Device for recirculating anode gas in an anode circuit of a fuel cell system, fuel cell system

Description

[0001] The invention relates to a device for recirculating anode gas in an anode circuit of a fuel cell system. Furthermore, a fuel cell system with a device according to the invention is proposed. State of the art

[0002] A fuel cell converts hydrogen and oxygen into electrical energy. The hydrogen is fed to the anode and the oxygen to the cathode of the fuel cell. Since the anode gas escaping from the fuel cell usually still contains residual amounts of hydrogen, it is recirculated and fed back to the anode. Recirculation can be achieved actively with the help of a recirculation fan and / or passively with the help of a jet pump.

[0003] A fluid supply device for a fuel cell is known from US 2002 / 0022172 A1. The fluid supply device for a fuel cell known from US 2002 / 0022172 A1 can have certain disadvantages. If a jet pump is used, this can prove problematic. This is because, without activating the recirculation, fresh hydrogen cannot usually be added. The decreasing recirculation performance of the jet pump in the partial load range is also problematic. To remedy this, a smaller second jet pump can be used, designed for the partial load range and arranged parallel to the first jet pump. If only one jet pump is activated, however, the flow rate of the active jet pump can flow back through the inactive jet pump, so that this flow path must be blocked, for example, using an integrated check valve.However, this creates a pressure loss that reduces the recirculation performance of the active jet pump.

[0004] The present invention addresses these problems. Firstly, it enables the addition of fresh hydrogen without activating recirculation. Secondly, in parallel jet pumps, it prevents backflow of anode gas through the inactive jet pump, while minimizing losses.

[0005] To solve these problems, the device having the features of claim 1 is proposed. Advantageous further developments of the invention are set forth in the subclaims. Furthermore, a fuel cell system with a device according to the invention is specified. Disclosure of the invention

[0006] The device proposed for recirculating anode gas in an anode circuit of a fuel cell system comprises at least one jet pump with a propulsion nozzle for introducing fresh anode gas, preferably hydrogen, an inlet for recirculated anode gas, and an outlet for fresh and recirculated anode gas. An actively controllable valve for closing and opening the inlet is arranged in the area of ​​the inlet. The valve comprises a magnet assembly for acting on a reciprocating magnet armature and a valve spring.

[0007] The actively controllable valve can be used to close or block the inlet, preventing anode gas from recirculating through the anode circuit. This allows fresh hydrogen to be introduced into the anode circuit via the jet pump without recirculation, for example, to dry the anode circuit. If the device comprises several jet pumps connected in parallel, the actively controllable valve can be used to specifically deactivate a jet pump to prevent backflow of anode gas through the inactive jet pump.

[0008] The actively controllable valve can be designed as a simple, cost-effective switching valve that closes or opens the inlet. This is possible because the valve does not require absolute tightness to shut off recirculation, and there is no risk of leakage to the outside.

[0009] The magnetic assembly of the actively controllable valve can be a simple linear solenoid actuator. Since only small differential pressures occur in the anode circuit, only a small actuator force is required, allowing the magnetic assembly to be designed accordingly.

[0010] Preferably, the valve's magnet assembly is located outside a hydrogen-carrying area of ​​the device. This allows for a high degree of sealing of the hydrogen-carrying area. Furthermore, potential ignition sources in the hydrogen-carrying area are avoided.

[0011] Alternatively or additionally, it is proposed that the effective direction of the magnet assembly be perpendicular to the main flow direction in the inlet. This means that the magnetic force generated by the magnet assembly acts on the magnet armature in such a way that it moves back and forth perpendicular to the main flow direction in the inlet. In this way, the inlet can be closed and opened by simply moving the magnet armature back and forth.

[0012] To close and release the inlet, the magnet armature is preferably coupled to a valve closing element. The magnet armature and the valve closing element can thus be made of different materials. Alternatively, it is proposed that the magnet armature also forms a valve closing element. In this way, the actively controllable valve can be manufactured even more simply and cost-effectively. To close the inlet, the valve closing element can preferably be brought into engagement with a lateral opening in the inlet. This means that when the valve is closed, the valve closing element is not only brought into contact with a wall surface delimiting the inlet, but also engages in an opening in the wall surface. In this way, the tightness of the valve can be improved.

[0013] In a further development of the invention, it is proposed that the magnet armature be penetrated axially by at least one pressure equalization opening. This is particularly advantageous when the magnet armature or the valve closing element engages a lateral opening of the inlet during closing. Since the opening is filled with anode gas, this avoids the need to close the valve against the pressure building up in the opening.

[0014] Furthermore, it is proposed that the magnet armature be sleeve-shaped, at least in sections, to accommodate the valve spring. The actively controllable valve can thus be designed very compactly, particularly in the axial direction. At the same time, the mass of the magnet armature is reduced.

[0015] According to a preferred embodiment of the invention, the magnet assembly comprises a magnet coil surrounded by an outer pole body, into which a pot-shaped or sleeve-shaped separating element made of a non-magnetic material is inserted, over which the magnet armature is guided. The outer pole body increases the magnetic force of the magnet coil. At the same time, it protects the magnet coil from external influences. The pot-shaped or sleeve-shaped separating element inserted into the magnet coil prevents a magnetic short circuit between the magnet armature and the magnet assembly when guiding the magnet armature. Furthermore, the separating element can be used to seal the hydrogen-carrying area from the magnet assembly.

[0016] Advantageously, the cup- or sleeve-shaped separating element is supported by an annular collar on an outer housing wall surface of the device, directly or indirectly via a sealing element. In this way, the separating element can also be used to seal the hydrogen-carrying area from the outside. The sealing effect can be optimized by arranging a sealing element, in particular a sealing ring, between the separating element and the outer housing wall surface. Furthermore, the separating element can be easily attached to the outer housing wall surface via the annular collar.

[0017] The inlet, in which the actively controllable valve is arranged, preferably opens into an intake chamber of the jet pump, wherein the drive nozzle is arranged in the intake chamber. With the help of the drive nozzle, a driving force can be generated which causes the anode gas to recirculate. However, if the inlet is closed using the actively controllable valve, the recirculation can be switched off in a targeted manner. The intake chamber is preferably connected to the outlet of the jet pump via a mixing tube and a diffuser. Recirculated and fresh anode gas meet in the intake chamber. The recirculated and fresh anode gas are mixed in the downstream mixing tube. In order to be able to arrange the drive nozzle coaxially to the mixing tube and diffuser, the inlet for recirculated anode gas preferably opens laterally into the intake chamber.

[0018] To enable the use of fresh anode gas as the propellant, a control valve can be installed upstream of the propellant nozzle. Alternatively, the propellant nozzle can be integrated into a metering valve for fresh anode gas, creating a particularly compact arrangement with few components.

[0019] Advantageously, the device comprises at least two jet pumps connected in parallel and activated depending on the load. This ensures sufficient recirculation capacity even in partial load conditions. At the same time, when only one jet pump is operating, the actively controllable valve located in the inlet can prevent the flow rate of the active jet pump from flowing back through the inactive jet pump.

[0020] Since the preferred area of ​​application is a fuel cell system, a fuel cell system with a device according to the invention is further proposed. The device is integrated into an anode circuit of the fuel cell system. With the aid of the device, anode gas escaping from at least one fuel cell can be recirculated, thus reducing fuel consumption. Recirculation can be deactivated using the actively controllable valve arranged in the inlet of the jet pump. If recirculation is achieved using several jet pumps connected in parallel, at least one jet pump can be deactivated, and backflow of anode gas through this jet pump can be actively prevented.

[0021] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Figure 1a schematic longitudinal section through a first device according to the invention for recirculating anode gas in an operating state in which the inlet is closed, Figure 2 a schematic longitudinal section through the device of the Figure 1 in an operating state in which the inlet is released, Figure 3 a schematic longitudinal section through a second device according to the invention for recirculating anode gas and Figure 4 a schematic representation of an anode circuit of a fuel cell system according to the invention. Detailed description of the drawings

[0022] The Figure 1 The schematically illustrated device 1 according to the invention serves for the recirculation of anode gas in an anode circuit 11 of a fuel cell system 10 (see Figure 4). The device 1 comprises a jet pump 2, which is or can be integrated into the anode circuit 11 via an inlet 4 and an outlet 5. The jet pump 2 also has a drive nozzle 3 with an upstream control valve 24, by means of which fresh anode gas can be introduced into an intake chamber 21 of the jet pump 2. The fresh anode gas also serves as a drive medium. This is because when fresh anode gas is introduced with the help of the drive nozzle, a drive force is generated which leads to the recirculation of anode gas in the anode circuit 11. The recirculated anode gas is introduced into the intake chamber 21 via the inlet 4. The inlet 4 opens laterally into the intake chamber 21, while the drive nozzle 3 is arranged coaxially with respect to a mixing tube 22 and a diffuser 23 of the jet pump 2.

[0023] An actively controllable valve 6 is integrated into the inlet 4. It has a magnet assembly 7 for acting on a reciprocating magnet armature 8. In this case, the valve 6 is designed as a normally closed valve, meaning that when the magnet assembly 7 is de-energized, the valve 6 is closed. In this switching position, the inlet 4 is also closed, so that recirculation is deactivated. The closing force is generated by a valve spring 9, which is supported on the magnet armature 8 for this purpose.

[0024] The magnet assembly 7 of the valve 6 is arranged externally, i.e., outside a hydrogen-conducting region 12. This facilitates the sealing of the hydrogen-conducting region 12 from the outside. Furthermore, the formation of a potential ignition source in the hydrogen-conducting region 12 is avoided. The magnet assembly 7 comprises an outer pole body 15 in which a magnet coil 16 is accommodated. A pot-shaped separating element 17 made of a non-magnetic material is inserted into the magnet coil 16. The pot-shaped separating element 17 serves to guide the magnet armature 8 and simultaneously prevents a magnetic short circuit between the magnet armature 8 and the magnet assembly 7. In addition, the separating element 17 fulfills a sealing function. On the one hand, it separates the hydrogen-conducting region 12 from the magnet assembly 7. On the other hand, it seals the hydrogen-conducting region 12 from the outside.For this purpose, the separating element 17 has an annular collar 18, via which it is supported on a housing outer wall surface 19 of the device 1. To increase the sealing effect, a sealing element 20 is inserted between the annular collar 18 and the housing outer wall surface 19.

[0025] The magnet armature 8 of the actively controllable valve 6 simultaneously forms a valve closing element, which, in the closed position, engages in a lateral opening 13 of a wall defining the inlet. To prevent the formation of a pressure cushion within the opening 13 that would impede the movement of the magnet armature 8, the magnet armature 8 has a pressure equalization opening 14. The magnet armature 8 is essentially sleeve-shaped so that it can accommodate the valve spring 9. At the other end, the valve spring 9 is supported on the cup-shaped separating element 17.

[0026] If the solenoid coil 16 of the solenoid assembly 7 is energized, a magnetic field is formed, the magnetic force of which moves the magnet armature 8 towards the solenoid coil 16. This leads to the opening of the valve 6, so that the inlet 4 is released. In this switching position of the valve 6, anode gas can be recirculated (see Figure 2 ). To deactivate the recirculation, valve 6 must be closed. To do this, the current supply to the solenoid coil 16 is stopped, so that the valve spring 9 returns the solenoid armature 8 to its initial position ( Figure 1 ).

[0027] The Figure 3 A further device 1 according to the invention for recirculating anode gas can be seen. This differs from the device of the Figures 1 and 2 only by the design of the valve 6. In the Figure 3The valve 6 is not designed as a normally closed valve, but as a normally open valve. The magnet armature 8 has a slightly different shape. Furthermore, the valve 6 can be designed analogously to the valve 6 of the Figures 1 and 2 be trained.

[0028] The exemplary ones in the Figures 1 to 3 The devices 1 according to the invention shown are used in particular in an anode circuit 11 of a fuel cell system 10. This is shown schematically in the Figure 4 shown.

[0029] The anode circuit 11 shown leads to an anode 25 of a fuel cell 30, which converts hydrogen together with oxygen into electrical energy. Air serves as the oxygen supplier, which is supplied via a Figure 4 not further shown cathode path of a cathode 26 of the fuel cell 30.

[0030] Fresh hydrogen (H 2 ) is introduced into the anode circuit 11 via a control valve 24 and a jet pump 2. The control valve 24 and the jet pump 2 form a device 1 for recirculating anode gas. Fresh and recirculated anode gas are therefore mixed in the jet pump 2. Since recirculated anode gas becomes enriched with nitrogen (N 2 ) over time, which diffuses from the cathode side to the anode side, the anode circuit must be purged from time to time. For this purpose, a purge valve 29 is integrated into the anode circuit 11. Upstream of the purge valve 29 are a water separator 27 and a drain valve 28, with the help of which product water (H 2 O) accumulating during operation of the fuel cell system 10 can be removed from the anode circuit 11.

[0031] The device 1 for recirculating anode gas is connected to the anode circuit 11 via an inlet 4 and an outlet 5. An actively controllable valve 6 is integrated into the inlet 4. Depending on the switching position of the valve 6, the inlet 4 is opened or closed. In this way, fresh anode gas can also be introduced via the jet pump 2 without recirculating the anode gas. The actively controllable valve 6 can thus be used to deactivate the recirculation.

Claims

1. Device (1) for recirculating anode gas in an anode circuit (11) of a fuel cell system (10), comprising at least one jet pump (2) with a driving nozzle (3) for introducing fresh anode gas, preferably hydrogen, an inlet (4) for recirculated anode gas and an outlet (5) for fresh and recirculated anode gas, characterized in that an actively controllable valve (6) intended for closing and opening the inlet (4) and comprising a magnet assembly (7), for acting on a reciprocating armature (8), and a valve spring (9) is arranged in the area of the inlet (4).

2. Device (1) according to Claim 1, characterized in that the magnet assembly (7) of the valve (6) is arranged outside a hydrogen-conducting area (12) of the device (1) and / or the direction of action of the magnet assembly (7) is perpendicular to the main flow direction in the inlet (4).

3. Device (1) according to Claim 1 or 2, characterized in that the armature (8) is coupled to a valve closing element or forms a valve closing element which can preferably be made to engage with a lateral opening (13) of the inlet (4) in order to close the inlet (4).

4. Device (1) according to one of the preceding claims, characterized in that the armature (8) is passed through in the axial direction by at least one pressure equalizing opening (14).

5. Device (1) according to one of the preceding claims, characterized in that the armature (8) is at least partly sleeve-shaped in order to receive the valve spring (9).

6. Device (1) according to one of the preceding claims, characterized in that the magnet assembly (7) comprises a magnetic coil (16) which is surrounded by an outer pole body (15) and inserted in which is a pot- or sleeve-shaped separating element (17) of a non-magnetic material, by way of which the armature (8) is guided.

7. Device (1) according to Claim 6, characterized in that the pot- or sleeve-shaped separating element (17) is supported by way of an annular collar (18) on an outer housing wall surface (19) of the device (1) directly or indirectly by way of a sealing element (20).

8. Device (1) according to one of the preceding claims, characterized in that the inlet (4) opens into a suction chamber (21) of the jet pump (2), wherein the driving nozzle (3) is arranged in the suction chamber (21) and / or wherein the suction chamber (21) is connected to the outlet (5) by way of a mixing tube (22) and a diffuser (23).

9. Device (1) according to one of the preceding claims, characterized in that a control valve (24) for metering in fresh anode gas is located upstream of the driving nozzle (3), or the driving nozzle (3) is integrated in a metering valve for fresh anode gas.

10. Device (1) according to one of the preceding claims, characterized in that at least two jet pumps (2) which can be activated load-dependently are connected in parallel.

11. Fuel cell system (10) having a device (1) according to one of the preceding claims, wherein the device (1) is integrated in an anode circuit (11) of the fuel cell system (10).