Fuel cell system and method for pressure balance control of expansion tank

Abstract

The invention discloses a fuel cell system and method for pressure balance control of an expansion tank. According to the fuel cell system disclosed by the invention, clean gas filtered by the air filter is introduced from the air inlet pipeline and enters the expansion water tank after passing through the air inlet valve, impurities and dust in the air cannot be brought into the valve body, and the phenomenon of failure of the air inlet valve and the air outlet valve and the influence of the impurities and the dust on other parts of the cooling system are avoided. According to the fuel cell system disclosed by the invention, through the arrangement of the pressure balance pipeline, when the fuel cell system is shut down, gas is stopped from entering an inlet at the anode side of the electric pile, and after hydrogen at the anode side of the electric pile is further consumed, the anode pressure is reduced, and a pressure difference is formed between the anode pressure and the cooling water side; a small amount of gas in the expansion water tank is released into the hydrogen outlet pipeline through the pressure balance pipeline, so that the air pressure is balanced, and the situation that the pressure difference between the anode side and the cooling water side of the pole plate in the electric pile is too large, the pole plate deforms, and the electric pile performance is affected is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a fuel cell system and method for pressure balance control of an expansion water tank. Background Art

[0002] A fuel cell system is a device that converts the chemical energy in hydrogen and oxygen into electrical energy through an electrochemical reaction. It has the advantages of high efficiency and zero pollution. While generating electricity, fuel cells also generate a lot of heat. Therefore, cooling systems such as cooling water pumps and radiators are needed to promptly remove the generated heat to ensure that the fuel cell system is maintained in a suitable temperature range. The expansion water tank is an important component of the cooling system and has the functions of replenishing water and exhausting air. Since the fuel cell system stack is composed of multiple single cells connected in series, in order to ensure the reliability of the seal and to ensure that the pressure of the coolant and the pressure on the hydrogen / air side are maintained within a suitable range, the pressure fluctuation of the fuel cell cooling system needs to be small.

[0003] For example, the invention application with publication number CN118099469A discloses a fuel cell thermal management system and method, including: a thermal management main system, the thermal management main system includes a battery circuit, a heating circuit and a heat dissipation circuit, the battery circuit and the heating circuit are both connected to the heat dissipation circuit; a thermal management auxiliary system, the thermal management auxiliary system includes an auxiliary circuit, and the auxiliary circuit is connected to its heat dissipation circuit; wherein the heat dissipation circuit includes a heat dissipation component, a three-way valve, an expansion water tank and a water pump.

[0004] For another example, the utility model with authorization announcement number CN221529991U discloses a fuel cell cooling system and a fuel cell. The fuel cell cooling system includes an expansion water tank, a water pump, a battery stack, a heat exchanger and an exhaust pipe. The expansion water tank has a liquid outlet and a first exhaust port. The liquid outlet is connected to the liquid inlet end of the water pump, the liquid outlet end of the water pump is connected to the liquid inlet end of the battery stack, the liquid outlet end of the battery stack is connected to the liquid inlet end of the heat exchanger, and the liquid outlet end of the battery stack is also connected to the liquid inlet end of the exhaust pipe, the liquid outlet end of the heat exchanger is connected to the liquid inlet end of the water pump, and the liquid outlet end of the exhaust pipe is connected to the first exhaust port. The layout height of the expansion water tank is higher than the layout height of the battery stack and the heat exchanger.

[0005] The existing ordinary expansion water tank is mainly composed of a pressure cap and a plastic expansion water tank. The pressure cap contains a vent valve and an inlet valve. When the internal pressure of the cooling system exceeds the opening pressure of the vent valve, the vent valve opens, the air and steam in the expansion water tank are discharged, and the internal pressure of the cooling system is reduced. When the pressure drops to exceed the opening pressure of the inlet valve, the inlet valve opens to maintain the pressure inside the expansion water tank within a certain range.

[0006] The bleed valve and intake valve of the above-mentioned expansion water tank are generally connected to the atmosphere. During the frequent changes in the internal pressure of the expansion water tank, impurities in the external air may enter the valve body, which will cause the bleed valve / intake valve to fail due to dust on the one hand, and on the other hand, it will contaminate the coolant in the expansion water tank and affect the components of the cooling system; the opening pressure of the bleed valve and intake valve of the expansion water tank is generally 30kpa (the opening pressure of the bleed valve is that the pressure inside the expansion water tank is greater than the pressure of the outside atmosphere) and 10kpa (the opening pressure of the intake valve is that the pressure inside the expansion water tank is less than the pressure of the outside atmosphere). Too high opening pressure of the bleed valve will cause excessive pressure in the internal cooling system, affecting the sealing of the fuel cell stack and other cooling systems; high opening pressure of the intake valve will cause cavitation of the coolant at the water pump inlet.

[0007] However, when the fuel cell system is shut down, the pressure in the anode chamber of the stack may reach -40kPa, while the pressure in the cooling system may reach 40kPa due to the influence of the bleed valve, layout position and water temperature. At this time, the water-vapor pressure difference reaches 80kPa. Excessive pressure difference acting on both sides of the plate may cause the plate to deform, seriously affecting the performance of the fuel cell system stack. Summary of the invention

[0008] In view of the above-mentioned deficiencies in the prior art, the present invention provides a fuel cell system and method for pressure balance control of an expansion water tank.

[0009] The present invention first provides a fuel cell system with expansion water tank pressure balance control, comprising a fuel cell stack and an expansion water tank, wherein the fuel cell stack has an air inlet pipeline, an air outlet pipeline, a hydrogen inlet pipeline, a hydrogen outlet pipeline, a cooling water inlet pipeline, and a cooling water outlet pipeline, wherein the air inlet pipeline is provided with an air filter, the hydrogen outlet pipeline is provided with an air-water separator, the cooling water inlet pipeline and the cooling water outlet pipeline are respectively connected to the expansion water tank, the hydrogen inlet pipeline is provided with a hydrogen inlet pressure sensor for detecting the hydrogen inlet pressure of the fuel cell stack, and the cooling water inlet pipeline is provided with a water inlet pressure sensor for detecting the cooling water inlet pressure of the fuel cell stack;

[0010] The air intake pipeline is provided with a water tank air intake pipeline between the downstream of the air filter and the expansion water tank, and the water tank air intake pipeline is provided with an air intake valve;

[0011] The expansion water tank is also provided with a water tank air release pipeline, and the water tank air release pipeline is provided with an air release valve;

[0012] A pressure balancing pipeline is provided between a section of the hydrogen outlet pipeline between the fuel cell stack and the gas-water separator and the expansion water tank, and the pressure balancing pipeline is provided with a pressure balancing valve.

[0013] Preferably, a section of the water tank venting pipeline between the venting valve and the expansion water tank and a section of the pressure balancing pipeline between the pressure balancing valve and the expansion water tank share the same pipeline section.

[0014] The pressure balance valve and the bleed valve share the same one-way valve, the outlet side of which is connected to a three-way valve, one outlet of which is used to connect to the atmosphere, and the other outlet of which is used to connect to a section of the hydrogen outlet pipeline between the fuel cell stack and the gas-water separator.

[0015] Preferably, an air compressor and an intercooler are sequentially provided on the air intake pipeline downstream of the air filter, and the water tank air intake pipeline is connected to a section of the air intake pipeline between the air filter and the air compressor.

[0016] Preferably, the air outlet pipeline is provided with a back pressure valve.

[0017] Preferably, a hydrogen storage system is provided on the hydrogen inlet pipeline, and a pressure reducing valve is provided downstream of the hydrogen storage system;

[0018] A circulation pump is provided on the hydrogen outlet pipeline downstream of the gas-water separator, and the outlet end of the hydrogen outlet pipeline is connected to a section of the hydrogen inlet pipeline between the pressure reducing valve and the hydrogen inlet pressure sensor.

[0019] Preferably, a water pump is provided on the cooling water inlet pipeline, and the water inlet pressure sensor is provided on the cooling water inlet pipeline at a side of the water pump close to the fuel cell stack;

[0020] A radiator is arranged on the cooling water outlet pipeline, and a water return pipe is arranged between the radiator and the water pump.

[0021] The present invention also provides a method for pressure balance control of an expansion water tank, and a fuel cell system using the pressure balance control of the expansion water tank, the method comprising:

[0022] When the fuel cell system is running, the pressure in the expansion water tank increases, and when the pressure in the expansion water tank reaches the valve opening pressure of the air release valve, the air release valve opens to exhaust and reduce the pressure;

[0023] When the fuel cell system is running at a low load, the pressure in the expansion water tank decreases, and when the pressure in the expansion water tank reaches the valve opening pressure of the intake valve, the intake valve opens to increase the intake pressure;

[0024] When the fuel cell system is shut down, when the difference between the pressure detected by the hydrogen inlet pressure sensor and the pressure detected by the water inlet pressure sensor reaches a set value, the pressure balancing valve opens to balance the pressure.

[0025] Preferably, the valve opening pressure of the air release valve is 20-50 kPa, and the valve opening pressure of the air intake valve is 5-20 kPa.

[0026] Preferably, the set value is 30-50 kPa.

[0027] The fuel cell system with expansion tank pressure balance control of the present invention introduces clean gas filtered by the air filter from the air inlet pipeline and then enters the expansion water tank through the air inlet valve. Therefore, impurities and dust in the air under harsh environment cannot be brought into the valve body, and the phenomenon of failure of the inlet and outlet valves and the influence of impurities and dust on other parts of the cooling system will not occur.

[0028] The fuel cell system with expansion water tank pressure balance control of the present invention is provided with a pressure balance pipeline. When the fuel cell system is shut down, the inlet on the anode side of the stack stops taking in air. After the hydrogen on the anode side of the stack is further consumed, the anode pressure is reduced, forming a pressure difference with the cooling water side. At this time, a small amount of gas in the expansion water tank is released into the hydrogen outlet pipeline through the pressure balance pipeline, thereby balancing the gas pressure and avoiding excessive pressure difference between the anode side and the cooling water side of the plate in the stack, which may cause deformation of the plate and affect the performance of the stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a fuel cell system with pressure balance control of an expansion tank according to the present invention.

[0030] Figure numerals: fuel cell stack 1, expansion water tank 2, air filter 3, air compressor 4, intercooler 5, back pressure valve 6, hydrogen storage system 7, pressure reducing valve 8, hydrogen inlet pressure sensor 9, gas-water separator 10, circulation pump 11, water pump 12, water inlet pressure sensor 13, air intake valve 14, air release valve 15, three-way valve 16, radiator 17, return pipe 18. DETAILED DESCRIPTION

[0031] like Figure 1 As shown, a fuel cell system with expansion water tank pressure balance control includes a fuel cell stack 1 and an expansion water tank 2. The fuel cell stack 1 has an air inlet pipeline, an air outlet pipeline, a hydrogen inlet pipeline, a hydrogen outlet pipeline, a cooling water inlet pipeline, and a cooling water outlet pipeline.

[0032] The air intake pipeline is used to intake air into the stack 1, and the air enters the cathode side of the stack 1 to provide oxygen required for the fuel cell reaction. The air intake pipeline is provided with an air filter 3, an air compressor 4 and an intercooler 5 from upstream to downstream (the upstream and downstream are divided according to the air flow direction, and the air intake end is the upstream). The air filter 3 is used to filter the air entering the stack to remove dust and other impurities. The air compressor 4 is used to provide power for the air intake, and the clean air filtered by the air filter 3 is compressed and enters the cathode side of the stack 1. The intercooler 5 is used to cool the air compressed by the air compressor 4 to prevent the air temperature entering the stack 1 from being too high.

[0033] The air outlet pipeline is used to discharge the remaining air after the cathode side reaction from the stack 1. A back pressure valve 6 is provided on the air outlet pipeline to ensure that the air on the cathode side of the stack 1 has a sufficient air pressure. The end of the air outlet pipeline can be connected to the atmosphere, and the cathode side tail of the air outlet pipeline is discharged to the atmosphere.

[0034] The hydrogen inlet pipeline is used to feed hydrogen into the anode side of the fuel cell stack 1. A hydrogen storage system 7 is provided on the hydrogen inlet pipeline, and a pressure reducing valve 8 is provided downstream of the hydrogen storage system 7. A hydrogen inlet pressure sensor 9 for detecting the hydrogen inlet pressure of the fuel cell stack 1 is provided on the hydrogen inlet pipeline, and the hydrogen inlet pressure sensor 9 is arranged near the fuel cell stack 1 on the hydrogen inlet pipeline.

[0035] The hydrogen outlet pipeline is used to receive the anode side tail discharge discharged from the anode side of the stack 1. The anode side tail discharge contains unreacted hydrogen, water generated by the reaction, and a small amount of air leaked from the cathode side. Since the anode side tail discharge still contains a large amount of hydrogen, which can be recycled and reused, a gas-water separator 10 is provided on the hydrogen outlet pipeline. The gas-water separator 10 is used to separate gas and water, that is, to separate the water in the anode tail discharge, and the remaining gas is mainly composed of hydrogen for recycling.

[0036] The outlet end of the hydrogen outlet pipeline is connected to a section of the hydrogen inlet pipeline between the pressure reducing valve 8 and the hydrogen inlet pressure sensor 9. A circulating pump 11 is provided on the hydrogen outlet pipeline downstream of the gas-water separator 10, and the circulating pump 11 is used to drive the gas portion after the water is separated by the gas-water separator 10 back to the hydrogen inlet pipeline.

[0037] The cooling water inlet pipeline is used to supply cooling water to the battery stack 1, and the cooling water outlet pipeline is used to receive cooling water from the battery stack 1. The cooling water inlet pipeline and the cooling water outlet pipeline are respectively connected to the expansion water tank 2. The expansion water tank 2 is used to store cooling water.

[0038] A water pump 12 is provided on the cooling water inlet pipeline, and the water pump 12 is used to drive the cooling water. A water inlet pressure sensor 13 is also provided on the cooling water inlet pipeline for detecting the pressure of the cooling water inlet to the stack 1. The water inlet pressure sensor 13 is arranged on the cooling water inlet pipeline on the side of the water pump 12 close to the stack 1.

[0039] A radiator 17 is provided on the cooling water outlet pipeline, and a return pipe 18 is provided between the radiator 17 and the water pump 12. During operation, the water pump drives the cooling water into the battery stack 1. After the cooling water cools the battery stack 1, the temperature rises. After coming out of the cooling water outlet pipeline, it enters the radiator 17 for heat dissipation and cooling. Part of the cooling water re-enters the water pump through the return pipe 18 and directly re-enters the battery stack 1, and the other part returns to the expansion water tank 2. The cooling water in the expansion water tank 2 is replenished through the cooling water inlet pipeline. An ambient pressure sensor is provided on the expansion water tank 2 for detecting the ambient atmospheric pressure.

[0040] The air intake pipeline is provided with a water tank intake pipeline between the downstream of the air filter 3 and the expansion water tank 2, and an intake valve 14 is provided on the water tank intake pipeline. The intake valve 14 is used to reduce the pressure in the expansion water tank 2 when the fuel cell system is running at a low load. When the pressure in the expansion water tank 2 reaches the valve opening pressure of the intake valve 14, the intake valve 14 opens to increase the intake pressure. The valve opening pressure of the intake valve 14 refers to the pressure difference existing when the atmospheric pressure in the environment is greater than the air pressure in the expansion water tank 2. After the intake valve 14 is opened, the clean air filtered by the air filter 3 can be fed into the expansion water tank 2 through the water tank intake pipeline to balance the pressure in the expansion water tank 2.

[0041] Since the air entering the expansion water tank 2 is clean gas filtered by the air filter 3, impurities and dust in the air under harsh conditions cannot be brought into the valve body, and the inlet and outlet valves will not fail, and impurities and dust will not affect other parts of the cooling system.

[0042] The expansion water tank 2 is also provided with a water tank venting pipeline, and the water tank venting pipeline is provided with a venting valve 15. The water tank venting pipeline is used to increase the pressure in the expansion water tank 2 when the fuel cell system is running. When the pressure in the expansion water tank 2 reaches the valve opening pressure of the venting valve 15, the venting valve 15 opens to exhaust and reduce the pressure.

[0043] A pressure balancing pipeline is provided between a section of the hydrogen outlet pipeline between the fuel cell stack 1 and the gas-water separator 10 and the expansion water tank 2. The pressure balancing pipeline is provided with a pressure balancing valve. The pressure balancing pipeline is used to open the pressure balancing valve to balance the pressure when the fuel cell system is shut down and the pressure detected by the hydrogen inlet pressure sensor 9 is less than the pressure detected by the water inlet pressure sensor 13 and the difference reaches a set value in order to prevent excessive pressure difference between the anode side and the cooling side of the plate.

[0044] In a preferred embodiment, a section of the water tank venting pipeline between the venting valve 15 and the expansion water tank 2 shares the same section of the pipeline with a section of the pressure balancing pipeline between the pressure balancing valve and the expansion water tank 2, the pressure balancing valve and the venting valve 15 share the same one-way valve, and a three-way valve 16 is connected to the outlet side of the one-way valve, one outlet of the three-way valve 16 is used to connect to the atmosphere, and this route serves as the water tank venting pipeline; the other outlet of the three-way valve 16 is used to connect to a section of the hydrogen outlet pipeline between the fuel cell stack and the gas-water separator, and this route serves as the pressure balancing pipeline.

[0045] The present invention also provides a method for pressure balance control of an expansion water tank, and a fuel cell system using the pressure balance control of the expansion water tank, the method comprising:

[0046] When the fuel cell system is running, the three-way valve 16 is connected to the water tank venting pipeline, and the pressure in the expansion tank 2 increases. When the pressure in the expansion tank 2 reaches the valve opening pressure of the venting valve 15, the venting valve 15 opens, exhausts the gas and reduces the pressure. The valve opening pressure of the venting valve 15 is 20-50 kPa.

[0047] When the fuel cell system is running at low load, the pressure in the expansion tank 2 decreases. When the pressure in the expansion tank 2 reaches the opening pressure of the intake valve 14, the intake valve 14 opens to increase the intake pressure. The opening pressure of the intake valve 14 is 5 to 20 kPa.

[0048] When the fuel cell system is shut down, when the pressure detected by the hydrogen inlet pressure sensor 9 is less than the pressure detected by the water inlet pressure sensor 13 and the difference reaches the set value, the three-way valve 16 connects the pressure balance pipeline, and the pressure balance valve (the structure shown in the figure is a shared vent valve 15) opens to balance the pressure. The pressure difference setting value of the two pressure sensors is 30-50 kPa, and the pressure difference setting value is not less than the valve opening pressure of the vent valve 15.

Claims

1. A fuel cell system with expansion tank pressure balance control, comprising a fuel cell stack and an expansion water tank, wherein the fuel cell stack has an air inlet pipeline, an air outlet pipeline, a hydrogen inlet pipeline, a hydrogen outlet pipeline, a cooling water inlet pipeline, and a cooling water outlet pipeline, wherein the air inlet pipeline is provided with an air filter, the hydrogen outlet pipeline is provided with a gas-water separator, the cooling water inlet pipeline and the cooling water outlet pipeline are respectively connected to the expansion water tank, and characterized in that: The hydrogen inlet pipeline is provided with a hydrogen inlet pressure sensor for detecting the hydrogen inlet pressure of the fuel cell stack, and the cooling water inlet pipeline is provided with a water inlet pressure sensor for detecting the cooling water inlet pressure of the fuel cell stack; The air intake pipeline is provided with a water tank air intake pipeline between the downstream of the air filter and the expansion water tank, and the water tank air intake pipeline is provided with an air intake valve; The expansion water tank is also provided with a water tank air release pipeline, and the water tank air release pipeline is provided with an air release valve; A pressure balancing pipeline is provided between a section of the hydrogen outlet pipeline between the fuel cell stack and the gas-water separator and the expansion water tank, and the pressure balancing pipeline is provided with a pressure balancing valve.

2. The fuel cell system with expansion tank pressure balance control according to claim 1, characterized in that: The section of the water tank venting pipeline between the venting valve and the expansion water tank and the section of the pressure balancing pipeline between the pressure balancing valve and the expansion water tank share the same pipeline section. The pressure balance valve and the bleed valve share the same one-way valve, the outlet side of which is connected to a three-way valve, one outlet of which is used to connect to the atmosphere, and the other outlet of which is used to connect to a section of the hydrogen outlet pipeline between the fuel cell stack and the gas-water separator.

3. The fuel cell system with expansion tank pressure balance control according to claim 1, characterized in that: The air intake pipeline is also provided with an air compressor and an intercooler in sequence downstream of the air filter, and the water tank air intake pipeline is connected to a section of the air intake pipeline between the air filter and the air compressor.

4. The fuel cell system with expansion tank pressure balance control according to claim 1, characterized in that: The air outlet pipeline is provided with a back pressure valve.

5. The fuel cell system with expansion tank pressure balance control according to claim 1, characterized in that: The hydrogen inlet pipeline is provided with a hydrogen storage system, and a pressure reducing valve is provided downstream of the hydrogen storage system; A circulation pump is provided on the hydrogen outlet pipeline downstream of the gas-water separator, and the outlet end of the hydrogen outlet pipeline is connected to a section of the hydrogen inlet pipeline between the pressure reducing valve and the hydrogen inlet pressure sensor.

6. The fuel cell system with expansion tank pressure balance control according to claim 1, characterized in that: A water pump is provided on the cooling water inlet pipeline, and the water inlet pressure sensor is provided on the cooling water inlet pipeline at a side of the water pump close to the fuel cell stack; A radiator is arranged on the cooling water outlet pipeline, and a water return pipe is arranged between the radiator and the water pump.

7. A method for pressure balance control of an expansion water tank, characterized in that: A fuel cell system using the expansion tank pressure balance control according to any one of claims 1 to 6, the method comprising: When the fuel cell system is running, the pressure in the expansion water tank increases, and when the pressure in the expansion water tank reaches the valve opening pressure of the air release valve, the air release valve opens to exhaust and reduce the pressure; When the fuel cell system is running at a low load, the pressure in the expansion water tank decreases, and when the pressure in the expansion water tank reaches the valve opening pressure of the intake valve, the intake valve opens to increase the intake pressure; When the fuel cell system is shut down, when the difference between the pressure detected by the hydrogen inlet pressure sensor and the pressure detected by the water inlet pressure sensor reaches a set value, the pressure balancing valve opens to balance the pressure.

8. The method for controlling the pressure balance of an expansion water tank according to claim 7, characterized in that: The opening pressure of the air release valve is 20-50 kPa. The opening pressure of the intake valve is 5-20 kPa.

9. The method for controlling the pressure balance of an expansion water tank according to claim 7, characterized in that: The set value is 30 to 50 kPa.

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