Air-cooled fuel cell system with energy recovery function and working method thereof

Abstract

The invention relates to an air-cooled fuel cell system with an energy recovery function and a working method of the air-cooled fuel cell system. The air-cooled fuel cell system comprises an electric pile, an oxygen supply cooling subsystem and a hydrogen supply subsystem, the oxygen supply cooling subsystem comprises an air filter, a turbine expansion type air compressor, a first vortex tube, a one-way valve, a first atomizer, a first electromagnetic valve, a second atomizer, a second vortex tube, a buffer tank, a first pump and a second pump. An oxygen supply cooling subsystem is arranged, a vortex tube is used for shunting, a hot flow part supplies oxygen for galvanic pile reaction, a cold flow part cools a galvanic pile, a cooling system with a complex structure does not need to be independently arranged, air provides gas participating in the reaction for a cathode, and the temperature of the galvanic pile can be reduced; and the defect of insufficient heat dissipation capability of the electric pile caused by insufficient fan capability of the traditional cathode open type air-cooled fuel cell is effectively overcome.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and in particular to an air-cooled fuel cell system with energy recovery function and a working method thereof. Background Art

[0002] Existing fuel cells can be divided into air-cooled fuel cells and water-cooled fuel cells according to different cooling methods. Among them, air-cooled fuel cells are mainly cathode open air-cooled fuel cells. For cathode open fuel cells, fans are used to cool the stack while providing air for the cathode to participate in the reaction. Due to the limitation of fan capacity, air-cooled fuel cells have the following disadvantages: it is difficult to humidify the cathode reaction gas; the maximum current density in the stack is usually very low; the heat dissipation is uneven; the upper limit of the cathode reaction gas flow is low, etc.

[0003] For water-cooled fuel cells, liquid water or antifreeze is usually used as the cooling electrolyte, and a special cooling system is designed. The cooling system has a complex structure, which greatly increases the complexity of the system and reduces the system volume power density and mass power density. If liquid water is used in the cooling system, it is easy to freeze in winter, affecting the normal use of the fuel cell stack. If antifreeze is used, the cost is too high, which increases the cost of system use. In addition, water-cooled fuel cells generally use air compressors to supply compressed air to the fuel cell stack, and use membrane humidifiers to humidify the cathode reaction gas. Membrane humidifiers have poor durability and high costs.

[0004] Therefore, it is urgent to design an air-cooled fuel cell system with energy recovery function and a working method thereof to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0005] In view of this, the present invention provides an air-cooled fuel cell system with energy recovery function and its working method, with the aim of effectively overcoming the defect of insufficient heat dissipation capacity of the stack due to insufficient fan capacity of the traditional cathode open air-cooled fuel cell by optimizing the structure and working method of the air-cooled fuel cell system.

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

[0007] An air-cooled fuel cell system with energy recovery function, the air-cooled fuel cell system comprising: a fuel cell stack, an oxygen supply and cooling subsystem and a hydrogen supply subsystem;

[0008] The oxygen supply and cooling subsystem includes an air filter, a turbo expansion air compressor, a first vortex tube, a one-way valve, a first atomizer, a first solenoid valve, a second atomizer, a second vortex tube, a buffer tank, a first pump, and a second pump;

[0009] The air filter is connected in sequence to the air compressor part and the first vortex tube of the turboexpansion air compressor, the hot flow outlet of the first vortex tube is connected to a T-shaped pipe, a branch of the T-shaped pipe is connected to a first solenoid valve, the first solenoid valve is used to control whether the gas flowing out through the hot flow outlet of the first vortex tube is discharged outside the oxygen supply cooling subsystem, the other branch of the T-shaped pipe is connected in sequence to a check valve, a first atomizer and a cathode inlet of the fuel cell stack, the cathode outlet of the fuel cell stack is connected to a second vortex tube, the hot flow outlet of the second vortex tube is connected to the expander part of the turboexpansion air compressor, the outlet of the expander part is connected to the end plate of the fuel cell stack for heating the end plate to avoid the end plate effect of the fuel cell stack;

[0010] The cold flow outlet of the first vortex tube is connected to the second atomizer and the cooling path inlet of the fuel cell stack in sequence, the cooling path outlet of the fuel cell stack is also connected to the second vortex tube, the cold flow outlet of the second vortex tube is connected to a buffer tank, and the buffer tank is used to collect and temporarily store the low-temperature gas and liquid water flowing out through the cold flow outlet of the second vortex tube, the first outlet of the buffer tank is connected to the first pump and the first atomizer in sequence, and the second outlet of the buffer tank is connected to the second pump and the second atomizer in sequence.

[0011] Furthermore, the compressor shaft of the compressor part of the turboexpansion air compressor is coaxially connected to the turbine shaft of the expander part.

[0012] Furthermore, a first temperature sensor is provided at the inlet of the cooling path of the fuel cell stack, a humidity sensor is provided at the cathode inlet of the fuel cell stack, and a second temperature sensor is provided at the cathode outlet of the fuel cell stack.

[0013] Furthermore, a branch pipeline is provided on the pipeline between the first atomizer and the cathode inlet of the fuel cell stack, connected to the pipeline between the second atomizer and the cooling path inlet of the fuel cell stack, and a second solenoid valve is provided on the branch pipeline.

[0014] The present invention also provides a working method based on the above-mentioned air-cooled fuel cell system with energy recovery function, which is as follows:

[0015] The air is filtered through an air filter to remove harmful gases and impurities, and is pressurized into high-temperature and high-pressure air by the air compressor part of the turboexpansion air compressor, and then enters the first vortex tube to be separated into cold flow and hot flow. The hot flow part flows out from the hot flow outlet of the first vortex tube. At this time, the first solenoid valve is closed, and the hot flow part flows into the first atomizer through the one-way valve. After being cooled and humidified by the first atomizer, it enters the battery stack from the cathode inlet to participate in the reaction. The cathode gas out of the stack enters the second vortex tube to be separated into cold flow and hot flow. The hot flow part flows out from the hot flow outlet of the second vortex tube, recovers energy through the expander part of the turboexpansion air compressor, and enters the end plate of the battery stack for heating the end plate to avoid the end plate effect of the battery stack. The cold flow part separated in the second vortex tube flows out from the cold flow outlet of the second vortex tube, and the low-temperature gas and liquid water enter the buffer tank for temporary storage;

[0016] The cold flow separated in the first vortex tube flows out from the cold flow outlet of the first vortex tube, enters the fuel cell stack from the cooling path inlet of the fuel cell stack for cooling the fuel cell stack after humidification by the second atomizer, then flows out from the cooling path outlet of the fuel cell stack, enters the second vortex tube to mix with the cathode outflow gas, and is separated into a cold flow and a hot flow, the cold flow part flows out through the cold flow outlet of the second vortex tube, and the hot flow part flows out through the hot flow outlet of the second vortex tube.

[0017] Furthermore, the gas from the cathode outlet of the fuel cell stack and the cooling path outlet in the second vortex tube is separated into a cold flow and a hot flow. The hot flow part is high-temperature gas with a temperature higher than 100°C, so all the water in the high-temperature gas exists in gaseous form. The high-temperature gas enters the expander part of the turbine expansion air compressor to recover the kinetic energy therein, and can effectively prevent liquid water from eroding the turbine blades of the expander part and damaging the life of the expander; the cold flow part is low-temperature gas and liquid water, and the cold flow part enters the buffer tank for temporary storage.

[0018] Furthermore, the first pump pumps the low-temperature air and liquid water in the buffer tank into the first atomizer, and the high-temperature and high-pressure air flowing out of the hot flow outlet of the first vortex tube is mixed with the low-temperature gas and the atomized liquid water in the first atomizer to meet the humidity requirement, and the first atomizer plays a role in cooling and humidifying; the second pump pumps the low-temperature air and liquid water in the buffer tank into the second atomizer, which is used together with the cold flow part separated by the first vortex tube to cool the fuel cell stack. The second atomizer atomizes the liquid water to make the liquid water distribution more even, which is convenient for cooling the fuel cell stack.

[0019] Furthermore, the water supply to the first atomizer is controlled by controlling the rotation speed of the first pump, thereby controlling the humidity of the air entering the cathode of the fuel cell stack; the water supply to the second atomizer is controlled by controlling the rotation speed of the second pump. When the temperature of the fuel cell stack is high, the rotation speed of the second pump is increased to increase the amount of liquid water entering the stack through the cooling path, thereby lowering the temperature of the fuel cell stack. When the temperature of the fuel cell stack is low, the rotation speed of the second pump is reduced to reduce the amount of liquid water entering the stack through the cooling path.

[0020] Furthermore, when the ambient temperature is lower than 0°C, a cold start strategy is implemented, and the cold start strategy is as follows:

[0021] When starting, the opening of the heat flow outlet of the first vortex tube is reduced, and the temperature of the gas entering the cooling path is monitored by the first temperature sensor arranged at the entrance of the cooling path of the fuel cell stack, and the temperature of the gas entering the stack is controlled to be an appropriate temperature, which is the maximum hot pressing temperature of the membrane electrode of the fuel cell stack, so as to avoid high-temperature attenuation of the proton exchange membrane;

[0022] The temperature of the gas leaving the stack is monitored by a second temperature sensor arranged at the cathode outlet of the fuel cell stack. When the second temperature sensor detects that the temperature of the gas leaving the stack exceeds 0° C., the cold start is stopped and the opening of the hot flow outlet of the first vortex tube is restored.

[0023] Furthermore, when the air-cooled fuel cell system is shut down, the first solenoid valve and the second solenoid valve in the normally closed state are opened, and the first pump and the second pump are stopped, and the opening of the hot flow outlet of the first vortex tube is controlled until the cold flow outlet temperature of the first vortex tube is the same as the outside temperature. At this time, part of the gas flowing out of the cold flow outlet enters the cathode inlet of the fuel cell stack for purging, and part of the gas enters the cooling path inlet of the fuel cell stack for purging. When the second temperature sensor arranged at the cathode outlet of the fuel cell stack monitors that the stack gas temperature is stable at room temperature, the purging is stopped; in this process, the gas flowing out of the hot flow outlet of the first vortex tube is discharged to the outside of the oxygen supply and cooling subsystem through the first solenoid valve.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) By setting up an oxygen supply and cooling subsystem and using vortex tubes for flow diversion, the hot flow part supplies oxygen for the fuel cell reaction, and the cold flow part cools the fuel cell. There is no need to set up a complex cooling system separately. The air can not only provide the cathode with gases involved in the reaction, but also reduce the temperature of the fuel cell. This effectively overcomes the defect of insufficient heat dissipation capacity of the fuel cell due to insufficient fan capacity in traditional cathode open air-cooled fuel cells.

[0026] (2) By setting a first vortex tube, the high-temperature and high-pressure air pressurized by the compressor part of the turboexpansion air compressor is separated into a cold flow and a hot flow. The cold flow part has a stronger heat dissipation capacity as a cooling medium, and the hot flow part is more easily mixed with the atomized water vapor for humidification as a reaction gas; by setting a second vortex tube, the gas at the cooling path outlet and the cathode outlet is mixed and separated into a hot flow and a cold flow. The hot flow part enters the expander part of the turboexpansion air compressor to recover the kinetic energy therein, and the cold flow part enters the buffer tank for temporary storage; by setting a first pump and a second pump, they are used to pump the low-temperature gas and liquid water in the buffer tank into the first atomizer and the second atomizer respectively, so as to efficiently recycle the system produced water.

[0027] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A schematic structural diagram of an air-cooled fuel cell system with energy recovery function according to an embodiment of the present invention is shown.

[0030] In the figure: 1. air filter; 2. turbo expansion air compressor; 3. first vortex tube; 4. second atomizer; 5. first temperature sensor; 6. fuel cell stack; 7. one-way valve; 8. first atomizer; 9. second solenoid valve; 10. humidity sensor; 11. first solenoid valve; 12. second pump; 13. first pump; 14. buffer tank; 15. second vortex tube; 16. second temperature sensor. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The embodiment of the present invention provides an air-cooled fuel cell system with energy recovery function, as shown in the attached Figure 1 As shown, the air-cooled fuel cell system includes: a fuel cell stack 6, an oxygen supply and cooling subsystem and a hydrogen supply subsystem;

[0033] The oxygen supply cooling subsystem includes an air filter 1, a turbo expansion air compressor 2, a first vortex tube 3, a one-way valve 7, a first atomizer 8, a first solenoid valve 11, a second atomizer 4, a second vortex tube 15, a buffer tank 14, a first pump 13 and a second pump 12;

[0034] The air filter 1 is connected in sequence to the air compressor part of the turboexpansion air compressor 2 and the first vortex tube 3. The hot flow outlet of the first vortex tube 3 is connected to a T-shaped pipe. A first solenoid valve 11 is connected to one branch of the T-shaped pipe. The first solenoid valve 11 is used to control whether the gas flowing out through the hot flow outlet of the first vortex tube 3 is discharged outside the oxygen supply and cooling subsystem. The other branch of the T-shaped pipe is connected in sequence to the one-way valve 7, the first atomizer 8 and the cathode inlet of the battery stack 6. The cathode outlet of the battery stack 6 is connected to the second vortex tube 15. The hot flow outlet of the second vortex tube 15 is connected to the expander part of the turboexpansion air compressor 2. The outlet of the expander part is connected to the end plate of the battery stack 6 for heating the end plate to avoid the end plate effect of the battery stack.

[0035] The cold flow outlet of the first vortex tube 3 is connected to the cooling path inlet of the second atomizer 4 and the fuel cell stack 6 in sequence. The cooling path outlet of the fuel cell stack 6 is also connected to the second vortex tube 15. The cold flow outlet of the second vortex tube 15 is connected to a buffer tank 14. The buffer tank 14 is used to collect and temporarily store low-temperature gas and liquid water flowing out through the cold flow outlet of the second vortex tube 15. The first outlet of the buffer tank 14 is connected to the first pump 13 and the first atomizer 8 in sequence. The second outlet of the buffer tank 14 is connected to the second pump 12 and the second atomizer 4 in sequence.

[0036] The compressor shaft of the compressor part of the turboexpansion air compressor 2 is coaxially connected with the turbine shaft of the expander part.

[0037] The hydrogen supply subsystem includes a hydrogen source, a high-pressure component, an ejector, a water separator and a tail drain valve. The hydrogen source is connected to the high-pressure component, the ejector and the anode inlet of the fuel cell stack 6 in sequence. The anode outlet of the fuel cell stack 6 is connected to the water separator. The gas outlet of the water separator is connected to a T-type pipe. One branch of the T-type pipe is connected to the ejector. The hydrogen flows back to the ejector and then enters the fuel cell stack 6 again. A tail drain valve is arranged on the other branch of the T-type pipe. The tail drain valve is used to control whether the hydrogen is discharged.

[0038] A first temperature sensor 5 is provided at the entrance of the cooling path of the fuel cell stack 6 , a humidity sensor 10 is provided at the cathode entrance of the fuel cell stack 6 , and a second temperature sensor 16 is provided at the cathode exit of the fuel cell stack 6 .

[0039] A branch pipeline is provided on the pipeline between the first atomizer 8 and the cathode inlet of the fuel cell stack 6, connected to the pipeline between the second atomizer 4 and the cooling path inlet of the fuel cell stack 6, and a second solenoid valve 9 is provided on the branch pipeline.

[0040] By setting up an oxygen supply and cooling subsystem and utilizing vortex tube diversion, the hot flow part supplies oxygen for the fuel cell reaction, and the cold flow part cools the fuel cell stack. There is no need to set up a separate complex cooling system. The air can not only provide the cathode with gases involved in the reaction, but also effectively reduce the temperature of the fuel cell stack, effectively overcoming the defect of insufficient heat dissipation capacity of the fuel cell stack due to insufficient fan capacity in traditional cathode open air-cooled fuel cells.

[0041] The embodiment of the present invention also proposes a working method of an air-cooled fuel cell system with an energy recovery function, which is specifically as follows:

[0042] The air is filtered out of harmful gases and impurities through the air filter 1, and is pressurized into high-temperature and high-pressure air through the air compressor part of the turboexpansion air compressor 2, and then enters the first vortex tube 3 to be separated into cold flow and hot flow, and the hot flow part flows out from the hot flow outlet of the first vortex tube 3. At this time, the first solenoid valve 11 is closed, and the hot flow part flows into the first atomizer 8 through the one-way valve 7. After being cooled and humidified by the first atomizer 8, it enters the battery stack from the cathode inlet of the battery stack 6 to participate in the reaction. The cathode gas out of the stack enters the second vortex tube 15 and is separated into cold flow and hot flow. The hot flow part flows out from the hot flow outlet of the second vortex tube 15, and after recovering energy through the expander part of the turboexpansion air compressor 2, it enters the end plate of the battery stack 6 for heating the end plate to avoid the battery stack end plate effect. The cold flow part separated in the second vortex tube 15 flows out from the cold flow outlet of the second vortex tube 15, and the low-temperature gas and liquid water enter the buffer tank 14 for temporary storage;

[0043] The cold flow separated in the first vortex tube 3 flows out from the cold flow outlet of the first vortex tube 3, and after humidification by the second atomizer 4, enters the fuel cell stack from the cooling path inlet of the fuel cell stack 6 for cooling the fuel cell stack, and then flows out from the cooling path outlet of the fuel cell stack 6, enters the second vortex tube 15 to mix with the cathode outflow gas, and is separated into a cold flow and a hot flow. The cold flow part flows out through the cold flow outlet of the second vortex tube 15, and the hot flow part flows out through the hot flow outlet of the second vortex tube 15.

[0044] The gas from the cathode outlet of the fuel cell stack 6 and the cooling path outlet in the second vortex tube 15 is separated into a cold flow and a hot flow. The hot flow portion is high-temperature gas with a temperature higher than 100°C, so all the water in the high-temperature gas exists in gaseous form. The high-temperature gas enters the expander part of the turbine expansion air compressor 2 to recover the kinetic energy therein, and can effectively prevent liquid water from eroding the turbine blades of the expander part and damaging the life of the expander; the cold flow portion is low-temperature gas and liquid water, and the cold flow portion enters the buffer tank 14 for temporary storage.

[0045] The first pump 13 pumps the low-temperature air and liquid water in the buffer tank 14 into the first atomizer 8. The high-temperature and high-pressure air flowing out of the hot flow outlet of the first vortex tube 3 is mixed with the low-temperature gas and the atomized liquid water in the first atomizer 8 to meet the humidity requirement. The first atomizer 8 plays a role in cooling and humidifying. The second pump 12 pumps the low-temperature air and liquid water in the buffer tank 14 into the second atomizer 4, which is used together with the cold flow part separated by the first vortex tube 3 to cool the fuel cell stack. The second atomizer 4 atomizes the liquid water to make the liquid water distribution more even, which is convenient for cooling the fuel cell stack.

[0046] The water supply to the first atomizer 8 is controlled by controlling the rotation speed of the first pump 13, thereby controlling the humidity of the air entering the cathode of the fuel cell stack 6; the water supply to the second atomizer 4 is controlled by controlling the rotation speed of the second pump 12. When the temperature of the fuel cell stack is high, the rotation speed of the second pump 12 is increased to increase the amount of liquid water entering the stack through the cooling path, thereby reducing the temperature of the fuel cell stack. When the temperature of the fuel cell stack is low, the rotation speed of the second pump 12 is reduced to reduce the amount of liquid water entering the stack through the cooling path.

[0047] When the ambient temperature is below 0°C, a cold start strategy is implemented. The cold start strategy is as follows:

[0048] When starting, the opening of the heat flow outlet of the first vortex tube 3 is reduced, and the temperature of the gas entering the cooling path is monitored by the first temperature sensor 5 arranged at the entrance of the cooling path of the stack 6, and the temperature of the gas entering the stack is controlled to be a suitable temperature, which is the maximum hot pressing temperature of the membrane electrode of the stack 6, to avoid high-temperature attenuation of the proton exchange membrane;

[0049] The temperature of the gas leaving the stack is monitored by a second temperature sensor 16 arranged at the cathode outlet of the fuel cell stack 6. When the second temperature sensor 16 detects that the temperature of the gas leaving the stack exceeds 0°C, the cold start is stopped and the opening of the hot flow outlet of the first vortex tube 3 is restored.

[0050] When the air-cooled fuel cell system is shut down, the first solenoid valve 11 and the second solenoid valve 9 in the normally closed state are opened, and the first pump 13 and the second pump 12 are stopped, and the opening of the hot flow outlet of the first vortex tube 3 is controlled until the cold flow outlet temperature of the first vortex tube 3 is the same as the outside temperature. At this time, part of the gas flowing out of the cold flow outlet enters the cathode inlet of the fuel cell stack 6 for purging, and part of the gas enters the cooling path inlet of the fuel cell stack 6 for purging. When the second temperature sensor 16 set at the cathode outlet of the fuel cell stack 6 monitors that the stack gas temperature is stable at room temperature, the purging is stopped; in this process, the gas flowing out of the hot flow outlet of the first vortex tube 3 is discharged to the outside of the oxygen supply and cooling subsystem through the first solenoid valve 11.

[0051] By setting a first vortex tube, the high-temperature and high-pressure air pressurized by the compressor part of the turboexpansion air compressor is separated into a cold flow and a hot flow. The cold flow part has a stronger heat dissipation capacity as a cooling medium, and the hot flow part is more easily mixed with the atomized water vapor for humidification as a reaction gas; by setting a second vortex tube, the gas at the cooling path outlet and the cathode outlet is mixed and separated into a hot flow and a cold flow. The hot flow part enters the expander part of the turboexpansion air compressor to recover the kinetic energy therein, and the cold flow part enters the buffer tank for temporary storage; by setting a first pump and a second pump, they are used to pump the low-temperature gas and liquid water in the buffer tank into the first atomizer and the second atomizer respectively, so as to efficiently recycle the system water.

[0052] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An air-cooled fuel cell system with energy recovery function, characterized in that: The air-cooled fuel cell system comprises: a fuel cell stack (6), an oxygen supply and cooling subsystem and a hydrogen supply subsystem; The oxygen supply cooling subsystem comprises an air filter (1), a turbo expansion air compressor (2), a first vortex tube (3), a one-way valve (7), a first atomizer (8), a first solenoid valve (11), a second atomizer (4), a second vortex tube (15), a buffer tank (14), a first pump (13) and a second pump (12); The air filter (1) is sequentially connected to the air compressor part of the turbo expansion air compressor (2) and the first vortex tube (3); the hot flow outlet of the first vortex tube (3) is connected to a T-shaped pipe; a first solenoid valve (11) is connected to one branch of the T-shaped pipe; the first solenoid valve (11) is used to control whether the gas flowing out of the hot flow outlet of the first vortex tube (3) is discharged outside the oxygen supply cooling subsystem; the other branch of the T-shaped pipe is sequentially connected to a check valve (7), a first atomizer (8) and the cathode inlet of the battery stack (6); the cathode outlet of the battery stack (6) is connected to a second vortex tube (15); the hot flow outlet of the second vortex tube (15) is connected to the expander part of the turbo expansion air compressor (2); the outlet of the expander part is connected to the end plate of the battery stack (6) for heating the end plate; The cold flow outlet of the first vortex tube (3) is connected in sequence to the second atomizer (4) and the cooling path inlet of the battery stack (6); the cooling path outlet of the battery stack (6) is also connected to the second vortex tube (15); the cold flow outlet of the second vortex tube (15) is connected to a buffer tank (14); the buffer tank (14) is used to collect and temporarily store low-temperature gas and liquid water flowing out through the cold flow outlet of the second vortex tube (15); the first outlet of the buffer tank (14) is connected in sequence to the first pump (13) and the first atomizer (8); and the second outlet of the buffer tank (14) is connected in sequence to the second pump (12) and the second atomizer (4).

2. The air-cooled fuel cell system with energy recovery function according to claim 1, characterized in that: The compressor shaft of the compressor part of the turboexpansion air compressor (2) is coaxially connected with the turbine shaft of the expander part.

3. The air-cooled fuel cell system with energy recovery function according to claim 2, characterized in that: A first temperature sensor (5) is provided at the entrance of the cooling path of the fuel cell stack (6), a humidity sensor (10) is provided at the cathode entrance of the fuel cell stack (6), and a second temperature sensor (16) is provided at the cathode exit of the fuel cell stack (6).

4. The air-cooled fuel cell system with energy recovery function as claimed in claim 3, characterized in that: A branch pipeline is provided on the pipeline between the first atomizer (8) and the cathode inlet of the fuel cell stack (6), connected to the pipeline between the second atomizer (4) and the cooling path inlet of the fuel cell stack (6), and a second solenoid valve (9) is provided on the branch pipeline.

5. A method for operating an air-cooled fuel cell system with energy recovery function according to any one of claims 1 to 4, characterized in that: The working method is as follows: The air is filtered through an air filter (1) to remove harmful gases and impurities, and is pressurized into high-temperature and high-pressure air by the air compressor part of a turbo expansion air compressor (2). The air then enters a first vortex tube (3) and is separated into a cold flow and a hot flow. The hot flow flows out from the hot flow outlet of the first vortex tube (3). At this time, the first solenoid valve (11) is closed, and the hot flow flows into the first atomizer (8) through a one-way valve (7). After being cooled and humidified by the first atomizer (8), the hot flow enters the cathode inlet of the fuel cell stack (6). The gas discharged from the cathode enters the fuel cell stack to participate in the reaction, and enters the second vortex tube (15) to be separated into a cold flow and a hot flow. The hot flow flows out from the hot flow outlet of the second vortex tube (15), recovers energy through the expander part of the turbine expansion air compressor (2), and then enters the end plate of the fuel cell stack (6) to be used for heating the end plate. The cold flow separated in the second vortex tube (15) flows out from the cold flow outlet of the second vortex tube (15), and the low-temperature gas and liquid water enter the buffer tank (14) for temporary storage. The cold flow portion separated in the first vortex tube (3) flows out from the cold flow outlet of the first vortex tube (3), enters the battery stack from the cooling path inlet of the battery stack (6) for cooling the battery stack after being humidified by the second atomizer (4), then flows out from the cooling path outlet of the battery stack (6), enters the second vortex tube (15) to mix with the cathode outflow gas, and is separated into a cold flow and a hot flow, the cold flow portion flows out through the cold flow outlet of the second vortex tube (15), and the hot flow portion flows out through the hot flow outlet of the second vortex tube (15).

6. The operating method of the air-cooled fuel cell system with energy recovery function according to claim 5, characterized in that: The gas from the cathode outlet and the cooling path outlet of the fuel cell stack (6) in the second vortex tube (15) is separated into a cold flow and a hot flow, wherein the hot flow is high-temperature gas with a temperature higher than 100° C., and the cold flow is low-temperature gas and liquid water, and enters the buffer tank (14) for temporary storage.

7. The operating method of the air-cooled fuel cell system with energy recovery function according to claim 6, characterized in that: The first pump (13) pumps the low-temperature air and liquid water in the buffer tank (14) into the first atomizer (8); the high-temperature and high-pressure air flowing out of the hot flow outlet of the first vortex tube (3) is mixed with the low-temperature gas and the atomized liquid water in the first atomizer (8) to meet the humidity requirement; the second pump (12) pumps the low-temperature air and liquid water in the buffer tank (14) into the second atomizer (4), and is used together with the cold flow part separated by the first vortex tube (3) to cool the fuel cell stack.

8. The operating method of the air-cooled fuel cell system with energy recovery function according to claim 7, characterized in that: The water supply of the first atomizer (8) is controlled by controlling the rotation speed of the first pump (13), thereby controlling the humidity of the air entering the cathode of the battery stack (6); the water supply of the second atomizer (4) is controlled by controlling the rotation speed of the second pump (12); when the temperature of the battery stack is high, the rotation speed of the second pump (12) is increased to increase the amount of liquid water entering the stack through the cooling path, thereby reducing the temperature of the battery stack; when the temperature of the battery stack is low, the rotation speed of the second pump (12) is reduced to reduce the amount of liquid water entering the stack through the cooling path.

9. The operating method of the air-cooled fuel cell system with energy recovery function as claimed in claim 5, characterized in that: When the ambient temperature is below 0°C, a cold start strategy is implemented. The cold start strategy is as follows: When starting, the opening of the heat flow outlet of the first vortex tube (3) is reduced, and the temperature of the gas entering the cooling path is monitored by a first temperature sensor (5) arranged at the entrance of the cooling path of the fuel cell stack (6), so as to control the temperature of the gas entering the stack to a suitable temperature, wherein the suitable temperature is the maximum hot pressing temperature of the membrane electrode of the fuel cell stack (6); The temperature of the gas leaving the stack is monitored by a second temperature sensor (16) arranged at the cathode outlet of the battery stack (6); when the second temperature sensor (16) detects that the temperature of the gas leaving the stack exceeds 0° C., the cold start is stopped and the opening of the hot flow outlet of the first vortex tube (3) is restored.

10. The operating method of the air-cooled fuel cell system with energy recovery function according to claim 5, characterized in that: When the air-cooled fuel cell system is shut down, the first solenoid valve (11) and the second solenoid valve (9) which are in a normally closed state are opened, and the first pump (13) and the second pump (12) are stopped, and the opening degree of the hot flow outlet of the first vortex tube (3) is controlled until the temperature of the cold flow outlet of the first vortex tube (3) is the same as the outside temperature. At this time, part of the gas flowing out of the cold flow outlet enters the cathode inlet of the stack (6) for purging, and part of the gas enters the cooling path inlet of the stack (6) for purging. When the second temperature sensor (16) arranged at the cathode outlet of the stack (6) detects that the stack gas temperature is stable at room temperature, the purging is stopped; in this process, the gas flowing out of the hot flow outlet of the first vortex tube (3) is discharged to the outside of the oxygen supply cooling subsystem through the first solenoid valve (11).

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