Cold start method of fuel cell system

Abstract

The invention relates to the technical field of fuel cells, and discloses a cold start method of a fuel cell system, which comprises the following steps: S100, detecting whether a hydrogen circulating pump is frozen or not, and if the hydrogen circulating pump is frozen, executing the step S200; s200, a heater is started to heat the cooling liquid to a preset temperature; s300, controlling a hydrogen source to supply hydrogen with preset pressure to the battery stack, controlling a drain valve to be opened according to a first preset frequency, controlling a nitrogen removal valve to be opened according to a second preset frequency, and controlling the battery stack to operate under preset power; s400, a starting instruction is sent to the hydrogen circulating pump every first preset time; if the hydrogen circulating pump can be normally started, the fuel cell system is started according to a normal operation mode; and if the hydrogen circulating pump cannot be normally started, the steps S300-S400 are repeated. According to the cold start method of the fuel cell system, the fuel cell system can be started under the condition that the hydrogen circulating pump is frozen, and the technical problem that the fuel cell system cannot be started due to the fact that the hydrogen circulating pump is frozen in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a cold start method for a fuel cell system. Background Art

[0002] When the fuel cell system is in normal working condition, the circulating gas composed of hydrogen water vapor and nitrogen that is circulated back from the tail of the stack after the water is separated by the gas-liquid separator will be transported through the hydrogen circulation pump and form a mixed gas with the original hydrogen supplied from the high-pressure hydrogen cylinder. The mixed gas will eventually re-enter the battery stack. Among them, the hydrogen circulation pump, as an important component of the anode loop, plays a vital role in improving the overall fuel efficiency of the fuel cell.

[0003] However, when the ambient temperature is low, ice will form inside the hydrogen circulation pump, causing the fuel cell system to fail to start. Therefore, in the traditional industry, especially in the design of fuel cell passenger cars, hydrogen circulation pumps are basically not used. Instead, ejectors are used instead of hydrogen circulation pumps. However, ejectors cannot provide enough hydrogen for the battery stack when the fuel cell system is running at low power, which in turn affects the service life of the battery stack.

[0004] Therefore, there is an urgent need to propose a cold start method for a fuel cell system to solve the above problems. Summary of the invention

[0005] The present invention provides a cold start method for a fuel cell system, which can start the fuel cell system when a hydrogen circulation pump is frozen, thereby solving the technical problem in the prior art that the fuel cell system cannot be started due to freezing of the hydrogen circulation pump.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A cold start method for a fuel cell system, wherein the cold start method for a fuel cell system is applied to a fuel cell system, wherein the fuel cell system comprises a battery stack, a hydrogen circulation system and a coolant circulation system;

[0008] The hydrogen circulation system comprises a hydrogen source, a heat exchanger, a gas-liquid separator, a drain valve, a hydrogen circulation pump and a nitrogen exhaust valve, wherein the hydrogen source is communicated with a first inlet of the heat exchanger, the first outlet of the heat exchanger is communicated with an air inlet of the battery stack, the air outlet of the battery stack is communicated with an air inlet of the gas-liquid separator, the air outlet of the gas-liquid separator is communicated with an inlet of the hydrogen circulation pump, the outlet of the hydrogen circulation pump is communicated with an air inlet of the battery stack, the drain valve is arranged at the drain outlet of the gas-liquid separator, and the nitrogen exhaust valve is arranged at the nitrogen exhaust outlet of the hydrogen circulation pump;

[0009] The coolant circulation system comprises a coolant circulation pipeline, a heater, a first heat exchange pipeline and a second heat exchange pipeline, the first end of the coolant circulation pipeline is communicated with the liquid inlet of the battery stack, the second end of the coolant circulation pipeline is communicated with the liquid outlet of the battery stack, the heater is arranged on the coolant circulation pipeline, and is used to heat the coolant in the coolant circulation pipeline, one end of the first heat exchange pipeline is communicated with the first end, and the other end is communicated with the second inlet of the heat exchanger, one end of the second heat exchange pipeline is communicated with the second outlet of the heat exchanger, and the other end is communicated with the second end;

[0010] The cold start method of the fuel cell system comprises:

[0011] S100, detecting whether the hydrogen circulation pump is frozen, if the hydrogen circulation pump is frozen, executing step S200;

[0012] S200, starting the heater to heat the coolant to a preset temperature;

[0013] S300, controlling the hydrogen source to supply hydrogen of a preset pressure to the battery stack, controlling the drain valve to open at a first preset frequency, controlling the nitrogen exhaust valve to open at a second preset frequency, and controlling the battery stack to operate at a preset power;

[0014] S400, sending a start instruction to the hydrogen circulation pump at a first preset time interval; if the hydrogen circulation pump can be started normally, the fuel cell system is started in a normal operation mode; if the hydrogen circulation pump cannot be started normally, repeating steps S300-S400.

[0015] Optionally, the specific steps of detecting whether the hydrogen circulation pump is frozen are:

[0016] The hydrogen circulation pump is controlled to start, and the rotation speed of the hydrogen circulation pump is detected. If the rotation speed of the hydrogen circulation pump cannot reach a set value within a second preset time, it is determined that the hydrogen circulation pump is frozen.

[0017] Optionally, the second preset time is 0s-5s.

[0018] Optionally, the preset temperature is the temperature corresponding to the shortest de-icing time of the hydrogen circulation pump under the current ambient temperature.

[0019] Optionally, the preset pressure, the first preset frequency and the second preset frequency may be set so that the battery stack does not experience a single low phenomenon.

[0020] Optionally, the specific steps of determining whether the battery stack has a single low phenomenon are:

[0021] The voltage of each single cell in the battery stack is detected to obtain multiple measured voltages, and the multiple measured voltages are compared one by one with the average voltage of the battery stack. If the difference between at least one measured voltage and the average voltage of the battery stack is greater than a preset value, the battery stack has a single low phenomenon; otherwise, the battery stack does not have a single low phenomenon.

[0022] Optionally, the preset power is the power required to be output when the fuel cell system is cold started.

[0023] Optionally, the first preset time is greater than a response time of the hydrogen circulation pump.

[0024] Optionally, the first preset time is 8s-15s.

[0025] Optionally, the fuel cell system further includes a hydrogen injection valve and a pressure sensor, the first outlet of the heat exchanger is communicated with the inlet of the hydrogen injection valve, the outlet of the hydrogen injection valve is communicated with the air inlet of the battery stack, and the pressure sensor is arranged at the air inlet of the battery stack;

[0026] The specific steps of controlling the hydrogen source to supply hydrogen of a preset pressure to the battery stack are:

[0027] The opening of the hydrogen injection valve is gradually increased from small to large, and when the pressure value detected by the pressure sensor is equal to the preset pressure, the adjustment of the hydrogen injection valve is stopped.

[0028] The beneficial effects of the present invention are:

[0029] The present invention provides a cold start method for a fuel cell system. When a hydrogen circulation pump is frozen, the cold start method for the fuel cell system starts the fuel cell system without starting the hydrogen circulation pump, heats hydrogen by coolant in the fuel cell system, heats the hydrogen circulation pump by the heated hydrogen, and breaks the ice of the hydrogen circulation pump. After the hydrogen circulation pump is broken, the hydrogen circulation pump is started again to make the fuel cell system work normally, thereby solving the technical problem in the prior art that the fuel cell system cannot be started due to the freezing of the hydrogen circulation pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the structure of a fuel cell system provided by an embodiment of the present invention;

[0031] Figure 2 A flowchart of a cold start method for a fuel cell system provided in an embodiment of the present invention.

[0032] In the figure:

[0033] 10. Battery stack; 20. Hydrogen circulation system; 21. Hydrogen source; 22. Heat exchanger; 23. Gas-liquid separator; 24. Drain valve; 25. Hydrogen circulation pump; 26. Nitrogen exhaust valve; 27. Hydrogen injection valve; 28. Pressure sensor; 30. Coolant circulation system; 31. Coolant circulation pipeline; 32. Heater; 33. First heat exchange pipeline; 34. Second heat exchange pipeline; 35. Water pump. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature "above", "above" and "above" the second feature include the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature include the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0038] This embodiment provides a cold start method for a fuel cell system, which can start the fuel cell system when the hydrogen circulation pump 25 is frozen, thereby solving the technical problem in the prior art that the fuel cell system cannot be started due to the freezing of the hydrogen circulation pump 25.

[0039] like Figure 1 As shown, the fuel cell system includes a battery stack 10 , a hydrogen circulation system 20 and a coolant circulation system 30 . The hydrogen circulation system 20 is used to transport hydrogen required for the reaction to the battery stack 10 .

[0040] The hydrogen circulation system 20 includes a hydrogen source 21, a heat exchanger 22, a gas-liquid separator 23, a drain valve 24, a hydrogen circulation pump 25 and a nitrogen exhaust valve 26. The hydrogen source 21 is connected to the first inlet of the heat exchanger 22, the first outlet of the heat exchanger 22 is connected to the air inlet of the battery stack 10, the air outlet of the battery stack 10 is connected to the air inlet of the gas-liquid separator 23, the air outlet of the gas-liquid separator 23 is connected to the inlet of the hydrogen circulation pump 25, the outlet of the hydrogen circulation pump 25 is connected to the air inlet of the battery stack 10, the drain valve 24 is arranged at the drain outlet of the gas-liquid separator 23, and the nitrogen exhaust valve 26 is arranged at the nitrogen exhaust outlet of the hydrogen circulation pump 25.

[0041] The coolant circulation system 30 includes a coolant circulation pipeline 31, a heater 32, a first heat exchange pipeline 33 and a second heat exchange pipeline 34. The first end of the coolant circulation pipeline 31 is connected to the liquid inlet of the battery stack 10, the second end of the coolant circulation pipeline 31 is connected to the liquid outlet of the battery stack 10, the heater 32 is arranged on the coolant circulation pipeline 31, and is used to heat the coolant in the coolant circulation pipeline 31, one end of the first heat exchange pipeline 33 is connected to the first end, and the other end is connected to the second inlet of the heat exchanger 22, and one end of the second heat exchange pipeline 34 is connected to the second outlet of the heat exchanger 22, and the other end is connected to the second end.

[0042] Specifically, see Figure 1 , part of the coolant in the coolant circulation pipeline 31 will enter the heat exchanger 22 through the first heat exchange pipeline 33, and return to the coolant circulation pipeline 31 from the second heat exchange pipeline 34 after heat exchange with the hydrogen in the heat exchanger 22. That is, the heat exchanger 22 realizes the heat exchange between the coolant and the hydrogen, thereby realizing the heating of the hydrogen by the coolant, and realizing the purpose of breaking the ice of the hydrogen circulation pump 25 by the heated hydrogen.

[0043] The working principle of the fuel cell system provided in this embodiment is as follows: the hydrogen supplied by the hydrogen source 21 first exchanges heat with the coolant in the coolant circulation pipeline 31 through the heat exchanger 22, and then enters the battery stack 10. The gas discharged from the tail of the battery stack 10 is separated by the gas-liquid separator 23 to obtain a circulating gas composed of hydrogen, water vapor and nitrogen, which will be transported through the hydrogen circulation pump 25 and form a mixed gas with the original hydrogen supplied from the hydrogen source 21. The mixed gas finally re-enters the battery stack 10.

[0044] Optionally, the heat exchanger 22 may be a plate heat exchanger, a fin heat exchanger, a shell and tube heat exchanger, etc., and may be configured according to actual needs.

[0045] Optionally, the coolant circulation system 30 further includes a water pump 35 , which is disposed on the coolant circulation pipeline 31 and is used to provide power for the circulation of the coolant.

[0046] Optionally, the hydrogen source 21 may be a hydrogen storage bottle.

[0047] Specifically, Figure 2 As shown, the cold start method of the fuel cell system includes:

[0048] S100, detecting whether the hydrogen circulation pump 25 is frozen, if the hydrogen circulation pump 25 is frozen, executing step S200.

[0049] It is worth noting that if it is detected that the hydrogen pump is not frozen, the fuel cell system can be directly started in the normal operating mode. Since the normal operating mode of the fuel cell is a prior art, the method for starting the normal operating mode of the fuel cell will not be introduced in detail.

[0050] Furthermore, in this embodiment, the specific steps of detecting whether the hydrogen circulation pump 25 is frozen are:

[0051] The hydrogen circulation pump 25 is controlled to start, and the rotation speed of the hydrogen circulation pump 25 is detected. If the rotation speed of the hydrogen circulation pump 25 cannot reach the set value within the second preset time, it is determined that the hydrogen circulation pump 25 is frozen.

[0052] It is understandable that the set value of the speed of the hydrogen circulation pump 25 is the speed value when the hydrogen circulation pump 25 is operating normally, and the size of the set value is generally set according to the model of the hydrogen circulation pump 25 and the operating conditions of the fuel cell system.

[0053] Optionally, the second preset time is generally set according to the response time of hydrogen. In the present embodiment, the second preset time is 0s-5s. Exemplarily, it can be 0s, 1s, 2s, 3s, 4s or 5s, etc., and can be set according to actual needs.

[0054] S200 , starting the heater 32 to heat the coolant to a preset temperature.

[0055] In this embodiment, the purpose of heating the coolant is to increase the temperature of the hydrogen through the heat exchanger 22, so that the high-temperature hydrogen can heat the hydrogen circulation pump 25 when passing through the hydrogen circulation pump 25, thereby helping the hydrogen circulation pump 25 to break ice.

[0056] Furthermore, the preset temperature is the temperature corresponding to the shortest deicing time of the hydrogen circulation pump 25 under the current ambient temperature. The preset temperature is generally obtained by calibration, that is, a database of deicing time of the hydrogen circulation pump 25 corresponding to different preset temperatures under different ambient temperatures is established through experiments, so as to serve as reference data for the cold start method of the fuel cell system.

[0057] S300, control the hydrogen source 21 to supply hydrogen of a preset pressure to the battery stack 10, control the drain valve 24 to open at a first preset frequency, control the nitrogen exhaust valve 26 to open at a second preset frequency, and control the battery stack 10 to operate at a preset power.

[0058] Further, see Figure 1 The fuel cell system further includes a hydrogen injection valve 27 and a pressure sensor 28. The first outlet of the heat exchanger 22 is connected to the inlet of the hydrogen injection valve 27. The outlet of the hydrogen injection valve 27 is connected to the air inlet of the battery stack 10. The pressure sensor 28 is arranged at the air inlet of the battery stack 10. The hydrogen injection valve 27 can control the pressure of the hydrogen input to the battery stack 10. The pressure sensor 28 is used to detect the pressure at the air inlet of the battery stack 10.

[0059] Therefore, in this embodiment, the specific steps of controlling the hydrogen source 21 to supply hydrogen of a preset pressure to the battery stack 10 are: gradually increasing the opening of the hydrogen injection valve 27 from small to large, and when the pressure value detected by the pressure sensor 28 is equal to the preset pressure, stopping adjusting the hydrogen injection valve 27.

[0060] It is worth noting that the preset pressure, the first preset frequency and the second preset frequency should be set so that the battery stack 10 does not experience a single low phenomenon.

[0061] The preset pressure, the first preset frequency and the second preset frequency are generally obtained by calibration, that is, a database of the battery stack 10 operating conditions corresponding to the opening and closing frequencies of the drain valve 24 and the nitrogen exhaust valve 26 under different preset pressures is established through experiments to serve as reference data for the cold start method of the fuel cell system.

[0062] Preferably, the operating condition in which the preset pressure value is the smallest and the first preset frequency and the second preset frequency are both the smallest (ie, the opening and closing frequencies of the drain valve 24 and the nitrogen exhaust valve 26 are the shortest) is selected as the optimal operating condition.

[0063] Furthermore, the preset power is the power required to be output when the fuel cell system is cold started, which can be set according to actual needs. The power can also be converted into the current of the battery stack 10, such as 50A, 70A, etc.

[0064] Furthermore, the specific steps of determining whether the battery stack 10 has a single low phenomenon are as follows:

[0065] The voltage of each single cell in the battery stack 10 is detected to obtain multiple measured voltages, and the multiple measured voltages are compared one by one with the average voltage of the battery stack 10. If the difference between at least one measured voltage and the average voltage of the battery stack 10 is greater than a preset value, the battery stack 10 has a single low phenomenon; otherwise, the battery stack 10 does not have a single low phenomenon.

[0066] It is worth noting that the preset value should be able to make the measured voltage significantly lower than the average voltage of the battery stack 10, that is, when the voltage of an individual battery cell is significantly lower than the average voltage of the battery stack 10, the surface battery stack 10 has a single low phenomenon.

[0067] S400, sending a start instruction to the hydrogen circulation pump 25 at every first preset time interval; if the hydrogen circulation pump 25 can be started normally, the fuel cell system is started in the normal operation mode; if the hydrogen circulation pump 25 cannot be started normally, repeat steps S300-S400.

[0068] Furthermore, the first preset time is greater than the response time of the hydrogen circulation pump 25 to give the hydrogen circulation pump 25 sufficient startup time. The response time of the hydrogen circulation pump 25 is related to the model of the hydrogen circulation pump 25 .

[0069] Optionally, in this embodiment, the first preset time is 8s-15s, and illustratively, it can be 8s, 9s, 10s, 11s, 12s, 13s, 14s or 15s, etc., and can be set according to actual needs.

[0070] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A cold start method for a fuel cell system, characterized in that: The cold start method of the fuel cell system is applied to the fuel cell system, wherein the fuel cell system comprises a battery stack (10), a hydrogen circulation system (20) and a coolant circulation system (30); The hydrogen circulation system (20) comprises a hydrogen source (21), a heat exchanger (22), a gas-liquid separator (23), a drain valve (24), a hydrogen circulation pump (25) and a nitrogen exhaust valve (26), wherein the hydrogen source (21) is communicated with a first inlet of the heat exchanger (22), a first outlet of the heat exchanger (22) is communicated with an air inlet of the battery stack (10), an air outlet of the battery stack (10) is communicated with an air inlet of the gas-liquid separator (23), an air outlet of the gas-liquid separator (23) is communicated with an inlet of the hydrogen circulation pump (25), an outlet of the hydrogen circulation pump (25) is communicated with an air inlet of the battery stack (10), the drain valve (24) is arranged at the drain outlet of the gas-liquid separator (23), and the nitrogen exhaust valve (26) is arranged at the nitrogen exhaust outlet of the hydrogen circulation pump (25); The coolant circulation system (30) comprises a coolant circulation pipeline (31), a heater (32), a first heat exchange pipeline (33) and a second heat exchange pipeline (34); the first end of the coolant circulation pipeline (31) is in communication with a liquid inlet of the battery stack (10); the second end of the coolant circulation pipeline (31) is in communication with a liquid outlet of the battery stack (10); the heater (32) is arranged on the coolant circulation pipeline (31) and is used to heat the coolant in the coolant circulation pipeline (31); one end of the first heat exchange pipeline (33) is in communication with the first end, and the other end is in communication with a second inlet of the heat exchanger (22); one end of the second heat exchange pipeline (34) is in communication with a second outlet of the heat exchanger (22), and the other end is in communication with the second end; The cold start method of the fuel cell system comprises: S100, detecting whether the hydrogen circulation pump (25) is frozen, and if the hydrogen circulation pump (25) is frozen, executing step S200; S200, starting the heater (32) to heat the coolant to a preset temperature; S300, controlling the hydrogen source (21) to supply hydrogen of a preset pressure to the battery stack (10), controlling the water discharge valve (24) to open at a first preset frequency, controlling the nitrogen discharge valve (26) to open at a second preset frequency, and controlling the battery stack (10) to operate at a preset power; S400, sending a start instruction to the hydrogen circulation pump (25) at intervals of a first preset time; if the hydrogen circulation pump (25) can be started normally, the fuel cell system is started in a normal operating mode; if the hydrogen circulation pump (25) cannot be started normally, repeating steps S300-S400.

2. The cold start method of the fuel cell system according to claim 1, characterized in that: The specific steps of detecting whether the hydrogen circulation pump (25) is frozen are: The hydrogen circulation pump (25) is controlled to start, and the rotation speed of the hydrogen circulation pump (25) is detected. If the rotation speed of the hydrogen circulation pump (25) cannot reach a set value within a second preset time, it is determined that the hydrogen circulation pump (25) is frozen.

3. The cold start method of the fuel cell system according to claim 2, characterized in that: The second preset time is 0s-5s.

4. The cold start method of the fuel cell system according to claim 1, characterized in that: The preset temperature is the temperature corresponding to the shortest time required for the hydrogen circulation pump (25) to melt ice under the current ambient temperature.

5. The cold start method of the fuel cell system according to claim 1, characterized in that: The preset pressure, the first preset frequency and the second preset frequency are set so that the battery stack (10) does not experience a single low phenomenon.

6. The cold start method of the fuel cell system according to claim 5, characterized in that: The specific steps of judging whether the battery stack (10) has a single low phenomenon are as follows: The voltage of each single cell in the battery stack (10) is detected to obtain a plurality of measured voltages, and the plurality of measured voltages are compared one by one with the average voltage of the battery stack (10); if the difference between at least one of the measured voltages and the average voltage of the battery stack (10) is greater than a preset value, the battery stack (10) has a single low phenomenon; otherwise, the battery stack (10) has no single low phenomenon.

7. The cold start method of the fuel cell system according to claim 1, characterized in that: The preset power is the power that needs to be output when the fuel cell system is cold started.

8. The cold start method of the fuel cell system according to claim 1, characterized in that: The first preset time is greater than the response time of the hydrogen circulation pump (25).

9. The cold start method of the fuel cell system according to claim 8, characterized in that: The first preset time is 8s-15s.

10. The cold start method of a fuel cell system according to any one of claims 1 to 9, characterized in that: The fuel cell system further comprises a hydrogen injection valve (27) and a pressure sensor (28); the first outlet of the heat exchanger (22) is in communication with the inlet of the hydrogen injection valve (27); the outlet of the hydrogen injection valve (27) is in communication with the air inlet of the battery stack (10); and the pressure sensor (28) is arranged at the air inlet of the battery stack (10); The specific steps of controlling the hydrogen source (21) to supply hydrogen of a preset pressure to the battery stack (10) are: The opening of the hydrogen injection valve (27) is gradually increased from small to large, and when the pressure value detected by the pressure sensor (28) is equal to the preset pressure, the adjustment of the hydrogen injection valve (27) is stopped.

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