Fuel cell air supply system based on compression expansion integrated machine and control method

Abstract

The application discloses a fuel cell air supply system based on a compression-expansion integrated machine and a control method. The system comprises a compressor, an air inlet of the compressor being used for connecting air; an air cooler, an air inlet of the air cooler being connected with an air outlet of the compressor, and an air outlet of the air cooler being connected with an air inlet of a fuel cell stack; and a turbo-expander, an air inlet of the turbo-expander being connected with an air outlet of the fuel cell stack. The compressor and the turbo-expander are coaxially and oppositely arranged, and are connected through a motor. A discharge valve is arranged on a connecting pipeline between the air outlet of the fuel cell stack and the air inlet of the turbo-expander, and the discharge valve can discharge exhaust gas discharged through the air outlet of the fuel cell stack. The application can guarantee the stability of the air supply system under low working conditions, and improve the variable working condition adaptability of the fuel cell air supply system based on the compression-expansion integrated machine.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fuel cells, and particularly relates to a fuel cell air supply system based on a compression-expansion integrated machine and a control method. BACKGROUND

[0002] At present, fuel cell systems are further applied in heavy-duty transportation, distributed power generation and other fields. Fuel cell stacks composed of fuel cell monomers, fuel cell auxiliary systems and fuel cell control units are configured to jointly form a fuel cell system, so that the fuel cell can normally operate.

[0003] In a fuel cell, hydrogen and oxygen are introduced, and an electrochemical reaction of hydrogen and oxygen generates an electric current. The oxygen can be pure oxygen or directly obtained from air. In order to be more convenient and economical, air is generally used. In order to achieve higher power density and better performance, it is necessary to work at a higher pressure. The pressure of the reactant (oxygen) in the cathode of the fuel cell is directly related to the performance of the fuel cell system. Increasing the air supply pressure (i.e. the partial pressure of oxygen) can increase the energy density of the fuel cell system. Increasing the air supply pressure of the fuel cell can also reduce the system size, improve the power efficiency of the battery stack and improve the water balance. Therefore, a special air supply subsystem is needed in the fuel cell to provide high-pressure air to the fuel cell.

[0004] The air supply condition of the compressor in the air supply system directly affects the electrochemical reaction of the fuel cell stack. At the same time, the reaction of the fuel cell stack also affects the working condition of the water supply system and the expander. These factors are related to the output power of the fuel cell system. For a fuel cell system based on a compression-expansion integrated machine, when the output power of the fuel cell is insufficient, the turbine expander gas may be blocked. Therefore, the air supply system of the fuel cell based on the compression-expansion integrated machine needs to have good variable condition adaptation capability. SUMMARY

[0005] In view of the problem of how to improve the variable condition adaptation capability of the air supply system of the fuel cell based on the compression-expansion integrated machine, the application provides an air supply system of a fuel cell based on a compression-expansion integrated machine and a control method, so that the efficiency of the air supply system is higher.

[0006] To achieve the above technical purpose, the application adopts the following technical scheme.

[0007] An air supply system of a fuel cell based on a compression-expansion integrated machine, comprising:

[0008] a compressor, an air inlet of the compressor being used to introduce air;

[0009] An air cooler, wherein the air inlet of the air cooler is connected to the exhaust port of the compressor, and the exhaust port of the air cooler is connected to the air inlet of the fuel cell stack;

[0010] A turbo expander, wherein the air inlet of the turbo expander is connected to the exhaust outlet of the fuel cell stack; wherein the compressor and the impeller of the turbo expander are arranged coaxially and opposite to each other, and the two are connected by a motor;

[0011] An exhaust valve is provided on the connecting pipe between the exhaust port of the fuel cell stack and the inlet of the turboexpander. The exhaust valve is capable of discharging the exhaust gas discharged through the exhaust port of the fuel cell stack.

[0012] As a further improvement to this application, the system also includes:

[0013] Dryer;

[0014] The inlet of the dryer is connected to the exhaust port of the fuel cell stack, and the outlet of the dryer is connected to the inlet of the turboexpander.

[0015] Furthermore, for high-power fuel cell systems, the power consumption of the fuel cell auxiliary system is significant, with the air compressor accounting for over 20% of the power consumption. Therefore, reducing the energy consumption of the fuel cell auxiliary system is paramount in reducing auxiliary power consumption.

[0016] In some embodiments, as a further improvement of this application, the system further includes:

[0017] Motor housing;

[0018] The motor housing includes an outer shell body, a receiving space is provided inside the outer shell body, the motor is placed in the receiving space, and an air inlet and an exhaust outlet of the motor housing are provided on the outer shell body.

[0019] The air inlet of the motor housing is connected to the exhaust port of the turbo expander, and is used to introduce the exhaust gas discharged from the turbo expander into the accommodating space;

[0020] The exhaust port on the motor housing is used to discharge the exhaust gas from the turboexpander.

[0021] As a further improvement of this application, the outer casing body is provided with a casing air inlet connector and a casing exhaust connector, the motor casing air inlet penetrates the casing air inlet connector, and the motor casing exhaust outlet penetrates the casing exhaust connector;

[0022] The housing air inlet connector includes a flange and a connector body, with the flange located on the side of the housing air inlet connector away from the housing body.

[0023] As a further improvement to this application, the motor bearing of the compressor is disposed in the receiving space.

[0024] As a further improvement to this application, the motor bearing of the compressor is a rolling bearing, a sliding bearing, or a magnetic levitation bearing.

[0025] As a further improvement to this application, the system also includes:

[0026] Liquid cooling pipes;

[0027] The liquid cooling pipe is connected to the outer casing;

[0028] The drain port of the fuel cell stack is connected to the liquid cooling pipe.

[0029] As a further improvement to this application, the liquid cooling pipeline is a ring pipeline.

[0030] As a further improvement of this application, the liquid cooling pipe is disposed on the inner wall of the outer shell body and is in the shape of an annular spiral.

[0031] As a further improvement to this application, an air filter is also provided in front of the compressor;

[0032] The air filter has an inlet that receives air and an outlet that is connected to the compressor. It is used to filter the input air, and the filtered air is then fed into the compressor.

[0033] On the other hand, this application provides a control method for a fuel cell air supply system based on an integrated compressor-expander, applied to an air supply control system for a fuel cell stack, wherein the air supply control system includes the fuel cell stack comprising:

[0034] A compressor, wherein the air inlet of the compressor is used to receive air;

[0035] An air cooler, wherein the air inlet of the air cooler is connected to the exhaust port of the compressor, and the exhaust port of the air cooler is connected to the air inlet of the fuel cell stack;

[0036] A turbo expander, wherein the air inlet of the turbo expander is connected to the exhaust outlet of the fuel cell stack; wherein the compressor and the impeller of the turbo expander are arranged coaxially and opposite to each other, and the two are connected by a motor;

[0037] An exhaust valve is provided on the connecting pipe between the exhaust port of the fuel cell stack and the air inlet of the turboexpander. The exhaust valve is capable of discharging the exhaust gas discharged through the exhaust port of the fuel cell stack.

[0038] The method includes:

[0039] Monitor the output power of the fuel cell stack;

[0040] When the output power is not greater than the set ratio of the installed power, the discharge valve is opened to discharge the exhaust gas discharged through the exhaust port of the fuel cell stack.

[0041] When the output power is greater than a set ratio of the installed power, the discharge valve is closed so that the exhaust gas discharged from the exhaust port of the fuel cell stack enters the turboexpander.

[0042] As a further improvement to this application, the set ratio is 10%.

[0043] The beneficial technical effects achieved by this application are as follows:

[0044] This application allows the exhaust gas generated by the fuel cell stack to be directly discharged by installing an exhaust valve in the exhaust pipe, which can prevent gas blockage in the turbine expander, ensure the stability of the gas supply system under low operating conditions, and ensure the adaptability of the gas supply system to changing operating conditions.

[0045] This application discharges exhaust gas into a turbine expander, where it is cooled and depressurized before entering the motor housing through the inlet and exiting through the exhaust outlet. This reduces system temperature and improves air compressor efficiency. By installing inlet and exhaust connectors on the motor housing and connecting the inlet and exhaust pipes with flanges, the airtightness and safety of the motor housing are enhanced. Furthermore, this application utilizes wastewater generated by the fuel cell to cool the motor housing, further reducing system temperature and making the equipment more reliable.

[0046] The fuel cell air supply system based on the integrated compressor-expander provided in this application achieves the beneficial effect of cooling the motor by introducing the liquid (water) generated by the fuel cell into the annular liquid cooling channel on the motor housing.

[0047] This application provides an air supply control method for a fuel cell, which monitors the output power of the fuel cell and controls the opening and closing of the discharge valve according to the output power, so that the operation of the turboexpander is controlled by the output power of the fuel cell, preventing airflow blockage at low power. Attached Figure Description

[0048] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of this application in any way. Furthermore, the shapes and scales of the components in the drawings are merely illustrative to aid in understanding this application and do not specifically limit the shapes and scales of the components. Those skilled in the art, guided by the teachings of this application, can select various possible shapes and scales to implement this application according to specific circumstances. In the drawings:

[0049] Figure 1 A schematic diagram of a fuel cell air supply system based on an integrated compressor-expander unit provided in one embodiment of this application;

[0050] Figure 2 A schematic diagram of the structure of the motor housing of a fuel cell air supply system based on an integrated compressor-expander provided in one embodiment of this application;

[0051] Figure 3 A schematic diagram of the liquid cooling pipeline of a fuel cell air supply system based on an integrated compression expander provided in one embodiment of this application;

[0052] Figure 4 This is a schematic diagram of an air supply method for a fuel cell provided in one embodiment of this application;

[0053] Explanation of reference numerals in the attached figures:

[0054] 1-Air filter, 2-Compressor, 3-Air cooler, 4-Fuel cell stack, 5-Dryer, 6-Emission valve, 7-Turbine expander, 8-Motor, 9-Magnetic levitation bearing, 10-Motor housing, 101-Compressor inlet, 102-Compressor exhaust port, 103-Fuel cell stack inlet, 104-Fuel cell stack exhaust port, 105-Fuel cell stack liquid drain, 106-Turbine expander inlet, 107-Turbine expander exhaust port, 108-Motor housing liquid inlet, 109-Motor housing inlet, 110-Motor housing liquid drain, 111-Motor housing exhaust port, 112-Outer shell body, 113-Liquid cooling pipe, 114-Shell inlet connector, 115-Shell exhaust connector, 1141-Flange, 1142-Connector body. Detailed Implementation

[0055] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0056] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0057] Please see Figure 1 As shown, a fuel cell air supply system based on an integrated compressor-expander is applied to fuel cell stack 4, comprising:

[0058] Compressor 2 includes a compressor inlet 101 for receiving air;

[0059] Air cooler 3, the air inlet of air cooler 3 is connected to compressor exhaust port 102, and the exhaust port of air cooler 3 is connected to fuel cell stack air inlet 103.

[0060] Turbine expander 7 includes a turbine expander inlet 106, which is connected to the fuel cell stack exhaust port 104.

[0061] In this design, the impellers of compressor 2 and turbine expander 7 are arranged coaxially and facing each other, and the two are connected by motor 8. Figure 1 As shown, the turbo expander 7, motor 8, and compressor 2 are designed as a coaxial unit. The motor 8 is coaxially mounted with the compressor 2 and is configured to drive the compressor 2. The turbo expander 7 is coaxially mounted with the motor 8, and the turbo expander 7 and compressor 2 are located on opposite sides of the motor 8.

[0062] The fuel cell stack 4 is composed of multiple fuel cell cells stacked in series. The fuel cell stack 4 includes a fuel cell stack air inlet 103, a fuel cell stack exhaust outlet 104, and a fuel cell stack liquid outlet 105; the fuel cell stack air inlet 103 is used to input air, the fuel cell stack exhaust outlet 104 is used to discharge exhaust gas, and the fuel cell stack liquid outlet 105 is used to discharge water.

[0063] An exhaust valve 6 is installed on the connecting pipe between the fuel cell stack exhaust port 104 and the turbine expander inlet 106. The exhaust valve 6 can discharge the exhaust gas discharged through the fuel cell stack exhaust port 104.

[0064] Air enters the fuel cell stack air inlet 103 through the air inlet pipe formed by compressor 2 and air cooler 3. Exhaust gas discharged from the fuel cell stack exhaust port 104 is discharged through the exhaust pipe formed by exhaust valve 6 and turbine expander 7.

[0065] Compressor 2 is a centrifugal air compressor. In a specific embodiment, the centrifugal compressor is equipped with a magnetic levitation bearing 9 to increase the upper limit of compressor 2 speed, providing high-flow-rate, high-quality air to the fuel cell stack 4. Motor 8 (such as a high-speed motor) provides energy input to the centrifugal compressor via a shared shaft, matching compressor 2 and turboexpander 7.

[0066] Centrifugal air compressors are characterized by high efficiency, compact design, fast dynamic response, and low noise, exhibiting excellent overall performance. They have become the mainstream technology and represent the most promising type of air compressor for fuel cells. The motor bearings of compressor 2 can be rolling bearings, sliding bearings, or magnetic bearings. To meet the high-quality requirements of fuel cells for compressed air, and to improve the reliability and lifespan of compressor 2 while ensuring oil-free gas supply, the motor bearings of compressor 2 employ magnetic bearing 9.

[0067] Centrifugal air compressors (i.e., centrifugal air compressors) traditionally include single-stage centrifugal, two-stage centrifugal, and centrifugal air compressors with turbine expanders. Among them, centrifugal air compressors with turbine expanders add a turbine expander 7 compared to the other two types of air compressors. The turbine expander 7 uses the waste energy of the exhaust gas emitted by the fuel cell stack 4 to do work, and outputs mechanical energy to supply the power consumption of the compressor 2, reducing the power consumption of the motor 8. Compared with the traditional design, the energy consumption of the compressor 2 is reduced by more than 30%, which has excellent economic efficiency.

[0068] The turbo expander 7 uses a radial impeller to recover residual energy from high-temperature and high-pressure exhaust gas.

[0069] The compressor 2 increases the amount of compressed air before it enters the fuel cell stack 4, accelerating the reaction of the proton exchange membrane. The air after the reaction is humid and pressurized exhaust gas. After gas-liquid separation, the liquid phase can enter the water storage tank, and the gas phase can enter the expansion turbine to cool and depressurize the exhaust gas and output mechanical work, thereby reducing the power consumption of the motor 8 and achieving the effect of energy saving.

[0070] exist Figure 1 In the illustrated embodiment, an exhaust valve 6 is installed in the exhaust pipe, which can directly discharge the exhaust gas generated by the fuel cell stack 4, or discharge the exhaust gas into the turbo expander inlet 106 for cooling and depressurization, and then discharge it through the turbo expander exhaust port 107. The exhaust valve 6 prevents gas blockage in the turbo expander 7, ensuring the stability of the gas supply system under low operating conditions and guaranteeing the gas supply system's adaptability to varying operating conditions.

[0071] In some embodiments, the low-temperature gas discharged from the turbine expander exhaust port 107 can be used to dissipate heat from the system, which can prevent gas blockage in the turbine expander 7, reduce the system temperature, and improve the efficiency of the air compressor.

[0072] In some embodiments, a dryer 5 is provided on the exhaust pipe between the fuel cell stack exhaust port 104 and the turbo expander 7. The dryer 5 is used to dry the exhaust gas discharged from the fuel cell stack exhaust port 104.

[0073] The air may contain a lot of moisture, and the fuel cell stack 4 will also produce water after the reaction. If this moisture enters the turboexpander 7, it may flow into the motor housing 10, thus corroding the motor 8 components. The dryer 5 dries the exhaust gas from the fuel cell stack 4, preventing moisture in the exhaust gas from corroding the motor 8 components connected to the turboexpander 7, and also filters out impurities in the gas, preventing them from entering the turboexpander 7. The turboexpander 7 rapidly reduces the gas velocity; due to the decrease in pressure and velocity, the internal energy of the gas decreases, and the gas temperature further decreases significantly, achieving the purpose of cooling.

[0074] In some embodiments, to reduce the energy consumption of the fuel cell auxiliary system, the system further includes a motor housing 10. The motor housing 10 includes an outer shell body 112, with a receiving space provided inside the outer shell body 112. The motor 8 is placed within the receiving space, and the outer shell body 112 is provided with a motor housing air inlet 109 and a motor housing exhaust port 111. Optionally, as... Figure 1 As shown, the motor housing air inlet 109 and the motor housing exhaust port 111 are respectively located on both sides of the outer shell body 112, which facilitates the flow of gas in the internal space of the motor housing 10 and improves the cooling effect.

[0075] The motor housing air inlet 109 can be connected to the turbine expander exhaust port 107 via a flange to introduce the exhaust gas discharged from the turbine expander 7 into the housing space. By introducing the cold air from the turbine expander exhaust port 107 into the motor, the beneficial effect of cooling the motor rotor and bearings is achieved. Finally, the cold air is discharged from the motor housing exhaust port 111.

[0076] In some embodiments, the motor bearing of the compressor 2 is disposed within a receiving space inside the housing body 112.

[0077] The exhaust gas from the turbo expander 7 enters the motor housing 10 and passes through it, carrying away the heat from the motor 8 and the magnetic bearing 9. The exhaust gas is then discharged through the exhaust port 111 of the motor housing. By utilizing the low-temperature gas discharged from the turbo expander exhaust port 107, the heat generated by the motor and bearings can be effectively removed, making the mechanical equipment more reliable.

[0078] In some embodiments, the air compressor with a turbine expander employs a magnetic levitation bearing 9 structure, which improves the reliability, stability, and lifespan of the compressor 2, and also ensures oil-free gas flow. Compared to air bearings, the magnetic levitation bearing 9 has a larger load-bearing capacity, longer lifespan, and stronger variable operating condition capability, making it more suitable for heavy-duty transportation applications.

[0079] In some embodiments, the system further includes: a liquid cooling pipe 113; the liquid cooling pipe 113 is connected to the outer shell body 112 of the motor housing; optionally, the liquid cooling pipe 113 may be integrally formed with the outer shell body 112, or connected to the outer shell body 112 by welding or other means.

[0080] Optionally, the liquid cooling pipe 113 is an annular channel.

[0081] like Figure 3 In the illustrated embodiment, the liquid cooling pipe 113 is disposed on the inner wall of the outer casing 112 and is in the shape of a ring-shaped spiral. This arrangement of the liquid cooling pipe 113 increases its heat dissipation area and improves its heat dissipation effect.

[0082] Optionally, the liquid cooling pipe 113 includes a liquid inlet and a liquid outlet, which are located on the outer casing, such as... Figure 2 As shown, a motor housing liquid inlet 108 and a motor housing liquid outlet 110 are provided on the lower side of the outer casing 112.

[0083] In other embodiments, such as Figure 1 As shown, the liquid inlet 108 and the liquid outlet 110 of the motor housing can also be respectively set on both sides of the outer shell body 112 to increase the liquid cooling heat exchange area and improve the cooling effect.

[0084] In some embodiments, the sizes of the motor housing liquid inlet 108 and the motor housing liquid outlet 110 can be set according to actual needs, such as according to the amount of wastewater flow generated by the fuel cell stack 4.

[0085] like Figure 2 As shown, a motor housing air inlet 109 and a motor housing exhaust outlet 111 are provided on the upper side of the outer casing 112. In order to increase the airtightness and safety of the motor housing 10, a housing air inlet connector 114 and a housing exhaust connector 115 are provided on the outer casing 112. The motor housing air inlet 109 passes through the housing air inlet connector 114, and the motor housing exhaust outlet 111 passes through the housing exhaust connector 115.

[0086] The housing inlet connector 114 and the housing exhaust connector 115 have the same structure.

[0087] The housing inlet connector 114 includes a flange 1141 and a connector body 1142. The flange 1141 is located on the side of the connector away from the housing body 112. The flange 1141 is used for pipe end connection or connection between two devices.

[0088] The fuel cell stack drain port 105 is connected to the liquid cooling pipe 113. The liquid cooling pipe 113 receives the water discharged from the fuel cell stack drain port 105 through the motor housing inlet 108, and discharges it from the motor housing drain port 110 through the liquid cooling pipe 113.

[0089] In some embodiments, the liquid cooling pipe can be connected to the motor housing by welding, gluing, snap-fitting, or other methods, and the specific connection method can be selected according to the actual situation. For example, the liquid cooling pipe can be directly welded to the surface of the motor housing, or an assembly groove can be provided on the motor housing to snap the liquid cooling pipe into the assembly groove.

[0090] Wastewater generated by fuel cell stack 4 is used to cool motor 8 and magnetic bearing 9 through liquid cooling pipe 113 connected to motor housing 10, which can effectively reduce the temperature of the system.

[0091] The fuel cell air supply system provided in this application can reduce the power consumption of the fuel cell auxiliary system by more than 30%, achieving high-efficiency energy saving.

[0092] For example, an air filter 1 is also installed on the intake pipe before the compressor 2 according to the gas flow direction. The air filter 1 is used to filter the input air, and the filtered air is input into the compressor 2. The air filter 1 filters the air to ensure that the air entering the compressor 2 is free of impurities.

[0093] Air filter 1 filters the air to ensure the quality of the air entering compressor 2.

[0094] The compressor inlet 101 draws in clean compressed air filtered by the air filter 1 and discharges it through the compressor outlet 102. After being cooled by the air cooler 3, the air enters the fuel cell stack inlet 103. The oxygen molecules in the air entering the fuel cell stack 4 react with hydrogen molecules through the proton exchange membrane, producing electricity, water and exhaust gas.

[0095] The fuel cell air supply system based on the integrated compressor-expander provided in this application uses the drainage of the fuel cell stack 4 and the low-temperature exhaust of the expansion to cool the motor 8, making the air supply system more efficient, the structure more compact, and the compressor 2 more stable in operation.

[0096] This application also provides a control method for a fuel cell air supply system based on an integrated compressor-expander, applicable to an air supply control system for a fuel cell stack. The air supply control system includes:

[0097] Compressor 2, the air inlet of compressor 2 is used to receive air;

[0098] Air cooler 3, the air inlet of the air cooler is connected to the exhaust port of the compressor, and the exhaust port of the air cooler is connected to the air inlet of the fuel cell stack;

[0099] The turbine expander 7 has an air inlet 106 connected to the fuel cell stack exhaust port 104; the compressor 2 and the impeller of the turbine expander 7 are arranged coaxially and opposite to each other, and the two are connected by a motor 8.

[0100] The exhaust valve 6 is installed on the connecting pipe between the fuel cell stack exhaust port 104 and the turbine expander inlet 106. The exhaust valve 6 is able to discharge the exhaust gas passing through the fuel cell stack exhaust port 104.

[0101] like Figure 4 As shown, the method includes the following steps:

[0102] Monitor the output power of fuel cell stack 4;

[0103] When the output power is not greater than the set ratio of the installed power, the exhaust valve 6 is opened to discharge the exhaust gas discharged through the fuel cell stack exhaust port 104.

[0104] When the output power is greater than the set ratio of the installed power, the exhaust valve 6 is closed so that the exhaust gas discharged from the fuel cell stack exhaust port 104 enters the turboexpander 7.

[0105] The working process of a fuel cell air supply system based on an integrated compressor-expander is also provided in this application as follows:

[0106] Air passes through air filter 1 and enters compressor 2. After being compressed, the high-pressure air exits compressor 2 and passes through air cooler 3 before entering fuel cell stack 4. It reacts with hydrogen molecules in fuel cell stack 4 through proton exchange membrane, producing electricity, water, and exhaust gas.

[0107] The electricity generated by the fuel cell stack 4 will be transmitted to the energy storage device for direct power conversion. The generated water will be discharged from the fuel cell stack's drain port 105, and this water can be used to cool the casing of the motor 8. The water discharged from the fuel cell stack 4 will enter the motor casing's inlet port 108 and be discharged from the motor casing's drain port 110.

[0108] The exhaust gas generated by the fuel cell stack 4 still has a certain pressure and temperature. It is discharged from the exhaust port 104 of the fuel cell stack. When the output power of the fuel cell stack 4 is less than the set ratio of the installed power (such as 10%), the exhaust valve 6 is opened and the gas is directly discharged after passing through the dryer 5. When the output power of the fuel cell stack 4 is greater than 10% of the installed power, the exhaust valve 6 is closed and the exhaust gas after passing through the dryer 5 enters the inlet 106 of the turbo expander. The residual pressure and temperature in the exhaust gas act on the turbo expander 7 and can be converted into mechanical work output, which is transmitted to the coaxial compressor 2. After the exhaust gas is cooled and depressurized by the turbo expander 7, it enters the motor housing through the inlet 109 of the motor housing to cool the motor 8 and / or magnetic levitation bearing inside the motor housing. Finally, it is discharged through the exhaust port 111 of the motor housing.

[0109] When the output power of fuel cell stack 4 is below 10%, it is in a low-power operating condition. The amount of gas entering fuel cell stack 4 from compressor 2 is reduced, and the amount of exhaust gas discharged from fuel cell stack 4 is also reduced. If it were to enter the turbo expander 7 to do work, the flow channel of turbo expander 7 would have resistance, which would cause poor exhaust of fuel cell stack 4, or even lead to insufficient gas supply to fuel cell stack 4, making fuel cell stack 4 unable to work. Therefore, in order to ensure that fuel cell stack 4 operates normally under low operating conditions, a threshold of 10% is set. When the rated output power is below 10%, in order to reduce exhaust resistance, the exhaust gas from fuel cell stack 4 does not enter the turbo expander 7 to do work, but is directly discharged through the exhaust valve 6.

[0110] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the foregoing claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed application subject matter.

Claims

1. A control method for a fuel cell air supply system based on a compression expansion integrated machine, characterized by, The application relates to an air supply control system for a fuel cell stack (4), which comprises: a compressor (2) with an air inlet connected to an air source, wherein the compressor (2) is a centrifugal air compressor, and a motor bearing of the compressor (2) is a magnetic bearing (9); an air cooler (3) with an air inlet connected to an air outlet of the compressor (2), and an air outlet connected to an air inlet of the fuel cell stack (4); a turbo-expander (7) with an air inlet connected to an air outlet of the fuel cell stack (4), wherein the compressor (2) and the turbo-expander (7) are coaxially arranged in opposite directions, and are connected by a motor (8); the turbo-expander (7), the motor (8) and the compressor (2) are coaxially integrated, and the turbo-expander (7) and the compressor (2) are respectively arranged on two sides of the motor (8); the motor (8) is configured to drive the compressor (2); a discharge valve (6) arranged on a connecting pipeline between an air outlet of the fuel cell stack (4) and an air inlet of the turbo-expander (7), and capable of discharging exhaust gas discharged from the air outlet of the fuel cell stack (4); a dryer (5) with an inlet connected to the air outlet of the fuel cell stack (4), and an outlet connected to the air inlet of the turbo-expander (7), and capable of drying the exhaust gas discharged from the fuel cell stack (4); wherein the exhaust gas discharged from the turbo-expander (7) enters an inside of a motor housing (10), and passes through the inside of the motor housing (10) to take away heat on the motor (8) and the magnetic bearing (9), and the exhaust gas is discharged through a motor housing air outlet (111). The control method comprises: monitoring an output power of the fuel cell stack (4); when the output power is not greater than a set proportion of an installed power, opening the discharge valve (6) to discharge the exhaust gas discharged from the air outlet of the fuel cell stack (4); and the set proportion is 10%; when the output power is greater than the set proportion of the installed power, closing the discharge valve (6) to make the exhaust gas discharged from the air outlet of the fuel cell stack (4) enter the turbo-expander (7).

2. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 1, characterized by, The system further comprises: a motor housing (10); the motor housing (10) comprises a housing body (112) with an accommodation space arranged in the housing body (112), and the motor (8) is arranged in the accommodation space; the housing body (112) is provided with a motor housing air inlet (109) and a motor housing air outlet (111); the motor housing air inlet (109) is connected to an air outlet of the turbo-expander (7) to introduce the exhaust gas discharged from the turbo-expander (7) into the accommodation space; the motor housing air outlet (111) is used for discharging the exhaust gas discharged from the turbo-expander (7).

3. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 2, characterized by, The housing body (112) is provided with a housing air inlet joint (114) and a housing air outlet joint (115), the motor housing air inlet (109) penetrates the housing air inlet joint (114), and the motor housing air outlet (111) penetrates the housing air outlet joint (115); The housing air inlet joint (114) comprises a flange (1141) and a joint body (1142), and the flange (1141) is arranged on the housing air inlet joint (114) away from the housing body (112).

4. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 2, characterized by, The motor bearing of the compressor (2) is arranged in the containing space.

5. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 1, characterized by, The motor bearing of the compressor (2) is a rolling bearing, a sliding bearing or a magnetic bearing.

6. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 3, characterized by, The system further comprises: A liquid cooling pipeline (113); The liquid cooling pipeline (113) is connected with the housing body (112); The liquid outlet of the fuel cell stack (4) is connected with the liquid cooling pipeline (113).

7. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 6, characterized by, The liquid cooling pipeline (113) is an annular pipeline.

8. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 6, characterized by, The liquid cooling pipeline (113) is arranged on the inner wall of the housing body (112) and has an annular spiral shape.

9. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 8, characterized by, The liquid cooling pipeline (113) comprises a liquid inlet and a liquid outlet, and the liquid inlet and the liquid outlet are arranged on the housing body (112).

10. The control method of the compressed expansion-based integrated fuel cell air supply system according to claim 1, characterized by, The compressor (2) is further provided with an air filter (1); The inlet of the air filter (1) accesses air, the outlet of the air filter (1) is connected with the compressor (2), the air filter (1) is used for filtering the input air, and the filtered air is input into the compressor (2).

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