Air subsystem and fuel cell system

Abstract

The utility model provides an air subsystem. The air subsystem comprises a cathode air supply pipeline, a compressor connected to the cathode air supply pipeline, a cathode exhaust pipeline, a turbine connected to the cathode exhaust pipeline and a first heat exchange device connected to the cathode air supply pipeline and the cathode exhaust pipeline. The first heat exchange device is switchable between a first state and a second state, and in the first state, the first heat exchange device establishes a first heat exchange path between the air flow upstream of the compressor and the cathode exhaust gas flow downstream of the turbine, so that the air flow exchanges heat with the cathode exhaust gas flow leaving the turbine before entering the compressor; in the second state, the first heat exchange path is disconnected without exchanging heat with the cathode exhaust gas stream exiting from the turbine prior to entering the compressor. The first heat exchange device enables the air to be cooled before it enters the compressor by selectively utilizing a cathode exhaust gas stream exiting from the turbine. The utility model also provides a fuel cell system comprising the air subsystem.

Description

Technical Field

[0001] The present application generally relates to the technical field of fuel cells, and in particular to an air subsystem for a fuel cell system and a fuel cell system including such an air subsystem. Background Art

[0002] Fuel cell systems that generate electricity through the electrochemical reaction of fuel and oxidant are increasingly widely used to provide power, especially in the field of electric vehicles. A proton exchange membrane fuel cell (PEMFC) system is a widely used fuel cell system that uses hydrogen as fuel and oxygen as oxidant. The PEMFC system includes a stack and a balance of plant (BoP). The stack is used to convert the chemical energy in the fuel and oxidant into electrical energy, and the balance of plant provides the operating conditions required for the reaction of the stack. A part of the power generated by the stack needs to be supplied for the consumption of the balance of plant, so the efficiency of the PEMFC system depends on the performance of the stack and the power consumption of the balance of plant. The balance of plant includes an air subsystem that is configured to consume a part of the power generated by the stack to supply air to the stack, and oxygen in the air is used as an oxidant. The working efficiency of the air subsystem directly affects the efficiency of the PEMFC system. Therefore, it is always desirable to improve the working efficiency of the air subsystem to improve the efficiency of the fuel cell system. Summary of the Utility Model

[0003] The object of the present application is to propose an air subsystem to improve the efficiency of the fuel cell system.

[0004] In one aspect, the present application proposes an air subsystem for a fuel cell system. The air subsystem includes: a cathode air supply pipeline configured to supply air to the stack of the fuel cell system; a compressor connected to the cathode air supply pipeline to pressurize the air; a cathode exhaust pipeline configured to receive cathode exhaust gas from the stack; a turbine connected to the cathode exhaust pipeline and driven by the cathode exhaust gas; and a first heat exchange device connected to the cathode air supply pipeline and the cathode exhaust pipeline and configured to be able to switch between a first state and a second state. The first heat exchange device establishes a first heat exchange path between the air flow upstream of the compressor and the cathode exhaust gas flow downstream of the turbine when in the first state, so that the air flow exchanges heat with the cathode exhaust gas flow leaving the turbine before entering the compressor, and disconnects the first heat exchange path when in the second state, without allowing the air flow to exchange heat with the cathode exhaust gas flow leaving the turbine before entering the compressor.

[0005] In some embodiments, the first heat exchange device is configured to switch between the first state and the second state based on a comparison between the exhaust gas outlet temperature of the cathode exhaust gas stream leaving the turbine and the air inlet temperature of the air stream before entering the compressor. The first heat exchange device is in the first state when the exhaust gas outlet temperature is lower than the air inlet temperature, and is in the second state when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature.

[0006] In some embodiments, the first heat exchange device includes a first heat exchange structure, which is connected upstream of the compressor in the cathode gas supply line and downstream of the turbine in the cathode exhaust gas line to establish the first heat exchange path. The first heat exchange device further includes: a first bypass line and a first line switch. The first bypass line is connected between a first upstream position of the cathode exhaust gas line between the first heat exchange structure and the turbine and a first downstream position downstream of the first heat exchange structure, so that the cathode exhaust gas stream leaving the turbine can bypass the first heat exchange structure via the first bypass line. The first line switch is configured to switch between the first bypass line and a first section between the first upstream position and the first downstream position of the cathode exhaust gas line based on the comparison between the exhaust gas outlet temperature and the air inlet temperature. The first line switch turns on the first section and closes the first bypass line when the exhaust gas outlet temperature is lower than the air inlet temperature, and turns on the first bypass line and closes the first section when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature; and / or a second bypass line and a second line switch. The second bypass line is connected between a second upstream position upstream of the first heat exchange structure in the cathode gas supply line and a second downstream position between the first heat exchange structure and the compressor, so that the air stream can bypass the first heat exchange structure via the second bypass line. The second line switch is configured to switch between the second bypass line and a second section between the second upstream position and the second downstream position of the cathode gas supply line based on the comparison between the exhaust gas outlet temperature and the air inlet temperature. The second line switch turns on the second section and closes the second bypass line when the exhaust gas outlet temperature is lower than the air inlet temperature, and turns on the second bypass line and closes the second section when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature.

[0007] In some embodiments, the first pipeline switch includes a first three-way valve configured to switch between the first bypass pipeline and the first section, or includes a first on-off valve provided on the first section and a second on-off valve provided on the first bypass pipeline.

[0008] In some embodiments, the second pipeline switch includes a second three-way valve configured to switch between the second bypass pipeline and the second section, or includes a third on-off valve provided on the second section and a fourth on-off valve provided on the second bypass pipeline.

[0009] In some embodiments, the first heat exchange structure is a gas-gas heat exchanger.

[0010] In some embodiments, only heat conduction occurs between the air flow upstream of the compressor and the cathode exhaust gas flow downstream of the turbine along the first heat exchange path, without mass exchange.

[0011] In some embodiments, the air subsystem further includes a second heat exchange device, which is connected to the cathode gas supply pipeline and the cathode exhaust gas pipeline and is configured to be able to switch between a third state and a fourth state. When the second heat exchange device is in the third state, a second heat exchange path is established between the air flow downstream of the compressor and the cathode exhaust gas flow upstream of the turbine, so that the cathode exhaust gas exchanges heat with the air flow leaving the compressor before entering the turbine, and when in the fourth state, the second heat exchange path is disconnected, and the cathode exhaust gas does not exchange heat with the air flow leaving the compressor before entering the turbine.

[0012] In some embodiments, the second heat exchange device is configured to switch between the third state and the fourth state based on a comparison of the exhaust gas inlet temperature of the cathode exhaust gas before entering the turbine and the air outlet temperature of the air flow leaving the compressor. The second heat exchange device is in the third state when the exhaust gas inlet temperature is lower than the air outlet temperature, and is in the fourth state when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature.

[0013] In some embodiments, the second heat exchange device includes a second heat exchange structure, which is connected downstream of the compressor in the cathode supply gas pipeline and upstream of the turbine in the cathode exhaust gas pipeline to establish the second heat exchange path. The second heat exchange device further includes: a third bypass pipeline and a third pipeline switch. The third bypass pipeline is connected between a third upstream position of the cathode supply gas pipeline between the second heat exchange structure and the compressor and a third downstream position downstream of the second heat exchange structure, so that the air flow leaving the compressor can bypass the second heat exchange structure via the third bypass pipeline. The third pipeline switch is configured to switch between the third bypass pipeline and a third section of the cathode supply gas pipeline between the third upstream position and the third downstream position based on a comparison between the waste gas inlet temperature and the air outlet temperature. The third pipeline switch turns on the third section and closes the third bypass pipeline when the waste gas inlet temperature is lower than the air outlet temperature, and turns on the third bypass pipeline and closes the third section when the waste gas inlet temperature is higher than or equal to the air outlet temperature; and / or a fourth bypass pipeline and a fourth pipeline switch. The fourth bypass pipeline is connected between a fourth upstream position upstream of the second heat exchange structure in the cathode exhaust gas pipeline and a fourth downstream position between the second heat exchange structure and the turbine, so that the cathode waste gas can bypass the second heat exchange structure via the fourth bypass pipeline. The fourth pipeline switch is configured to switch between the fourth bypass pipeline and a fourth section of the cathode exhaust gas pipeline between the fourth upstream position and the fourth downstream position based on a comparison between the waste gas inlet temperature and the air outlet temperature. The fourth pipeline switch turns on the fourth section and closes the fourth bypass pipeline when the waste gas inlet temperature is lower than the air outlet temperature, and turns on the fourth bypass pipeline and closes the fourth section when the waste gas inlet temperature is higher than or equal to the air outlet temperature.

[0014] In some embodiments, the third pipeline switch includes a third three-way valve configured to switch between the third bypass pipeline and the third section, or includes a fifth on-off valve provided on the third section and a sixth on-off valve provided on the third bypass pipeline.

[0015] In some embodiments, the fourth pipeline switch includes a fourth three-way valve configured to switch between the fourth bypass pipeline and the fourth section, or includes a seventh on-off valve provided on the fourth section and an eighth on-off valve provided on the fourth bypass pipeline.

[0016] In some embodiments, the second heat exchange structure is a gas-gas heat exchanger.

[0017] In some embodiments, there is only conductive heat transfer and no mass exchange between the air flow downstream of the compressor and the cathode exhaust gas flow upstream of the turbine along the second heat exchange path.

[0018] In some embodiments, the compressor is partially driven by the turbine. In some embodiments, the air subsystem further includes an intercooler that is connected to the cathode supply pipeline downstream of the second heat exchange structure.

[0019] The air subsystem having the first heat exchange device enables selective utilization of the cathode exhaust gas flowing out of the turbine to cool the air before the air enters the compressor, so as to reduce the power consumption of the compressor and improve its working efficiency, thereby improving the working efficiency of the air subsystem and thus the efficiency of the fuel cell system.

[0020] The air subsystem having the second heat exchange device enables selective utilization of the air flow flowing out of the compressor to heat the cathode exhaust gas before the cathode exhaust gas enters the turbine, so as to improve the working efficiency of the turbine, thereby improving the working efficiency of the air subsystem and thus the efficiency of the fuel cell system.

[0021] In another aspect, the present application also provides an air subsystem for a fuel cell system. The air subsystem includes: a cathode supply pipeline configured to supply air to the stack of the fuel cell system; a compressor connected to the cathode supply pipeline to pressurize the air; a cathode exhaust pipeline configured to receive cathode exhaust gas from the stack; a turbine connected to the cathode exhaust pipeline to be driven by the cathode exhaust gas; and a second heat exchange device connected to the cathode supply pipeline and the cathode exhaust pipeline and configured to be able to switch between a third state and a fourth state. The second heat exchange device establishes a second heat exchange path between the air flow downstream of the compressor and the cathode exhaust gas flow upstream of the turbine when in the third state, so that the cathode exhaust gas exchanges heat with the air flow flowing out of the compressor before entering the turbine, and disconnects the second heat exchange path when in the fourth state, without enabling the cathode exhaust gas to exchange heat with the air flow flowing out of the compressor before entering the turbine.

[0022] In some embodiments, the second heat exchange device is configured to switch between the third state and the fourth state based on a comparison between the exhaust gas inlet temperature of the cathode exhaust gas stream before entering the turbine and the air outlet temperature of the air stream leaving the compressor. The second heat exchange device is in the third state when the exhaust gas inlet temperature is lower than the air outlet temperature, and is in the fourth state when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature.

[0023] In some embodiments, the second heat exchange device includes a second heat exchange structure, which is connected downstream of the compressor in the cathode supply pipeline and upstream of the turbine in the cathode exhaust pipeline to establish the second heat exchange path. The second heat exchange device further includes: a third bypass pipeline and a third pipeline switch. The third bypass pipeline is connected between a third upstream position of the cathode supply pipeline between the second heat exchange structure and the compressor and a third downstream position downstream of the second heat exchange structure, so that the air stream leaving the compressor can bypass the second heat exchange structure via the third bypass pipeline. The third pipeline switch is configured to switch between the third bypass pipeline and a third section of the cathode supply pipeline between the third upstream position and the third downstream position based on a comparison between the exhaust gas inlet temperature and the air outlet temperature. The third pipeline switch turns on the third section and closes the third bypass pipeline when the exhaust gas inlet temperature is lower than the air outlet temperature, and turns on the third bypass pipeline and closes the third section when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature; and / or a fourth bypass pipeline and a fourth pipeline switch. The fourth bypass pipeline is connected between a fourth upstream position of the cathode exhaust pipeline upstream of the second heat exchange structure and a fourth downstream position between the second heat exchange structure and the turbine, so that the cathode exhaust gas can bypass the second heat exchange structure via the fourth bypass pipeline. The fourth pipeline switch is configured to switch between the fourth bypass pipeline and a fourth section of the cathode exhaust pipeline between the fourth upstream position and the fourth downstream position based on a comparison between the exhaust gas inlet temperature and the air outlet temperature. The fourth pipeline switch turns on the fourth section and closes the fourth bypass pipeline when the exhaust gas inlet temperature is lower than the air outlet temperature, and turns on the fourth bypass pipeline and closes the fourth section when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature.

[0024] In some embodiments, the third pipeline switch includes a third three-way valve configured to switch between the third bypass pipeline and the third section, or includes a fifth on-off valve disposed on the third section and a sixth on-off valve disposed on the third bypass pipeline.

[0025] In some embodiments, the fourth pipeline switch includes a fourth three-way valve configured to switch between the fourth bypass pipeline and the fourth section, or includes a seventh on-off valve disposed on the fourth section and an eighth on-off valve disposed on the fourth bypass pipeline.

[0026] In some embodiments, the second heat exchange structure is a gas-gas heat exchanger; and / or

[0027] In some embodiments, along the second heat exchange path, there is only heat conduction between the air flow downstream of the compressor and the cathode exhaust gas flow upstream of the turbine, without mass exchange.

[0028] In some embodiments, the compressor is partially driven by the turbine.

[0029] In some embodiments, the air subsystem further includes an intercooler, which is connected to the cathode supply pipeline downstream of the second heat exchange structure.

[0030] The air subsystem having the second heat exchange device enables selectively using the air flow leaving the compressor to heat the cathode exhaust gas before the cathode exhaust gas enters the turbine, so as to improve the working efficiency of the turbine, thereby improving the working efficiency of the air subsystem and thus the efficiency of the fuel cell system.

[0031] In yet another aspect, the present application also proposes a fuel cell system. The fuel cell system includes: a fuel cell stack; and the aforementioned air subsystem, wherein the cathode supply pipeline and the cathode exhaust pipeline of the air subsystem are connected to the fuel cell stack.

[0032] These techniques can be used alone or in any suitable combination. The foregoing summary is provided by way of illustration and is not meant to be limiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other aspects of the present application will be more thoroughly understood and recognized by referring to the accompanying drawings. It should be noted that the drawings are only schematic and not drawn to scale. In different drawings, the same components are denoted by the same reference numerals. In addition, for the sake of brevity, not all components or parts of the fuel cell system and the air subsystem according to the present application are shown or marked in the drawings. It should be understood that the dimensions, proportional relationships, and the number of components in the drawings do not limit the present application. In the drawings:

[0034] Figure 1 is a block diagram schematically showing a fuel cell system including an air subsystem according to a first embodiment of the present application;

[0035] Figure 2A is similar to Figure 1 and shows that Figure 1 the first heat exchange device of the air subsystem shown is in the first state and the second heat exchange device is in the third state;

[0036] Figure 2B is similar to Figure 1 and shows that the first heat exchange device is in the second state and the second heat exchange device is in the fourth state;

[0037] Figure 3 is a block diagram schematically showing a fuel cell system including an air subsystem according to a second embodiment of the present application;

[0038] Figure 4A is similar to Figure 3 and shows that Figure 3 the first heat exchange device of the air subsystem shown is in the first state and the second heat exchange device is in the third state; and

[0039] Figure 4B is similar to Figure 3 and shows that the first heat exchange device is in the second state and the second heat exchange device is in the fourth state. Detailed Description of the Specific Embodiments

[0040] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following embodiments, in order to facilitate the description of the air subsystem for the fuel cell system according to the present application, the air subsystem for the PEMFC system is taken as an example. It should be understood that such an example does not mean any limitation to the present application, and the air subsystem according to the present application can also be used in other types of fuel cell systems. In addition, the features in the embodiments of the present application can be combined with each other without conflict.

[0041] Figures 1 to 2B Schematically shows a fuel cell system 1 according to a first embodiment of the present application. Figure 1 is a block diagram schematically showing the fuel cell system 1. The fuel cell system 1 can be a proton exchange membrane fuel cell (PEMFC) system, which uses hydrogen as fuel and oxygen as oxidant, and generates electricity by the electrochemical reaction of the fuel and the oxidant. For example, the fuel cell system 1 can be used in a vehicle to provide power, so as to drive a vehicle motor to provide power or enable an in-vehicle system to perform various functions.

[0042] As Figure 1 shown, the fuel cell system 1 includes a fuel cell stack 3 and an auxiliary system (not shown). The fuel cell stack 3 is used to convert the chemical energy in fuel and oxidant into electrical energy, and the auxiliary system provides the operating conditions required for the reaction of the fuel cell stack 3. The fuel cell stack 3 may include an anode 31, a cathode 32, and a cooling chamber (not shown). The auxiliary system may include an air subsystem 100, a fuel subsystem (not shown), and a thermal management subsystem (not shown). The fuel subsystem, the air subsystem 100, and the thermal management subsystem may be respectively configured to introduce fuel, air, and coolant into the anode 31, the cathode 32, and the cooling chamber of the fuel cell stack 3 to provide stable operating conditions for the fuel cell stack 3.

[0043] Although the fuel subsystem is not shown in the drawings, it should be understood that the fuel subsystem may have any suitable configuration to supply hydrogen (i.e., the fuel in the present application) to the anode inlet (not shown) of the anode 31 and receive unconsumed hydrogen, inert gas (inert gas refers to the gas that does not participate in the reaction, mainly nitrogen), and product water from the anode outlet (not shown) of the anode 31. The fuel subsystem may also mix the unconsumed hydrogen with fresh hydrogen from a hydrogen source to be supplied again to the anode inlet of the anode 31, thereby improving the utilization efficiency of the fuel.

[0044] Although the thermal management subsystem is not shown in the drawings, it should be understood that the thermal management subsystem may have any suitable configuration to regulate the temperature of the fuel cell stack 3 using coolant. For example, the thermal management subsystem may include a radiator and a coolant loop. The radiator is exposed to the ambient atmosphere around the fuel cell system 1, and the coolant loop is connected between the radiator and the fuel cell stack 3 to circulate the coolant between the radiator and the fuel cell stack 3. The thermal management subsystem may transfer the heat generated by the fuel cell stack 3 to the radiator through the coolant and dissipate it to the ambient atmosphere through the radiator, thereby cooling the fuel cell stack 3.

[0045] Please continue to refer to Figure 1 , the air subsystem 100 includes a cathode air supply pipeline 110 configured to supply air to the fuel cell stack 3, a cathode exhaust pipeline 120 configured to receive cathode exhaust gas from the fuel cell stack 3, a compressor 130 connected to the cathode air supply pipeline 110 to pressurize the air, and a turbine 140 connected to the cathode exhaust pipeline 120 to be driven by the cathode exhaust gas.

[0046] The cathode air supply pipeline 110 is connected between the cathode inlet 32a of the cathode 32 of the fuel cell stack 3 and the ambient atmosphere around the fuel cell system 1 to suck air from the ambient atmosphere. In the present application, oxygen in the air is used as the oxidant. It should be understood that the present application is not limited thereto.

[0047] The compressor 130 is connected to the cathode supply pipeline 110 and can be enabled and disabled. When enabled, the compressor 130 sucks in air from the ambient atmosphere around the fuel cell system 1 via the cathode supply pipeline 110, pressurizes it, and delivers the pressurized air to the cathode inlet 32a of the cathode 32 of the fuel cell stack 3 via the cathode supply pipeline 110. Air enters the compressor 130 from the compressor inlet 130a, is pressurized, and exits from the compressor outlet 130b. When air flows through the compressor 130, the temperature and pressure of the air increase. When the compressor 130 is disabled, it stops supplying air to the cathode inlet 32a.

[0048] The cathode exhaust pipeline 120 is connected to the cathode outlet 32b of the cathode 32 of the fuel cell stack 3 to receive the cathode exhaust gas from the cathode 32. For example, the cathode exhaust pipeline 120 can be connected between the cathode outlet 32b and an exhaust pipe (not shown) or the ambient atmosphere around the fuel cell system 1 to direct the cathode exhaust gas to the exhaust pipe or the ambient atmosphere. The cathode exhaust gas can include unconsumed oxygen, inert gas, and product water.

[0049] The turbine 140 is connected to the cathode exhaust pipeline 120 to be driven by the cathode exhaust gas, thereby recovering energy from the cathode exhaust gas. The cathode exhaust gas enters the turbine 140 from the turbine inlet 140a and flows out from the turbine outlet 140b. When the cathode exhaust gas flows through the turbine 140, the turbine (not shown) of the turbine 140 is driven by the cathode exhaust gas to rotate, so as to recover energy from the cathode exhaust gas, and the temperature and pressure of the cathode exhaust gas decrease.

[0050] The compressor 130 can be configured to be at least partially driven by the turbine 140. In some embodiments, as Figure 1 shown, the compressor 130 is partially driven by the turbine 140. Specifically, the transmission shaft 150 can rotatably couple the turbine of the turbine 140 and the impeller (not shown) of the compressor 130 to each other. The turbine of the turbine 140 is driven by the cathode exhaust gas, so as to drive the impeller of the compressor 130 to rotate through the transmission shaft 150, so that the compressor 130 pressurizes the air in the cathode supply pipeline 110. The compressor 130 can also be additionally driven by the motor 160. The motor 160 is also coupled to the transmission shaft 150 to drive the transmission shaft 150 to rotate when powered on. In this way, the motor 160 and the turbine 140 can drive the transmission shaft 150 to rotate together, so as to drive the impeller of the compressor 130 to rotate. In other embodiments, the compressor 130 can also be driven only by the turbine 140. In still other embodiments, the energy recovered from the cathode exhaust gas by the turbine 140 can drive other devices or be stored through other suitable mechanisms. In this case, the compressor 130 can be driven only by, for example, the motor 160.

[0051] The working efficiency of the compressor 130 is mainly affected by multiple parameters such as temperature and humidity of the air flow entering the compressor 130 from the compressor inlet 130a. For example, the lower the temperature of the air flow entering the compressor 130 from the compressor inlet 130a, the higher the working efficiency of the compressor 130. The working efficiency of the turbine 140 is mainly affected by multiple parameters such as temperature, pressure and humidity of the cathode exhaust gas flow entering the turbine 140 from the turbine inlet 140a. For example, the higher the temperature of the cathode exhaust gas flow entering the turbine 140 from the turbine inlet 140a, the higher the working efficiency of the turbine 140. Improving the working efficiency of the compressor 130 and / or the turbine 140 can improve the working efficiency of the air subsystem 100, thereby improving the efficiency of the fuel cell system 1.

[0052] As Figure 1 shown, the air subsystem 100 further includes a first heat exchange device 170, which is connected to the cathode supply pipeline 110 and the cathode exhaust pipeline 120 and is configured to be able to switch between a first state and a second state. Figure 2A shows the first heat exchange device 170 in the first state, and Figure 2B shows the first heat exchange device 170 in the second state. In Figure 2A and Figure 2B , the pipelines in the air subsystem 100 that are turned on are represented by solid lines, and the flow direction of the fluid is represented by arrows on the solid lines, while the pipelines that are turned off are represented by dashed lines. As Figure 2A shown, when in the first state, the first heat exchange device 170 establishes a first heat exchange path P1 (schematically represented by the broken-line arrow in Figure 2A ) between the air flow upstream of the compressor 130 and the cathode exhaust gas flow downstream of the turbine 140, so that the air flow exchanges heat with the cathode exhaust gas flow leaving the turbine 140 before entering the compressor 130. That is to say, when in the first state, the first heat exchange device 170 can make the air flow to enter the compressor 130 exchange heat with the cathode exhaust gas flow leaving the turbine 140, so that the temperature of the air flow is regulated by the cathode exhaust gas flow. The air flow with the regulated temperature then enters the compressor 130 from the compressor inlet 130a. As Figure 2B shown, when in the second state, the first heat exchange device 170 disconnects the first heat exchange path P1 and does not make the air flow exchange heat with the cathode exhaust gas flow leaving the turbine 140 before entering the compressor 130. In this case, the air flow to enter the compressor 130 does not exchange heat with the cathode exhaust gas flow leaving the turbine 140.

[0053] The first heat exchange device 170 with the foregoing configuration enables selective utilization of the cathode exhaust gas stream exiting the turbine 140 to adjust the temperature of the air stream before it enters the compressor 130. For example, when the exhaust gas outlet temperature of the cathode exhaust gas stream exiting the turbine 140 is lower than the air inlet temperature of the air stream before it enters the compressor 130, the first heat exchange device 170 can be switched to the first state to establish a first heat exchange path P1 between the air stream upstream of the compressor 130 and the cathode exhaust gas stream downstream of the turbine 140, such that the air stream is cooled by the cathode exhaust gas stream exiting the turbine 140 before entering the compressor 130, thereby reducing the temperature of the air stream entering the compressor 130. In this way, the compressor 130 can pressurize the air stream according to the original requirements with reduced energy consumption, thereby reducing the power consumption of the compressor 130 and improving its operating efficiency. This enables improvement of the operating efficiency of the air subsystem 100 and thus the efficiency of the fuel cell system 1. When the exhaust gas outlet temperature of the cathode exhaust gas stream exiting the turbine 140 is higher than the air inlet temperature of the air stream before it enters the compressor 130, the first heat exchange device 170 can be switched to the second state to disconnect the first heat exchange path P1 and prevent the air stream from being heated by the cathode exhaust gas stream exiting the turbine 140 before entering the compressor 130. In addition, when the exhaust gas outlet temperature is equal to the air inlet temperature, the first heat exchange device 170 can also be switched to the second state. Thus, it can be seen that the air subsystem 100 with the first heat exchange device 170 enables selective utilization of the cathode exhaust gas stream exiting the turbine 140 to cool the air before it enters the compressor 130, so as to reduce the power consumption of the compressor 130 and improve its operating efficiency, thereby improving the operating efficiency of the air subsystem 100 and thus the efficiency of the fuel cell system 1.

[0054] The fuel cell system 1 or the air subsystem 100 may include a first temperature sensor 191 configured to sense the air inlet temperature of the air stream before it enters the compressor 130. As an example, as Figure 1 shown, the first temperature sensor 191 may be connected to the cathode supply pipeline 110 between the first heat exchange device 170 and the compressor inlet 130a of the compressor 130. In other exemplary embodiments, the first temperature sensor 191 may also be connected to the cathode supply pipeline 110 upstream of the first heat exchange device 170 (e.g., at the inlet of the cathode supply pipeline 110).

[0055] The fuel cell system 1 or the air subsystem 100 may further include a second temperature sensor 192 configured to sense the exhaust gas outlet temperature of the cathode exhaust gas stream exiting the turbine 140. As an example, as Figure 1As shown, the second temperature sensor 192 can be connected to the cathode exhaust pipeline 120, between the first heat exchange device 170 and the turbine outlet 140b of the turbine 140. In other exemplary embodiments, the second temperature sensor 192 can also be connected to the cathode exhaust pipeline 120, downstream of the first heat exchange device 170 (e.g., at the outlet of the cathode exhaust pipeline 120).

[0056] The first heat exchange device 170 can be configured to switch between a first state ( Figure 2A ) and a second state ( Figure 2B ) in a manual or automatic manner. In some embodiments, the first heat exchange device 170 can be manually controlled by a user to switch between the first state and the second state. For example, the user can manually switch the first heat exchange device 170 between the first state and the second state based on a comparison of the exhaust gas outlet temperature of the cathode exhaust gas flowing out of the turbine 140 (i.e., the reading of the second temperature sensor 192) and the air inlet temperature of the air flow before entering the compressor 130 (i.e., the reading of the first temperature sensor 191). In other embodiments, the first heat exchange device 170 can automatically switch between the first state and the second state based on a comparison of the exhaust gas outlet temperature of the cathode exhaust gas flowing out of the turbine 140 and the air inlet temperature of the air flow before entering the compressor 130. Specifically, the first heat exchange device 170 is in the first state when the exhaust gas outlet temperature is lower than the air inlet temperature, and is in the second state when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature. This can be implemented by hardware such as a control circuit.

[0057] Figures 1 to 2B A specific type of the first heat exchange device 170 is schematically shown in Figures 1 to 2B As shown, the first heat exchange device 170 includes a first heat exchange structure 171, a first bypass pipeline 172, and a first pipeline switch 173.

[0058] The first heat exchange structure 171 is connected upstream of the compressor 130 on the cathode supply gas pipeline 110 and downstream of the turbine 140 on the cathode exhaust gas pipeline 120 to establish a first heat exchange path P1 between the air flow upstream of the compressor 130 and the cathode exhaust gas flow downstream of the turbine 140. The first heat exchange structure 171 may include an air inlet 1711, an air outlet 1712, an exhaust gas inlet 1713, and an exhaust gas outlet 1714. The air inlet 1711 and the air outlet 1712 are connected to the cathode supply gas pipeline 110. The air flow flowing along the cathode supply gas pipeline 110 enters the first heat exchange structure 171 from the air inlet 1711, leaves the first heat exchange structure 171 from the air outlet 1712, and flows towards the downstream compressor 130. The exhaust gas inlet 1713 and the exhaust gas outlet 1714 are connected to the cathode exhaust gas pipeline 120. The cathode exhaust gas flow leaving the turbine 140 flows along the cathode exhaust gas pipeline 120, enters the first heat exchange structure 171 from the exhaust gas inlet 1713, and leaves the first heat exchange structure 171 from the exhaust gas outlet 1714. When the air flow flows through the first heat exchange structure 171 along the cathode supply gas pipeline 110 and the cathode exhaust gas flow flows through the first heat exchange structure 171 along the cathode exhaust gas pipeline 120, the air flow and the cathode exhaust gas flow can exchange heat with each other in the first heat exchange structure 171.

[0059] As an example, the first heat exchange structure 171 may be a gas-gas heat exchanger, and the air flow and the cathode exhaust gas flow can exchange heat with each other when flowing through the gas-gas heat exchanger. As another example, the first heat exchange structure 171 may include a heat pipe (not shown), the heat absorption end of which may be disposed on the cathode supply gas pipeline 110, and its heat dissipation end may be disposed on the cathode exhaust gas pipeline 120. The working medium in the heat pipe can evaporate and absorb heat at the heat absorption end, flow inside the heat pipe to the heat dissipation end. The working medium in the vapor state releases heat when it encounters cold at the heat dissipation end, condenses into a liquid state, and then returns to the heat absorption end under the action of gravity and / or capillary action. During the heat absorption-heat release process, heat can be transferred from the heat absorption section end to the heat dissipation end. Thus, when the air flow and the cathode exhaust gas flow flow through the first heat exchange structure 171, heat can be transferred from the air flow to the cathode exhaust gas flow. It should be understood that the first heat exchange structure 171 is not limited thereto and may have any other suitable form to establish the first heat exchange path P1 between the air flow upstream of the compressor 130 and the cathode exhaust gas flow downstream of the turbine 140.

[0060] In addition, in some embodiments, the first heat exchange structure 171 may be configured such that only heat conduction occurs between the air flow upstream of the compressor 130 and the cathode exhaust gas flow downstream of the turbine 140 along the first heat exchange path P1, without mass exchange. It should be understood that the first heat exchange structure 171 is not limited thereto. In some other embodiments, the first heat exchange structure 171 may be configured such that heat conduction and mass exchange occur between the air flow upstream of the compressor 130 and the cathode exhaust gas flow downstream of the turbine 140 along the first heat exchange path P1. For example, the first heat exchange structure 171 may include a water-permeable but air-impermeable membrane to enable heat conduction and mass exchange between the air flow upstream of the compressor 130 and the cathode exhaust gas flow downstream of the turbine 140.

[0061] The first bypass pipeline 172 is connected between a first upstream position of the cathode exhaust pipeline 120 between the first heat exchange structure 171 and the turbine 140 and a first downstream position downstream of the first heat exchange structure 171, so that the cathode exhaust gas flow leaving the turbine 140 can bypass the first heat exchange structure 171 via the first bypass pipeline 172. As Figure 1 shown, the first upstream position of the cathode exhaust pipeline 120 between the first heat exchange structure 171 and the turbine 140 is located between the turbine outlet 140b of the turbine 140 and the exhaust gas inlet 1713 of the first heat exchange structure 171, and the first downstream position of the cathode exhaust pipeline 120 downstream of the first heat exchange structure 171 is located downstream of the exhaust gas outlet 1714 of the first heat exchange structure 171. Thus, the cathode exhaust gas flow leaving the turbine 140 can bypass the first heat exchange structure 171 via the first bypass pipeline 172 and flow downstream of the cathode exhaust pipeline 120. The cathode exhaust pipeline 120 includes a first section 120a between the first upstream position and the first downstream position.

[0062] The first pipeline switch 173 is configured to be able to switch between the first bypass pipeline 172 and the first section 120a of the cathode exhaust pipeline 120 to connect the first section 120a and close the first bypass pipeline 172, or connect the first bypass pipeline 172 and close the first section 120a, so that the first heat exchange device 170 can be switched between a first state ( Figure 2A ) and a second state ( Figure 2B ). As Figure 2AAs shown, when the first pipeline switch 173 connects the first section 120a and closes the first bypass pipeline 172, the first heat exchange device 170 is in the first state. The cathode exhaust gas flow leaving the turbine 140 flows through the first heat exchange structure 171 via the first section 120a, without flowing through the first bypass pipeline 172, and the air flow flows through the first heat exchange structure 171 before entering the compressor 130. The cathode exhaust gas flow exchanges heat with the air flow in the first heat exchange structure 171, and then the air flow enters the compressor 130. As Figure 2B As shown, when the first pipeline switch 173 connects the first bypass pipeline 172 and closes the first section 120a, the first heat exchange device 170 is in the second state. The cathode exhaust gas flow leaving the turbine 140 flows through the first bypass pipeline 172, without flowing through the first heat exchange structure 171, and the air flow flows through the first heat exchange structure 171 before entering the compressor 130, and no heat exchange occurs between the air flow and the cathode exhaust gas flow.

[0063] The first pipeline switch 173 can be configured to switch between the first bypass pipeline 172 and the first section 120a of the cathode exhaust pipeline 120 manually or automatically. In some embodiments, the first pipeline switch 173 can be manually controlled by a user (e.g., based on a comparison between the exhaust gas outlet temperature of the cathode exhaust gas flow leaving the turbine 140 and the air inlet temperature of the air flow before entering the compressor 130) to switch between the first bypass pipeline 172 and the first section 120a. In other partial embodiments, the first pipeline switch 173 can automatically switch between the first bypass pipeline 172 and the first section 120a based on a comparison between the exhaust gas outlet temperature of the cathode exhaust gas flow leaving the turbine 140 and the air inlet temperature of the air flow before entering the compressor 130. Specifically, the first pipeline switch 173 connects the first section 120a and closes the first bypass pipeline 172 when the exhaust gas outlet temperature is lower than the air inlet temperature, so that the first heat exchange device 170 is in the first state, and connects the first bypass pipeline 172 and closes the first section 120a when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature, so that the first heat exchange device 170 is in the second state. This can be implemented by hardware such as a control circuit.

[0064] In some embodiments, as Figure 1 As shown, the first pipeline switch 173 can include a three-way valve configured to switch between the first bypass pipeline 172 and the first section 120a. The three-way valve has a first outlet 173a, a second outlet 173b, and an inlet 173c. The three-way valve is configured to be able to switch between a first flow state and a second flow state. As Figure 2AAs shown, when placed in the first flow state, the three-way valve allows fluid flow from the inlet 173c to the first outlet 173a while blocking fluid flow from the inlet 173c to the second outlet 173b, thereby turning on the first section 120a and closing the first bypass line 172. In this case, the first heat exchange device 170 is in the first state. As Figure 2B shown, when placed in the second flow state, the three-way valve allows fluid flow from the inlet 173c to the second outlet 173b while blocking fluid flow from the inlet 173c to the first outlet 173a, thereby turning on the first bypass line 172 and closing the first section 120a. In this case, the first heat exchange device 170 is in the second state. The first pipeline switch 173 can be switched between the first bypass line 172 and the first section 120a of the cathode exhaust pipeline 120 by switching the three-way valve between the first flow state and the second flow state, so that the first heat exchange device 170 is switched between the first state and the second state.

[0065] In other embodiments, the first pipeline switch 173 may include on-off valves (not shown) provided on the first section 120a of the cathode exhaust pipeline 120 and on-off valves (not shown) provided on the first bypass line 172 to control the on and off of the first section 120a and the first bypass line 172. In this case, the first pipeline switch 173 can be switched between the first bypass line 172 and the first section 120a of the cathode exhaust pipeline 120 by controlling these on-off valves, so that the first heat exchange device 170 is switched between the first state and the second state. It should be understood that the present application is not limited thereto, and the first pipeline switch 173 can be in any other suitable form to achieve switching between the first bypass line 172 and the first section 120a of the cathode exhaust pipeline 120.

[0066] Please continue to refer to Figure 1 , the air subsystem 100 may further include a second heat exchange device 180, which is connected to the cathode supply pipeline 110 and the cathode exhaust pipeline 120 and is configured to be able to switch between a third state and a fourth state. Figure 2A shows the second heat exchange device 180 in the third state, and Figure 2B shows the second heat exchange device 180 in the fourth state. As described above, in Figure 2A and Figure 2B , the pipelines in the air subsystem 100 that are turned on are represented by solid lines, and the flow direction of the fluid is represented by arrows on the solid lines, while the pipelines that are closed are represented by dashed lines. As Figure 2A shown, when in the third state, the second heat exchange device 180 establishes a second heat exchange path P2 between the air flow downstream of the compressor 130 and the cathode exhaust gas flow upstream of the turbine 140 (asFigure 2A shown schematically by the broken-line arrow in [reference], so that the cathode exhaust gas flow exchanges heat with the air flow leaving the compressor 130 before entering the turbine 140. That is, the second heat exchange device 180 can, when in the third state, exchange heat between the cathode exhaust gas flow about to enter the turbine 140 and the air flow leaving the compressor 130, so that the temperature of the cathode exhaust gas flow is regulated by the air flow. The cathode exhaust gas flow with regulated temperature then enters the turbine 140 from the turbine inlet 140a. As Figure 2B shown, the second heat exchange device 180 disconnects the second heat exchange path P2 when in the fourth state, without allowing the cathode exhaust gas flow to exchange heat with the air flow leaving the compressor before entering the turbine 140. In this case, the cathode exhaust gas flow about to enter the turbine 140 does not exchange heat with the air flow leaving the compressor 130.

[0067] The second heat exchange device 180 having the foregoing configuration enables selective utilization of the air flow leaving the compressor 130 to regulate the temperature of the cathode exhaust gas flow before it enters the turbine 140. For example, when the exhaust gas inlet temperature of the cathode exhaust gas flow before entering the turbine 140 is lower than the air outlet temperature of the air flow leaving the compressor 130, the second heat exchange device 180 can be switched to the third state to establish the second heat exchange path P2 between the air flow downstream of the compressor 130 and the cathode exhaust gas flow upstream of the turbine 140, so that the cathode exhaust gas flow is heated by heat exchange with the air flow leaving the compressor 130 before entering the turbine 140, thereby increasing the temperature of the cathode exhaust gas flow entering the turbine 140. In this way, the operating efficiency of the turbine 140 can be improved. This is particularly beneficial when the compressor 130 is at least partially driven by the turbine 140, because the turbine 140 can generate more power to drive the rotating shaft 160 to drive the compressor 130. This enables reduction of the power consumption of the air subsystem 100 and improvement of its operating efficiency, thereby improving the efficiency of the fuel cell system 1. When the exhaust gas inlet temperature of the cathode exhaust gas flow before entering the turbine 140 is higher than the air outlet temperature of the air flow leaving the compressor 130, the second heat exchange device 180 can be switched to the fourth state to disconnect the second heat exchange path P2 and prevent the cathode exhaust gas flow from being cooled by the air flow leaving the compressor 130 before entering the turbine 140. In addition, when the exhaust gas inlet temperature is equal to the air outlet temperature, the second heat exchange device 180 can also be switched to the fourth state. Thus, it can be seen that the air subsystem 100 having the second heat exchange device 180 enables selective utilization of the air flow leaving the compressor 130 to heat the cathode exhaust gas flow before it enters the turbine 140, so as to improve the operating efficiency of the turbine 140 and thereby improve the efficiency of the fuel cell system 1.

[0068] The fuel cell system 1 or the air subsystem 100 may include a third temperature sensor 193 configured to sense the air outlet temperature of the air flow exiting the compressor 130. As an example, as Figure 1 shown, the third temperature sensor 193 may be connected to the cathode supply line 110 between the compressor outlet 130b of the compressor 130 and the second heat exchanger 180. In other exemplary embodiments, the third temperature sensor 193 may also be connected to the cathode supply line 110 downstream of the second heat exchanger 180. For example, the intercooler 190 may be connected to the cathode supply line 110 between the second heat exchanger 180 and the cathode inlet 32a of the cathode 32 of the fuel cell stack 3. The third temperature sensor 193 may be located between the second heat exchanger 180 and the intercooler 190.

[0069] The fuel cell system 1 or the air subsystem 100 may further include a fourth temperature sensor 194 configured to sense the exhaust gas inlet temperature of the cathode exhaust gas before entering the turbine 140. As an example, as Figure 1 shown, the fourth temperature sensor 194 may be connected to the cathode exhaust line 120 between the second heat exchanger 180 and the turbine inlet 140a of the turbine 140. In other exemplary embodiments, the fourth temperature sensor 194 may also be connected to the cathode exhaust line 120 upstream of the second heat exchanger 180. For example, the fourth temperature sensor 194 may be located between the second heat exchanger 180 and the cathode outlet 32b of the cathode 32 of the fuel cell stack 3.

[0070] Similar to the first heat exchanger 170, the second heat exchanger 180 may be configured to be in a third state ([[]]END]] Figure 2A ) and a fourth state ( Figure 2B) switch between them. In some embodiments, the second heat exchange device 180 can be manually controlled by the user to switch between the third state and the fourth state. For example, the user can manually switch the second heat exchange device 180 between the third state and the fourth state based on the comparison of the exhaust gas inlet temperature of the cathode exhaust gas stream before entering the turbine 140 (i.e., the reading of the fourth temperature sensor 194) and the air outlet temperature of the air stream leaving the compressor 130 (i.e., the reading of the third temperature sensor 193). In other partial embodiments, the second heat exchange device 180 can automatically switch between the third state and the fourth state based on the comparison of the exhaust gas inlet temperature of the cathode exhaust gas stream before entering the turbine 140 and the air outlet temperature of the air stream leaving the compressor 130. Specifically, the second heat exchange device 180 is in the third state when the exhaust gas inlet temperature is lower than the air outlet temperature, and is in the fourth state when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature. This can be achieved by hardware such as a control circuit.

[0071] Figure 1 A specific type of the second heat exchange device 180 is schematically shown in Figures 1 to 2B As shown, the second heat exchange device 180 includes a second heat exchange structure 181, a third bypass pipeline 182, and a third pipeline switch 183.

[0072] The second heat exchange structure 181 is connected downstream of the compressor 130 on the cathode supply pipeline 110 and upstream of the turbine 140 on the cathode exhaust pipeline 120 to establish a second heat exchange path P2 between the air stream downstream of the compressor 130 and the cathode exhaust gas stream upstream of the turbine 140. The second heat exchange structure 181 can include an air inlet 1811, an air outlet 1812, an exhaust gas inlet 1813, and an exhaust gas outlet 1814. The air inlet 1811 and the air outlet 1812 are connected to the cathode supply pipeline 110. The air stream leaving the compressor 130 flows along the cathode supply pipeline 110, enters the second heat exchange structure 181 from the air inlet 1811, and leaves the second heat exchange structure 181 from the air outlet 1812. The exhaust gas inlet 1813 and the exhaust gas outlet 1814 are connected to the cathode exhaust pipeline 120. The cathode exhaust gas stream flowing along the cathode exhaust pipeline 120 enters the second heat exchange structure 181 from the exhaust gas inlet 1813 and leaves the second heat exchange structure 181 from the exhaust gas outlet 1814. When the air stream flows through the second heat exchange structure 181 along the cathode supply pipeline 110 and the cathode exhaust gas stream flows through the second heat exchange structure 181 along the cathode exhaust pipeline 120, the air stream and the cathode exhaust gas stream can exchange heat with each other in the second heat exchange structure 181.

[0073] Similar to the first heat exchange structure 171, the second heat exchange structure 181 can be a gas-gas heat exchanger or can include heat pipes (not shown). These similar parts will not be elaborated here. It should be understood that the second heat exchange structure 181 is not limited thereto and can have any other suitable form to establish a second heat exchange path P2 between the air flow downstream of the compressor 130 and the cathode exhaust gas flow upstream of the turbine 140.

[0074] In addition, in some embodiments, the second heat exchange structure 181 can be configured such that only heat conduction occurs between the air flow downstream of the compressor 130 and the cathode exhaust gas flow upstream of the turbine 140 along the second heat exchange path P2, without mass exchange. It should be understood that the second heat exchange structure 181 is not limited thereto. In other partial embodiments, the second heat exchange structure 181 can be configured such that heat conduction and mass exchange occur between the air flow downstream of the compressor 130 and the cathode exhaust gas flow upstream of the turbine 140 along the second heat exchange path P2. For example, the second heat exchange structure 181 can include a water-permeable but air-impermeable membrane to enable heat conduction and mass exchange between the air flow downstream of the compressor 130 and the cathode exhaust gas flow upstream of the turbine 140.

[0075] The third bypass pipeline 182 is connected between a third upstream position of the cathode gas supply pipeline 110 between the second heat exchange structure 181 and the compressor 130 and a third downstream position downstream of the second heat exchange structure 181, so that the air flow leaving the compressor 130 can bypass the second heat exchange structure 181 via the third bypass pipeline 182. As Figure 1 shown, the third upstream position of the cathode gas supply pipeline 110 between the second heat exchange structure 181 and the compressor 130 is located between the compressor outlet 130b of the compressor 130 and the air inlet 1811 of the second heat exchange structure 181, and the third downstream position of the cathode gas supply pipeline 110 downstream of the second heat exchange structure 181 is located downstream of the air outlet 1812 of the second heat exchange structure 181. Thus, the air flow leaving the compressor 130 can bypass the second heat exchange structure 181 via the third bypass pipeline 182 and flow downstream of the cathode gas supply pipeline 110. The cathode gas supply pipeline 110 includes a third section 110a between the third upstream position and the third downstream position.

[0076] The third pipeline switch 183 is configured to be able to switch between the third bypass pipeline 182 and the third section 110a of the cathode gas supply pipeline 110 to connect the third section 110a and close the third bypass pipeline 182, or connect the third bypass pipeline 182 and close the third section 110a, so that the second heat exchange device 180 can be switched between the third state ( Figure 2A ) and the fourth state ( Figure 2B ). As Figure 2AAs shown, when the third pipeline switch 183 connects the third section 110a and closes the third bypass pipeline 182, the second heat exchange device 180 is in the third state. The air flow leaving the compressor 130 flows through the second heat exchange structure 181 via the third section 110a, without flowing through the third bypass pipeline 182, and the cathode exhaust gas flow flows through the second heat exchange structure 181 before entering the turbine 140. The air flow exchanges heat with the cathode exhaust gas flow in the second heat exchange structure 181, and then the cathode exhaust gas flow enters the turbine 140. When the third pipeline switch 183 connects the third bypass pipeline 182 and closes the third section 110a, the second heat exchange device 180 is in the fourth state. The air flow leaving the compressor 130 flows through the third bypass pipeline 182, without flowing through the second heat exchange structure 181, and the cathode exhaust gas flow flows through the second heat exchange structure 181 before entering the turbine 140. No heat exchange occurs between the air flow and the cathode exhaust gas flow.

[0077] Similar to the first pipeline switch 173, the third pipeline switch 183 can be configured to switch between the third bypass pipeline 182 and the third section 110a of the cathode gas supply pipeline 110 manually or automatically. In some embodiments, the third pipeline switch 183 can be manually controlled by a user (e.g., based on a comparison of the exhaust gas inlet temperature of the cathode exhaust gas flow before entering the turbine 140 and the air outlet temperature of the air flow leaving the compressor 130) to switch between the third bypass pipeline 182 and the third section 110a. In other partial embodiments, the third pipeline switch 183 can automatically switch between the third bypass pipeline 182 and the third section 110a based on a comparison of the exhaust gas inlet temperature of the cathode exhaust gas flow before entering the turbine 140 and the air outlet temperature of the air flow leaving the compressor 130. Specifically, the third pipeline switch 183 connects the third section 110a and closes the third bypass pipeline 182 when the exhaust gas inlet temperature is lower than the air outlet temperature, so that the second heat exchange device 180 is in the third state, and connects the third bypass pipeline 182 and closes the third section 110a when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature, so that the second heat exchange device 180 is in the fourth state. This can be achieved by hardware such as a control circuit.

[0078] In some embodiments, as Figure 1 shown, the third pipeline switch 183 can include a three-way valve configured to switch between the third bypass pipeline 182 and the third section 110a. The three-way valve has a first outlet 183a, a second outlet 183b, and an inlet 183c. The three-way valve is configured to be able to switch between a first flow state and a second flow state. As Figure 2AAs shown, when placed in the first flow state, the three-way valve allows fluid flow from the inlet 183c to the first outlet 183a while blocking fluid flow from the inlet 183c to the second outlet 183b, thereby turning on the third section 110a and closing the third bypass line 182 to place the second heat exchange device 180 in the third state. As Figure 2B As shown, when placed in the second flow state, the three-way valve allows fluid flow from the inlet 183c to the second outlet 183b while blocking fluid flow from the inlet 183c to the first outlet 183a, thereby turning on the third bypass line 182 and closing the third section 110a to place the second heat exchange device 180 in the fourth state. The third pipeline switch 183 can be switched between the third bypass line 182 and the third section 110a of the cathode gas supply line 110 by switching the three-way valve between the first flow state and the second flow state, thereby switching the second heat exchange device 180 between the third state and the fourth state.

[0079] In other partial embodiments, the third pipeline switch 183 may include on-off valves (not shown) provided on the third section 110a of the cathode gas supply line 110 and on-off valves (not shown) provided on the third bypass line 182 to control the on and off of the third section 110a and the third bypass line 182. In this case, the third pipeline switch 183 can be switched between the third bypass line 182 and the third section 110a of the cathode gas supply line 110 by controlling these on-off valves, thereby switching the second heat exchange device 180 between the third state and the fourth state. It should be understood that the present application is not limited thereto, and the third pipeline switch 183 may be in any other suitable form to achieve switching between the third bypass line 182 and the third section 110a of the cathode gas supply line 110.

[0080] Figures 3 to 4B The fuel cell system 1 according to the second embodiment of the present application is schematically shown. The configuration of the fuel cell system 1 according to the second embodiment of the present application is similar to that of the fuel cell system 1 according to the first embodiment of the present application. Therefore, in Figures 1 to 2B and Figures 3 to 4B the same reference numerals are used to denote the same or similar components or parts in the two embodiments, and for the sake of brevity, the details of these same or similar components or parts will not be described again.

[0081] Similar to Figures 1 to 2B the fuel cell system 1 shown, as Figure 3As shown, the air subsystem 100 of the fuel cell system 1 according to the second embodiment of the present application includes a cathode air supply pipeline 110 configured to supply air to the stack 3, a cathode exhaust pipeline 120 configured to receive cathode exhaust gas from the stack 3, a compressor 130 connected to the cathode air supply pipeline 110 to pressurize the air, and a turbine 140 connected to the cathode exhaust pipeline 120 and driven by the cathode exhaust gas.

[0082] Figure 3 The air subsystem 100 shown also includes a first heat exchange device 170'. Similar to the first heat exchange device 170, the first heat exchange device 170' is connected to the cathode air supply pipeline 110 and the cathode exhaust pipeline 120, and is configured to be able to switch between a first state and a second state. Figure 4A It is shown that the first heat exchange device 170' is in the first state, and Figure 4B It is shown that the first heat exchange device 170' is in the second state. In Figure 4A and Figure 4B the pipelines in the air subsystem 100 that are turned on are represented by solid lines, and the flow direction of the fluid is indicated by arrows on the solid lines, while the pipelines that are turned off are represented by dashed lines. Similar to the first heat exchange device 170, as Figure 4A shown, when the first heat exchange device 170' is in the first state, it establishes a first heat exchange path P1 (schematically indicated by the broken-line arrow in Figure 4A ) between the air flow upstream of the compressor 130 and the cathode exhaust gas flow downstream of the turbine 140, so that the air flow exchanges heat with the cathode exhaust gas flow leaving the turbine 140 before entering the compressor 130. As Figure 4B shown, when the first heat exchange device 170' is in the second state, it disconnects the first heat exchange path P1, and does not allow the air flow to exchange heat with the cathode exhaust gas flow leaving the turbine 140 before entering the compressor 130.

[0083] The first heat exchange device 170' with the foregoing configuration enables the temperature of the air flow to be selectively adjusted by using the cathode exhaust gas flow leaving the turbine 140 before the air flow enters the compressor 130. Similar to the above description, the air subsystem 100 with the first heat exchange device 170' enables the air to be selectively cooled by using the cathode exhaust gas flow leaving the turbine 140 before the air enters the compressor 130, so as to reduce the power consumption of the compressor 130 and improve its working efficiency, thereby improving the working efficiency of the air subsystem 100 and thus the efficiency of the fuel cell system 1.

[0084] Similar to the first heat exchange device 170, the first heat exchange device 170' can be configured to switch between the first state ( Figure 4A ) and the second state ( Figure 4B) switch between them. In some embodiments, the first heat exchange device 170 can be manually controlled by the user to switch between the first state and the second state. In some other embodiments, the first heat exchange device 170' can switch between the first state and the second state based on a comparison between the exhaust gas outlet temperature of the cathode exhaust gas stream leaving the turbine 140 and the air inlet temperature of the air stream before entering the compressor 130. The first heat exchange device 170' is in the first state when the exhaust gas outlet temperature is lower than the air inlet temperature, and is in the second state when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature. This can be achieved by hardware such as a control circuit.

[0085] Figures 3 to 4B A specific type of the first heat exchange device 170' is schematically shown. Similar to the first heat exchange device 170, as Figures 3 to 4B shown, the first heat exchange device 170' can include a first heat exchange structure 171. Details of the first heat exchange structure 171 will not be elaborated here again.

[0086] Different from the first heat exchange device 170, the first heat exchange device 170' includes a second bypass pipeline 172' and a second pipeline switch 173', and does not have a first bypass pipeline 172 and a first pipeline switch 173.

[0087] The second bypass pipeline 172' is connected between a second upstream position of the cathode gas supply pipeline 110 upstream of the first heat exchange structure 171 and a second downstream position between the first heat exchange structure 171 and the compressor 130, so that the air stream can bypass the first heat exchange structure 171 via the second bypass pipeline 172'. As Figure 3 shown, the second upstream position of the cathode gas supply pipeline 110 upstream of the first heat exchange structure 171 is upstream of the air inlet 1711 of the first heat exchange structure 171, and the second downstream position of the cathode gas supply pipeline 110 between the first heat exchange structure 171 and the compressor 130 is between the air outlet 1712 of the first heat exchange structure 171 and the compressor inlet 130a of the compressor 130. In this way, the air stream flowing along the cathode gas supply pipeline 110 can bypass the first heat exchange structure 171 via the second bypass pipeline 172', flow downstream and enter the compressor 130 from the compressor inlet 130a. The cathode gas supply pipeline 110 includes a second section 110b between the second upstream position and the second downstream position.

[0088] Similar to the first pipeline switch 173, the second pipeline switch 173' is configured to be able to switch between the second bypass pipeline 172' and the second section 110b of the cathode supply pipeline 110, so as to connect the second section 110b and close the second bypass pipeline 172', or connect the second bypass pipeline 172' and close the second section 110b, thereby enabling the first heat exchange device 170' to be in the first state ( Figure 4A ) and the second state ( Figure 4B ) to switch between. As Figure 4A shown, when the second pipeline switch 173' connects the second section 110b and closes the second bypass pipeline 172', the first heat exchange device 170' is in the first state, and the air flow flowing along the cathode supply pipeline 110 flows through the first heat exchange structure 171 via the second section 110b, without flowing through the second bypass pipeline 172', and the cathode exhaust gas flow leaving the turbine 140 flows through the first heat exchange structure 171. The air flow exchanges heat with the cathode exhaust gas flow in the first heat exchange structure 171, and then the air flow enters the compressor 130. As Figure 4B shown, when the second pipeline switch 173' connects the second bypass pipeline 172' and closes the second section 110b, the first heat exchange device 170' is in the second state, and the air flow flowing along the cathode supply pipeline 110 flows through the second bypass pipeline 172', without flowing through the first heat exchange structure 171, and the cathode exhaust gas flow leaving the turbine 140 flows through the first heat exchange structure 171. No heat exchange occurs between the air flow and the cathode exhaust gas flow.

[0089] Similar to the first pipeline switch 173, the second pipeline switch 173' can be configured to switch between the second bypass pipeline 172' and the second section 110b of the cathode gas supply pipeline 110 manually or automatically. In some embodiments, the second pipeline switch 173' can be manually controlled by a user (e.g., based on a comparison of the exhaust gas outlet temperature of the cathode exhaust gas leaving the turbine 140 and the air inlet temperature of the air stream before entering the compressor 130) to switch between the second bypass pipeline 172' and the second section 110b. In other embodiments, the second pipeline switch 173' can automatically switch between the second bypass pipeline 172' and the second section 110b based on a comparison of the exhaust gas outlet temperature of the cathode exhaust gas leaving the turbine 140 and the air inlet temperature of the air stream before entering the compressor 130. Specifically, the second pipeline switch 173' turns on the second section 110b and closes the second bypass pipeline 172' when the exhaust gas outlet temperature is lower than the air inlet temperature, so that the first heat exchange device 170' is in the first state, and turns on the second bypass pipeline 172' and closes the second section 110b when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature, so that the first heat exchange device 170' is in the second state. This can be achieved by hardware such as a control circuit.

[0090] In addition, similar to the first pipeline switch 173, the second pipeline switch 173' can include a three-way valve configured to switch between the second bypass pipeline 172' and the second section 110b, or can include an on-off valve provided on the second section 110b and an on-off valve provided on the second bypass pipeline 172'. These details are not elaborated here.

[0091] Please continue to refer to Figure 3 , Figure 3 The air subsystem 100 shown can also include a second heat exchange device 180'. Similar to the second heat exchange device 180, the second heat exchange device 180' is connected to the cathode gas supply pipeline 110 and the cathode exhaust pipeline 120, and is configured to be able to switch between a third state and a fourth state. Figure 4A shows the second heat exchange device 180' in the third state, and Figure 4B shows the second heat exchange device 180' in the fourth state. As described above, in Figure 4A and Figure 4B , the pipelines in the air subsystem 100 that are turned on are represented by solid lines, and the flow direction of the fluid is represented by arrows on the solid lines, while the pipelines that are closed are represented by dashed lines. Similar to the second heat exchange device 180, as Figure 4A shown, when the second heat exchange device 180' is in the third state, a second heat exchange path P2 is established between the air stream downstream of the compressor 130 and the cathode exhaust gas stream upstream of the turbine 140 (asFigure 4A is schematically represented by the broken-line arrow in FIG. such that the cathode exhaust gas stream exchanges heat with the air stream exiting the compressor 130 before entering the turbine 140. As Figure 4B shown, the second heat exchange device 180' disconnects the second heat exchange path P2 in the fourth state, without causing the cathode exhaust gas stream to exchange heat with the air stream exiting the compressor before entering the turbine 140.

[0092] The second heat exchange device 180 having the foregoing configuration enables the temperature of the cathode exhaust gas stream to be selectively adjusted by using the air stream exiting the compressor 130 before the cathode exhaust gas stream enters the turbine 140. Similar to that described above, the air subsystem 100 having the second heat exchange device 180' enables the air stream exiting the compressor 130 to be selectively used to heat the cathode exhaust gas stream before the cathode exhaust gas stream enters the turbine 140, so as to improve the operating efficiency of the turbine 140 and thus improve the efficiency of the fuel cell system 1.

[0093] Similar to the second heat exchange device 180, the second heat exchange device 180' can be configured to switch between a third state ( Figure 4A ) and a fourth state ( Figure 4B ) in a manual or automatic manner. In some embodiments, the second heat exchange device 180' can be manually controlled by a user to switch between the third state and the fourth state. In other partial embodiments, the second heat exchange device 180' can automatically switch between the third state and the fourth state based on a comparison of the exhaust gas inlet temperature of the cathode exhaust gas stream before entering the turbine 140 and the air outlet temperature of the air stream exiting the compressor 130. The second heat exchange device 180 is in the third state when the exhaust gas inlet temperature is lower than the air outlet temperature, and is in the fourth state when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature. This can be achieved by hardware such as a control circuit.

[0094] Figures 3 to 4B FIG. schematically shows a specific form of the second heat exchange device 180'. Similar to the second heat exchange device 180, as Figures 3 to 4B shown, the second heat exchange device 180' can include a second heat exchange structure 181. Details of the second heat exchange structure 181 will not be described herein again.

[0095] Different from the second heat exchange device 180, the second heat exchange device 180' includes a fourth bypass pipeline 182' and a fourth pipeline switch 183', and does not have a third bypass pipeline 182 and a third pipeline switch 183.

[0096] The fourth bypass pipeline 182' is connected between a fourth upstream position of the cathode exhaust pipeline 120 upstream of the second heat exchange structure 181 and a fourth downstream position between the second heat exchange structure 181 and the turbine 140, so that the cathode exhaust gas can bypass the second heat exchange structure 181 via the fourth bypass pipeline 182'. As Figure 3 shown, the fourth upstream position of the cathode exhaust pipeline 120 upstream of the second heat exchange structure 181 is upstream of the exhaust gas inlet 1813 of the second heat exchange structure 181, and the fourth downstream position of the cathode exhaust pipeline 120 between the second heat exchange structure 181 and the turbine 140 is between the exhaust gas outlet 1814 of the second heat exchange structure 181 and the turbine inlet 140a of the turbine 140. Thus, the cathode exhaust gas flow flowing along the cathode exhaust pipeline 120 can bypass the second heat exchange structure 171 via the fourth bypass pipeline 182', flow downstream and enter the turbine 140 from the turbine inlet 140a. The cathode exhaust pipeline 120 includes a fourth section 120b between the fourth upstream position and the fourth downstream position.

[0097] Similar to the third pipeline switch 183, the fourth pipeline switch 183' is configured to be able to switch between the fourth bypass pipeline 182' and the fourth section 120b of the cathode exhaust pipeline 120, to connect the fourth section 120b and close the fourth bypass pipeline 182', or connect the fourth bypass pipeline 182' and close the fourth section 120b, so that the second heat exchange device 180' is in the third state ( Figure 4A ) and the fourth state ( Figure 4B ) to switch. As Figure 4A shown, when the fourth pipeline switch 183' connects the fourth section 120b and closes the fourth bypass pipeline 182', the second heat exchange device 180' is in the third state, the air flow leaving the compressor 130 flows through the second heat exchange structure 181, and the cathode exhaust gas flow flowing along the cathode exhaust pipeline 120 flows through the second heat exchange structure 181 via the fourth section 120b and does not flow through the fourth bypass pipeline 182'. The cathode exhaust gas flow exchanges heat with the air flow in the second heat exchange structure 181, and then the cathode exhaust gas flow enters the turbine 140. When the fourth pipeline switch 183' connects the fourth bypass pipeline 182' and closes the fourth section 120b, the second heat exchange device 180' is in the fourth state, the air flow leaving the compressor 130 flows through the second heat exchange structure 181, and the cathode exhaust gas flow flowing along the cathode exhaust pipeline 120 bypasses the second heat exchange structure 181 via the fourth bypass pipeline 182'. No heat exchange occurs between the air flow and the cathode exhaust gas flow.

[0098] Similar to the third pipeline switch 183, the fourth pipeline switch 183' can be configured to switch between the fourth bypass pipeline 182' and the fourth section 120b of the cathode exhaust pipeline 120 in a manual or automatic manner. In some embodiments, the fourth pipeline switch 183' can be manually controlled by a user (e.g., based on a comparison of the exhaust gas inlet temperature of the cathode exhaust gas stream before entering the turbine 140 and the air outlet temperature of the air stream leaving the compressor 130) to switch between the fourth bypass pipeline 182' and the fourth section 120b. In other partial embodiments, the fourth pipeline switch 183' can automatically switch between the fourth bypass pipeline 182' and the fourth section 120b based on a comparison of the exhaust gas inlet temperature of the cathode exhaust gas stream before entering the turbine 140 and the air outlet temperature of the air stream leaving the compressor 130. Specifically, the fourth pipeline switch 183' turns on the fourth section 120b and closes the fourth bypass pipeline 182' when the exhaust gas inlet temperature is lower than the air outlet temperature, so that the second heat exchange device 180' is in the third state, and turns on the fourth bypass pipeline 182' and closes the fourth section 120b when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature, so that the second heat exchange device 180' is in the fourth state. This can be achieved by hardware such as a control circuit.

[0099] In addition, similar to the third pipeline switch 183, the fourth pipeline switch 183' can include a three-way valve configured to switch between the fourth bypass pipeline 182' and the fourth section 120b, or can include an on-off valve provided on the fourth section 120b and an on-off valve provided on the fourth bypass pipeline 182'. These details are not elaborated here.

[0100] It should be understood that the air subsystem 100 is not limited to the content described above and can also include devices such as an intercooler and a humidifier. For example, as described above and as Figures 1 to 4B shown, the intercooler 190 can be connected to the cathode supply pipeline 110, located between the second heat exchange device 180 or 180' and the cathode inlet 32a of the cathode 32 of the fuel cell stack 3. When the exhaust gas inlet temperature is lower than the air outlet temperature and the second heat exchange device 180 or 180' is in the third state, the air stream leaving the compressor 130 is cooled by the cathode exhaust gas stream when passing through the second heat exchange structure 181. This can reduce the power consumption of the intercooler 190, thereby improving the working efficiency of the air subsystem 100 and thus the efficiency of the fuel cell system 1.

[0101] Although the above has been described in connection with embodiments in which the air subsystem 100 has a combination of the first heat exchange device 170 and the second heat exchange device 180 or has a combination of the first heat exchange device 170' and the second heat exchange device 180', it should be understood that the air subsystem 100 may include any one or more of the first heat exchange device 170, the second heat exchange device 180, the first heat exchange device 170', and the second heat exchange device 180'.

[0102] Although the above has been described in connection with embodiments in which the first heat exchange device 170 includes the first heat exchange structure 171, the first bypass pipeline 172, and the first pipeline switch 173 and the first heat exchange device 170' includes the first heat exchange structure 171, the second bypass pipeline 172', and the second pipeline switch 173', it should be understood that the air subsystem 100 may have a heat exchange device that includes a combination of the first heat exchange structure 171, the first bypass pipeline 172, the first pipeline switch 173, the second bypass pipeline 172', and the second pipeline switch 173' to achieve the above functions.

[0103] Although the above has been described in connection with embodiments in which the second heat exchange device 180 includes the second heat exchange structure 181, the third bypass pipeline 182, and the third pipeline switch 183 and the second heat exchange device 180' includes the second heat exchange structure 181, the fourth bypass pipeline 182', and the fourth pipeline switch 183', it should be understood that the air subsystem 100 may have a heat exchange device that includes a combination of the second heat exchange structure 181, the third bypass pipeline 182, the third pipeline switch 183, the fourth bypass pipeline 182', and the fourth pipeline switch 183' to achieve the above functions.

[0104] It should be understood that the configuration of the heat exchange device that allows switching between two states to establish and cut off the heat exchange path is not limited to the combination of the bypass pipeline and the pipeline switch, but may include any suitable mechanism. It should also be understood that whether it is a three-way valve or an on-off valve, it can be controlled manually or automatically (for example, implemented by hardware such as a control circuit).

[0105] In this application, the terms "first", "second", "third", "fourth", "fifth", "sixth", "seventh", and "eighth" are only used to distinguish one component, pipeline, or state from another component, pipeline, or state, but these components, pipelines, and states should not be limited by such terms.

[0106] The present application has been described in detail in connection with specific embodiments. Obviously, the above description and the embodiments shown in the drawings should be understood as exemplary and do not constitute a limitation to the present application. For those skilled in the art, various variations or modifications can be made without departing from the spirit of the present application, and these variations or modifications do not depart from the scope of the present application.

Claims

1. An air subsystem for a fuel cell system (1), characterized in that, The air subsystem (100) includes: a cathode air supply line (110) configured to supply air to the stack (3) of the fuel cell system; a compressor (130) connected to the cathode air supply line to pressurize the air; a cathode exhaust line (120) configured to receive cathode exhaust gas from the stack; a turbine (140) connected to the cathode exhaust line and driven by the cathode exhaust gas; and a first heat exchange device (170) connected to the cathode air supply line and the cathode exhaust line and configured to be switchable between a first state and a second state. In the first state, the first heat exchange device establishes a first heat exchange path (P1) between the air flow upstream of the compressor and the cathode exhaust gas flow downstream of the turbine, so that the air flow exchanges heat with the cathode exhaust gas flow leaving the turbine before entering the compressor. In the second state, the first heat exchange path is disconnected, and the air flow does not exchange heat with the cathode exhaust gas flow leaving the turbine before entering the compressor.

2. The air subsystem according to claim 1, wherein The first heat exchange device is configured to switch between the first state and the second state based on a comparison between the exhaust gas outlet temperature of the cathode exhaust gas flow leaving the turbine and the air inlet temperature of the air flow before entering the compressor. The first heat exchange device is in the first state when the exhaust gas outlet temperature is lower than the air inlet temperature, and in the second state when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature.

3. The air subsystem according to claim 2, characterized in that, The first heat exchange device includes a first heat exchange structure (171) connected upstream of the compressor on the cathode air supply line and downstream of the turbine on the cathode exhaust line to establish the first heat exchange path. The first heat exchange device further includes: a first bypass line (172) and a first line switch (173). The first bypass line is connected between a first upstream position of the cathode exhaust line between the first heat exchange structure and the turbine and a first downstream position downstream of the first heat exchange structure, so that the cathode exhaust gas flow leaving the turbine can bypass the first heat exchange structure via the first bypass line. The first line switch is configured to switch between the first bypass line and a first section (120a) of the cathode exhaust line between the first upstream position and the first downstream position based on a comparison between the exhaust gas outlet temperature and the air inlet temperature. The first line switch connects the first section and closes the first bypass line when the exhaust gas outlet temperature is lower than the air inlet temperature, and connects the first bypass line and closes the first section when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature; and / or A second bypass pipeline (172') and a second pipeline switch (173'), the second bypass pipeline being connected between a second upstream position of the cathode gas supply pipeline upstream of the first heat exchange structure and a second downstream position between the first heat exchange structure and the compressor, so that an air flow can bypass the first heat exchange structure via the second bypass pipeline, the second pipeline switch being configured to switch between the second bypass pipeline and a second section (110b) of the cathode gas supply pipeline between the second upstream position and the second downstream position based on a comparison of the exhaust gas outlet temperature and the air inlet temperature, the second pipeline switch turning on the second section and closing the second bypass pipeline when the exhaust gas outlet temperature is lower than the air inlet temperature, and turning on the second bypass pipeline and closing the second section when the exhaust gas outlet temperature is higher than or equal to the air inlet temperature.

4. The air subsystem according to claim 3, wherein: The first pipeline switch includes a first three-way valve configured to switch between the first bypass pipeline and the first section, or includes a first on-off valve provided on the first section and a second on-off valve provided on the first bypass pipeline; and / or The second pipeline switch includes a second three-way valve configured to switch between the second bypass pipeline and the second section, or includes a third on-off valve provided on the second section and a fourth on-off valve provided on the second bypass pipeline; and / or The first heat exchange structure is a gas-gas heat exchanger; and / or Only heat conduction occurs between the air flow upstream of the compressor and the cathode exhaust gas flow downstream of the turbine along the first heat exchange path, without mass exchange.

5. The air subsystem according to claim 1, characterized in that, The air subsystem further includes a second heat exchange device (180), the second heat exchange device being connected to the cathode gas supply pipeline and the cathode exhaust gas pipeline and being configured to be able to switch between a third state and a fourth state, the second heat exchange device establishing a second heat exchange path (P2) between the air flow downstream of the compressor and the cathode exhaust gas flow upstream of the turbine when in the third state, so that the cathode exhaust gas exchanges heat with the air flow leaving the compressor before entering the turbine, and disconnecting the second heat exchange path when in the fourth state, without allowing the cathode exhaust gas to exchange heat with the air flow leaving the compressor before entering the turbine.

6. An air subsystem for a fuel cell system (1), characterized in that, The air subsystem (100) includes: A cathode gas supply pipeline (110) configured to supply air to the fuel cell system stack (3); A compressor (130) connected to the cathode gas supply pipeline to pressurize the air; A cathode exhaust gas pipeline (120) configured to receive cathode exhaust gas from the stack; A turbine (140) connected to the cathode exhaust gas pipeline and driven by the cathode exhaust gas; and A second heat exchange device (180) is connected to the cathode supply pipeline and the cathode exhaust pipeline and is configured to be switchable between a third state and a fourth state. When in the third state, the second heat exchange device establishes a second heat exchange path (P2) between the air flow downstream of the compressor and the cathode exhaust gas flow upstream of the turbine, so that the cathode exhaust gas flow exchanges heat with the air flow leaving the compressor before entering the turbine. When in the fourth state, the second heat exchange path is disconnected, and the cathode exhaust gas flow does not exchange heat with the air flow leaving the compressor before entering the turbine.

7. The air subsystem according to claim 5 or 6, characterized in that The second heat exchange device is configured to switch between the third state and the fourth state based on a comparison between the exhaust gas inlet temperature of the cathode exhaust gas flow before entering the turbine and the air outlet temperature of the air flow leaving the compressor. The second heat exchange device is in the third state when the exhaust gas inlet temperature is lower than the air outlet temperature, and is in the fourth state when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature.

8. The air subsystem according to claim 7, wherein The second heat exchange device includes a second heat exchange structure (181). The second heat exchange structure is connected downstream of the compressor on the cathode supply pipeline and upstream of the turbine on the cathode exhaust pipeline to establish the second heat exchange path. The second heat exchange device further includes: A third bypass pipeline (182) and a third pipeline switch (183). The third bypass pipeline is connected between a third upstream position of the cathode supply pipeline between the second heat exchange structure and the compressor and a third downstream position downstream of the second heat exchange structure, so that the air flow leaving the compressor can bypass the second heat exchange structure via the third bypass pipeline. The third pipeline switch is configured to switch between the third bypass pipeline and a third section (110a) of the cathode supply pipeline between the third upstream position and the third downstream position based on a comparison between the exhaust gas inlet temperature and the air outlet temperature. The third pipeline switch turns on the third section and closes the third bypass pipeline when the exhaust gas inlet temperature is lower than the air outlet temperature, and turns on the third bypass pipeline and closes the third section when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature; and / or A fourth bypass pipeline (182') and a fourth pipeline switch (183'), the fourth bypass pipeline being connected between a fourth upstream position of the cathode exhaust pipeline upstream of the second heat exchange structure and a fourth downstream position between the second heat exchange structure and the turbine, so that cathode exhaust gas can bypass the second heat exchange structure via the fourth bypass pipeline, the fourth pipeline switch being configured to switch between the fourth bypass pipeline and a fourth section (120b) of the cathode exhaust pipeline between the fourth upstream position and the fourth downstream position based on a comparison of the exhaust gas inlet temperature and the air outlet temperature, the fourth pipeline switch turning on the fourth section and closing the fourth bypass pipeline when the exhaust gas inlet temperature is lower than the air outlet temperature, and turning on the fourth bypass pipeline and closing the fourth section when the exhaust gas inlet temperature is higher than or equal to the air outlet temperature.

9. The air subsystem according to claim 8, wherein the third pipeline switch includes a third three-way valve configured to switch between the third bypass pipeline and the third section, or includes a fifth on-off valve provided on the third section and a sixth on-off valve provided on the third bypass pipeline; and / or the fourth pipeline switch includes a fourth three-way valve configured to switch between the fourth bypass pipeline and the fourth section, or includes a seventh on-off valve provided on the fourth section and an eighth on-off valve provided on the fourth bypass pipeline; and / or the second heat exchange structure is a gas-gas heat exchanger; and / or only heat conduction exists between the air flow downstream of the compressor and the cathode exhaust gas flow upstream of the turbine along the second heat exchange path, without mass exchange; and / or the compressor (130) is partially driven by the turbine (140); and / or the air subsystem further includes an intercooler (190), the intercooler being connected to the cathode supply pipeline downstream of the second heat exchange structure.

10. A fuel cell system (1), characterized in that, The fuel cell system includes: a fuel cell stack (3); and the air subsystem (100) according to any one of claims 1 to 9, the cathode supply pipeline (110) and the cathode exhaust pipeline (120) of the air subsystem being connected to the fuel cell stack.

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