22.

[0049] Advantageously, a pivoting flap 22 is movable in rotation around a fixed axis in the reference frame of the propulsion group 1.

[0050] Advantageously, each pivoting flap 22 is aerodynamically profiled, and in other words each pivoting flap 22 is profiled so as to minimize its drag whatever its position.

[0051] The closing device 12 may comprise a column of pivoting shutters 22, so as to form a louver.

[0052] The pivoting shutters 22 can be actuated independently of each other by one or more actuators. Each pivoting shutter 22 can be actuated di- directly or indirectly by the actuator(s).

[0053] Advantageously, each pivoting shutter 22 is actuated by an electric motor 23.

[0054] Conversely, the pivoting shutters 22 can be operated in common by a or more actuators. The pivoting shutters 22 can be actuated directly or indirectly by the actuator(s).

[0055] The actuator(s) are for example electric and / or hydraulic and / or mechanical. The actuator(s) may be linked to one or more pivoting flaps 22 via a transmission mechanism. The mechanism may comprise one or more connecting rods, one or more reduction systems, or even a particular kinematic system depending on the installation requirements.

[0056] The pivoting shutters can be adjusted independently of each other or in common or in groups.

[0057] Each pivoting flap 22 is movable in rotation between an open position and a closed position.

[0058] Advantageously, the adjacent edges of two successive flaps 22 may be provided with sealing elements, in order to limit in particular air leaks between the flaps 22 when they are in the closed position.

[0059] Advantageously, the cooling system 8 is controlled by a computer 24. The computer 24 thus controls the actuator(s) 21, 23 of the closure device 12 based in particular on information reported by different sensors 25 and a program pre-recorded in the computer 24.

[0060] The computer 24 can be specific to the cooling system 8. The computer can then be informed about the status of various parameters (core temperature, flight altitude, flight speed, etc.) via different sensors specific to this computer, so as to improve the safety of the cooling system.

[0061] The computer 24 can also be the computer controlling the fuel cell 6 or even be integrated into the general computer of the propulsion group 1.

[0062] Advantageously, the computer 24 is configured to carry out the various methods of adjusting the cooling system 8, as described in the remainder of the description.

[0063] According to the first embodiment illustrated in Figures 1 and 2, the closure device 12 comprises a single sliding shutter 19 which is movable in translation between an open position ([Fig.l]) and an at least partially closed position ([Fig.2]).

[0064] The sliding shutter 19 here comprises several blades 20 which are articulated and sealed relative to each other.

[0065] In the open position ([Fig.l]), the sliding shutter 19 is housed entirely in an interior compartment 17 which is radially defined between the conduit 13 and a fairing 18 of nacelle 15.

[0066] For example, the open position ([Fig. 1]) is used during takeoff of aircraft 2 while the closed position ([Fig.2]) is used when aircraft 2 is cruising.

[0067] According to the second embodiment illustrated in Figures 3 and 4, the closure device 12 comprises a column of pivoting flaps 22, so as to form a shutter. Each pivoting flap 22 is movable in rotation around a fixed axis in the reference frame of the propulsion group 1.

[0068] In [Fig. 3], the closure device 12 is in an open position in which all of the pivoting flaps 22 are in the open position. In [Fig. 4], the closure device 12 is in an intermediate position in which two central flaps 22 are in the open position and four peripheral flaps 22 are in the closed position. The closure device 12 could be in a closed position in which all of the pivoting flaps 22 would be in the closed position.

[0069] Each pivoting shutter 22 is here actuated by an electric motor 23.

[0070] For example, the open position ([Fig.3]) is used when aircraft 2 takes off while the intermediate position ([Fig.4]) is used when aircraft 2 is cruising.

[0071] According to the invention, the cooling system 8 is configured to be adjusted by an adjustment method.

[0072] More specifically, the adjustment method chronologically comprises the steps of: a) measuring the temperature of the core 7 of the fuel cell 6; c) determining the setting of the shutter device 12 from the temperature of the core 7 measured in step a), so that the temperature of the core 7 remains below a predetermined threshold temperature; d) adjusting the closure device 12 according to the setting determined in step c), so as to adjust the air flow entering the vein 10.

[0073] Such an adjustment method takes into account the temperature of the core of the fuel cell so as to quickly adapt the flow rate of air entering the vein according to the cooling requirements of the core, and to minimize the aerodynamic drag produced by the passage of air in the vein throughout a flight (from takeoff to landing), for the benefit of the overall performance of the propulsion unit and the aircraft (consumption, flight autonomy, etc.).

[0074] The method may comprise a step consisting of: b) measuring the flight altitude of aircraft 2 and / or measuring the flight speed of aircraft 2 and / or measuring the air temperature in vein 10; the setting of the shutter device 12 being determined in step c) from the temperature of the core 7 measured in step a), the flight altitude measured in step b) and / or the flight speed measured in step b) and / or the air temperature measured in step b).

[0075] Advantageously, when the method comprises step b), step b) is carried out before step c).

[0076] When the method comprises step b), step c) may comprise the sub-steps consisting of: cl) comparing the core temperature 7 measured in step a) with the predetermined threshold temperature; c2) modulating the result of the comparison made in sub-step cl) with the flight altitude measured in step b) and / or the flight speed measured in step b) and / or the air temperature measured in step b).

[0077] Advantageously, the predetermined threshold temperature corresponds to the maximum temperature admissible by the core 7 of the fuel cell 6. A margin may possibly be applied.

[0078] Advantageously, the temperature of the core 7 is measured in step a) by means of a temperature sensor 25 which is specific to the core 7 of the fuel cell 6.

[0079] As illustrated in Figures 1 to 4, the temperature of the core 7 which is measured via the temperature sensor 25 is reported to the computer 24 which controls the cooling system 8.

[0080] The different steps of the process can be repeated in a loop via a Proportional Integral Derivative regulator called "PID", this PID regulator is also known as a PID corrector. A PID regulator is a universal regulator which combines the possibilities of proportional, derivative and integral regulations.

[0081] According to the first embodiment illustrated in [Fig.5], the adjustment method chronologically comprises steps a), c) and d).

[0082] According to the second embodiment illustrated in [Fig.6], the adjustment method chronologically comprises steps a), b), c) and d).

Claims

Claims

1. Method for adjusting a cooling system (8) of a fuel cell (6) which is intended to power an electric thruster (3) of a propulsion unit (1) of an aircraft (2), the cooling system (8) comprising at least one heat exchanger (9) placed in a vein (10) supplied with air by an inlet (11) and a device (12) for closing the inlet (11) which is movable, the fuel cell (6) comprising a core (7) placed in the vein (10) downstream of the heat exchanger (9), the core (7) being formed by a stack of electrochemical cells, the method chronologically comprising the steps of: a) measuring the temperature of the core (7) of the fuel cell (6); c) determining the setting of the sealing device (12) from the temperature of the core (7) measured in step a), so that the temperature of the core (7) remains below a predetermined threshold temperature;d) adjusting the closure device (12) according to the setting determined in step c), so as to adjust the flow of air entering the vein (10).;

2. Method according to claim 1, characterized in that the method comprises the step of: b) measuring the flight altitude of the aircraft (2) and / or measuring the flight speed of the aircraft (2) and / or measuring the temperature of the air in the vein (10); the setting of the closure device (12) being determined in step c) from the temperature of the core (7) measured in step a), the flight altitude measured in step b) and / or the flight speed measured in step b) and / or the air temperature measured in step b).

3. Method according to claim 2, characterized in that step c) comprises the sub-steps consisting of: cl) comparing the temperature of the core (7) measured in step a) with the predetermined threshold temperature; c2) modulating the result of the comparison carried out in sub-step cl) with the flight altitude measured in step b) and / or the flight speed measured in step b) and / or the air temperature measured in step b).

4. Method according to one of the preceding claims, characterized in that the temperature of the core (7) is measured in step a) by means of a temperature sensor (25) which is specific to the core (7) of the fuel cell combustible (6).

5. Method according to one of the preceding claims, characterized in that the different steps of the method are repeated in a loop via a Proportional Integral Derivative regulator known as PID.

6. Propulsion unit (1) of an aircraft (2) comprising an electric thruster (3) powered by a fuel cell (6) which is cooled by a cooling system (8), the cooling system (8) comprising at least one heat exchanger (9) placed in a vein (10) supplied with air by an inlet (11) and a device (12) for closing the inlet (11) which is movable, the fuel cell (6) comprising a core (7) placed in the vein (10) downstream of the heat exchanger (9), the core (7) being formed by a stack of electrochemical cells, the cooling system (8) being configured to be adjusted by the adjustment method according to one of claims 1 to 5.

7. Propulsion unit (1) according to the preceding claim, characterized in that the closure device (12) is configured to be housed at least partly in an interior compartment (17) in one of its positions, the compartment (17) being defined at least by a conduit (13) delimiting the vein (10) and a fairing (18) of a nacelle (15).

8. Propulsion unit (1) according to one of claims 6 or 7, characterized in that the closure device (12) comprises at least one flap (19) movable in translation, the flap (19) being guided by a guide device which is integral with the inlet (11).

9. Propulsion unit (1) according to the preceding claim, characterized in that the flap (19) comprises several blades (20) which are articulated and sealed relative to each other.

10. Propulsion unit (1) according to claim 6, characterized in that the closure device (12) comprises a column of rotating movable flaps (22).

11. Propulsion unit (1) according to the preceding claim, characterized in that the flaps (22) are adjusted independently of each other or in common or in groups.

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