Improved fuel cell system

Abstract

The invention relates to an assembly (24) formed by an air transport circuit (21) and a device (23) for thermally regulating the air transport circuit (21) for a fuel cell stack (6), the thermal-regulation device (23) comprising a heat exchanger (4) mounted on the upstream air duct (21A) in order to regulate the air temperature therein and supplied with heat-transfer fluid by a distribution element (8) selectively mixing the streams of heat-transfer fluid from the heat-transfer fluid inlet duct (25A) leading from the outlet of another heat exchanger (9) into the fuel cell stack (6), and from the heat-transfer fluid outlet duct (25B) leading out of the fuel cell stack (6) in order to control the air temperature in the upstream air duct (21A).

Description

Improved fuel cell system Technical field of the invention

[0001] The invention relates to the field of fuel cells such as proton exchange membrane fuel cells. More specifically, the invention relates to an assembly formed by an air transport circuit and a thermal regulation device for a fuel cell stack, a fuel cell system connected to such an assembly, a vehicle comprising such a fuel cell system, a method for thermal regulation of such an assembly, a computer program and a computer-readable recording medium for implementing the steps of such a method. Technical background

[0002] A proton exchange membrane fuel cell (commonly abbreviated as "PEMFC" from the English term "polymer electrolyte membrane fuel cell") typically comprises a membrane electrode arranged between two unipolar half-plates. A membrane electrode comprises an electrolytic solution contained in a proton-conducting membrane arranged between an anode and a cathode. A set of fuel cells forms what is commonly called a fuel cell stack (also called "fuel cell stack") intended to generate electrical energy. In a fuel cell stack, several fuel cells are connected in parallel in the stack and are electrically connected in series so that the fuel cell stack produces sufficient electrical energy.In a known manner, the anode is supplied with a gas rich in H2 (dihydrogen, commonly called hydrogen) and the cathode is supplied with a gas containing O2 (dioxygen, commonly called oxygen), air for example, in order to produce electricity and in particular water at a cathode outlet, water being a reaction product of each fuel cell. In the case where air is used as a gas containing oxygen, N2 (dinitrogen, commonly called nitrogen) is another product present at an outlet of the anode. Indeed, in this case, the nitrogen present in the air migrates from the cathode to the anode through the electrode membrane.

[0003] To achieve good fuel cell stack performance and minimize its degradation over time, each membrane of the fuel cell stack needs adequate humidification at all operating states of the fuel cell system, such as startup, steady-state operation, dynamic load, and shutdown. Typically, the water produced at the cathode outlet can be used to humidify the oxygen-containing gas feeding the fuel cell stack. Furthermore, if the oxygen-containing gas is obtained from ambient air, the air humidity already provides some humidity, i.e., it contains water in gaseous form (water vapor), but this humidity is insufficient. It is therefore common to provide a humidifier upstream of the fuel cell stack to increase the relative humidity of the oxygen-containing gas.Examples of fuel cells are disclosed in CN215731815U and WO2009004253.

[0004] In order to achieve adequate humidification at each operating state of the fuel cell system, it is necessary that the humidity in the fuel cell stack be precisely controlled according to the operating pressure and temperature of the fuel cell system, in particular, the humidity must be adapted to the temperature of the fuel cell stack.

[0005] The invention aims in particular to propose a fuel cell system which is reliable and robust regardless of the operating states of the fuel cell system.

[0006] For this purpose, the subject of the invention is an assembly formed by an air transport circuit and a device for thermal regulation of the air transport circuit for a fuel cell stack comprising an anode and a cathode, the air transport circuit comprising at least one upstream air pipe, called the cathode air inlet pipe, intended to supply oxygen to the fuel cell stack, the thermal regulation device comprising a network of heat transfer fluid pipes cooled by a first heat exchanger, the network of heat transfer fluid pipes comprising at least one upstream heat transfer fluid pipe, called the heat transfer fluid inlet pipe of the fuel cell stack, intended to supply heat transfer fluid to the fuel cell stack and a downstream heat transfer fluid pipe, called the heat transfer fluid outlet pipe of the fuel cell stack,intended to receive the heat transfer fluid after heat exchange with the fuel cell stack coming from the upstream heat transfer fluid pipe, the first heat exchanger being mounted between the upstream heat transfer fluid pipe and the downstream heat transfer fluid pipe, and a bypass element making it possible to selectively either connect the downstream heat transfer fluid pipe to the first heat exchanger, or connect the downstream heat transfer fluid pipe to the upstream heat transfer fluid pipe without passing through the first heat exchanger, or both at the same time in order to control the temperature of the heat transfer fluid at the inlet of the fuel cell stack, characterized in that the thermal regulation device comprises a second heat exchanger mounted on the upstream air pipe, upstream of a humidifier,in order to regulate the air temperature in the upstream air pipe upstream of the humidifier by the heat transfer fluid pipe network and in that the second heat exchanger is supplied with heat transfer fluid by a distribution element selectively mixing the heat transfer fluid flows from the upstream heat transfer fluid pipe at the outlet of the first heat exchanger upstream of the outlet of the bypass element, and from the downstream heat transfer fluid pipe upstream of the inlet of the bypass element, in order to control the air temperature in the upstream air pipe independently of that of the fuel cell stack.,

[0007] Advantageously, thanks to the regulation device according to the invention, whatever the operating states of the fuel cell system, the temperature of the air contained in the upstream air duct intended to supply oxygen to the fuel cell stack will be managed by a control unit of the regulation device in order to optimize the temperature and humidity conditions. It is understood in particular that the second heat exchanger is mounted upstream of the humidifier in order to guarantee the proper functioning of the latter. By guaranteeing the proper functioning of the humidifier, its service life is increased on the one hand, and the overall operation of the fuel cell system is made more reliable and robust on the other hand, by adapting the humidity of the air supplied to the fuel cell stack, for example, as a function of the temperature of the fuel cell stack and / or the temperature measured by the temperature measuring element.Of course, air is only one possible example of an oxygen-containing gas. Alternatively, oxygen alone, for example pure oxygen, could be transported in the upstream line of the transport circuit.

[0008] The heat transfer fluid flow bypass element may, for example, be mounted on the downstream heat transfer fluid pipe upstream of the first heat exchanger or on the upstream heat transfer fluid pipe downstream of the first heat exchanger. It is the mixing carried out by the bypass element managed by the control unit which makes it possible to bring the heat transfer fluid to the correct temperature at the inlet of the fuel cell stack.

[0009] Furthermore, the management by the control unit of the regulating device of the distribution element makes it possible, advantageously according to the invention, to widen the range of temperatures controllable by the regulating device by selectively controlling the state of the distribution element independently of the temperature range of the fuel cell stack managed by the bypass element. Thus, depending on the characteristics of the air present in the upstream air duct, it may be preferable to heat the air (for example very low air temperature upstream of the second heat exchanger) or on the contrary to cool the air (for example very high air temperature upstream of the second heat exchanger) or even not to modify the air temperature.Indeed, it is preferable to have a maximum of possibilities between the temperature of the heat transfer fluid at the outlet of the first heat exchanger generally between ambient temperature and approximately 70°C (upstream heat transfer fluid pipe) and the temperature of the heat transfer fluid at the outlet of the fuel cell stack generally between ambient temperature and approximately 85°C (downstream heat transfer fluid pipe). This also makes it possible to avoid having to oversize the second heat exchanger by providing the lowest possible temperature of the fuel cell system (upstream heat transfer fluid pipe) or the highest possible temperature of the fuel cell system (downstream heat transfer fluid pipe) or a mixture of the two (upstream heat transfer fluid pipe and downstream heat transfer fluid pipe).The first heat exchanger is preferably connected to an existing cooling device in the environment of the fuel cell system.

[0010] Finally, advantageously according to the invention, depending on the operating states of the fuel cell system, the control unit of the regulation device according to the invention makes it possible to dynamically control the desired air temperature in the upstream air duct.

[0011] The invention alternatively comprises one or more of the following optional features, taken alone or in combination.

[0012] The humidity of the humidifier can be provided by a downstream air line of the air transport circuit, called the cathode air outlet line, intended to receive the air, after reduction of the oxygen of the air in the fuel cell stack, coming from the upstream air line, and a reaction product of the fuel cell stack. Indeed, a reduction of the oxygen takes place at the cathode giving, as the main reaction product, water which can be advantageously recycled to humidify the air circulating in the air transport circuit. Alternatively, a water source can be used to supply the humidifier.

[0013] The air transport circuit may comprise an ambient air compression device mounted on the upstream air pipe upstream of the second heat exchanger in order to supply air to the upstream air pipe. Thus, the compression device supplies air at a predetermined pressure higher than atmospheric pressure by command from the control unit of the regulation device but also avoids the use of a pressurized oxygen storage source or pressurized air. This is particularly advantageous for improving the compactness and weight of the fuel cell system when it is mounted in a vehicle. Of course, as an alternative to the compression device, the air transport circuit could however provide for the use of a pressurized oxygen storage source or pressurized air without departing from the scope of the invention.

[0014] The heat transfer fluid piping network may comprise a heat transfer fluid flow generating element in order to force a movement of heat transfer fluid in the heat transfer fluid piping network. The heat transfer fluid flow generating element may, for example, be mounted on the downstream heat transfer fluid pipe upstream of the first heat exchanger or on the upstream heat transfer fluid pipe downstream of the first heat exchanger.

[0015] The thermal control device may comprise a third heat exchanger mounted between the upstream heat transfer fluid pipe and the downstream heat transfer fluid pipe. The inlet of the third heat exchanger is in fluid communication with the outlet of the first heat exchanger in order to improve the cooling of the heat transfer fluid present in the heat transfer fluid pipe network. The third heat exchanger is preferably connected to an existing cooling device in the environment of the fuel cell system.

[0016] The distribution element may be configured to be supplied by the heat transfer fluid flow from the downstream heat transfer fluid pipe and the heat transfer fluid flow exiting the third heat exchanger in order to provide a wider range of air temperature control in the upstream air pipe. Indeed, the third heat exchanger as described above lowers the temperature of the heat transfer fluid at the outlet of the third heat exchanger to a maximum temperature of 60°C.

[0017] The heat transfer fluid piping network may include an auxiliary heat transfer fluid pipe connecting the outlet of the third heat exchanger to the downstream heat transfer fluid pipe in order to lower the heat transfer fluid temperature in the auxiliary heat transfer fluid pipe. Typically, as explained below, components may thus be configured to be cooled by the flow of heat transfer fluid from the auxiliary pipe.

[0018] The invention also relates to a fuel cell system comprising a stack of fuel cells connected to a hydrogen source, characterized in that the fuel cell system is connected to the assembly as presented above, the stack of fuel cells being connected to the air transport circuit of the assembly in order to supply oxygen to the stack of fuel cells and to the network of heat transfer fluid pipes of the assembly in order to exchange heat with the stack of fuel cells.

[0019] The invention also relates to a vehicle comprising an electric powertrain and an electrical energy storage element, characterized in that the vehicle comprises a fuel cell system as presented above.

[0020] The invention also relates to a method of thermal regulation, preferably implemented by computer, of a fuel cell system as presented above.

[0021] Finally, the invention also relates to a computer program comprising instructions which, when the program is executed by a computer, lead the latter to implement the steps of the method as presented above and a computer-readable recording medium comprising instructions which, when executed by a computer, lead the latter to implement the steps of the method as presented above. Brief description of the figures

[0022] Other features and advantages of the invention will emerge clearly from the description given below, for information purposes only and in no way limiting, with reference to the appended drawings, in which:

[0023] is a schematic top view of an exemplary vehicle comprising an exemplary fuel cell system according to the invention;

[0024] is a diagram of an exemplary first embodiment of a fuel cell system according to the invention;

[0025] is a diagram of an exemplary second embodiment of a fuel cell system according to the invention. Detailed description

[0026] In the various figures, identical or similar elements bear the same references, possibly with the addition of an index. The description of their structure and function is therefore not systematically repeated.

[0027] In all that follows, the orientations are the orientations of the figures. In particular, the terms "upper", "lower", "left", "right", "above", "below", "forward" and "backward" are generally understood in relation to the direction of representation of the figures. In addition, the terms "upstream" and "downstream" are generally understood in relation to the direction of pumping flow, that is to say in particular the direction of movement between an inlet and an outlet of the circuit or network.

[0028] In this description, to clarify the explanation of the invention, heat exchangers are arbitrarily declared as a first heat exchanger, a second heat exchanger, etc. This is a simple nomenclature to differentiate and name non-identical elements. This nomenclature does not imply a priority of one heat exchanger over another and such names can easily be interchanged without departing from the scope of this description. This nomenclature also does not imply an order, i.e., a third heat exchanger could be used without a first heat exchanger and / or a second heat exchanger being necessary for the implementation of the invention.

[0029] The invention applies to any type of fuel cell system 1 that can be used in a mobile manner such as, for example, mounted in a vehicle 31 (passenger car, industrial vehicles (utility, truck, etc.), transport vehicles (tram, metro, bus, etc.), agricultural vehicles (tractor, harvester, etc.), civil engineering vehicles (mechanical shovel, bulldozer, etc.), train, boat, aircraft, spacecraft, etc.) or in a stationary manner such as, for example, in power plants or generator sets.

[0030] In the example illustrated in 1, a fuel cell system 1 is integrated into a vehicle 31. The vehicle 31 mainly comprises a powertrain 15, an electrical energy storage element 29, a cooling device 33 and the fuel cell system 1. In the example illustrated in 1, the powertrain 15 is preferably of the electric type and comprises an electric motor and its electronic power elements such as at least one DC-DC converter 14 (chopper) intended to reduce the electrical power supplying the electrical energy storage element 29 (battery) of the vehicle 31 to that of the on-board network of the vehicle 31 and at least one DC-AC converter (inverter) intended to transform the DC electrical power supplying the on-board network of the vehicle 31 into AC electrical power to supply the electric motor.The cooling device 33 comprises at least one heat exchanger such as a heat transfer fluid radiator (condenser) in order to use the movement of the vehicle 31 and the ambient air around the vehicle 31 to form the cold zone of the cooling device 33, that is to say the place where the heat transfer fluid is the coldest.

[0031] The electrical energy storage element 29 is preferably designed to provide a direct voltage, for example between 12 V and 800 V, and comprises for example electrical energy accumulation cells, i.e. all types of electrochemical accumulators capable of storing electrical energy and, reversibly, of restoring the stored electrical energy, such as a rechargeable battery (for example using an external power cable). The electrical energy storage element 29 will not be described further below because it does not form part of the core of the invention.

[0032] The fuel cell system 1 mainly comprises a stack 6 of fuel cells, an air transport circuit 21, a thermal regulation device 23 and a hydrogen source 27. The combination of the air transport circuit 21 and the thermal regulation device 23 forms an assembly 24. The stack 6 of fuel cells is connected in a known manner, at its anode, to the hydrogen source 27 in order to supply hydrogen to the stack 6 of fuel cells and, at its cathode, to the air transport circuit 21 in order to supply oxygen to the stack 6 of fuel cells. In addition, the stack 6 of fuel cells is connected in a known manner to a network 25 of heat transfer fluid pipes of the thermal regulation device 23 in order to exchange heat with the stack 6 of fuel cells.

[0033] In the examples illustrated in Figures 2 and 3, the air transport circuit 21 comprises, from an inlet E to an outlet S, at least one upstream air pipe 21A, called the cathode air inlet pipe, intended to supply oxygen to the fuel cell stack 6 and a downstream air pipe 21B, called the cathode air outlet pipe, intended to receive the air, after reduction of the oxygen in the air in the fuel cell stack 6, coming from the upstream air pipe 21A, and any reaction product of the fuel cell stack 6 such as water.

[0034] In the examples illustrated in Figures 2 and 3, the air transport circuit 21 comprises an optional filter 2 intended to retain any pollution from the air sucked in at the inlet E, a compression device 3, a second heat exchanger 4, a temperature measuring element 7 such as a temperature sensor (thermistor of the NTC (Negative Temperature Coefficient) type or equivalent) and a humidifier 5.

[0035] The ambient air compression device 3 is mounted on the upstream air pipe 21A upstream of the second heat exchanger 4 in order to supply air to the upstream air pipe 21A. Thus, the compression device 3 supplies air at a predetermined pressure higher than atmospheric pressure by command of a control unit 20 of the regulation device 23 such as an electronic control unit, but also avoids the use of a pressurized oxygen storage source or pressurized air. This is particularly advantageous for improving the compactness and weight of the fuel cell system 1, in particular when it is mounted in the vehicle 31 as in the examples of FIGS. 1 to 3. By way of non-limiting example, the compression device 3 may comprise a compressor such as an electric turbocharger.

[0036] Of course, air is only one possible example of a gas containing oxygen. Alternatively, oxygen alone, for example pure oxygen, could be transported in the pipe 21A upstream of the transport circuit 21. Furthermore, as an alternative to the compression device 3, the air transport circuit 21 could provide for the use of a source (not shown) for storing pressurized oxygen or pressurized air without departing from the scope of the invention.

[0037] To achieve good performance of the fuel cell stack 6 and minimize its degradation over time, each membrane of the fuel cell stack 6 needs adequate humidification at all operating states of the fuel cell system 1, such as startup, steady-state operation, dynamic load, and shutdown. In the examples of FIGS. 2 and 3, the humidifier 5 is mounted upstream of the fuel cell stack 6 to increase the relative humidity of the air moved in the air transport circuit 21.

[0038] In the examples of Figures 2 and 3, the humidity of the humidifier 5 is supplied by a downstream air pipe 21B of the air transport circuit 21, called the cathode air outlet pipe. Indeed, the reduction of oxygen which takes place at the cathode gives, as the main reaction product, water which can be advantageously recycled to humidify the air circulating in the air transport circuit 21. Consequently, the water produced at the cathode outlet can be used to humidify the air moved in the air transport circuit 21 in addition to the humidity present in the ambient air drawn in by the inlet E.

[0039] Of course, alternatively or in addition, a water source can be used to supply the humidifier 5.

[0040] In the examples of Figures 2 and 3, the thermal regulation device 23 comprises a network 25 of heat transfer fluid pipes cooled by the first heat exchanger 9. The network 25 of heat transfer fluid pipes comprises at least one upstream heat transfer fluid pipe 25A, called the heat transfer fluid inlet pipe of the fuel cell stack 6, intended to supply heat transfer fluid to the fuel cell stack 6 and a downstream heat transfer fluid pipe 25B, called the heat transfer fluid outlet pipe of the fuel cell stack 6, intended to receive the heat transfer fluid after heat exchange with the fuel cell stack 6 coming from the upstream heat transfer fluid pipe 25A.In the examples of Figures 2 and 3, the first heat exchanger 9 is mounted between the upstream heat transfer fluid pipe 25A and the downstream heat transfer fluid pipe 25B, forming a closed loop moving heat transfer fluid between the stack 6 of fuel cells and the first heat exchanger 9.

[0041] In the examples of Figures 2 and 3, the thermal regulation device 23 comprises the second heat exchanger 4 mounted on the upstream air duct 21A in order to also regulate the air temperature in the upstream air duct 21A upstream of the humidifier 5 by the network 25 of heat transfer fluid pipes. By way of non-limiting example, the second heat exchanger 4 may be a charge air cooler (also known by the English abbreviation “CAC” coming from the terms “charge air cooler”).

[0042] More specifically, the second heat exchanger 4 is supplied with heat transfer fluid by the inlet pipe 25E of the second heat exchanger 4 by means of a distribution element 8 selectively mixing the heat transfer fluid flows of the upstream heat transfer fluid pipe 25A at the outlet of the first heat exchanger 9 (directly in the first embodiment of the and indirectly in the second embodiment of the), and of the downstream heat transfer fluid pipe 25B in order to control the air temperature in the upstream air pipe 21A. The second heat exchanger 4 comprises an outlet pipe 25F connected to the downstream heat transfer fluid pipe 25B upstream of a flow generation element 10, such as a centrifugal pump.By way of non-limiting example, the distribution element 8 may be a three-way proportional valve having two heat transfer fluid inlets and a heat transfer fluid outlet capable of being closed, partially open (multitude of positions) or fully open. The output of the distribution element 8 when it is open may be supplied, by management of the control unit 20, either solely by the first inlet, or solely by the second inlet, or by a mixture of the two inlets according to proportions managed by the control unit 20 for example as a function of a temperature measuring element such as the temperature measuring element 7 downstream of the second heat exchanger 4 and / or the operating state of the fuel cell stack 6.

[0043] Advantageously, thanks to the regulation device 23 according to the invention, whatever the operating states of the fuel cell system 1, the temperature of the air contained in the upstream air pipe 21A intended to supply oxygen to the stack 6 of fuel cells will be managed by the control unit 20 of the regulation device 23 in order to optimize the temperature and incidentally the humidity conditions. It is understood in particular that the second heat exchanger 4 is mounted upstream of the humidifier 5 in order to guarantee the proper functioning of the latter.Indeed, by ensuring the proper functioning of the humidifier, its service life is increased on the one hand, and the overall operation of the fuel cell system 1 is made more reliable and robust on the other hand, by adapting the temperature and incidentally the humidity of the air supplied to the fuel cell stack 6, for example, as a function of the temperature of the fuel cell stack 6 (given by a temperature sensor (not shown) mounted in the fuel cell stack 6 and known per se) and / or as a function of the temperature measured by the temperature measuring element 7.

[0044] Furthermore, the management by the control unit 20 of the device 23 for regulating the distribution element 8 makes it possible, advantageously according to the invention, to widen the range of temperatures controllable by the regulation device 23 by selectively controlling the state of the distribution element 8. Thus, depending on the characteristics of the air present in the upstream air duct 21A, it may be preferable to heat the air (for example very low air temperature upstream of the second heat exchanger 4) or on the contrary to cool the air (for example very high air temperature upstream of the second heat exchanger 4) or even not to modify the air temperature.Indeed, it is preferable to have a maximum of possibilities between the temperature of the heat transfer fluid at the outlet of the first heat exchanger 9 generally between ambient temperature and approximately 70°C (pipe 25A upstream of the heat transfer fluid) and the temperature of the heat transfer fluid at the outlet of the stack 6 of fuel cells generally between ambient temperature and approximately 85°C (pipe 25B downstream of the heat transfer fluid).

[0045] This also makes it possible to avoid having to oversize the second heat exchanger 4 by providing the lowest possible temperature of the fuel cell system 1 (upstream heat transfer fluid pipe 25A) or the highest possible temperature of the fuel cell system 1 (downstream heat transfer fluid pipe 25B) or a mixture of the two (upstream heat transfer fluid pipe 25A and downstream heat transfer fluid pipe 25B).

[0046] Preferably, the first heat exchanger 9 can be directly connected, or indirectly connected by an intermediate circuit, to an existing radiator of the vehicle 31 such as that of the cooling device 33. The first heat exchanger 9 thus makes it possible to evacuate into the ambient air the (unused) heat produced by the stack 6 of fuel cells. The first heat exchanger 9 is preferably sized so that the temperature of the heat transfer fluid at its outlet is always lower than the temperature at the inlet of the stack 6 of fuel cells.

[0047] Finally, advantageously according to the invention, depending on the operating states of the fuel cell system 1, the control unit 20 of the regulation device 23 according to the invention makes it possible to dynamically control the desired air temperature in the upstream air duct 21A. Indeed, the temperature measuring element 7 is only an element for verifying the actual temperature but is not essential for the execution of the invention. Thus, control is possible solely by the operating state of the fuel cell system 1, the usual average temperatures of which are already known, without departing from the scope of the invention.

[0048] In the examples of Figures 2 and 3, the network 25 of heat transfer fluid pipes preferably comprises the element 10 for generating heat transfer fluid flow in order to force a movement of heat transfer fluid in the network 25 of heat transfer fluid pipes. In the examples of Figures 2 and 3, the element 10 for generating heat transfer fluid flow is mounted on the downstream heat transfer fluid pipe 25B upstream of the first heat exchanger 9. Of course, alternatively, the element 10 for generating heat transfer fluid flow could be mounted on the upstream heat transfer fluid pipe 25A downstream of the first heat exchanger 9 without departing from the scope of the invention.

[0049] Furthermore, in the examples of figures 2 and 3, the network 25 of heat transfer fluid pipes comprises a heat transfer fluid flow bypass element 11 in order to selectively either connect the downstream heat transfer fluid pipe 25B to the first heat exchanger 9, or connect the downstream heat transfer fluid pipe 25B to the upstream heat transfer fluid pipe 25A without passing through the first heat exchanger 9, or both at the same time in order to control the heat transfer fluid temperature in the upstream heat transfer fluid pipe 25A, that is to say to control the temperature of the heat transfer fluid at the inlet of the fuel cell stack 6. In the examples of figures 2 and 3, the heat transfer fluid flow bypass element 11 is mounted on the downstream heat transfer fluid pipe 25B upstream of the first heat exchanger 9 and downstream of the flow generation element 10.It is the mixing produced by the bypass element 11 managed by the control unit 20 which makes it possible to bring the heat transfer fluid to the correct temperature at the inlet of the fuel cell stack 6. Of course, the heat transfer fluid flow bypass element 11 could be mounted on the upstream heat transfer fluid pipe 25A downstream of the first heat exchanger 9 without departing from the scope of the invention.

[0050] As a non-limiting example, the heat transfer fluid flow bypass element 11 may be a three-way proportional valve having a heat transfer fluid inlet capable of being closed, partially open (multitude of positions) or fully open and two heat transfer fluid outlets. In the examples of FIGS. 2 and 3, the inlet of the bypass element 11 when it is open can supply, by management of the control unit 20, either only the first outlet to a bypass pipe 25D to the upstream heat transfer fluid pipe 25A, or only the second outlet to the first heat exchanger 9, or a mixture of the two outlets according to proportions managed by the control unit 20 for example as a function of a temperature measuring element of the fuel cell stack 6.

[0051] In the first embodiment illustrated in the example of 1a, the distribution element 8 is directly connected to the upstream heat transfer fluid pipe 25A at the outlet of the first heat exchanger 9 and upstream of the outlet of the bypass element 11 in order to control the air temperature in the upstream air pipe 21A independently of that of the fuel cell stack 6. Indeed, the second inlet pipe 25H of the distribution element 8 is mounted directly at the outlet of the first heat exchanger 9 on the upstream heat transfer fluid pipe 25A. Furthermore, in the example visible in 1a, the first inlet pipe 25G of the distribution element 8 is mounted directly at the outlet of the flow generation element 10 (and upstream of the flow bypass element 11) on the downstream heat transfer fluid pipe 25B.Advantageously according to the invention, the second heat exchanger 4 is therefore supplied with heat transfer fluid by the distribution element 8 by selectively mixing the heat transfer fluid flows from the upstream heat transfer fluid pipe 25A directly at the outlet of the first heat exchanger 9 and from the downstream heat transfer fluid pipe 25B in order to control the air temperature in the upstream air pipe 21A, which makes it possible to maximize the range of temperatures controllable by the regulation device 23 by selectively controlling the state of the distribution element 8 between the two zones, theoretically respectively the coldest and the hottest.

[0052] In the second embodiment illustrated in the example of the, the thermal regulation device 23 comprises a third heat exchanger 12 mounted on an auxiliary heat transfer fluid pipe 25C between the upstream heat transfer fluid pipe 25A and the downstream heat transfer fluid pipe 25B. The inlet of the third heat exchanger 12 is in fluid communication with the outlet of the first heat exchanger 9 in order to improve the cooling of the heat transfer fluid present in the network 25 of heat transfer fluid pipes. Preferably, the third heat exchanger 12 can be directly connected, or indirectly connected by an intermediate circuit, to an existing radiator of the vehicle 31 such as that of the cooling device 33.In the example of the, the third heat exchanger 12 thus makes it possible to evacuate into the ambient air the heat (unused) produced by other components present in the environment of the stack 6 of fuel cells such as the DC-DC converter 14 (chopper) and the powertrain 15.

[0053] Of course, said organs can be other electronic power elements such as a converter (chopper, inverter, dimmer or rectifier) ​​connected to an electrical energy storage element 29 such as a battery or to an actuator such as an electric motor. It is also possible to imagine using the auxiliary 25C pipe for an organ of the fuel cell system 1.

[0054] In the second embodiment illustrated in the example of 1a, the distribution element 8 is therefore connected indirectly to the upstream heat transfer fluid pipe 25A at the outlet of the first heat exchanger 9 in order to use the coldest zone of the network 25 of heat transfer fluid pipes which is no longer at the outlet of the first heat exchanger 9 but at the outlet of the third heat exchanger 12. In the example of 1a, the auxiliary heat transfer fluid pipe 25C is connected at the outlet of the first heat exchanger 9 to the upstream heat transfer fluid pipe 25A and opens into the downstream heat transfer fluid pipe 25B.The auxiliary heat transfer fluid pipe 25C thus comprises, depending on the direction of flow of the heat transfer fluid, the third heat exchanger 12, another flow generation element 13 intended in particular to compensate for the pressure losses of the passage of the heat transfer fluid in the members 14 then 15 downstream of the other flow generation element 13.

[0055] In the example of 1a, the distribution element 8 is therefore supplied by the flow of heat transfer fluid from the downstream heat transfer fluid pipe 25B, by the first inlet pipe 25G of the distribution element 8 connected between the flow generation element 10 and the flow bypass element 11, and the flow of heat transfer fluid leaving the third heat exchanger 12, by the second inlet pipe 25H' of the distribution element 8 connected between the other flow generation element 13 and the member 14, in order to offer a wider range of air temperature control in the upstream air pipe 21A. Indeed, the third heat exchanger 12 as described in the example of 1a lowers the temperature of the heat transfer fluid at the outlet of the third heat exchanger 12 to a maximum temperature of 60°C.

[0056] The invention also relates to a method of thermal regulation, preferably implemented by computer, of the assembly 24 formed by the air transport circuit 21 and the device 23 for thermal regulation of the air transport circuit 21 comprising the following steps:

[0057] – Measure the air temperature at the outlet of the second heat exchanger 4;

[0058] – Compare the temperature measured at the outlet of the second heat exchanger 4 with a predetermined target temperature;

[0059] – Selectively modify the state of the distribution element 8 in order to bring the outlet temperature of the second heat exchanger 4 closer to said target temperature when the comparison value exceeds a predetermined threshold.

[0060] Advantageously, the control unit 20 applies the method according to the invention to allow the regulation device 23, whatever the operating states of the fuel cell system 1, to optimize the temperature and humidity conditions of the air contained in the upstream air pipe 21A intended to supply oxygen to the stack 6 of fuel cells. It is understood in particular that the proper functioning of the humidifier 5 is guaranteed and thus makes the overall operation of the fuel cell system 1 more reliable and robust by adapting the temperature and humidity of the air supplied to the stack 6 of fuel cells. In addition, by guaranteeing the proper functioning of the humidifier 5, its service life is increased.The temperature of the fuel cell stack 6 can also be used to refine the control of the distribution element 8 in addition to the temperature measured by the temperature measuring element 7 measured at the outlet of the second heat exchanger 4. Thus, depending on the characteristics of the air present in the upstream air pipe 21A, it may be preferable to heat the air (supply via the preferred downstream heat transfer fluid pipe 25B) or on the contrary to cool the air (supply via the preferred upstream heat transfer fluid pipe 25A (or auxiliary 25C)) or even not to modify the air temperature (maintaining the supply with the current state of the distribution element 8).

[0061] The comparison step is preferably implemented by a calculation module of the control unit 20 of the thermal regulation device 23. The predetermined target temperature may be between 60°C and 95°C. Indeed, it has been observed that above these temperatures the humidifier 5 could be damaged. The predetermined target temperature may for example be determined as a function of the operating state of the fuel cell system 1, in particular, as a function of the operating state of the humidifier 5. Indeed, the predetermined target temperature must be chosen so that, whatever the temperature of the air leaving the compression device 3, the humidifier 5 always provides sufficient humidity to the air entering the fuel cell stack 6.

[0062] The step of controlling, i.e. changing the state, of the distribution element 8 is preferably managed by the control unit 20 of the thermal regulation device 23 in order to bring the air temperature at the outlet of the second heat exchanger 4 closer to the target temperature. In order to make the control simpler, a predetermined threshold is preferably provided in order to change the control of the distribution element 8 when the comparison value determined by the calculation module exceeds said predetermined threshold. The predetermined threshold may be ± 2°C between the air temperature measured at the outlet of the second heat exchanger 4 compared to the predetermined target temperature.Typically, as explained above, the distribution element 8 can be controlled from a data table parameterized in advance or, possibly, from a calculation, for example, by linear interpolation, in the event of a situation of correspondence between two data items in said table parameterized in advance.

[0063] Finally, the invention also relates to a computer program comprising instructions which, when the program is executed by a computer, lead the latter to implement the steps of the method as presented above and a computer-readable recording medium comprising instructions which, when executed by a computer, lead the latter to implement the steps of the method as presented above.

[0064] The invention is not limited to the embodiments and variants presented and other embodiments and variants will become clear to those skilled in the art. Thus, the embodiments and variants can be combined with one another without departing from the scope of the invention. Without any limitation being implied, it is possible for the distribution element 8 to be supplied by the flow of heat transfer fluid from the downstream heat transfer fluid pipe 25B, by the first inlet pipe 25G of the distribution element 8 connected between the flow generation element 10 and the flow bypass element 11, and the flow of heat transfer fluid leaving the first heat exchanger 9, by the second inlet pipe 25H of the distribution element 8 mounted directly at the outlet of the first heat exchanger 9 as in the, even if the auxiliary pipe 25C of the is used. List of references

[0065] 1: fuel cell system2: filter3: compression device4: second heat exchanger5: humidifier6: fuel cell stack7: temperature measuring element8: distribution element9: first heat exchanger10: flow generation element11: flow bypass element12: third heat exchanger13: other flow generation element14: chopper15: powertrain20: control unit21: air transport circuit21A: upstream air duct21B: downstream air duct23: thermal control device24: assembly of air transport circuit 21 and thermal control device 2325: heat transfer fluid pipe network25A: upstream heat transfer fluid pipe25B: downstream heat transfer fluid pipe25C: auxiliary heat transfer fluid pipe25D: bypass pipe25E: inlet pipe of the second heat exchanger 425F: outlet pipe of the secondheat exchanger 425G: first inlet pipe of distribution element 825H: second inlet pipe of distribution element 8 (first embodiment)25H': second inlet pipe of distribution element 8 (second embodiment)27: hydrogen source29: electrical energy storage element31: vehicle33: vehicle cooling device 31E: air inletS: air outlet

Claims

Assembly (24) formed by an air transport circuit (21) and a device (23) for thermal regulation of the air transport circuit (21) for a stack (6) of fuel cells comprising an anode and a cathode, the air transport circuit (21) comprising at least one upstream air pipe (21A), called the cathode air inlet pipe, intended to supply oxygen to the stack (6) of fuel cells, the thermal regulation device (23) comprising a network (25) of heat transfer fluid pipes cooled by a first heat exchanger (9), the network (25) of heat transfer fluid pipes comprising at least one upstream heat transfer fluid pipe (25A), called the heat transfer fluid inlet pipe of the stack (6) of fuel cells, intended to supply heat transfer fluid to the stack (6) of fuel cells and a downstream heat transfer fluid pipe (25B),said heat transfer fluid outlet pipe of the fuel cell stack (6), intended to receive the heat transfer fluid after heat exchange with the fuel cell stack (6) coming from the upstream heat transfer fluid pipe (25A), the first heat exchanger (9) being mounted between the upstream heat transfer fluid pipe (25A) and the downstream heat transfer fluid pipe (25B), and a bypass element (11) making it possible to selectively either connect the downstream heat transfer fluid pipe (25B) to the first heat exchanger (9), or connect the downstream heat transfer fluid pipe (25B) to the upstream heat transfer fluid pipe (25A) without passing through the first heat exchanger (9), or both at the same time in order to control the temperature of the heat transfer fluid at the inlet of the fuel cell stack (6),characterized in that the thermal regulation device (23) comprises a second heat exchanger (4) mounted on the upstream air pipe (21A), upstream of a humidifier (5), in order to regulate the air temperature in the upstream air pipe (21A) upstream of the humidifier (5) by the network (25) of heat transfer fluid pipes and in that the second heat exchanger (4) is supplied with heat transfer fluid by a distribution element (8) selectively mixing the heat transfer fluid flows from the upstream heat transfer fluid pipe (25A) at the outlet of the first heat exchanger (9) upstream of the outlet of the bypass element (11), and from the downstream heat transfer fluid pipe (25B) upstream of the inlet of the bypass element (11), in order to control the air temperature in the upstream air pipe (21A) independently of that of the stack (6) of fuel cells., Assembly (24) according to the preceding claim, in which the humidity of the humidifier (5) is supplied by a downstream air pipe (21B) of the air transport circuit (21), called the cathode air outlet pipe, intended to receive the air, after reduction of the oxygen in the air in the stack (6) of fuel cells, coming from the upstream air pipe (21A), and a reaction product of the stack (6) of fuel cells. Assembly (24) according to any one of the preceding claims, in which the air transport circuit (21) comprises a device (3) for compressing ambient air mounted on the upstream air pipe (21A) upstream of the second heat exchanger (4) in order to supply air to the upstream air pipe (21A). An assembly (24) according to any preceding claim, wherein the heat transfer fluid pipe network (25) comprises a heat transfer fluid flow generating element (10) for forcing heat transfer fluid movement in the heat transfer fluid pipe network (25). Assembly (24) according to any one of the preceding claims, in which the thermal regulation device (23) comprises a third heat exchanger (12) mounted between the upstream heat transfer fluid pipe (25A) and the downstream heat transfer fluid pipe (25B) in order to improve the cooling of the heat transfer fluid present in the network (25) of heat transfer fluid pipes. Assembly (24) according to the preceding claim, in which the distribution element (8) is configured to be supplied by the flow of heat transfer fluid from the downstream heat transfer fluid pipe (25B) and the flow of heat transfer fluid leaving the third heat exchanger (12) in order to offer a wider range of air temperature control in the upstream air pipe (21A). An assembly (24) according to claim 5 or 6, wherein the network (25) of heat transfer fluid pipes comprises an auxiliary heat transfer fluid pipe (25C) connecting the outlet of the third heat exchanger (12) to the downstream heat transfer fluid pipe (25B) in order to lower the heat transfer fluid temperature in the auxiliary heat transfer fluid pipe (25C). Fuel cell system (1) comprising a stack (6) of fuel cells connected to a hydrogen source, characterized in that the fuel cell system (1) is connected to the assembly (24) according to any one of the preceding claims, the stack (6) of fuel cells being connected to the air transport circuit (21) of the assembly in order to supply oxygen to the stack (6) of fuel cells and to the network (25) of heat transfer fluid pipes of the assembly in order to exchange heat with the stack (6) of fuel cells. Vehicle (31) comprising an electric powertrain (15) and an electrical energy storage element (29), characterized in that the vehicle (31) comprises a fuel cell system (1) according to the preceding claim. Method for thermal regulation of the assembly according to any one of claims 1 to 7 comprising the following steps: - measuring the air temperature at the outlet of the second heat exchanger (4); - comparing the temperature measured at the outlet of the second heat exchanger (4) with a predetermined target temperature; - selectively modifying the state of the distribution element (8) in order to bring the temperature at the outlet of the second heat exchanger (4) closer to said target temperature when the comparison value exceeds a predetermined threshold. Computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement the steps of the method according to the preceding claim. A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of claim 10.

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