Fuel cell system and purge control method thereof

Abstract

The application discloses a fuel cell system and a purging control method thereof. The fuel cell system comprises a fuel cell system controller, a stack module, an air supply system and a cooling system. The air supply system comprises an air filter, a flow meter, an air compressor, an intercooler, an electromagnetic valve, a humidifier and an air compressor controller. The air compressor comprises a motor, a compressor and an expander. The intercooler is provided with two air outlets, namely a first air outlet and a second air outlet. External air is divided into two passages after passing through the air filter, the flow meter, the compressor of the air compressor and the intercooler. The air discharged from the stack module and the air discharged from the motor jointly enter the expander to drive the rotation of the expander, so as to reduce the energy loss of the motor. When the fuel cell system controller receives a shutdown instruction, the air compressor is kept to run at low power, the electromagnetic valve and the back pressure valve are closed, the low-temperature compressed air of the second air outlet of the intercooler flows through the motor, and then purges the expander and drives the rotation of the expander.

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 a purge control method thereof. Background technology:

[0002] A fuel cell system is an energy conversion device that generates electricity through the electrochemical reaction of hydrogen and oxygen. It boasts high energy conversion efficiency, a simple structure, low noise, and zero pollution. Current fuel cell systems generally require three auxiliary systems: a hydrogen supply system, an air supply system, and a cooling system to maintain normal operation.

[0003] In the air supply system, in order to ensure the air supply in the stack module of the fuel cell system, an air compressor is generally used to pressurize the air to improve the air supply efficiency. The air compressor is a major energy consumer in the entire fuel cell system, and the power consumed accounts for about 15%-20% of the output power of the fuel cell stack. In order to save energy and improve the efficiency of the entire fuel cell system, the expander is usually designed and integrated into the air compressor. The expander improves the air supply efficiency of the entire air compressor by recovering the energy of the high-temperature exhaust gas discharged from the stack module of the fuel cell system, and at the same time reduces the energy consumption of the motor. In this process, there is no need to increase power consumption, which can save energy.

[0004] However, the air compressor generates heat when working. To ensure that the temperature of the air compressor does not continue to rise, cooling air is generally introduced from the outside or from inside the air compressor itself to cool the stator and bearing system of the motor inside it. However, the air after cooling the air compressor is directly discharged without further utilization, resulting in energy waste. In addition, the high-temperature exhaust gas discharged from the stack module of the fuel cell system has a very high water content. After the fuel cell system is shut down, the high-temperature water vapor in the exhaust gas will condense into liquid water in the pipes of the air supply system and the expander. The liquid water that stays in the expander for a long time will corrode the impeller and volute, and under low temperature conditions, the liquid water will condense into ice, condensing the impeller and volute in the expander together. When the fuel cell system is started again, the impeller in the expander will be frozen and unable to rotate. The discharge of the exhaust gas will be blocked, which will damage the expander and even bring system risks. To reduce the moisture in the high-temperature exhaust gas discharged from the stack module of the fuel cell system, the current practice is to set a water separator on the air inlet side of the expander to separate the moisture in the gas entering the expander. For details, please refer to the publication number: CN114122454A, the invention name is: A fuel cell and its air supply system invention patent application. Although this solution is equipped with a cathode water separator at the fuel cell tail outlet, it can only separate and discharge part of the liquid water in the exhaust gas. The water vapor in the high-temperature exhaust gas cannot be completely separated and discharged. The high-temperature exhaust gas with water vapor is directly discharged into the expander. After the fuel cell system is shut down, the water vapor in the high-temperature exhaust gas will condense into liquid water in the expander. At low temperatures, the liquid water will condense into ice, posing a risk to the fuel cell system. Therefore, after the fuel cell system is shut down, it is necessary to purge the pipelines and expander of the fuel cell system. Summary of the invention:

[0005] One object of the present invention is to provide a fuel cell system and a purge control method thereof, which can solve the technical problem in the prior art that the air after cooling and dissipating heat from the air compressor is directly discharged without further utilization, resulting in energy waste.

[0006] Another object of the present invention is to provide a fuel cell system and a purge control method thereof, which can solve the technical problem that the water separator in the prior art cannot completely separate and discharge the water vapor in the high-temperature tail gas of the fuel cell stack module, so that after the fuel cell system is shut down, the water vapor in the tail gas will condense into liquid water in the expander, and under low temperature conditions, the liquid water will condense into ice, which brings risks to the fuel cell system.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] One object of the present invention is to provide a fuel cell system, including a fuel cell system controller, a stack module, a hydrogen supply system, an air supply system and a cooling system; the air supply system includes an air filter, a flow meter, an air compressor, an intercooler, a solenoid valve, a humidifier and an air compressor controller, the air compressor includes a motor, a compressor and an expander, the compressor and the expander are respectively mounted at both ends of the motor and directly connected to the two ends of the motor's rotating shaft; the intercooler is provided with two air outlets, namely a first air outlet and a second air outlet, and the external air passes through the air filter, the flow meter, the compressor of the air compressor and the intercooler in sequence and is divided into two paths, the first path starts from the first air outlet of the intercooler, passes through the solenoid valve, the humidifier, the stack module, the back pressure valve, the water separator and the expander in sequence, and is finally discharged from the expander; the second path The air path starts from the second air outlet of the intercooler, passes through the motor and the expander in sequence, and is finally discharged from the expander; the low-temperature compressed air output from the second air outlet of the intercooler passes through the motor to dissipate heat for the motor, and then enters the expander and is discharged; when the fuel cell system is running, the fuel cell system controller controls the solenoid valve to be turned on to provide air to the stack module, and the air discharged from the air outlet of the stack module and the air discharged from the motor enter the expander together to drive the expander to rotate to reduce the energy loss of the motor. When the fuel cell system controller receives a shutdown command, it stops the operation of the hydrogen supply system, keeps the air compressor running at low power, and closes the solenoid valve and the back-pressure valve, so that the low-temperature compressed air from the second air outlet of the intercooler flows through the motor to purge the expander, and continues to drive the expander to rotate to reduce the energy loss of the motor.

[0009] Preferably, when the fuel cell system controller receives a shutdown command, the cooling system is kept running so that the cooling system can continuously provide coolant to the intercooler to cool the high-temperature compressed air output by the compressor, and then output low-temperature compressed air. The low-temperature compressed air is output from the second air outlet of the intercooler and passes through the motor to dissipate heat from the motor.

[0010] Preferably, when the fuel cell system controller receives a shutdown command, the fuel cell system controller accumulates the purge time of the expander. When the accumulated purge time of the expander reaches a preset purge time H, the purge is deemed to be completed. The fuel cell system controller controls the air compressor to stop running through the air compressor controller, and at the same time controls the cooling system to stop running.

[0011] Preferably, the low-temperature compressed air output from the second air outlet of the intercooler enters the interior of the motor to dissipate heat from the stator assembly and the bearing system inside the motor.

[0012] Preferably, the expander is provided with two air inlets, namely a first air inlet and a second air inlet, the water separator is connected to the first air inlet of the expander, and the motor is connected to the second air inlet of the expander.

[0013] Preferably, the expander is provided with an air inlet, and the water separator and the motor are respectively connected to the air inlet of the expander.

[0014] Preferably, the solenoid valve is a two-way valve.

[0015] Preferably, a muffler is connected to the gas outlet of the expander, and the muffler is used to reduce the noise when the gas is discharged from the expander.

[0016] Another object of the present invention is to provide a purge control method for a fuel cell system, using the fuel cell system described above, the purge control method comprises the following steps:

[0017] Step 1: After receiving a shutdown command during operation, the fuel cell system controller stops the operation of the hydrogen supply system, keeps the cooling system running and the air compressor running at low power, and closes the solenoid valve and back pressure valve, allowing the low-temperature compressed air from the second outlet of the intercooler to flow through the motor and then purge the expander, and continuously drives the expander to rotate to reduce the energy loss of the motor;

[0018] Step 2: The fuel cell system controller accumulates the purge time of the expander. When the accumulated purge time of the expander reaches the preset purge time H, the purge is considered completed. The fuel cell system controller controls the air compressor to stop running through the air compressor controller, and also controls the cooling system to stop running.

[0019] Step 3: The fuel cell system controller controls the solenoid valve and the back pressure valve to reset.

[0020] Compared with the prior art, the present invention has the following effects:

[0021] 1) The fuel cell system provided by the present invention allows the air discharged from the air outlet of the fuel cell module and the air discharged from the motor to enter the expander together and drive the expander to rotate, thereby reducing the load on one end of the motor shaft. The energy of the air discharged after cooling the motor is recovered to reduce the energy loss of the motor, thereby achieving the purpose of energy saving.

[0022] 2) In the fuel cell system provided by the present invention, after the fuel cell system is shut down, the low-temperature compressed air from the second air outlet of the intercooler flows through the motor and then purges the expander, so that the liquid water condensed from the water vapor in the high-temperature tail gas of the stack module after the fuel cell system is shut down can be quickly discharged from the expander, effectively removing the liquid water accumulated inside the expander, and preventing the liquid water inside the expander from condensing into ice under low-temperature conditions. This ensures that when the fuel cell system is started at low temperature, the first wind wheel in the expander can rotate normally, and the tail gas of the stack module can be discharged smoothly, so that the fuel cell system can start and operate normally under low-temperature conditions, and can also prevent the liquid water retained in the expander from corroding components. , which can extend the service life of the fuel cell system. The air exhausted from the motor has a low moisture content. The air exhausted from the motor is directly used to purge the expander, so that the air inside the expander is relatively dry after the purge, which can reduce the risk of the air inside the expander condensing into liquid water after the fuel cell system is shut down, thereby avoiding excessive accumulation of liquid water inside the expander again. The low-temperature compressed air from the second air outlet of the intercooler flows through the motor and continuously drives the expander to rotate, which can reduce the load on one end of the motor shaft. The energy of the air exhausted after cooling the motor can be recovered to reduce the energy loss of the motor, thereby achieving the purpose of saving energy, and the air exhausted after cooling the motor can be fully utilized.

[0023] 3) Other advantages of the present invention are described in detail in the embodiment section. Description of the drawings:

[0024] Figure 1 is a block diagram of a fuel cell system provided in accordance with the first embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the electrical connection of the fuel cell system provided in Example 1 of the present invention (the expander is provided with two air inlets);

[0026] Figure 3 This is a schematic diagram of the electrical connection of the fuel cell system provided in Example 1 of the present invention (the expander is provided with one air inlet);

[0027] Figure 4 is a block diagram of the control principle of the fuel cell system provided in the first embodiment of the present invention;

[0028] Figure 5 This is a flow chart of a purge control method for a fuel cell system according to a second embodiment of the present invention. Specific implementation method:

[0029] The present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0030] Example 1:

[0031] like Figure 1 As shown, this embodiment provides a fuel cell system, including a fuel cell system controller 10, a fuel cell stack module 20, a hydrogen supply system 30, an air supply system 40 and a cooling system 50. The fuel cell system controller 10 controls the operation of the fuel cell stack module 20, the hydrogen supply system 30, the air supply system 40 and the cooling system 50.

[0032] like Figures 2 to 4 As shown, the air supply system 40 includes an air filter 1, a flow meter 2, an air compressor 3, an intercooler 4, a solenoid valve 5, a humidifier 6 and an air compressor controller 7. The three-way valve and the air compressor controller 7 are controlled by the fuel cell system controller 10. The air compressor 3 includes a motor 31, a compressor 32 and an expander 33. The motor 31 is controlled by the air compressor controller 7. The compressor 32 and the expander 33 are respectively installed at both ends of the motor 31 and are directly connected to the two ends of the rotating shaft of the motor 31; specifically, the expander 33 includes a first volute and a first impeller, and the compressor 32 includes a second volute. and the second wind wheel, the first volute and the second volute are both provided with an air inlet and an air outlet, wherein the first volute can be provided with one air inlet or two air inlets, the first wind wheel is directly connected to the two ends of the rotating shaft of the second wind wheel motor 31, and the second wind wheel of the compressor 32 is driven to rotate by the motor 31, so that the external air entering the compressor 32 can be compressed by the compressor 32 and then output high-temperature compressed air. The cooling system 50 provides coolant for the fuel cell module 20, and also provides coolant for the intercooler 4 to cool the high-temperature compressed air output by the compressor 32 of the air compressor 3.

[0033] like Figure 2 and Figure 3As shown, the intercooler 4 is provided with two air outlets, i.e. a first air outlet and a second air outlet, and the external air is divided into two passages after passing through the air filter 1, the flow meter 2, the compressor 32 of the air compressor 3 and the intercooler 4 in sequence. The first passage starts from the first air outlet of the intercooler 4, passes through the electromagnetic valve 5, the humidifier 6, the stack module 20, the back pressure valve 8, the water distributor 9 and the expander 33 in sequence, and is finally discharged from the expander 33. The second passage starts from the second air outlet of the intercooler 4, passes through the motor 31 and the expander 33 in sequence, and is finally discharged from the expander 33. The low-temperature compressed air output from the second air outlet of the intercooler 4 enters the interior of the motor 31 to dissipate heat for the stator assembly and bearing system in the interior of the motor 31, and the air discharged after heat dissipation enters the expander 33 and is then discharged. Specifically, when the fuel cell system is running, the fuel cell system controller 10 controls the electromagnetic valve 5 to be conductive to provide air for the stack module 20. The air discharged from the air outlet of the stack module and the air discharged from the motor jointly enter the expander 33 and jointly drive the first impeller of the expander 33 to rotate, thereby reducing the load of the motor 31 at one end of the shaft, recovering the energy of the air discharged after the motor 31 is cooled, reducing the energy loss of the motor 31, and achieving the purpose of saving energy.

[0034] When the fuel cell system controller 10 receives a shutdown instruction, the hydrogen supply system 30 is stopped, the air compressor 3 is kept running at low power, and the electromagnetic valve 5 and the back pressure valve 8 are closed, so that the low-temperature compressed air from the second outlet of the intercooler 4 flows through the motor 31 and then purges the expander 33, and the expander 33 is continuously driven to reduce the energy loss of the motor 31. After the fuel cell system is shut down, the low-temperature compressed air from the second outlet of the intercooler 4 flows through the motor 31 and then purges the expander 33, so that the liquid water condensed from the water vapor in the high-temperature exhaust gas of the fuel cell system after shutdown can be quickly discharged from the expander 33, effectively removing the accumulated liquid water in the expander 33, preventing the liquid water in the expander 33 from freezing in a low-temperature state, ensuring that the first impeller in the expander 33 can rotate normally when the fuel cell system is started in a low-temperature state, and the exhaust gas of the fuel cell system can be smoothly discharged, so that the fuel cell system can also be started and run normally in a low-temperature state. It can also avoid the corrosion of the liquid water remaining in the expander 33 to the parts, prolong the service life of the fuel cell system, and the water content in the air discharged from the motor 31 is low, so that the air in the expander 33 is relatively dry after purging, which can reduce the risk of condensation of the air in the expander 33 into liquid water after the fuel cell system is shut down, thereby avoiding the accumulation of too much liquid water in the pipeline of the air supply system 40 and the expander 33. The low-temperature compressed air from the second outlet of the intercooler flows through the motor and continuously drives the expander, which can reduce the load on the one end of the motor 31, recover the energy of the air discharged after cooling the motor 31 to reduce the energy loss of the motor 31, thereby achieving the purpose of saving energy, and making full use of the air discharged after cooling the motor 31.

[0035] When the fuel cell system controller 10 receives a shutdown instruction, the cooling system 50 is kept running, so that the cooling system 50 can continuously provide cooling liquid to the intercooler 4 to cool the high-temperature compressed air output by the compressor 32, and then output low-temperature compressed air. The low-temperature compressed air output from the second outlet of the intercooler 4 passes through the motor 31 to dissipate heat from the motor 31. Delaying the shutdown of the cooling system 50 can ensure that the air compressor 3 is continuously cooled and dissipated when working, thereby better protecting the air compressor 3.

[0036] When the fuel cell system controller 10 receives the shutdown command, the fuel cell system controller 10 accumulates the purge time of the expander 33. When the accumulated purge time of the expander 33 reaches the preset purge time H, the purge is deemed to be completed, and the fuel cell system controller 10 controls the air compressor 3 to stop running through the air compressor controller 7, and controls the cooling system 50 to stop running at the same time; of course, to ensure that the fuel cell system can run immediately after it is started up next time, after the fuel cell system controller 10 controls the cooling system 50 to stop running and controls the air compressor 3 to stop running through the air compressor controller 7, it can also control other components of the fuel cell system (controlled elements in the hydrogen supply system 30, air supply system 40 and cooling system 50 that are controlled by the fuel cell system controller 10, such as the solenoid valve 5, the back pressure valve 8 and other components) to reset, and then power off the fuel cell system.

[0037] like Figure 2 As shown, the first volute of the expander 33 is provided with two air inlets, namely the first air inlet and the second air inlet. The water separator 9 is connected to the first air inlet of the expander 33, and the motor 31 is connected to the second air inlet of the expander 33. The two air inlets are designed according to the pipeline layout to facilitate the connection between the first volute and the two passages. Of course, in order to reduce the openings on the first volute of the expander 33 to ensure the structural integrity of the first volute of the expander 33, only one air inlet can be provided on the first volute of the expander 33 (such as Figure 3 As shown), the water separator 9 and the motor 31 can be connected to the air inlet of the first volute of the expander 33 by using a Y-type pipe joint.

[0038] The solenoid valve 5 is a two-way valve. Appropriate components can be selected according to the pipeline layout to control manufacturing costs.

[0039] like Figure 2 and Figure 3 As shown, the gas outlet of the expander 33 is connected to a muffler 60, which is used to reduce the noise when the gas is discharged from the expander 33. At the same time, the liquid water inside the expander 33 and the liquid water separated by the water separator 9 can also be discharged through the muffler 60.

[0040] Example 2:

[0041] like Figure 5 As shown, this embodiment provides a purge control method for a fuel cell system. Using the fuel cell system described above, the purge control method includes the following steps:

[0042] Step 1: After receiving a shutdown instruction during operation, the fuel cell system controller 10 stops the operation of the hydrogen supply system 30, keeps the cooling system 50 continuously operating and the air compressor 3 continuously operating at low power, and closes the electromagnetic valve 5 and the back pressure valve 8, so that the low-temperature compressed air at the second outlet of the intercooler 4 flows through the motor 31 and then purges the expander 33, and continuously drives the expander 33 to rotate to reduce the energy loss of the motor 31;

[0043] Step 2: The fuel cell system controller 10 accumulates the purging time of the expander 33, and when the accumulated purging time of the expander 33 reaches the preset purging time H, it is considered that the purging is completed, and the fuel cell system controller 10 controls the air compressor 3 to stop operating through the air compressor controller 7, and controls the cooling system 50 to stop operating at the same time;

[0044] Step 3: The fuel cell system controller 10 controls the electromagnetic valve 5 and the back pressure valve 8 to reset.

[0045] After the fuel cell system controller 10 controls the electromagnetic valve 5 and the back pressure valve 8 to reset, the fuel cell system is powered off and shut down.

[0046] The above embodiment is a preferred embodiment of the present application, but the embodiments of the present application are not limited thereto, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A fuel cell system comprising a fuel cell system controller, a stack module, a hydrogen supply system, an air supply system, and a cooling system; characterized in that: The air supply system includes an air filter, a flow meter, an air compressor, an intercooler, a solenoid valve, a humidifier and an air compressor controller. The air compressor includes a motor, a compressor and an expander. The compressor and expander are respectively installed at both ends of the motor and directly connected to both ends of the motor's rotating shaft; The intercooler is equipped with two air outlets, namely the first outlet and the second outlet. The external air passes through the air filter, flow meter, compressor of the air compressor, and intercooler in sequence and is divided into two paths. The first path starts from the first outlet of the intercooler, passes through the solenoid valve, humidifier, fuel cell module, back pressure valve, water separator and expander in sequence, and is finally discharged from the expander. The second path starts from the second air outlet of the intercooler, passes through the motor and the expander in sequence, and is finally discharged from the expander; the low-temperature compressed air output from the second air outlet of the intercooler passes through the motor to dissipate heat for the motor, then enters the expander and is discharged; When the fuel cell system is running, the fuel cell system controller controls the solenoid valve to provide air to the stack module. The air discharged from the air outlet of the stack module and the air discharged from the motor enter the expander together to drive the expander to rotate to reduce the energy loss of the motor. When the fuel cell system controller receives a shutdown command, it stops the operation of the hydrogen supply system, keeps the air compressor running at low power, and closes the solenoid valve and back pressure valve, so that the low-temperature compressed air from the second outlet of the intercooler flows through the motor to purge the expander, and continues to drive the expander to rotate to reduce the energy loss of the motor.

2. A fuel cell system according to claim 1, characterized in that: When the fuel cell system controller receives a shutdown command, it keeps the cooling system running continuously so that the cooling system can continuously provide coolant to the intercooler to cool the high-temperature compressed air output by the compressor, and then output low-temperature compressed air. The low-temperature compressed air is output from the second air outlet of the intercooler and passes through the motor to dissipate heat from the motor.

3. A fuel cell system according to claim 2, characterized in that: When the fuel cell system controller receives a shutdown command, the fuel cell system controller accumulates the purge time of the expander. When the accumulated purge time of the expander reaches the preset purge time H, the purge is deemed to be completed. The fuel cell system controller controls the air compressor to stop running through the air compressor controller, and at the same time controls the cooling system to stop running.

4. A fuel cell system according to claim 1, 2 or 3, characterized in that: The low-temperature compressed air output from the second air outlet of the intercooler enters the interior of the motor to dissipate heat from the stator assembly and the bearing system inside the motor.

5. A fuel cell system according to claim 4, characterized in that: The expander is provided with two air inlets, namely a first air inlet and a second air inlet. The water separator is connected to the first air inlet of the expander, and the motor is connected to the second air inlet of the expander.

6. A fuel cell system according to claim 4, characterized in that: The expander is provided with an air inlet, and the water separator and the motor are respectively connected to the air inlet of the expander.

7. The fuel cell system according to claim 4, characterized in that: The solenoid valve is a two-way valve.

8. The fuel cell system according to claim 4, characterized in that: The gas outlet of the expander is connected to a muffler, which is used to reduce the noise when the gas is discharged from the expander.

9. A purge control method for a fuel cell system, characterized in that: According to any one of claims 1 to 8, the fuel cell system, wherein the purge control method comprises the following steps: Step 1: After receiving a shutdown command during operation, the fuel cell system controller stops the operation of the hydrogen supply system, keeps the cooling system running and the air compressor running at low power, and closes the solenoid valve and back pressure valve, allowing the low-temperature compressed air from the second outlet of the intercooler to flow through the motor and then purge the expander, and continuously drives the expander to rotate to reduce the energy loss of the motor; Step 2: The fuel cell system controller accumulates the purge time of the expander. When the accumulated purge time of the expander reaches the preset purge time H, the purge is considered completed. The fuel cell system controller controls the air compressor to stop running through the air compressor controller, and also controls the cooling system to stop running. Step 3: The fuel cell system controller controls the solenoid valve and the back pressure valve to reset.

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