Fuel cell air supply system and low-temperature cold start and shutdown control method

Abstract

The invention discloses a fuel cell air supply system and a low-temperature cold start and shutdown control method, and relates to the technical field of fuel cells. The fuel cell air supply system comprises an air compressor, an intercooler, an inlet valve, an outlet valve, a membrane humidifier, a first three-way valve, a second three-way valve, an expansion machine and a bypass valve. The first three-way valve and the second three-way valve are arranged to form bypass pipelines on the primary side and the secondary side of the membrane humidifier, part of gas is allowed not to pass through the membrane humidifier, the phenomenon that the interior of the galvanic pile is flooded due to the fact that all gas is used for humidification is avoided, and the overall requirement for the membrane humidifier is reduced.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a fuel cell air supply system and a low-temperature cold start and shutdown control method. Background Art

[0002] As a representative of clean energy, the fuel cell system has become an important part of modern energy solutions with its high energy conversion efficiency, compact structure, low noise and zero emissions. The hydrogen supply system, air supply system and cooling system are used to maintain the normal operation of the fuel cell system. The air compressor in the air supply system is used to provide high-pressure air to ensure the air supply of the fuel cell stack to increase the output power of the stack. As the power of the fuel cell system increases, the power consumption of the air compressor increases. For this reason, an expander is integrated on the air compressor to recover the high-temperature exhaust energy discharged from the stack and reduce the power consumption of the motor.

[0003] The core component of the membrane humidifier is a water-permeable but air-impermeable membrane, which uses the hot and humid air at the cathode outlet to humidify the dry air at the cathode inlet, thereby ensuring a good hydration state of the proton exchange membrane. The internal flow resistance of the membrane humidifier is relatively large, which places higher requirements on the air compressor pressure ratio. The internal water production of the fuel cell stack at high electrical density can meet the humidification needs, but if all gases are humidified, it will cause water flooding inside the fuel cell stack. Summary of the invention

[0004] The purpose of this application is to provide a fuel cell air supply system and a low-temperature cold start and shutdown control method, which can avoid water flooding inside the fuel cell stack.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a fuel cell air supply system, the fuel cell air supply system comprising: an air compressor, an intercooler, an inlet valve, an outlet valve, a membrane humidifier, a first three-way valve, a second three-way valve, an expander and a bypass valve;

[0007] The air compressor is connected to the intercooler, the intercooler is connected to one end of the secondary side of the membrane humidifier, and the other end of the secondary side of the membrane humidifier is connected to the cathode inlet of the fuel cell stack through the inlet valve;

[0008] The cathode outlet of the stack is connected to the input port of the first three-way valve through the outlet valve, the first output port of the first three-way valve is connected to one end of the primary side of the membrane humidifier, the other end of the secondary side of the membrane humidifier is connected to the first input port of the second three-way valve, the second output port of the first three-way valve is connected to the second input port of the second three-way valve, and the output port of the second three-way valve is connected to the expander;

[0009] The power output end of the expander is connected to the power supply end of the air compressor;

[0010] The pipeline connecting the second output port of the first three-way valve and the second input port of the second three-way valve is a bypass pipeline;

[0011] One end of the bypass valve is connected to the pipeline between the secondary side of the membrane humidifier and the inlet valve, and the other end of the bypass valve is connected to the pipeline between the outlet valve and the first three-way valve.

[0012] Optionally, the fuel cell air supply system comprises: an air filter, and the air filter is connected to the air inlet of the air compressor.

[0013] Optionally, the fuel cell air supply system comprises: a drain valve, which is arranged on the pipeline between the second three-way valve and the expander.

[0014] In a second aspect, the present application provides a low-temperature cold start control method, which is applied to the above-mentioned fuel cell air supply system, and the low-temperature cold start control method includes:

[0015] Controlling an air compressor in a fuel cell air supply system to purge a membrane humidifier and an expander in the fuel cell air supply system;

[0016] After the membrane humidifier and the expander are purged, the air compressor in the fuel cell air supply system is controlled to purge the fuel cell stack;

[0017] After the stack is purged, the stack is controlled to start, and the fuel cell air supply system is controlled to humidify the air.

[0018] Optionally, controlling an air compressor in the fuel cell air supply system to purge a membrane humidifier and an expander in the fuel cell air supply system specifically includes:

[0019] Controlling the closing of the inlet valve and the outlet valve in the fuel cell air supply system, and controlling the opening of the bypass valve, the drain valve and the expander in the fuel cell air supply system;

[0020] The air compressor is controlled to run at a first preset speed so that the air output by the air compressor is output through the intercooler, the bypass valve, the secondary side of the membrane humidifier and the expander.

[0021] Optionally, controlling an air compressor in the fuel cell air supply system to purge the fuel cell stack specifically includes:

[0022] Controlling the bypass valve in the fuel cell air supply system to close, and controlling the inlet valve, outlet valve, drain valve and expander in the fuel cell air supply system to open;

[0023] The fuel cell stack is controlled to load at a preset power, and the air compressor is controlled to run at a second preset speed, so that the gas output by the air compressor is output through the intercooler, the fuel cell stack and the expander.

[0024] Optionally, controlling the fuel cell air supply system to humidify the air specifically includes:

[0025] Control the bypass valve and the drain valve in the fuel cell air supply system to close, and control the inlet valve, the outlet valve and the expander in the fuel cell air supply system to open;

[0026] The air compressor in the fuel cell air supply system is controlled to operate at a third preset speed.

[0027] In a third aspect, the present application provides a low temperature cold shutdown control method, which is applied to the above-mentioned fuel cell air supply system, and the low temperature cold shutdown control method includes:

[0028] Control the air compressor in the fuel cell air supply system to purge the fuel cell stack;

[0029] After the stack is purged, the air compressor in the fuel cell air supply system is controlled to purge the membrane humidifier and the expander in the fuel cell air supply system;

[0030] After the membrane humidifier and expander are purged, the stack and fuel cell air supply system are controlled to enter a shutdown state.

[0031] Optionally, controlling an air compressor in the fuel cell air supply system to purge the fuel cell stack specifically includes:

[0032] Controlling the bypass valve in the fuel cell air supply system to close, and controlling the inlet valve, outlet valve, drain valve and expander in the fuel cell air supply system to open;

[0033] The fuel cell stack is controlled to load at a preset power, and the air compressor is controlled to run at a second preset speed, so that the gas output by the air compressor is output through the intercooler, the fuel cell stack and the expander.

[0034] Optionally, controlling an air compressor in the fuel cell air supply system to purge a membrane humidifier and an expander in the fuel cell air supply system specifically includes:

[0035] Controlling the closing of the inlet valve and the outlet valve in the fuel cell air supply system, and controlling the opening of the bypass valve, the drain valve and the expander in the fuel cell air supply system;

[0036] The air compressor is controlled to run at a first preset speed so that the air output by the air compressor is output through the intercooler, the bypass valve, the secondary side of the membrane humidifier and the expander.

[0037] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0038] The present application provides a fuel cell air supply system and a low-temperature cold start and shutdown control method. The fuel cell air supply system described in the present application includes: an air compressor, an intercooler, an inlet valve, an outlet valve, a membrane humidifier, a first three-way valve, a second three-way valve, an expander and a bypass valve. The present application sets a first three-way valve and a second three-way valve to form a bypass line on the primary and secondary sides of the membrane humidifier, allowing part of the gas to not pass through the membrane humidifier, avoiding the phenomenon of flooding inside the stack due to humidification of all gases, and reducing the overall demand for membrane humidifiers.

[0039] The present application performs step-by-step purges on the fuel cell system during startup and shutdown to remove accumulated moisture, eliminate unreacted fuel or oxidant, prevent the stack from freezing, and remove possible contaminants, thereby preventing residual moisture from freezing and causing damage to the membrane humidifier and expander. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, without paying creative work, other drawings obtained based on these drawings belong to the patent of this invention.

[0041] Figure 1 A schematic structural diagram of a fuel cell air supply system provided in one embodiment of the present application;

[0042] Figure 2 A flowchart of a low-temperature cold start control method provided in one embodiment of the present application;

[0043] Figure 3 A flowchart of a low temperature shutdown control method provided in one embodiment of the present application. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0045] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0046] In an exemplary embodiment, Figure 1 As shown, a fuel cell air supply system is provided, the fuel cell air supply system comprising: an air compressor, an intercooler, an inlet valve, an outlet valve, a membrane humidifier, a first three-way valve ( Figure 1 Not shown), the second three-way valve ( Figure 1 ), an expander and a bypass valve; the air compressor is connected to the intercooler, the intercooler is connected to one end of the secondary side of the membrane humidifier, and the other end of the secondary side of the membrane humidifier is connected to the cathode inlet of the stack through the inlet valve; the cathode outlet of the stack is connected to the input port of the first three-way valve through the outlet valve, the first output port of the first three-way valve is connected to one end of the primary side of the membrane humidifier, the other end of the secondary side of the membrane humidifier is connected to the first input port of the second three-way valve, the second output port of the first three-way valve is connected to the second input port of the second three-way valve, and the output port of the second three-way valve is connected to the expander; the power output end of the expander is connected to the power supply end of the air compressor; the pipeline connecting the second output port of the first three-way valve and the second input port of the second three-way valve is a bypass pipeline; one end of the bypass valve is connected to the pipeline between the secondary side of the membrane humidifier and the inlet valve, and the other end of the bypass valve is connected to the pipeline between the outlet valve and the first three-way valve.

[0047] Exemplarily, the expander in this embodiment can utilize a variable geometry turbine (VGT) for energy recovery and back pressure control, thereby reducing the overall parasitic power consumption of the system and improving energy utilization efficiency.

[0048] As a preferred implementation, the fuel cell air supply system includes: an air filter connected to the air inlet of the air compressor. Further, the fuel cell air supply system includes: a drain valve disposed on the pipeline between the second three-way valve and the expander.

[0049] In view of the characteristics of membrane humidifiers that they are easily damaged at low temperatures, are too large in size, and that the water produced by the stack itself can meet the humidification needs under high current density, the bypass line is innovatively introduced to allow some air to not pass through the membrane humidifier, reducing the overall demand for membrane humidifiers. The size of the membrane humidifier has been reduced, which not only reduces the burden on the system and reduces costs, but also enhances the flexibility and adaptability of the system. Especially at high current density, when the stack has a lower demand for humidification, the smaller membrane humidifier design avoids waste of resources, not only improves the performance of the fuel cell system under different working conditions, but also promotes the overall energy conservation, emission reduction and cost-effectiveness of the system.

[0050] In this embodiment, the optimal membrane humidifier flow distribution can be obtained through theoretical calculation and actual calibration, so that a small humidifier can be used, the overall system volume is reduced, the cost is reduced, and the flexibility and adaptability of the system are enhanced.

[0051] Advantageously, the value and consistency of the stack voltage can reflect the humidification condition in the stack. If the humidification in the stack is not sufficient, the stack voltage will be too low and unstable. By observing whether the voltage value is within the normal range (i.e., the stack voltage value is greater than a certain threshold to avoid being too low) and stable, the optimal membrane humidifier flow distribution can be obtained.

[0052] At low temperatures, the residual moisture in the membrane humidifier may freeze into ice, causing physical damage to the membrane material or related components, thus affecting the life and performance of the membrane.

[0053] Moreover, the high-temperature exhaust gas discharged from the fuel cell stack contains a large amount of water vapor. After the system is shut down, the water vapor at the cathode outlet will condense into liquid water inside the air supply system pipes and components. Especially under low temperature conditions, liquid water will condense into ice, causing the impeller and casing in the expander to freeze, making it impossible for the expander to operate normally when the system is started again, resulting in a cold start failure of the system. In order to solve this problem, the existing technology usually sets a water separator on the air inlet side of the expander to separate the moisture in the gas entering the expander. However, the water separator is large in size, which affects the pipeline layout.

[0054] In an exemplary embodiment, a low temperature cold start control method and a low temperature cold shutdown control method are provided.

[0055] Wherein, the low temperature cold start control method comprises:

[0056] The air compressor in the fuel cell air supply system is controlled to purge the membrane humidifier and the expander in the fuel cell air supply system.

[0057] After the membrane humidifier and the expander are purged, the air compressor in the fuel cell air supply system is controlled to purge the fuel cell stack.

[0058] After the stack is purged, the stack is controlled to start, and the fuel cell air supply system is controlled to humidify the air.

[0059] Figure 2 It is a flow chart of the low temperature cold start control method, as shown in Figure 2 As shown, the low temperature cold start control method in the embodiment of the present application includes three stages:

[0060] S11, membrane humidifier and expander are purged to remove possible moisture or other impurities to ensure their good performance in subsequent operations. In this step, the inlet valve and outlet valve are closed, while the bypass valve, drain valve and expander are all opened, the air compressor runs at the speed under idle conditions, and the expander runs at the opening degree under idle speed.

[0061] S12, stack purge, at this time the bypass valve is closed, the inlet valve, outlet valve and drain valve are fully opened, the stack runs at idle speed, and the air compressor and expander both run at idle speed parameters to ensure proper air supply and pressure.

[0062] S13, the system enters the normal operation state, the bypass valve and the drain valve are closed, while the inlet valve and the outlet valve are still open, the fuel cell stack starts to operate normally, and the speed of the air compressor and the opening of the expander are adjusted according to the actual power request. By monitoring the voltage and current output of the fuel cell stack, the actual power output of the fuel cell stack is calculated, and closed-loop control is achieved to maintain the optimal air supply and pressure.

[0063] The low temperature cold shutdown control method includes:

[0064] Control the air compressor in the fuel cell air supply system to purge the fuel cell stack.

[0065] After the stack is purged, the air compressor in the fuel cell air supply system is controlled to purge the membrane humidifier and the expander in the fuel cell air supply system.

[0066] After the membrane humidifier and expander are purged, the stack and fuel cell air supply system are controlled to enter a shutdown state.

[0067] Figure 3 This is a flow chart of the low temperature shutdown control method, as shown in Figure 3 As shown, the low temperature cold shutdown control method in the embodiment of the present application includes three stages:

[0068] S21, the stack is purged to remove any moisture or other impurities that may be present to ensure good performance at the next startup. In this step, the bypass valve is closed, and the inlet valve, outlet valve, drain valve and expander are all opened. The stack stops running, and the air compressor runs at a predetermined speed.

[0069] S22, membrane humidifier and expander are purged. At this time, the inlet valve and outlet valve are closed, while the bypass valve, drain valve and expander are all opened, and the air compressor runs at the set speed to ensure the cleanliness of the inside of the membrane humidifier and expander.

[0070] S23, shut down and cut off the power, the inlet valve, outlet valve, bypass valve and expander are closed, while the drain valve remains open, the air compressor stops running, and the system enters the shutdown state.

[0071] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0072] The present application uses an innovative bypass line design to allow part of the air to bypass the membrane humidifier, thereby avoiding over-humidification at high current density, reducing the size and cost of the membrane humidifier, and facilitating the overall integration and economy of the system.

[0073] This application eliminates the water separator at the inlet of the expander, simplifies the system structure, and develops a cascade purge strategy for the battery stack and components, which can effectively drain the moisture in the system, reduce the risk of freezing of system components under low temperature conditions, and improve the cold start performance of the system.

[0074] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A fuel cell air supply system, characterized in that: The fuel cell air supply system comprises: an air compressor, an intercooler, an inlet valve, an outlet valve, a membrane humidifier, a first three-way valve, a second three-way valve, an expander and a bypass valve; The air compressor is connected to the intercooler, the intercooler is connected to one end of the secondary side of the membrane humidifier, and the other end of the secondary side of the membrane humidifier is connected to the cathode inlet of the fuel cell stack through the inlet valve; The cathode outlet of the stack is connected to the input port of the first three-way valve through the outlet valve, the first output port of the first three-way valve is connected to one end of the primary side of the membrane humidifier, the other end of the secondary side of the membrane humidifier is connected to the first input port of the second three-way valve, the second output port of the first three-way valve is connected to the second input port of the second three-way valve, and the output port of the second three-way valve is connected to the expander; The power output end of the expander is connected to the power supply end of the air compressor; The pipeline connecting the second output port of the first three-way valve and the second input port of the second three-way valve is a bypass pipeline; One end of the bypass valve is connected to the pipeline between the secondary side of the membrane humidifier and the inlet valve, and the other end of the bypass valve is connected to the pipeline between the outlet valve and the first three-way valve.

2. The fuel cell air supply system according to claim 1, characterized in that: The fuel cell air supply system comprises an air filter connected to the air inlet of the air compressor.

3. The fuel cell air supply system according to claim 1, characterized in that: The fuel cell air supply system comprises a drain valve, which is arranged on a pipeline between the second three-way valve and the expander.

4. A low temperature cold start control method, characterized in that: The low-temperature cold start control method is applied to the fuel cell air supply system according to any one of claims 1 to 3, and the low-temperature cold start control method comprises: Controlling an air compressor in a fuel cell air supply system to purge a membrane humidifier and an expander in the fuel cell air supply system; After the membrane humidifier and the expander are purged, the air compressor in the fuel cell air supply system is controlled to purge the fuel cell stack; After the stack is purged, the stack is controlled to start, and the fuel cell air supply system is controlled to humidify the air.

5. The low temperature cold start control method according to claim 4, characterized in that: Controlling the air compressor in the fuel cell air supply system to purge the membrane humidifier and expander in the fuel cell air supply system, specifically including: Controlling the closing of the inlet valve and the outlet valve in the fuel cell air supply system, and controlling the opening of the bypass valve, the drain valve and the expander in the fuel cell air supply system; The air compressor is controlled to run at a first preset speed so that the air output by the air compressor is output through the intercooler, the bypass valve, the secondary side of the membrane humidifier and the expander.

6. The low temperature cold start control method according to claim 4, characterized in that: Control the air compressor in the fuel cell air supply system to purge the fuel cell stack, including: Controlling the bypass valve in the fuel cell air supply system to close, and controlling the inlet valve, outlet valve, drain valve and expander in the fuel cell air supply system to open; The fuel cell stack is controlled to load at a preset power, and the air compressor is controlled to run at a second preset speed, so that the gas output by the air compressor is output through the intercooler, the fuel cell stack and the expander.

7. The low temperature cold start control method according to claim 4, characterized in that: Control the fuel cell air supply system to humidify the air, including: Control the bypass valve and the drain valve in the fuel cell air supply system to close, and control the inlet valve, the outlet valve and the expander in the fuel cell air supply system to open; The air compressor in the fuel cell air supply system is controlled to operate at a third preset speed.

8. A low temperature cold shutdown control method, characterized in that: The low temperature cold shutdown control method is applied to the fuel cell air supply system according to any one of claims 1 to 3, and the low temperature cold shutdown control method comprises: Control the air compressor in the fuel cell air supply system to purge the fuel cell stack; After the stack is purged, the air compressor in the fuel cell air supply system is controlled to purge the membrane humidifier and the expander in the fuel cell air supply system; After the membrane humidifier and expander are purged, the stack and fuel cell air supply system are controlled to enter a shutdown state.

9. The low temperature cold shutdown control method according to claim 8, characterized in that: Control the air compressor in the fuel cell air supply system to purge the fuel cell stack, including: Controlling the bypass valve in the fuel cell air supply system to close, and controlling the inlet valve, outlet valve, drain valve and expander in the fuel cell air supply system to open; The fuel cell stack is controlled to load at a preset power, and the air compressor is controlled to run at a second preset speed, so that the gas output by the air compressor is output through the intercooler, the fuel cell stack and the expander.

10. The low temperature cold shutdown control method according to claim 8, characterized in that: Controlling the air compressor in the fuel cell air supply system to purge the membrane humidifier and expander in the fuel cell air supply system, specifically including: Controlling the closing of the inlet valve and the outlet valve in the fuel cell air supply system, and controlling the opening of the bypass valve, the drain valve and the expander in the fuel cell air supply system; The air compressor is controlled to run at a first preset speed so that the air output by the air compressor is output through the intercooler, the bypass valve, the secondary side of the membrane humidifier and the expander.

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