CN113330616A

CN113330616A - Fuel cell system

Info

Publication number: CN113330616A
Application number: CN201980089349.8A
Authority: CN
Inventors: M·赫尔曼; H·克默尔
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-01-16
Filing date: 2019-11-26
Publication date: 2021-08-31
Anticipated expiration: 2039-11-26
Also published as: CN113330616B; WO2020148010A1; EP3912214A1; DE102019200459A1

Abstract

The invention relates to a fuel cell system (10) having at least one fuel cell (14), a hydrogen storage (26), in which hydrogen is stored under overpressure, and which is connected to an anode chamber (18) of the fuel cell (14) by means of a hydrogen supply line (22), and having an anode circuit (58), by means of which unconsumed hydrogen can be returned to an inlet (42) of the anode chamber (18) at an outlet (50) of the anode chamber (18), wherein at least one electrically driven recirculation blower (62), by means of which unconsumed hydrogen can be supplied to the inlet (42) of the anode chamber (18), is arranged between the outlet (50) and the inlet (42) of the anode chamber (18), and wherein at least a part of the hydrogen supplied from the hydrogen storage (26) to the anode chamber (18) can be supplied to the electrically driven recirculation blower The fan (62) is arranged in at least one gas bearing (70), and the gas bearing (70) can therefore be mounted statically.

Description

Fuel cell system

Technical Field

The present invention relates to a fuel cell system. The invention further relates to a recirculation blower for such a fuel cell system and to a method for operating such a recirculation blower.

Background

In mobile applications, polymer electrolyte membrane fuel cells (PEM-BZ) are preferred due to the low temperature levels in operation. This fuel cell type is operated with an excess of hydrogen in stoichiometric excess. Unconsumed hydrogen is recycled and supplied again to the reaction together with fresh hydrogen. Starting from a hydrogen tank (typically 350 or 700bar standard pressure), the hydrogen pressure is reduced in several stages to an operating pressure of <10 bar. To overcome the pressure drop from the anode outlet to the anode inlet, a recycle blower is typically used.

DE 102007037096 a1 discloses a fuel cell system with a recirculation blower arranged in the fuel circuit. The recirculation blower is operated here by a drive turbine, which is charged with compressed air.

Background of the invention it is the background of the invention that there are still many different solutions for the recycling of hydrogen mixtures. Conventional fluid machines do not fully exploit their advantages in the boundary conditions of hydrogen systems. The small pressure difference between the anode outlet and the anode inlet can in principle be overcome by means of a compact radial compressor. However, the high demands on the bearings (oil-free, high rotational speed) are contrary to today's demands. Due to the limited rotational speed, the machine is limited in pressure ratio and power density. Operation of the recirculation blower in humid conditions results in high material loads.

Disclosure of Invention

It is therefore the object of the present invention to provide a fuel cell system with which the recirculation of hydrogen can be achieved in an economical manner and in which the durability of the recirculation blower is extended. In addition, the object of the invention is to provide a recirculation blower which can be operated in such a fuel cell system. A further object of the invention is to provide a method for operating such a recirculation blower.

This object is achieved by a fuel cell system having the features of claim 1 and a recirculation blower for such a fuel cell system having the features of claim 8. The invention additionally provides a method for operating such a recirculation blower with the features according to claim 9. The dependent claims cited in each case represent advantageous developments of the invention.

The invention relates to a fuel cell system comprising at least one fuel cell, a hydrogen accumulator, in which hydrogen is stored under an overpressure. The hydrogen accumulator is connected to the anode chamber of the fuel cell by means of a hydrogen supply line. The fuel cell system additionally comprises an anode circuit, by means of which unconsumed hydrogen can be returned at the outlet of the anode chamber into the inlet of the anode chamber, wherein at least one electrically driven recirculation blower is arranged between the outlet and the inlet of the anode chamber, by means of which recirculation blower unconsumed hydrogen can be supplied to the inlet of the anode chamber.

At least a part of the hydrogen supplied by the hydrogen accumulator to the anode compartment can be introduced into at least one gas bearing of the electrically driven recirculation blower, so that the gas bearing can be supported statically.

The hydrogen accumulator is preferably a hydrogen tank. The electrically driven recirculation blower is preferably a radial compressor. A gas bearing is understood here to mean a bearing in which a gas pressure builds up in the bearing gap between the shaft and the bearing shell, by means of which gas pressure the shaft is supported. In dynamic gas bearings, this gas pressure builds up from a certain rotational speed of the shaft. In static gas bearings, the gas pressure is built up by the gas supplied from the outside, so that the shaft is already supported from the start.

The invention has the following advantages: wear in the gas bearings can be avoided precisely at the start-up or at the run-down of the electric recirculation blower. Thereby extending the durability of the recirculation blower. By supplying hydrogen, which mostly has a medium or low pressure level, no additional pump has to be provided in order to supply the gas bearing with pressure. Whereby such a fuel cell system can be economically provided.

Furthermore, such gas bearings often have leakage. By supplying hydrogen into the gas bearing, no elaborate seals of the bearing are required for avoiding hydrogen escaping from the gas bearing to unconsumed hydrogen. This makes it possible to provide such a fuel cell system economically.

In a preferred embodiment of the invention, the fuel cell system has a line section which is connected to the hydrogen supply line and the recirculation blower so that at least a portion of the hydrogen can be supplied to the gas bearing. A simple connection between the recirculation blower and the hydrogen supply line is achieved by the line section. This line section is thus independent of the hydrogen supply line and can therefore be switched on separately by a valve.

In a further preferred embodiment of the invention, the line section is connected to the hydrogen supply line between the low-pressure shut-off valve and the hydrogen metering valve. Here, the hydrogen dosing valve doses hydrogen for the fuel cell. Thus, before opening the hydrogen dosing valve, a pressure can be built up in the gas bearing for static support. Thus, a static bearing is already ensured before the recirculation blower is started, so that wear can be reduced.

Preferably, the line section has an additional hydrogen dosing valve for dosing hydrogen supplied to the gas bearing of the recirculation blower. Here, the additional hydrogen dosing valve can dose the amount of hydrogen as well as the hydrogen dosing valve, so that the amount of hydrogen supplied to the gas bearing can be adjusted. The additional hydrogen metering valve in the line section additionally has the following advantages: this makes it possible to switch from static gas bearing operation to dynamic gas bearing operation. In dynamic gas bearing operation, the additional hydrogen metering valve is closed here. Thus, hydrogen from the hydrogen supply line can be directly supplied only to the anode chamber.

In an advantageous embodiment, the line section is connected to the hydrogen supply line via an additional outlet of the hydrogen metering valve. In the hydrogen dosing valve, the two outlets are switched by means of a sealing assembly of the hydrogen dosing valve. Whereby no additional hydrogen dosing valve is required, whereby such a fuel cell system can be provided economically.

Advantageously, the line section is connected to the hydrogen supply line between the pressure reducer and the low-pressure shut-off valve. In this way, pressure can also build up in the gas bearing for static support before the low-pressure shut-off valve or the hydrogen metering valve is opened. As a result, a sufficient pressure can be built up in the gas bearing before the recirculation blower is started. Thereby, wear in the gas bearing is reduced, especially during start-up or run-down. Preferably, a shut-off valve is arranged in the line section, so that the hydrogen supply is stopped at a sufficient rotational speed in the gas bearing, which ensures dynamic support.

In a further advantageous embodiment, the hydrogen supply line is connected to the anode chamber by a recirculation blower. Thus, all the hydrogen supplied to the anode chamber is first introduced into the gas bearing. The hydrogen thus first bears against the gas bearing, so that there is a static bearing when the recirculation blower is started. The static support is realized here throughout the operation of the fuel cell. Thereby minimizing wear of the gas bearings and thereby extending the durability of the recirculation blower. Additionally, only a single hydrogen dosing valve is required. Whereby the fuel cell system can be economically realized.

The invention is additionally solved by a recirculation blower for use in a fuel cell system according to the invention. The recirculation blower comprises at least one compressor unit, an electric motor, by means of which the hydrogen can be compressed, a gas bearing, by means of which the compressor unit can be driven electrically, and a supply device, by means of which the compressor unit can be supported, by means of which a gas for static support can be supplied to the gas bearing, wherein the gas is part of the hydrogen supplied from a hydrogen accumulator of a fuel cell of the fuel cell system, and wherein the gas bearing has a bearing leak, by means of which the supplied hydrogen can be discharged into the compressor unit.

In the sense of the present invention, an arrangement on each structure is understood to be a feed mechanism by means of which gas can be supplied to the gas bearing. Here, a bearing leak is a gas flow exiting the gas bearing because the gas bearing is not sealed. Therefore, the bearing leakage must be compensated for by additional gas supplied to the gas bearing. The recirculation blower is structurally adapted such that bearing leakage can be diverted into the compressor assembly. This means that there is no seal between the gas bearing and the compressor package.

By continuously replacing the dry hydrogen supplied to the gas bearing, the water accumulated in the gas bearing and the recirculation blower is discharged, so that the rest of the gas bearing and the recirculation blower is dried. Corrosion of the recirculation blower components by the corrosive water can thereby be reduced. Thereby extending the durability of the recirculation blower. It is thus also possible to select materials that are less corrosion resistant, which are less expensive.

The invention further relates to a method for operating a recirculation blower, wherein hydrogen is supplied to the gas bearing in a rotational speed range below a limit rotational speed, so that a static mounting of the gas bearing is possible, and the supplied hydrogen is at least partially reduced in a rotational speed range above the limit rotational speed.

In the sense of the present invention, the limit rotational speed is understood here to be a predefined or calculated rotational speed of the recirculation blower. The rotational speed can be a rotational speed at which dynamic operation of the gas bearing is ensured. Likewise, the limit rotational speed can also be a rotational speed at which a transition between static bearing and dynamic bearing begins.

This method has the advantage that it is not necessary to supply hydrogen unnecessarily to the gas bearing. Thereby, the fuel cell system can be operated economically. Additionally, wear of the recirculation blower can be reduced.

Preferably, the supply of hydrogen into the gas bearing is stopped above a limit rotational speed. The limit rotational speed is preferably a rotational speed at which dynamic operation of the gas bearing is ensured. This has the advantage that no dosing valve is required.

In an advantageous embodiment, the hydrogen supply into the gas bearing is reduced linearly after the limit rotational speed is reached as the rotational speed increases. The limit rotational speed is preferably the rotational speed at which the transition region between the static operation and the dynamic operation of the gas bearing begins. Thus, as the proportion of the dynamic support increases, the hydrogen supply can already be reduced accordingly.

Drawings

Embodiments of the invention are illustrated in the drawings and are set forth in detail in the following description. The figures show:

figure 1 a first embodiment of a fuel cell system according to the invention,

figure 2 a second embodiment of a fuel cell system according to the invention,

figure 3 shows a third embodiment of a fuel cell system according to the invention,

figure 4 a fourth embodiment of a fuel cell system according to the invention,

figure 5 an embodiment of an electrically driven recirculation blower for a fuel cell system,

FIG. 6 first embodiment of a method for operating a recirculation blower, and

FIG. 7 is a second embodiment of a method for operating a recirculation blower.

Detailed Description

A first embodiment of a fuel cell system 10 according to the present invention is shown in fig. 1. Here, the fuel cell system 10 includes a fuel cell 14, of which only an anode chamber 18 is shown here. The anode chamber 18 is fluidically connected via a hydrogen supply line 22 to a hydrogen accumulator 26, which is designed here as a hydrogen tank. In the hydrogen supply line 22, a tank shutoff valve 30 is arranged downstream of the hydrogen storage 26 in order to shut off the hydrogen supply from the hydrogen storage 26.

Downstream of the tank shut-off valve 30, a pressure reducer 34 is arranged in the hydrogen supply line 22 in order to bring the high pressure of the hydrogen reservoir 26 to a low pressure level. Downstream of this pressure reducer 34, a low-pressure shutoff valve 38 is arranged in the hydrogen supply line 22 in order to interrupt the hydrogen supply in the low-pressure region. Between low-pressure shut-off valve 38 and inlet 42 of anode chamber 18, a hydrogen metering valve 46 is arranged, by means of which the amount of hydrogen introduced into anode chamber 18 can be metered. The hydrogen quantity is metered in such a way that the fuel cell 14 is operated in a stoichiometric excess.

A condensate separator 54 is disposed after outlet 50 of anode chamber 18. Condensate can be discharged by means of the condensate separator 54, which condensate has accumulated in the unconsumed hydrogen leaving the anode chamber 18. The unconsumed hydrogen may then be directed back to inlet 42 of anode chamber 18 in anode loop 58. An electrically driven recirculation blower 62 is required due to the pressure differential Δ p between inlet 42 and outlet 50 of anode chamber 18. The recirculation blower 62 is disposed in anode loop 58 between outlet 50 and inlet 42 of anode chamber 18. Unconsumed hydrogen exiting outlet 50 of anode chamber 18 may thereby be supplied to anode chamber 18. Downstream of the anode circuit in the flow direction, a purge valve 64 is arranged, by means of which contaminants accumulated in the anode circuit 58 can be removed.

In the first exemplary embodiment, the fuel cell system 10 additionally has a line section 66, via which hydrogen can be supplied to a gas bearing 70 of the recirculation blower 62 (see fig. 5). Thereby, hydrogen can be supplied to the gas bearing 70, in particular during a start-up or coasting phase, so that a static gas bearing 70 is formed. The line section 66 is connected to the hydrogen supply line 22 between the low-pressure shut-off valve 38 and the hydrogen metering valve 46. A portion of the hydrogen can thereby be supplied to the gas bearing 70, so that additionally the water accumulated in the recirculation blower 62 can be discharged from the recirculation blower 62 by the dry hydrogen. In order to control the hydrogen supplied to the recirculation blower 62, an additional hydrogen metering valve 74 is arranged in the line section 66.

Fig. 2 shows a second embodiment of a fuel cell system 10 according to the invention. This second exemplary embodiment differs from the first exemplary embodiment shown in fig. 1 essentially in that the line section 66 starts from an additional outlet 78 of the hydrogen metering valve 46. Thus, an additional metering valve 74, as shown in fig. 1, is not necessary in the line section 66.

A third embodiment of a fuel cell system 10 according to the present invention is shown in fig. 3. This embodiment differs from the above-described embodiments in that all of the hydrogen supplied to anode chamber 18 from hydrogen storage 26 is directed through recycle blower 62. Thus, the hydrogen supply line 22 is directly connected to the recycle blower 62. Thus, a line section 66 as shown in fig. 1 and 2 is not required. Furthermore, an additional hydrogen dosing valve 74 as shown in fig. 1 is not required. A large amount of water in the recirculation blower 62 can be conveyed out by the arrangement shown in fig. 3.

Fig. 4 shows a fourth exemplary embodiment of a fuel cell system 10 according to the present invention. This fourth exemplary embodiment differs from the first exemplary embodiment according to fig. 1 in that a line section 66 is connected to the hydrogen supply line 22 between the pressure reducer 34 and the low-pressure shut-off valve 38. In the line section 66, an additional shut-off valve 82 is thus arranged in place of the additional hydrogen metering valve 74, by means of which the hydrogen supply of the recirculation blower 62 can be shut off.

Fig. 5 shows an embodiment of an electrically driven recirculation blower 62 for the fuel cell system 10. Here, the recirculation blower 62 comprises a compressor train 86, which in this embodiment is configured as a compressor wheel. Unconsumed hydrogen (shown here as hydrogen recycle stream 88) can be delivered from outlet 50 to inlet 42 of anode chamber 18 by compressor train 86. The compressor package 86 is connected to a shaft 90 which is supported in the recirculation blower 62 by two gas bearings 70. The recirculation blower 62 additionally has a feed 94, which is embodied in this exemplary embodiment in the form of a plurality of radially extending channels, through which fresh hydrogen (shown here as a hydrogen feed stream 96) can be introduced into the gas bearing 70. As a result, a radial gas cushion 98 is formed in the gas bearing 70, by means of which radial gas cushion the shaft 90 can be supported statically. Additionally, an axial gas cushion 102 is formed opposite the gas bearing 70.

The gas bearing 70 has a bearing leak 106, by means of which the hydrogen supplied to the gas bearing 70 can be discharged into the compressor block 86. Thus, the hydrogen supplied to the gas bearing 70 is also delivered to the inlet 42 of the anode chamber 18 as unconsumed hydrogen. Thereby, the gas bearing 70 is continuously flushed with the supplied hydrogen, so that moisture can be transported out of the gas bearing 70.

The recirculation blower 62 additionally has an electric motor 110, by means of which the compressor unit 86 can be driven. In this embodiment, the motor 110 has a rotor 114 that is connected to the shaft 90 between two gas bearings 70. The rotor 114 is radially surrounded by a stator 118 of the electric motor 110, by means of which the rotor 114 can be driven. Radially on the outside, cooling ribs 122 are arranged on the stator 118, by means of which cooling ribs the stator 118 can be cooled. Additionally, recirculation blower 62 has a housing 126 in which compressor package 86, gas bearing 70, and motor 110 are received. In this case, the housing 126 is designed in a sealed manner, so that the hydrogen supplied to the gas bearing 70 is not discharged into the surroundings, but rather can be conducted to the inlet 42 of the anode chamber 18.

Fig. 6 shows a first exemplary embodiment of a method for operating the recirculation blower 62. In this figure, a graph is shown, wherein the rotational speed N of the recirculation blower 62 is plotted on the X-axis and the amount of hydrogen supplied to the gas bearing 70 is plotted on the Y-axis. The hydrogen supplied to the gas bearing 70 can be controlled here, for example, by means of an additional shut-off valve 82. From the limit speed N_GThe supply of the supplied hydrogen into the gas bearing 70 is stopped. The limit speed N here_GIt may be the rotational speed N of the recirculation blower 62 at which dynamic support of the gas bearing 70 is possible. Likewise, when the rotational speed N is lower than the limit rotational speed N_GIn this case, the hydrogen supplied can be supplied again. Thus, sufficient support in the gas bearing 70 can be ensured even when the recirculation blower 62 is coasting.

A second embodiment of a method for operating recirculation blower 62 is shown in fig. 7. This embodiment differs from the embodiment in fig. 6 in that the speed is limited from the limit speed N_GThe supply is linearly reduced with increasing rotational speed N. This reduction in hydrogen fed can be controlled, for example, by attaching a hydrogen dosing valve 74. In this example, from the second limit speed N_2GInitially, the slope of the linear decrease is additionally increased, so that the supply of the hydrogen fed in is stopped at a predetermined rotational speed Nx.

In this case, the limit speed N is_GAnd a predetermined rotational speed N_XThe rotational speed range in between may be a rotational speed range in which there is a transition between the static bearing to the dynamic bearing of the gas bearing 70. In this case, as the predetermined rotational speed Nx is approached, the dynamic proportion of the bearing prevails, so that the hydrogen supply for the static bearing of the gas bearing 70 can be correspondingly reduced. As in the embodiment of fig. 6, the hydrogen supplied may be newly supplied when the revolution speed N is lower than the predetermined limit revolution speed Nx. Thus, sufficient support in the gas bearing 70 can be ensured even when the recirculation blower 62 is coasting.

Claims

1. A fuel cell system (10) having at least one fuel cell (14), a hydrogen storage (26), in which hydrogen is stored under overpressure and which is connected to an anode chamber (18) of the fuel cell (14) by means of a hydrogen supply line (22), and having an anode circuit (58), by means of which unconsumed hydrogen can be led back into an inlet (42) of the anode chamber (18) at an outlet (50) of the anode chamber (18), wherein at least one electrically driven recirculation blower (62), by means of which unconsumed hydrogen can be supplied to the inlet (42) of the anode chamber (18), is arranged between the outlet (50) and the inlet (42) of the anode chamber (18),

it is characterized in that the preparation method is characterized in that,

at least a portion of the hydrogen supplied from the hydrogen accumulator (26) to the anode chamber (18) can be introduced into at least one gas bearing (70) of the electrically driven recirculation blower (62), and the gas bearing (70) can therefore be mounted statically.

2. The fuel cell system (10) of claim 1, wherein the fuel cell system (10) has a pipe section (66) connected with the hydrogen supply pipe (22) and the recirculation blower (62) such that at least a portion of the hydrogen can be supplied to the gas bearing (70).

3. A fuel cell system (10) according to claim 2, wherein the line section (66) is connected with the hydrogen supply line (22) between a low pressure shut-off valve (38) and a hydrogen dosing valve (46).

4. A fuel cell system (10) according to claim 3, characterized in that the pipe section (66) has an additional hydrogen dosing valve (74) for dosing hydrogen supplied to a gas bearing (70) of the recirculation blower (62).

5. A fuel cell system (10) according to claim 2, characterized in that the line section (66) is connected with the hydrogen supply line (22) via an additional outlet (78) of a hydrogen dosing valve (46).

6. The fuel cell system (10) according to claim 2, wherein the pipe section (66) is connected to the hydrogen supply pipe (22) between a pressure reducer (34) and a low pressure cutoff valve (38).

7. A fuel cell system (10) according to claim 1, wherein the hydrogen supply line (22) is connected to the anode chamber (18) by the recirculation blower (62).

8. A recirculation blower (62) for use in a fuel cell system (10) according to any of the preceding claims, wherein the recirculation blower (62) comprises at least:

a compressor unit (86) by means of which hydrogen can be compressed,

-an electric motor (110) by means of which the compressor group (86) can be electrically driven,

-a gas bearing (70) by which the compressor unit (86) can be supported, and

-a feeding mechanism (94) by means of which a gas for static support can be fed into the gas bearing (70),

it is characterized in that the preparation method is characterized in that,

the gas is part of the hydrogen supplied from a hydrogen accumulator (26) of a fuel cell (14) of the fuel cell system (10), and the gas bearing (70) has a bearing leak (106) by means of which the supplied hydrogen can be discharged into the compressor assembly (86).

9. Method for operating a recirculation blower (62) according to claim 8, wherein below a limit rotational speed (N)_G) Is supplied to the gas bearing (70) in a rotational speed range such that a static bearing of the gas bearing (70) is enabled and above the limit rotational speed (N)_G) At least partially reducing the supplied hydrogen in the rotational speed range of (a).

10. Method according to claim 9, characterised in that above said limit speed (N)_G) The supply of hydrogen into the gas bearing (70) is stopped.

11. Method according to claim 9 or 10, characterized in that the limit rotational speed (N) is reached_G) The supply of hydrogen into the gas bearing (70) is then reduced in a linear manner with increasing rotational speed (N).