WO2023066628A1

WO2023066628A1 - Jet pump module for a fuel cell system

Info

Publication number: WO2023066628A1
Application number: PCT/EP2022/076986
Authority: WO
Inventors: Michael Kurz
Original assignee: Robert Bosch Gmbh
Priority date: 2021-10-20
Filing date: 2022-09-28
Publication date: 2023-04-27
Also published as: DE102021211824A1

Abstract

The invention relates to a jet pump module (1) for recirculating anode gas in an anode circuit of a fuel cell system, comprising a first propelling nozzle (2) and a second propelling nozzle (3) which is arranged parallel to the first propelling nozzle (2). Each propelling nozzle (2, 3) is paired with an actively actuatable hydrogen metering valve (4, 5) so that the propelling nozzles (2, 3) can be activated independently of each other. The jet pump module additionally comprises a first mixing tube (6), into which the first propelling nozzle (2) opens, and a second mixing tube (7) which is arranged parallel to the first mixing tube (6) and into which the second propelling nozzle (3) opens, wherein each mixing tube (6, 7) is arranged downstream of an antehamber (8, 9) that can be connected to a common inlet region (12) for recirculated anode gas on the basis of the position of a piston (11), which can be moved back and forth, of a pressure-controlled valve (10). The invention likewise relates to a fuel cell system comprising such a jet pump module (1).

Description

Title:

JET PUMP MODULE FOR A FUEL CELL SYSTEM

The invention relates to a jet pump module for recirculating anode gas in an anode circuit of a fuel cell system. Furthermore, a fuel cell system with a jet pump module according to the invention is proposed.

State of the art

Hydrogen-based fuel cells require hydrogen and oxygen to convert them into electrical energy, heat and water. The hydrogen is supplied to an anode via an anode circuit. The air, which serves as the oxygen supplier, reaches a cathode via an air system. The two gas spaces within a fuel cell are each separated from one another by an electrolyte membrane that is permeable to protons.

A mobile fuel cell system is usually operated with an excess of hydrogen (lambda > 1). The excess hydrogen is recirculated via a recirculation path of the anode circuit and fed back to the fuel cells. The recirculation can be effected actively and/or passively, a recirculation pump being used for active recirculation and a jet pump with a propulsion nozzle being used for passive recirculation. Since a single jet pump can only inadequately cover the entire load range of a fuel cell system, concepts are known from the prior art that use two jet pumps or propulsion nozzles connected in parallel. In order to be able to operate these independently of one another depending on the load, the inactive jet pump or motive nozzle must be encapsulated, otherwise no anode gas is recirculated. The known concepts therefore provide a control valve, by means of which the flow path over the respective inactive jet pump can be disconnected. However, the control valve causes additional costs, so that the costs of the entire system increase.

When using a jet pump for the purely passive recirculation of anode gas in a fuel cell system, an additional hydrogen metering valve may also be required in order to free the fuel cell system of water residues by flushing with pure hydrogen in the event of a shutdown. This further increases the costs. In addition, the space requirement increases.

The present invention is therefore concerned with the task of specifying a more cost-effective and at the same time more space-saving solution for the operation of two jet pumps or driving nozzles for the passive recirculation of anode gas in an anode circuit of a fuel cell system.

To solve the problem, the jet pump module with the features of claim 1 is proposed. Advantageous developments of the invention can be found in the dependent claims. Furthermore, a fuel cell system with a jet pump module according to the invention is specified.

Disclosure of Invention

The jet pump module proposed for the recirculation of anode gas in an anode circuit of a fuel cell system comprises a first driving nozzle and a second driving nozzle arranged parallel to the first driving nozzle. Each propulsion nozzle is assigned an actively controllable hydrogen metering valve, so that the propulsion nozzles can be activated independently of one another. The jet pump module also includes a first mixing tube, into which the first propulsion nozzle opens, and a second mixing tube, which is arranged parallel to the first mixing tube and into which the second propulsion nozzle opens, with each mixing tube being preceded by an antechamber which, depending on the position, has a reciprocating Piston of a pressure-controlled valve can be connected to a common inlet area for recirculated anode gas.

The pressure applied to the piston can be used to move it into at least two positions, into a first position in which the first antechamber is connected to the common inlet area and the second antechamber is connected to the inlet Is let area decoupled, and in a second position in which the second anteroom is connected to the common inlet area and the first antechamber is decoupled from the inlet area. This prevents anode gas from being circulated through the jet pump module when a driving nozzle is activated. This means that the anode gas is reliably fed to the common outlet area and, via this area, to at least one fuel cell of the fuel cell system.

The movements of the piston are controlled via the pressure applied to the piston, i.e. passively. For this purpose, the pressure prevailing in the first antechamber is preferably applied to the piston on the one hand and the pressure prevailing in the second antechamber on the other hand. If a hydrogen dosing valve is now opened to activate a propulsion nozzle, the pressure in the respective antechamber drops so that a pneumatic force that moves the piston is generated via the pressure difference. In this way, the respective inactive propulsion nozzle is decoupled from the common inlet area. An additional control valve for controlling the two propulsion nozzles is therefore not necessary. This means that the costs for an actively switchable control valve are saved and the overall costs are reduced.

Another advantage results from the arrangement of the pressure-controlled valve on the inlet side. Because in this arrangement the flow resistance of the recirculated anode gas deteriorates only insignificantly. As a result, high efficiency can be achieved.

According to a preferred embodiment of the invention, the two mixing tubes are connected on the outlet side via a common outlet area. Since the antechamber of the respective inactive propulsion nozzle can be decoupled from the common inlet area with the aid of the pressure-controlled valve, there is no risk of anode gas being circulated through the jet pump module, despite the connection via the common outlet area. This is because the flow path through the respective inactive propulsion nozzle is blocked.

Advantageously, in a jet pump module according to the invention, the propulsion nozzles and/or the mixing tubes are designed for system loads of different magnitudes. In this way, a wide range of loads can be covered by either the low load motive nozzle or the high load motive nozzle is activated.

In a further development of the invention, it is proposed that the piston of the pressure-controlled valve, which can be moved back and forth, is prestressed in the direction of at least one end position by the spring force of at least one spring. The spring force causes an additional force acting on the piston, preferably compressive force, which can be designed such that when a hydrogen metering valve opens, the pressure increasing in the respective antechamber is not sufficient to move the piston from a position in which both antechambers are separated from the common inlet area are decoupled. This means that in this position no anode gas is recirculated, but only fresh hydrogen is metered in via the open hydrogen metering valve. This eliminates the need to provide an additional or third hydrogen metering valve, with the help of which the anode circuit can be flushed with fresh hydrogen in the event of a shutdown. This means that further costs and installation space can be saved.

Only when the hydrogen metering valve is opened so far that the pressure in the associated anteroom rises above the opening pressure of the pressure-controlled valve is fresh hydrogen not only metered in, but also anode gas recirculated with its help.

The piston is preferably biased in opposite directions with the aid of at least two springs. When the hydrogen metering valves are closed, the piston is then essentially balanced in terms of pressure or force, so that it can assume a type of central position in which both antechambers are decoupled from the common inlet area. In order to meter in fresh hydrogen without simultaneous recirculation of anode gas, both hydrogen metering valves can be opened selectively or together.

Furthermore, at least one end position of the piston, which can be moved back and forth, is preferably predetermined by a stop surface on the housing side. The abutment surface on the housing side is preferably ring-shaped and/or has a connecting channel passing through it, which opens into an antechamber. This ensures that the pressure prevailing in the antechamber is applied to the piston, even when the piston is in contact with the stop surface. The stop surface on the housing side preferably interacts with a stop surface formed on the end face of the piston. At the same time, this serves as an effective surface on which the pressure prevailing in the respective antechamber is applied to control the movements of the piston.

Both end positions of the piston are preferably specified by a stop surface on the housing side. Furthermore, each stop surface preferably interacts with a stop surface formed on the end face of the piston. The piston can then be moved back and forth between the two end positions to open and/or block the flow paths that connect the common inlet area with the antechambers, and preferably assume a middle position between the two end positions.

Alternatively, it is proposed that an end position be formed by a movable stop sleeve that is spring-loaded in the direction of the piston. In this case, the end position is variable, depending in particular on the pressures in the two antechambers. In this way, further design options or functionalities are created, which are described in more detail below in connection with a preferred embodiment of a jet pump module according to the invention.

Furthermore, the piston preferably has a longitudinal axis which is aligned perpendicular to the longitudinal axes of the propulsion nozzles. This alignment of the piston of the pressure-controlled valve is particularly space-saving. In particular, the piston can be arranged between the two vestibules with a corresponding alignment, so that the pressure prevailing in the respective vestibule is present on both sides of the piston.

As already mentioned, the piston of the pressure-controlled valve preferably assumes a middle position when the hydrogen metering valves are closed, in which both antechambers are decoupled from the common inlet area for recirculated anode gas. In this position, fresh hydrogen can be metered in by opening at least one hydrogen metering valve, without anode gas being recirculated at the same time. This is particularly important in the event of part in order to remove water residues with the help of the dosed fresh hydrogen.

Since the preferred area of application of a jet pump module according to the invention is a fuel cell system, a fuel cell system with an anode circuit is also proposed, in which a jet pump module according to the invention is integrated. With the help of this module, costs and installation space can be saved. Furthermore, a high level of efficiency can be achieved in the passive recirculation of anode gas, since the flow resistance of the recirculated anode gas is only slightly worsened by the proposed configuration of the jet pump module.

Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show:

1 shows a schematic longitudinal section through a first jet pump module according to the invention, a) with an active first motive nozzle with an inactive second motive nozzle and b) with an active second motive nozzle with an inactive first motive nozzle,

Fig. 2 shows a schematic longitudinal section through a second jet pump module according to the invention, a) with inactive first and second driving nozzle, b) with active second driving nozzle with inactive first driving nozzle, c) with active first driving nozzle with inactive second driving nozzle, d) with active first driving nozzle simultaneous decoupling from the inlet area and e) with active first and second propulsion nozzle with simultaneous decoupling from the inlet area, and

3 shows a schematic longitudinal section through a third jet pump module according to the invention, a) with activated second drive nozzle for recirculation of anode gas and b) with activated second drive nozzle with simultaneous decoupling from the inlet area.

Detailed description of the drawings

The jet pump module 1 shown in FIGS. 1a) and 1b) is used for the passive recirculation of anode gas in an anode circuit of a fuel cell system in which the jet pump module 1 is integrated. The jet pump For this purpose, module 1 comprises a first propulsion nozzle 2 and a second propulsion nozzle 3, which are arranged in parallel. The two propulsion nozzles 2, 3 are each assigned a hydrogen metering valve 4, 5 and a mixing tube 6, 7. Based on the design of the mixing tubes 6, 7, it can be seen that they are designed in conjunction with the respective propulsion nozzle 2, 3 for system loads of different magnitudes. The motive nozzle 2 with the mixing tube 6 is designed for higher loads, while the motive nozzle 3 with the mixing tube 7 is designed for lower loads. The driving nozzles 2, 3 can be activated separately from one another via the hydrogen metering valves 4, 5, so that the amount of recirculated anode gas can be controlled as a function of the load.

The mixing tubes 6 , 7 are connected on the outlet side via a common outlet area 13 of the jet pump module 1 . On the inlet side, the mixing tubes 6 , 7 are each preceded by an antechamber 8 , 9 which can be coupled or decoupled to a common inlet area 12 depending on the position of a reciprocating piston 11 of a pressure-controlled valve 10 . Recirculated anode gas can be fed to the jet pump module 1 via the common inlet area 12 . If an antechamber 8, 9 is decoupled from the inlet area 12, no recirculated anode gas gets into it. The inlet area 12 is then only connected to the outlet area 13 via the anteroom 8, 9, which is not decoupled in each case, while the other flow path is blocked. This ensures that no recirculated anode gas is circulated within the jet pump module 1 .

In FIG. 1a), the first propulsion nozzle 2 is activated and the second propulsion nozzle 3 is deactivated. The first propulsion nozzle 2 is activated via the associated hydrogen metering valve 4 . This is opened so that fresh hydrogen is taken from a tank 21 and fed to the propulsion nozzle 2 . The pressure is previously set to medium pressure with the aid of a pressure regulator 22 . The fluid jet generated by the driving nozzle 2 causes a negative pressure pi in the antechamber 8 that is smaller than a pressure P2 in the antechamber 9 . Since the pressures p1, p2 prevailing in the two vestibules 8, 9 are applied to the piston 11, the pressure difference causes a pneumatic force which moves the piston 11 in the direction of a first stop surface 16 on the housing side. In this position, the antechamber 8 is connected to the inlet area 12 so that recirculated anode gas is sucked into the mixing tube 6 . Due to the design of the driving nozzle 2 and of the mixing tube 6 for high loads, a comparatively large amount of recirculated anode gas is supplied to the outlet section 13 .

When the system load decreases, it is possible to switch from the driving nozzle 2 to the driving nozzle 3 by closing the hydrogen metering valve 4 and opening the hydrogen metering valve 5 (see FIG. 1b)). As a result, a negative pressure p4 is established in the antechamber 9, which is lower than a pressure pa in the antechamber 8, so that the piston 11 moves in the direction of a further stop surface 17 on the housing side. In this position, the vestibule 9 is connected to the inlet area 12, while at the same time the vestibule 8 is decoupled from the inlet area 12. Accordingly, recirculated anode gas is sucked into the mixing tube 7 and fed to the outlet area 13 via the mixing tube 7 .

The deactivation of one propulsion nozzle 2, 3 of the jet pump module 1 of FIG. 1 ensures that no anode gas is pumped within the jet pump module 1 in a circuit. Furthermore, by switching between the driving nozzles 2, 3, the amount of recirculated anode gas can be varied depending on the load.

A further preferred embodiment of a jet pump module 1 according to the invention is shown in FIG. This differs from that of FIG. 1 in particular in that springs 14, 15 are provided, the spring forces of which pretension the piston 11 in the direction of a first and a second end position. Via the spring forces of the springs 14, 15, the piston 11 can be held in a central position in which both vestibules 8, 9 are decoupled from the common inlet area 12 (see FIG. 2a)). The correct length adjustment of the two springs 14, 15 is responsible for the middle position of the piston 11.

In FIG. 2b), the hydrogen metering valve 5 is open to activate the driving nozzle 3. This creates a negative pressure ps in the antechamber 9, which pulls the piston 11 against the spring force F2 of the spring 15 against the stop surface 17. The softer the spring 15 is designed, the less vacuum is required to pull the piston 11 up to the stop surface 17 . In this position, a connection between the vestibule 9 and the inlet region 12 is established, while the vestibule 8 remains uncoupled from the inlet region 12—despite the changed position of the piston 11. Figure 2c) shows the opposite case. To activate the propulsion nozzle 2, the hydrogen metering valve 4 is open, so that there is a negative pressure ps in the antechamber 8, which pulls the piston 11—against the spring force Fi of the spring 14—to the stop surface 16 on the housing side. In this position, the vestibule 8 is connected to the inlet region 12 , while the vestibule 9 remains decoupled from the inlet region 12 .

Further functions are described below with reference to FIGS. 2d) and 2e), which can be implemented with the aid of the jet pump module 1 of FIG. This is because the central position of the piston 11 makes it possible, if required, to meter in fresh or dry hydrogen from the tank 21 without admixing recirculated and therefore moist anode gas.

If only a small amount of hydrogen is metered in from the tank 21 via the open hydrogen metering valve 4, the pressure in the antechamber 8 hardly changes. This means that in the antechamber 8 there is a negative pressure p? sets, which is not sufficient to move the piston 11 against the spring force of the spring 14 from its central position. Depending on the coordination of a length L of a blocking piston cross section and a diameter D of the inlet area 12, the antechamber 8 remains decoupled even when the piston 11 moves (see FIG. 2d)). Only when a larger quantity of hydrogen is metered in from the tank 21 via the hydrogen metering valve 4 does the pressure p? in the vestibule 8 significantly, so that the piston 11 is pulled against the stop surface 16 on the housing side. In this position, the antechamber 8 is connected to the inlet area 12 so that anode gas is recirculated and mixed with the fresh hydrogen from the tank 21 .

If the hydrogen metering valve 4 is operated below the design limit of the driving nozzle 2, small amounts of hydrogen can thus be metered in from the tank 21 without the admixture of recirculated (moist) anode gas. As shown by way of example in FIG. 2e), this also applies to the hydrogen metering valve 5. If this—at the same time as the hydrogen metering valve 4—is operated below a design limit for the propulsion nozzle 3, the forces acting on the piston 11 are comparatively small or cancel each other out. Can for rinsing thus fresh (dry) hydrogen can be removed from the tank 21 via both hydrogen metering valves 4, 5 without recirculated (moist) anode gas being admixed.

A further preferred embodiment of a jet pump module 1 according to the invention can be seen in FIG. Instead of the springs 14, 15, only one spring 15 is provided, by means of which a stop sleeve 20 is pretensioned against a stop surface 23 on the housing side. Depending on the position of the piston 11, a stop surface 19 of the piston 11 comes into contact with the stop sleeve 20. At the other end, the piston 11 has a stop surface 18 which interacts with a stop surface 16 on the housing side.

The stop sleeve 20 is arranged on the side of the piston 11 which faces the driving nozzle 3 for smaller system loads. If only so much hydrogen is metered in with the hydrogen metering valve 5 that the driving nozzle 3 is still operated below the upper design limit, a negative pressure ps occurs in the antechamber 9, which causes a pneumatic force that pulls the piston 11 up to the stop sleeve 20. In this position, the anteroom 9 is connected to the inlet area 12 . Since the spring force F3 of the spring 15 is greater than the pneumatic counterforce acting on the piston 11, the stop sleeve 20 remains on the stop surface 23 on the housing side (see FIG. 3a)).

If the motive nozzle 3 is operated above the upper design limit, the pressure in the antechamber 9 drops to a negative pressure pg, which is significantly lower than the negative pressure ps. As a result, a pneumatic force F _p acts on the piston 11 which is greater than the spring force F3 of the spring 15, so that the piston 11 and the stop sleeve 20 move in the direction of the stop surface 17 on the housing side. In this position of the piston 11, the antechamber 9 is decoupled from the inlet area 12, so that the outlet area 13 can be supplied with fresh (dry) hydrogen from the tank 21 without the admixture of recirculated (moist) anode gas (see FIG. 3b)).

The embodiments shown in FIGS. 1 to 3 have in common that the longitudinal axis A3 of the piston 11 of the pressure-controlled valve 10 is aligned perpendicular to the longitudinal axes Ai, A2 of the two driving nozzles 2, 3. This enables a compact arrangement of the valve 10, which therefore requires little installation space.

Claims

Expectations

1. Jet pump module (1) for recirculating anode gas in an anode circuit of a fuel cell system, comprising a first driving nozzle (2) and a second driving nozzle (3) arranged parallel to the first driving nozzle (2), each driving nozzle (2, 3) having an actively controllable assigned to the hydrogen metering valve (4, 5), so that the propellant nozzles (2, 3) can be activated independently of one another, further comprising a first mixing tube (6), into which the first propellant nozzle (2) opens, and a mixing tube (6 ) arranged second mixing tube (7) into which the second propulsion nozzle (3) opens, with each mixing tube (6, 7) being preceded by an antechamber (8, 9) which, depending on the position of a reciprocating piston (11) a pressure-controlled valve (10) can be connected to a common inlet area (12) for recirculated anode gas.

2. Jet pump module (1) according to claim 1, characterized in that the mixing tubes (6, 7) are connected on the outlet side via a common outlet region (13).

3. jet pump module (1) according to claim 1 or 2, characterized in that the propulsion nozzles (2, 3) and / or the mixing tubes (6, 7) are designed for different levels of system loads.

4. Jet pump module (1) according to one of the preceding claims, characterized in that the reciprocating piston (11) of the pressure-controlled valve (10) is prestressed in the direction of at least one end position by the spring force of at least one spring (14, 15).

5. Jet pump module (1) according to claim 4, characterized in that at least one end position is predetermined by a housing-side stop surface (16, 17) which preferably interacts with a stop surface (18, 19) formed on the front side of the piston (11).

6. Jet pump module (1) according to claim 4 or 5, characterized in that an end position is formed by a movable stop sleeve (20) which is spring-loaded in the direction of the piston (11).

7. Jet pump module (1) according to one of the preceding claims, characterized in that the piston (11) has a longitudinal axis (A3) which is perpendicular to the longitudinal axes (Ai, A2) of the propulsion nozzles (2, 3) is aligned.

8. Jet pump module (1) according to one of the preceding claims, characterized in that the piston (11) when the hydrogen metering valves (4, 5) are closed assumes a central position in which both vestibules (8, 9) are separated from the common inlet area (12) for recirculated Anode gas are decoupled.

9. Fuel cell system with an anode circuit, in which a jet pump module (1) according to one of the preceding claims is integrated.