Fuel cell

Abstract

The invention relates to a fuel-cell system (1) having a "ping-pong" architecture, in which two groups (10, 20) of electrochemical cells are alternately supplied by a fluidic circuit (3, 4) comprising at least one expansion member and two switching members on the supply lines of the groups (100a, 200a). Advantageously, the switching members are formed by injectors (101, 201) configured to expand the supply fluid delivered by a main duct (300a). The injectors (101, 201) both allow the fluid to be expanded, and passage of the fluid to the inlets (11, 21) of the groups (10, 20) to be permitted or blocked.

Description

[0001] "Fuel cell"

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention relates to the field of fuel cells, in particular proton exchange membrane fuel cells (or PEMFCs). It can be used to condition or activate a PEMFC, and optimize its performance.

[0004] STATE OF THE ART

[0005] A fuel cell is made up of a stack of "unit" electrochemical cells, each comprising an anode and a cathode electrically separated from each other by an electrolyte. In the case of a hydrogen fuel cell, the fuel (hydrogen) is brought into contact with the anode, and the oxidant (oxygen) is brought into contact with the cathode. Oxidation and reduction reactions take place respectively at the anode and the cathode, producing electricity, water and heat. The electrolyte can be in the form of a membrane allowing the protons resulting from the hydrogen oxidation reaction to pass through. This is the case with proton exchange membrane fuel cells (PEMFC).

[0006] The cell stack is only the place where the reaction takes place: the reactants must be brought in, the products and non-reactive species must be removed, as must the heat produced. Generally separate fluid circuits are used to supply the cell stack with fuel and oxidant respectively, and to remove the products from the stack.

[0007] When the fuel is hydrogen, it can come from a pressurized tank. The fluid circuit intended to bring the hydrogen to the anode then includes one or more expansion stages to reduce the hydrogen pressure at the inlet of the cell stack.

[0008] The fluid circuit can be more complex in the case of particular battery architectures. In the so-called "ping-pong" architecture disclosed by patent document FR2975227, the battery is divided into several groups of cells fluidically connected to each other by their respective outlets.

[0009] In this known architecture illustrated in Figure 1, the supply at the input 11, 21 of the different groups 10, 20 is done alternately during certain operating phases of the cell. A first group 10 is supplied at the input 11 by the combustible fluid (hydrogen) while the supply of a second group 20 is cut off at the input 21. The combustible fluid passes through the first group, which then operates nominally, and leaves moistened and slightly depleted at the output 12 of the first group 10. This fluid then supplies the second group 20 via the output 22 of the second group 20. This direct supply of the first group and in the opposite direction of the second group makes it possible to dissipate pockets of highly depleted fluid formed within the cells of the first group. This prevents cells of the first group from operating for a prolonged period in the presence of a highly depleted stagnant fluid.The second group 20 is then supplied at inlet 21 with the combustible fluid while the supply to the first group 10 is cut off at inlet 11. The combustible fluid passes through the second group, which then operates nominally, and leaves moistened and slightly depleted at outlet 22 of the second group 20. This fluid then supplies the first group 10 via outlet 12 of the first group 10. This direct supply of the second group and in the opposite direction of the first group also makes it possible to dissipate pockets of highly depleted fluid formed within the cells of the second group during the previous cycle. This prevents cells of the second group from operating for a prolonged period in the presence of a highly depleted stagnant fluid.

[0010] The principle of this ping-pong architecture consists of alternately supplying the different groups of cells so as to alternate nominal operating phases with supply phases in the opposite direction. The fluid circuit 3, 4 of such an architecture thus comprises a separate supply line 100, 200 for each group 10, 20 and a switching valve 101v, 201v per supply line 100, 200. The fluid circuit of such a fuel cell is relatively large. This increases the total size of the cell.

[0011] An object of the present invention is therefore to propose a fuel cell having reduced bulk, in particular at the level of the fluid circuit.

[0012] Other objects, features, and advantages of the present invention will become apparent from the following description and accompanying drawings. It is understood that other advantages may be incorporated.

[0013] SUMMARY OF THE INVENTION

[0014] To achieve this objective, according to one embodiment, a fuel cell is provided comprising:

[0015] • a first group of electrochemical cells having a first input and a first output,

[0016] • a second group of electrochemical cells having a second input and a second output,

[0017] • a fluid circuit intended to supply said first and second groups with a fluid, and to evacuate said fluid from said first and second groups.

[0018] The fluid circuit includes a so-called upstream part comprising:

[0019] • a main supply conduit configured to conduct the fluid at a so-called medium pressure, and connected to secondary supply lines,

[0020] • a first secondary supply line connected to the main supply conduit and connected to the first inlet of the first group,

[0021] • a second secondary supply line connected to the main supply conduit and connected to the second inlet of the second group.

[0022] The fluid circuit includes a so-called downstream part comprising:

[0023] • a main exhaust duct connected to secondary exhaust lines, and configured to be connected to an exhaust,

[0024] • a first secondary evacuation line connected to the first outlet of the first group, to the main evacuation conduit, and to the second outlet of the second group so as to allow a supply of fluid to the second group via the second outlet, by the fluid having passed through the first group,

[0025] • a second secondary discharge line connected to the second outlet of the second group, to the main discharge duct, and to the first outlet of the first group, so as to allow a supply of fluid to the first group via the first outlet, by the fluid having passed through the second group.

[0026] The stack further includes:

[0027] • at least one expansion member located in the upstream part of the fluid circuit, configured to reduce the pressure of the fluid coming from the reservoir, from medium pressure to low pressure,

[0028] • a first switching member on the first secondary supply line, configured to authorize or block a flow of fluid towards the first inlet,

[0029] • a second switching member on the second secondary supply line, configured to allow or block a flow of fluid towards the second inlet,

[0030] • preferably a purge member on the main exhaust duct, configured to allow or block a flow of fluid to the exhaust.

[0031] Advantageously, the at least one expansion member comprises a first expansion member on the main supply conduit, configured to reduce the pressure of the fluid coming from the reservoir, from high pressure to medium pressure.

[0032] Advantageously, the first switching member is formed by a first injector allowing or blocking the flow of fluid towards the first inlet, and configured to reduce the pressure of the fluid coming from the first expansion member, from medium pressure to a first low pressure.

[0033] Advantageously, the second switching member is formed by a second injector allowing or blocking the flow of fluid towards the second inlet, and configured to reduce the pressure of the fluid coming from the first expansion member, from medium pressure to a second low pressure.

[0034] Thus, the at least one expansion member is formed by the first and second injectors.

[0035] Thus, the first and second injectors perform both a role of expanding the fluid, from the medium pressure to the first and second low pressures respectively, and a switching role to authorize or block the flow of the fluid to the first and second inlets respectively of the first and second groups.

[0036] In a conventional ping-pong architecture as illustrated in Figure 1, the fluid is expanded in practice by means of two expanders 31, 32 mounted on the main supply duct 300 successively ensuring a first expansion from high pressure to medium pressure, then a second expansion from medium pressure to low pressure. To maintain a constant fluid volume flow rate, the section 300a of the main supply duct increases at the outlet of the first expander 31 (high pressure - medium pressure), and increases again at the outlet of the second expander 32 (medium pressure - high pressure). This increased section 300b is then constant along the secondary supply lines 100, 200 provided with the switching valves 101v, 201v.

[0037] In the context of the development of the present invention, it was identified that the size of the fluid circuit of the classic ping-pong architecture was linked to:

[0038] • Number of triggering organs 31, 32 and switching organs 101v, 102v,

[0039] • The size of the second regulator 32 requiring a very large membrane to go from medium pressure to low pressure,

[0040] • At the large section 300b of the parts of the fluid circuit 3 where the fluid circulates at low pressure.

[0041] By replacing the second regulator 32 with an injector, the compactness of the fluid circuit is already improved. An injector has a high pressure drop coefficient, compatible with good compactness.

[0042] In the context of the present invention, however, it has been observed that the injector could also provide a switching function, a function which is usually assigned to on / off valves. Therefore, instead of replacing the second regulator with an injector as a person skilled in the art could have done, it was decided to remove the second regulator and replace the switching valves on each of the secondary supply lines with injectors. Thus, the number of components in the fluid circuit is reduced. We move from a set of two switching valves and a medium pressure - low pressure regulator in the case of the conventional ping-pong architecture, to a set of two injectors in the case of the ping-pong architecture according to the invention. The compactness of the circuit is therefore further improved. This also simplifies the design of the fluid circuit and the management of the various components.The energy consumption of the fluid circuit is also reduced, since it is sufficient to electrically power only one injector out of the two, alternately, to supply the fuel cell with the ping-pong architecture according to the invention with combustible fluid. On the contrary, in the case of the conventional ping-pong architecture, it is necessary to permanently electrically power two members for expansion and switching, these functions being carried out separately.

[0043] The use of injectors instead of switching valves, and the elimination of the second regulator, also makes it possible to shorten the total length of the circuit having a large cross-section for the circulation of the low-pressure fluid. Indeed, only the parts of the fluid circuit located respectively between the first injector and the first inlet, on the first secondary supply line, and between the second injector and the second inlet, on the second secondary supply line, actually require a large cross-section compatible with the flow of combustible fluid at low pressure. The total size of the fluid circuit is further reduced. Due to its reduced size, the injector can also be partially or totally integrated at the inlet of the cell, which can completely eliminate the need for low-pressure pipes.

[0044] In addition to their improved compactness, these injectors offer high operational reliability and improved responsiveness, allowing easy adjustment of the set pressure.

[0045] Consequently and advantageously, the fuel cell having a ping-pong architecture according to the present invention makes it possible in particular to gain in compactness, to simplify the fuel fluid (hydrogen) supply line, and to reduce the energy consumption dedicated to the injection of fuel fluid.

[0046] BRIEF DESCRIPTION OF THE FIGURES

[0047] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings in which:

[0048] Figure 1 represents a fuel cell having a ping-pong architecture according to the prior art.

[0049] Figure 2A represents a fuel cell having a ping-pong architecture according to a first operating phase, according to a first embodiment of the present invention.

[0050] Figure 2B represents a fuel cell having a ping-pong architecture according to a second operating phase, according to a first embodiment of the present invention.

[0051] Figure 2C represents a fuel cell having a ping-pong architecture according to a third operating phase, according to a first embodiment of the present invention.

[0052] Figure 3 shows a fuel cell having a ping-pong architecture according to a second embodiment of the present invention.

[0053] Figure 4 shows a fuel cell having a ping-pong architecture according to a third embodiment of the present invention.

[0054] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular, the different members and the different parts of the fluid circuit are illustrated by diagrams which are not representative of reality.

[0055] DETAILED DESCRIPTION OF THE INVENTION

[0056] Before commencing a detailed review of embodiments of the invention, optional features which may optionally be used in combination or alternatively are set out below:

[0057] According to one example, the fuel cell system comprises:

[0058] • a first group of electrochemical cells having a first input and a first output,

[0059] • a second group of electrochemical cells having a second input and a second output,

[0060] • a fluid circuit intended to supply said first and second groups with a fluid, and to evacuate said fluid from said first and second groups, and

[0061] The fluid circuit includes a so-called upstream part comprising:

[0062] • a main supply conduit configured to be connected to a tank storing the fluid at a pressure P1, called high pressure, and connected to secondary supply lines,

[0063] • a first secondary supply line connected to the main supply conduit and connected to the first inlet of the first group,

[0064] • a second secondary supply line connected to the main supply conduit and connected to the second inlet of the second group, and

[0065] The fluid circuit includes a so-called downstream part comprising:

[0066] • a main exhaust duct connected to secondary exhaust lines, and configured to be connected to an exhaust,

[0067] • a first secondary evacuation line connected to the first outlet of the first group, to the main evacuation conduit, and to the second outlet of the second group so as to allow a supply of fluid to the second group via the second outlet, by the fluid having passed through the first group,

[0068] • a second secondary discharge line connected to the second outlet of the second group, to the main discharge duct, and to the first outlet of the first group, so as to allow a supply of fluid to the first group via the first outlet, by the fluid having passed through the second group, and

[0069] The stack further includes:

[0070] • at least one expansion member located in the upstream part of the fluid circuit, configured to reduce the pressure of the fluid coming from the reservoir, from high pressure to low pressure,

[0071] • a first switching member on the first secondary supply line, configured to authorize or block a flow of fluid towards the first inlet,

[0072] • a second switching member on the second secondary supply line, configured to allow or block a flow of fluid towards the second inlet,

[0073] • preferably a purge member on the main exhaust duct, configured to allow or block a flow of fluid to the exhaust.

[0074] According to one example, the at least one expansion member comprises a first expansion member on the main supply conduit, configured to reduce the pressure of the fluid from the reservoir, from high pressure to medium pressure.

[0075] According to one example, the first switching member is formed by a first injector configured to reduce the pressure of the fluid coming from the first expansion member, from medium pressure to a first low pressure.

[0076] According to one example, the second switching member is formed by a second injector configured to reduce the pressure of the fluid coming from the first expansion member, from medium pressure to a second low pressure.

[0077] According to one example, the first and second injectors are pressure-regulated respectively by first and second sensors located respectively on the first and second secondary supply lines. Each of the injectors is thus connected to its own sensor. This allows independent regulation of the injectors.

[0078] According to one example, the first and second injectors are pressure-regulated by a sensor located in the downstream part of the fluid circuit, for example on the main discharge pipe, typically between the first and second outlets and the purge member. The injectors are thus regulated via a measurement downstream of the stack. This measurement is more representative of the actual pressures within the groups of the stack. The measurement is thus more reliable and the pressure control can be more precise. Furthermore, a single sensor here makes it possible to regulate the injection in both groups. This minimizes the number of members present on the fluid circuit. The compactness of the stack is improved.

[0079] In one example, the sensor is positioned such that, for given constant supply conditions of the first group or the second group, the sensor measures the same constant pressure.

[0080] According to one example, the sensor is positioned equidistant from the first and second outputs of the first and second groups.

[0081] According to one example, the cell further comprises a controller configured to control the first and second injectors based on a pressure measurement from the sensor and optionally a pressure drop model established for the first and second groups of electrochemical cells. This improves the regulation of the first and second injectors. Such a model may take into account parameters additional to the pressure drops, such as for example the temperature of the cell or the current density.

[0082] According to one example, the fluid circuit further comprises in the upstream part:

[0083] • A third secondary supply line in parallel with the first secondary supply line, connected to the main supply conduit and connected to the first inlet of the first group,

[0084] • a fourth secondary supply line in parallel with the second secondary supply line, connected to the main supply conduit and connected to the second input of the second group.

[0085] According to one example, the stack further comprises:

[0086] • A third injector on the third secondary supply line, allowing or blocking the flow of fluid to the first inlet, and configured to reduce the pressure of the fluid from the main supply line, from medium pressure to a third low pressure,

[0087] • A fourth injector on the fourth secondary supply line, allowing or blocking the flow of fluid to the second inlet, and configured to reduce the pressure of the fluid from the main supply line, from medium pressure to a fourth low pressure.

[0088] The first and second secondary feeders are thus doubled or supported by the third and fourth secondary feeders, respectively. The term "parallel" does not necessarily mean that these secondary feeders have parallel structures with each other. The term "parallel" is not understood as "structurally parallel". It means that the assembly of these secondary feeders is carried out in parallel. It also means that these secondary feeders are comparable with each other. A third secondary feeder provided with a third injector allows hardware redundancy with the first secondary feeder provided with the first injector. A fourth secondary feeder provided with a fourth injector allows hardware redundancy with the second secondary feeder provided with the second injector.This improves the reliability of the stack. It also extends the flow range accessible to the first and second groups of cells. It also limits pressure oscillations at the inlet of the stack groups. The third and fourth secondary feed lines are not necessarily identical to the first and second secondary feed lines. The third and fourth injectors are not necessarily identical to the first and second injectors. Injectors sized differently from each other, for example, a large injector and a small injector in parallel, typically allow the flow range to be swept with less pressure oscillations. Two identical injectors in parallel typically double the flow range.

[0089] According to one example, the first, second, third and fourth injectors are pressure-regulated by a sensor located on the downstream part of the fluid circuit, for example on the main discharge pipe, typically between the first and second outlets and the purge member. This minimizes the number of members present on the fluid circuit. The compactness of the stack is improved.

[0090] According to one example, the stack further comprises an additional sensor intended to supplement the sensor located on the downstream part of the fluid circuit. The additional sensor forms a redundancy with the sensor located on the downstream part of the fluid circuit. This improves the reliability of the stack.

[0091] According to one example, the main supply conduit is connected to a first expansion member configured to reduce the pressure of the fluid coming from a reservoir storing the fluid at a so-called high pressure, from high pressure to medium pressure.

[0092] According to one example, the first expansion member is formed by an injector different from the first and second injectors. This improves the compactness of the fluid circuit. An injector is more compact than a regulator.

[0093] In one example, the first expansion organ is a simple regulator.

[0094] In one example, the secondary supply lines comprise only one or more injectors with possibly their associated sensors, without switching valves. In one example, the secondary supply lines are directly connected to the main supply conduit and to the inlets of the groups considered.

[0095] Unless inconsistent, technical features described in detail for a given embodiment may be combined with technical features described in the context of other embodiments described by way of example and not limitation. In particular, elements described or illustrated for certain embodiments of the cell may be combined so as to form another embodiment which is not necessarily illustrated or described. Such an embodiment is obviously not excluded from the invention. A fuel cell according to the present invention comprises at least two groups of electrochemical cells. A person skilled in the art will have no difficulty in implementing an embodiment comprising more than two groups of electrochemical cells.

[0096] In the context of the present invention, the term "ping-pong architecture fuel cell system" means a system comprising at least two groups of electrochemical cells distributed in one or more stacks. Each group is thus made up of a series of electrochemical cells electrically and fluidically interconnected. The cells are typically in the form of a membrane-electrode assembly commonly referred to as MEA. The cell here comprises at least five stacked cells, and preferably at least ten.

[0097] The ping-pong architecture fuel cell system typically has different operating phases, in particular, a first phase during which a first group is supplied directly by a first injector, the second group being supplied only by the gas leaving the first group, a second phase during which the second group is supplied directly by a second injector, the first group being supplied only by the gas leaving the second group, a third phase of simultaneous operation of the first and second groups and / or a purge phase. The first and second phases are carried out alternately. The third operating phase and / or the purge phase follow the first and second phases.

[0098] The terms "high pressure", "medium pressure" and "low pressure" are perfectly clear to those skilled in the art. A high pressure is strictly higher than a medium pressure. A medium pressure is strictly higher than a low pressure. A high pressure is generally higher than 50 bars, or even higher than 100 bars. A high pressure can reach up to 700 bars, or even more depending on the conditions. A medium pressure is generally between 5 and 40 bars, typically between 5 and 20 bars. A low pressure is generally lower than 4 bars. In the context of the present invention, an inlet or an outlet of a group of the cell, typically each have a structural aspect and a functional aspect. Thus structurally, the inlet and the outlet correspond to first and second passage orifices for the combustible fluid.Functionally, the inlet and outlet respectively designate the intake and discharge of the combustible fluid. To the extent that the direction of circulation of the fluid within the group is alternately reversed, the inlet and outlet can be functionally interchanged. Thus, the first passage orifice can form the inlet or the outlet functionally, and conversely, the second passage orifice can form the outlet or the inlet functionally.

[0099] To facilitate understanding of the fluid circulation in the battery cells, we retain only the inlet / outlet terms and their corresponding references on the accompanying drawings, respectively X1 (X= 1...2) for the inlet and X2 (X= 1...2) for the outlet, regardless of their functional assignment.

[0100] In the context of the present invention, the outlets of the groups are in fluid communication with each other, via the secondary discharge lines specific to each of the groups. Each secondary discharge line extends between the outlet of the group in question and a common main discharge conduit. Each secondary discharge line may use sections of other lines, for example other secondary discharge lines. Thus, sections of a given secondary discharge line may be common with sections of other secondary discharge lines. Tap-off points or branches may be physically present along the secondary discharge line(s). Members may also be present along these secondary discharge lines, for example regulating members. All of the secondary discharge lines may form an outlet manifold of the stack connected to the main discharge conduit of the stack.

[0101] The operation of the battery according to the invention is based on a succession of supply and / or discharge phases that differ from each other. Unless explicitly stated, the terms "succession" or "successive" do not necessarily imply, even if this is generally preferred, that the phases follow one another immediately, with intermediate phases or stages possibly separating them.

[0102] In the attached figures, a direction of flow of the fluid in the fluid circuit is indicated by an arrow. The dotted lines illustrate data links, typically between sensors and injectors, valves or regulators. In the attached figures, for the sake of clarity, the illustrated stack system comprises a single stack comprising two groups. It is understood that the description of this stack extends to the stack system and all variants in number of stacks, groups etc.

[0103] In the following examples, the fuel cell is described and illustrated for a ping-pong architecture comprising two groups of substantially identical cells. However, it is perfectly possible to implement more than two groups and / or groups of different dimensions, without departing from the general principle of the fluid circuit explained below. The groups can also be distributed in different stacks fluidically connected to each other.

[0104] The original idea implemented in the development of the present invention consists in particular in replacing the members separately ensuring the expansion and switching along the fluid circuit, by a single member ensuring both the expansion and the switching, in particular by an injector. This makes it possible to gain in compactness, responsiveness and reliability.

[0105] In particular, it was observed that it was not necessary to use switching valves to ensure the switching function in the fluid circuit, contrary to a technical prejudice. This function is advantageously performed by an injector.

[0106] A hydrogen injector is typically a solenoid valve sized to achieve very short opening-closing cycles, on the order of hundredths or tenths of a second up to a second. This device allows the injection of a pulsed flow of hydrogen at a variable flow rate and with improved responsiveness, for example compared to a regulated proportional solenoid valve. Its operation requires the application of a pressure difference of a few bars between the inlet and outlet of the injector, in particular in order to obtain a wide flow range. Injectors are significantly more compact than diaphragm pressure reducers. Pressure regulation by an injector is typically achieved by adapting the ratio of the opening-closing cycles of the injector in operation.

[0107] In the context of the present invention, an injector has at least one pressure regulating function, in particular for reducing a medium pressure to a low pressure, and at least one chopping or switching function. In contrast, a switching valve has a single chopping or switching function.

[0108] As mentioned above, Figure 1 illustrates a fuel cell 1 having a ping-pong architecture according to the prior art. It is connected to a high-pressure hydrogen tank 2 and comprises a fluid circuit composed of a part 3 upstream of the groups 10, 20 of electrochemical cells, and a part 4 downstream of the groups 10, 20 of electrochemical cells. The upstream part 3 according to the prior art comprises a shut-off valve 30 at the outlet of the tank 2, a main supply conduit 300 on which are successively mounted a first pressure reducer 31 and a second pressure reducer 32. The first pressure reducer 31 makes it possible to reduce the pressure of the fluid coming from the tank 2 from a so-called high pressure of the order of a few hundred bars to a so-called average pressure of the order of a few tens of bars. Consequently, the section of the main supply conduit 300a increases at the outlet of the first pressure reducer 31.The second regulator 32 makes it possible to reduce the pressure of the fluid coming from the first regulator 31 from medium pressure to a so-called low pressure of the order of a few bars. Consequently, the section of the main supply conduit 300b increases at the outlet of the second regulator 32.

[0109] The upstream part 3 of the fluid circuit according to the prior art also comprises a first secondary supply line 100 connecting the main supply conduit 300b to the inlet 11 of the first group 10 of electrochemical cells, and a second secondary supply line 200 connecting the main supply conduit 300b to the inlet 21 of the second group 20 of electrochemical cells. The first and second secondary supply lines 100, 200 respectively comprise a first switching valve 101v and a second switching valve 201v ensuring either the passage or the blocking of the fluid to each of said groups 10, 20.

[0110] The downstream part 4 of the fluid circuit according to the prior art comprises a first secondary discharge line 120 connecting the outlet 12 of the first group 10 of electrochemical cells to the main discharge conduit 400, and a second secondary discharge line 220 connecting the outlet 22 of the second group 20 of electrochemical cells to the main discharge conduit 400. The first and second secondary discharge lines 120, 220 typically form an outlet manifold of the cell 1. The main discharge conduit 400 is connected to an exhaust 41, and is provided with a purge valve 40.

[0111] Figure 2A illustrates a first embodiment of a fuel cell with ping-pong architecture according to the invention, incorporating certain elements of the fuel cell illustrated in Figure 1. In particular, the groups 10, 20 of electrochemical cells and the downstream part 4 of the fluidic circuit are substantially identical to those of the prior art. Preferably, the two groups 10, 20 of cells have the same number of cells, but they may also be different. The groups 10, 20 may be nested in a single stack, with alternating cells of the first group and the second group, as described in patent document FR2975227. In this first embodiment illustrated in Figure 2A, the modifications with respect to the prior art are located in the upstream part 3 of the fluidic circuit.

[0112] The upstream part 3 according to the first embodiment of the invention preferably comprises a shut-off valve 30 at the outlet of the tank 2, a main supply conduit 300 on which is mounted a first pressure reducer 31, preferably a single first pressure reducer 31, for example a double-stage pressure reducer 31, possibly regulated by a pressure sensor 33, and configured to reduce the pressure of the fluid coming from the tank 2 from high pressure to medium pressure. The section of the main supply conduit 300a increases at the outlet of the first pressure reducer 31. It should be noted that the presence of high-pressure fluid and the need for expansion by the pressure reducer 31 to medium pressure is linked to a hypothesis of supply by a high-pressure tank 2.In the case of a supply of another type, for example by medium pressure storage or via a gas network, this supply may be made directly at medium pressure by an interconnection on the main supply conduit 300a.

[0113] The upstream part 3 of the fluid circuit according to the first embodiment of the invention also comprises a first secondary supply line 100a, 100b connecting the main supply conduit 300a to the inlet 11 of the first group 10 of electrochemical cells, and a second secondary supply line 200a, 200b connecting the main supply conduit 300a to the inlet 21 of the second group 20 of electrochemical cells. The first and second secondary supply lines 100, 200 respectively comprise a first injector 101 and a second injector 102.

[0114] The first and second injectors 101, 201 advantageously make it possible to:

[0115] • Reduce the pressure of the fluid coming from the first regulator 31 from the medium pressure to a first low pressure and a second low pressure respectively,

[0116] • Allow or block the passage of fluid to the first inlet 11 and the second inlet 21 respectively.

[0117] Each injector 101, 201 thus fulfills both the function of a pressure regulator and a switching valve. The first and second injectors 101, 201 are preferably pressure-regulated respectively by sensors 102, 202 located downstream of the injectors 101, 201, respectively on the first and second secondary supply lines 100b, 200b. A high-frequency opening / closing cycle (up to several cycles per second) can be applied to each injector 101, 201 depending on the difference between the pressure setpoint and the pressure value measured downstream by the sensors 102, 202. This makes them more responsive, flexible and precise with respect to the desired conditions for the cell.

[0118] According to one possibility, the first and second injectors 101, 201 are substantially identical and the first low pressure is substantially equal to the second low pressure. According to another possibility, the first and second injectors 101, 201 may be sized differently from each other, and the first low pressure may be different from the second low pressure.

[0119] Advantageously, the cross-section of the first secondary supply line 100a upstream of the injector 101 is substantially the same as that of the main supply duct 300a. In the same way, the cross-section of the second secondary supply line 200a upstream of the injector 201 is substantially the same as that of the main supply duct 300a. Only the secondary supply lines 100b, 200b downstream of the first and second injectors 101, 201 have an increased cross-section capable of conducting a constant volume flow rate of fluid at low pressure. The total size of the upstream part 3 of the fluid circuit is thus reduced.

[0120] Figure 2A illustrates a first operating phase of the cell 1 in which only the first group 10 is supplied with combustible fluid. In this configuration, the first injector 101 is in operation while the second injector 201 is closed. The operation of the first injector 101 typically corresponds to a rapid alternation of openings and closings. The purge valve 40 is closed. As illustrated by the arrows along the fluid circuit, the combustible fluid from the tank 2 first passes through the first regulator 31. The combustible fluid then has an average pressure of the order of 5 to 20 bars (typically 6 to 8 bars) at the outlet of the first regulator 31. The combustible fluid is then led to the inlet 11 of the first group 10 by the first secondary supply line 100a, 100b, through the first injector 101.The combustible fluid then has a first low pressure of less than 4 bars at the outlet of the first injector 101. The combustible fluid then passes through the first group 10 and then successively takes the first secondary discharge line 120, the second secondary discharge line 220, and reaches the second group 20 via the outlet 22.

[0121] Figure 2B illustrates a second operating phase of the cell 1 in which only the second group 20 is supplied with combustible fluid. In this configuration, the first injector 101 is closed and the second injector 201 is in operation. The operation of the second injector 201 typically corresponds to a rapid alternation of openings and closings. The purge valve 40 is closed. As illustrated by the arrows along the fluid circuit, the combustible fluid from the tank 2 first passes through the first regulator 31. The combustible fluid then has an average pressure of the order of 5 to 20 bars (typically 6 to 8 bars) at the outlet of the first regulator 31. The combustible fluid is then led to the inlet 21 of the second group 20 by the second secondary supply line 200a, 200b, through the second injector 201. The combustible fluid then has at the outlet of the second injector 201 a second low pressure of less than 4 bars.The combustible fluid then passes through the second group 20 and then successively takes the second secondary discharge line 220, the first secondary discharge line 120, and reaches the first group 10 via the outlet 12.

[0122] The transition between the first and second phases can be instantaneous, or can be done with a time lag. If a transition is used where both injectors 101, 201 are closed, this transition is preferably short (of the order of a few milliseconds for example) to avoid a drop in pressure in the stack. In the same way, if both injectors 101, 201 are operating simultaneously during the transition, its duration is preferably short (of the order of a second) to avoid switching to a “dead-end” type operating mode.

[0123] Figure 2C illustrates a third operating phase of the cell 1 in which the first and second groups 10, 20 are simultaneously supplied with combustible fluid. In this configuration, the first injector 101 is in operation and the second injector 201 is in operation. The purge valve 40 is either open to evacuate the fluid and the reaction products to the outside, or closed to accumulate certain products or reactants, for example nitrogen. As illustrated by the arrows along the fluid circuit, the combustible fluid from the tank 2 first passes through the first regulator 31. The combustible fluid then has at the outlet of the first regulator 31 an average pressure of the order of 5 to 20 bars (typically 6 to 8 bars).A portion of the combustible fluid is then conducted to the inlet 11 of the first group 10 by the first secondary supply line 100a, 100b, through the first injector 101, and another portion of the combustible fluid is conducted to the inlet 21 of the second group 20 by the second secondary supply line 200a, 200b, through the second injector 201. The combustible fluid then has at the outlet of the first injector 201 a first low pressure of less than 4 bars. The combustible fluid then has at the outlet of the second injector 201 a second low pressure of less than 4 bars. The combustible fluid then passes through the first and second groups 10, 20 respectively and then takes the first and second secondary discharge lines 120, 220, to the main discharge conduit 400.The fuel-depleted fluid may be accumulated in the downstream part 4 of the fluid circuit if the purge valve 40 is closed, or discharged to the exhaust 41 if the purge valve 40 is open.

[0124] The use of two injectors 101, 201 instead of conventional switching valves upstream of the inlets 11, 21 of each group 10, 20 advantageously makes it possible to apply different and / or time-varying pressure setpoints to the groups 10, 20, during the different operating phases of the cell 1. It is thus possible to apply different pressure setpoints for the first injector 101 and for the second injector 201. It is also possible to gradually reduce the pressure at the end of the first operating phase (respectively at the end of the second operating phase). This makes it possible to increase the pressure difference in the fluid circuit and within the groups 10, 20 between the end of the first operating phase and the start of the second operating phase following it. The fluid flow rate is thus increased.This makes it possible to improve the displacement of the liquid phase in the groups 10, 20 of cells. Furthermore, if performance differences appear between the two groups 10, 20 of cells, the application of different pressures during the first and second phases can remedy this problem. The use of two injectors 101, 201 therefore advantageously provides more responsiveness and operating flexibility for the operation of the cell 1. The operation of the injectors is also advantageously independent of the fluid flow rate, which presents large variations in a fuel cell. These flow rate variations can generate inaccuracies in the behavior of the regulator 31, which can be corrected by the injectors 101, 201 through the control thereof. The injectors therefore make it possible to simplify the pressure control of the cell.This is all the more true when the regulator 31 does not have regulation by a downstream sensor 33, an element of economy and simplicity for the system.

[0125] Structurally, the main discharge conduit 400 common to the two groups 10, 20 can be included in the stack of the groups 10, 20 of cells, as described in document FR2975227. It then plays the role of phase separator and makes it possible to collect the liquid water. A dedicated member can be added to improve the efficiency of this separation, for example a porous material, one or more baffles, etc.

[0126] Figure 3 illustrates a second embodiment of a fuel cell with ping-pong architecture according to the invention. Only the characteristics that differ from the first embodiment of this second embodiment are described below. The other characteristics are deemed to be identical to those of the first embodiment.

[0127] In this second embodiment, the first and second injectors 101, 201 are no longer each associated with an independent pressure sensor. A single pressure sensor 401, mounted on the downstream part 4 of the fluid circuit at the outlet of the first and second groups 10, 20, is used for regulating the first and second injectors 101, 201. This makes it possible to limit the number of pressure sensors and therefore to reduce costs and improve the compactness of the stack 1. The control of the first and second injectors 101, 201 is also simplified. In this position of the sensor 401, the pressure measurement is preferably carried out halfway between the outlet of the group 10 and the outlet of the group 20. If the two groups 10, 20 are identical, this makes it possible to measure the same pressure value independently of the supplied group.

[0128] As the sensor 401 is here mounted on the downstream part 4 of the fluid circuit, it may be advantageous to introduce a model of pressure losses in the two groups 10, 20 of cells, for the control-command of the injectors 101, 201. This improves the regulation of the injectors 101, 201. This model of pressure losses can be established from a precise characterization of the fluid behavior of the groups 10, 20 of cells. One or more injection controllers (not shown) configured to control the injectors 101, 201, can typically take into account this model of pressure losses for the control and command of the injectors 101, 201.

[0129] Figure 4 illustrates a third embodiment of a fuel cell with ping-pong architecture according to the invention. Only the characteristics different from the third embodiment compared to the first embodiment or the second embodiment are described below. The other characteristics are deemed identical to those of the first embodiment or the second embodiment.

[0130] In this third embodiment, two injectors are mounted in parallel on each of the secondary supply lines. This makes it possible both to obtain hardware redundancy, in the event of failure of one of the injectors for example, and to increase the flow rate range for each group 10, 20. Thus, the first secondary supply line 100 is divided into two branches 100a, 100c respectively carrying injectors 101, 103 each supplying the inlet 11 of the first group 10. The second secondary supply line 200 is also divided into two branches 200a, 200c respectively carrying injectors 201, 203 each supplying the inlet 21 of the second group 20. The injectors 101, 103, 201, 203 can all be identical, identical two by two, or all different depending on the needs. Using several injectors in parallel advantageously makes it possible to obtain a wider range of flow rates.This also helps limit pressure fluctuations by averaging the opening / closing cycles of each injector. This also helps mitigate injector failure. It can also help increase the lifespan of an injector, as it may only be used once in two.

[0131] This third embodiment is illustrated here with a sensor 401 downstream of the groups 10, 20, configured to regulate all of the injectors 101, 103, 201, 203, as for the second embodiment. A second sensor 403 is provided here for safety reasons: in the event of failure of the sensor 401, the sensor 403 replaces the sensor 401.

[0132] In this third embodiment, the purge valve is replaced by two valves 42, 43 mounted in parallel. This allows both redundancy and the possibility of modulating the purge flow rate depending on whether the opening of one or both valves 42, 43 is controlled simultaneously. The valves 42, 43 may be identical or different.

[0133] Through the examples described above, it appears clearly that the fuel cell system according to the invention, presenting improved compactness, reactivity, control and reliability, is perfectly suited for automotive or heavy transport applications (land, sea, air, etc.).

[0134] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

[0135] In particular, the number of injectors per secondary supply line, the number of pressure sensors and the position of these pressure sensors on the fluid circuit may vary. A person skilled in the art will easily be able to adapt the number of injectors and sensors and their positions to form a fluid circuit configuration corresponding to his needs.

[0136] Similarly, the capacity of one or more injectors to ensure the expansion of a relatively high upstream pressure to a low downstream pressure depends on the choice of injector sizing and the energy that one is prepared to supply to it in order to ensure its expansion cycles, and may be adapted by a person skilled in the art to the specificity of his installation. The concept of medium pressure described for the invention may thus be greater than 50 bars, using suitable injectors.

[0137] Several batteries, with groups of nested cells, can also be envisaged within the framework of the present invention, by implementing the principle of relaxation / switching by injectors.

Claims

CLAIMS System of at least one fuel cell (1), comprising: • a first group (10) of electrochemical cells having a first input (11) and a first output (12), • a second group (20) of electrochemical cells having a second input (21) and a second output (22), • a fluid circuit (3, 4) intended to supply said first and second groups (10, 20) with a fluid, and to evacuate said fluid from said first and second groups (10, 20), said fluid circuit (3, 4) comprising a part (3) called upstream comprising: a main supply conduit (300a) configured to conduct the fluid at a so-called medium pressure, and connected to secondary supply lines (100a, 200a), a first secondary supply line (100, 100a, 100b) connected to the main supply conduit (300a) and connected to the first inlet (11) of the first group (10), a second secondary supply line (200, 200a, 200b) connected to the main supply conduit (300a) and connected to the second inlet (21) of the second group (20), said fluid circuit (3, 4) comprising a part (4) called downstream comprising: a main evacuation conduit (400) connected to secondary evacuation lines (120, 220),and configured to be connected to an exhaust (41), a first secondary discharge line (120) connected to the first outlet (12) of the first group (10), to the main discharge duct (400), and to the second outlet (22) of the second group (20) so as to allow a supply of fluid to the second group (20) via the second outlet (22), by the fluid having passed through the first group (10), a second secondary discharge line (220) connected to the second outlet (22) of the second group (20), to the main discharge duct (400), and to the first outlet (12) of the, first group (10), so as to allow a supply of fluid to the first group (10) via the first outlet (12), by the fluid having passed through the second group (20), • at least one expansion member located in the upstream part (3) of the fluid circuit, configured to reduce the pressure of the fluid from medium pressure to low pressure, • a first switching member on the first secondary supply line (100a, 100b), configured to authorize or block a flow of fluid towards the first inlet (11), • a second switching member on the second secondary supply line (200a, 200b), configured to authorize or block a flow of fluid towards the second inlet (21), • preferably, a purge member (40) on the main discharge duct (400), configured to allow or block a flow of the fluid towards the exhaust (41), said system being characterized in that the first switching member is formed by a first injector (101) allowing or blocking the flow of the fluid towards the first inlet (11), and said first injector (101) is further configured to decrease the pressure of the fluid from the medium pressure to a first low pressure, the second switching member is formed by a second injector (201) allowing or blocking the flow of the fluid towards the second inlet (21), and said second injector (201) is further configured to decrease the pressure of the fluid from the medium pressure to a second low pressure, so that the at least one expansion member is formed by the first injector (101) and the second injector (201).

2. System according to the preceding claim in which the first and second injectors (101, 201) are pressure regulated respectively by first and second sensors (102, 202) located respectively on the first and second secondary supply lines (100b, 200b).

3. System according to claim 1 in which the first and second injectors (101, 201) are pressure regulated by a sensor (401) located in the downstream part (4) of the fluid circuit.

4. System according to the preceding claim in which the sensor (401) is positioned so that, for given constant supply conditions of the first group (10) or of the second group (20), the sensor (401) measures the same constant pressure.

5. System according to the preceding claim in which the sensor (401) is positioned at an equal distance from the first and second outputs (12, 22) of the first and second groups (10, 20).

6. System according to any one of claims 3 to 5 further comprising a controller configured to control the first and second injectors (101, 201) as a function of a pressure measurement of the sensor (401) and of a pressure drop model established for the first and second groups (10, 20) of electrochemical cells.

7. System according to claim 1 in which the fluid circuit (3, 4) further comprises in the upstream part (3): • A third secondary supply line (100c) in parallel with the first secondary supply line (100a), connected to the main supply conduit (300a) and connected to the first inlet (11) of the first group (10), • a fourth secondary supply line (200c) in parallel with the second secondary supply line (200a), connected to the main supply conduit (300a) and connected to the second inlet (21) of the second group (20), the system further comprising: • A third injector (103) on the third secondary supply line (100c), allowing or blocking the flow of fluid towards the first inlet (11), and configured to reduce the pressure of the fluid coming from the main supply conduit (300a), from medium pressure to a third low pressure, • A fourth injector (203) on the fourth secondary supply line (200c), allowing or blocking the flow of fluid towards the second inlet (21), and configured to reduce the pressure of the fluid coming from the main supply conduit (300a), from medium pressure to a fourth low pressure.

8. System according to the preceding claim in which the first, second, third and fourth injectors (101, 201, 102, 203) are pressure regulated by a sensor (401) located on the downstream part (4) of the fluid circuit.

9. System according to the preceding claim in which the sensor (401) is positioned so that, for given constant supply conditions of the first group (10) or of the second group (20), the sensor (401) measures the same constant pressure.

10. System according to any one of the two preceding claims further comprising an additional sensor (403) intended to replace the sensor (401) on the downstream part (4) of the fluid circuit.

11. System according to any one of the preceding claims in which the main supply conduit (300a) is connected to a first expansion member (31) configured to reduce the pressure of the fluid coming from a reservoir (2) storing the fluid at a so-called high pressure, from high pressure to medium pressure, 12. System according to the preceding claim in which the first expansion member (31) is formed by an injector different from the first and second injectors (101, 201).

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