Fuel cell engine waste heat utilization system based on co2 heat pump and control method

Abstract

The present application relates to fuel cell waste heat utilization technical field, specifically to a kind of based on CO2 heat pump's fuel cell engine waste heat utilization system and control method, including fuel cell engine intake and exhaust system, fuel cell engine cooling system and fuel cell waste heat utilization system, fuel cell engine intake and exhaust system is equipped with air compressor, fuel cell stack and condensing heat exchanger, air compressor built-in expander, fuel cell engine intake and exhaust system is connected fuel cell waste heat utilization system by condensing heat exchanger, fuel cell waste heat utilization system is equipped with CO2 compressor and evaporative heat exchanger, evaporative heat exchanger connects CO2 compressor, fuel cell waste heat utilization system is connected fuel cell engine cooling system by evaporative heat exchanger, fuel cell engine cooling system is equipped with cooling water pump and radiator, the present application improves the energy conversion efficiency of whole vehicle, reduces the heat dissipation load of fuel cell engine radiator.

Description

Technical Field

[0001] This invention relates to the field of fuel cell waste heat utilization technology, specifically to a fuel cell engine waste heat utilization system and control method based on a CO2 heat pump. Background Technology

[0002] Hydrogen fuel cells are considered the best way to utilize hydrogen energy due to their advantages of high energy density, low noise, zero emissions, and the fact that the only byproduct is water. Among them, proton exchange membrane fuel cells (PEMFCs) have become a research hotspot due to their advantages such as low operating temperature, fast start-up, high power density, and modularity for easy promotion, and are currently the most widely used fuel cells.

[0003] Reliability and durability have always been important factors restricting the further application and commercialization of PEMFC. Thermal management is considered an important factor affecting the performance and durability of fuel cells. Among them, heat dissipation is the main challenge faced by high-power operation in high-temperature environments. Especially in harsh environments such as high temperature, high altitude, and dryness, the heat dissipation capacity often cannot meet the requirements, and the proportion of parasitic energy consumption in heat dissipation is high, resulting in poor fuel cell performance and low operating efficiency.

[0004] For high-power water-cooled fuel cell systems, liquid cooling is generally used to remove heat generated by the fuel cell stack through liquid cooling media such as deionized water, deionized water and ethylene glycol solutions, nanofluids containing nanoparticles, and phase change materials, before releasing it to the external environment or utilizing it. However, the heat dissipation requirements of high-power fuel cell engines are approximately 1.5-1.8 times their power output. For example, a 200kW fuel cell engine requires approximately 300kW of heat dissipation. Since all the heat from the fuel cell engine is removed by the cooling system, there is an urgent need to increase the heat dissipation capacity of the fuel cell cooling system. Therefore, it is necessary to design a waste heat utilization system and control method for fuel cell engines based on CO2 heat pumps to solve the problems of high energy consumption, poor performance, and low operating efficiency in existing fuel cell cooling systems. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a waste heat utilization system and control method for a fuel cell engine based on a CO2 heat pump.

[0006] The technical solution adopted by this invention to solve its technical problem is: a fuel cell engine waste heat utilization system based on a CO2 heat pump, comprising a fuel cell engine intake and exhaust system, a fuel cell engine cooling system, and a fuel cell waste heat utilization system. The fuel cell engine intake and exhaust system is equipped with an air compressor, a fuel cell stack, and a condenser heat exchanger. The air compressor has a built-in expander. The fuel cell engine intake and exhaust system is connected to the fuel cell waste heat utilization system through the condenser heat exchanger. The fuel cell waste heat utilization system is equipped with a CO2 compressor and an evaporator heat exchanger. The evaporator heat exchanger is connected to the CO2 compressor. The CO2 compressor is connected to the condenser heat exchanger through a fifth three-way valve. The fuel cell waste heat utilization system is connected to the fuel cell engine cooling system through the evaporator heat exchanger. The fuel cell engine cooling system is equipped with a cooling water pump and a radiator. The cooling water pump is connected to the fuel cell stack and the evaporator heat exchanger. The evaporator heat exchanger is connected to the radiator.

[0007] Preferably, the fuel cell engine intake and exhaust system further includes an air filter, an intercooler, a first three-way valve, a second three-way valve, a gas-water separator, a first temperature sensor, a fourth three-way valve, a gas flow meter, a blower, and a gas injection device. The air filter is mounted on an air compressor, which is connected to the intercooler. The intercooler is connected to the air inlet of the fuel cell stack. The air outlet of the fuel cell stack is connected to the intercooler and the condenser heat exchanger via the first three-way valve. The intercooler and the condenser heat exchanger are then connected back to the air compressor via the second three-way valve. The air compressor is connected to the gas-water separator, which is connected to the fourth three-way valve via a gas pipeline. The first temperature sensor is installed on the first gas pipeline. The fourth three-way valve is connected to the blower via a gas pipeline. A gas flow meter is installed on the second gas pipeline. The blower is connected to the gas injection device.

[0008] Preferably, the gas injection device is located near the surface of the radiator, and the gas injection device injects low-temperature exhaust gas onto the surface of the radiator.

[0009] Preferably, the fuel cell waste heat utilization system also includes a vehicle air conditioner, a third three-way valve, and an expansion valve. The vehicle air conditioner is connected to the third three-way valve and a fifth three-way valve. The fifth three-way valve is connected to the outlet of the CO2 compressor. The inlet of the CO2 compressor is connected to the evaporator heat exchanger. The fifth three-way valve is connected to the condenser heat exchanger. The condenser heat exchanger is connected to the third three-way valve. The third three-way valve is connected to the expansion valve. The expansion valve is connected back to the evaporator heat exchanger. The vehicle air conditioner uses the waste heat for heating the cab, or uses the waste heat through the condenser heat exchanger to heat the exhaust gas.

[0010] Preferably, the fuel cell engine cooling system is further provided with a second temperature sensor and a third temperature sensor. The inlet of the cooling water pump is connected to the coolant outlet of the fuel cell stack through a water pipe. The third temperature sensor is installed on the water pipe. The outlet of the cooling water pump is connected to the radiator. The radiator is connected to the coolant inlet of the fuel cell stack through a water pipe. The second temperature sensor is installed on the water pipe.

[0011] A control method for a waste heat recovery system of a fuel cell engine based on a CO2 heat pump includes the following steps:

[0012] S1. When the fuel cell engine starts, the vehicle control braking signal is obtained, and the connection direction of the fifth three-way valve in the fuel cell waste heat utilization system based on the braking signal is determined.

[0013] S2. When the vehicle air conditioning system requests heating, the fifth three-way valve turns on the vehicle air conditioning system and uses the waste heat of the vehicle air conditioning system to heat the cab.

[0014] S3. When the vehicle's air conditioning does not request heating, the fifth three-way valve connects to the condenser heat exchanger, using the waste heat from the condenser heat exchanger to heat the exhaust gas, and then recovering the waste heat through the air compressor with an expander in the fuel cell engine's intake and exhaust system.

[0015] Preferably, in step S1, when the fuel cell engine starts, the real-time ambient temperature Th and exhaust gas temperature Tp of the system are obtained.

[0016] If Th≥2*Tp, the gas injection device for the low-temperature exhaust gas of the fuel cell is turned on towards the blower, and the exhaust gas is injected onto the radiator core.

[0017] If Th < 2*Tp, the gas injection device for the low-temperature exhaust gas of the fuel cell is shut off towards the blower, and the exhaust gas is directly discharged.

[0018] The present invention has the following beneficial effects:

[0019] The present invention relates to a waste heat utilization system and control method for fuel cell engines based on CO2 heat pumps. In summer, the heat generated by the fuel cell engine is used to heat the exhaust gas of the engine and to recover energy by using an expander. In winter, the heat is mainly used for heating the vehicle's cab, thereby achieving all-weather utilization of fuel cell engine waste heat, improving the energy conversion efficiency of the vehicle, reducing the heat dissipation load of the fuel cell engine radiator, and improving the performance and operating efficiency of the fuel cell engine. Attached Figure Description

[0020] Figure 1This is a structural block diagram of a waste heat utilization system for a fuel cell engine based on a CO2 heat pump.

[0021] In the diagram: 1-Air filter; 2-Air compressor; 3-Intercooler; 4-Fuel cell stack; 5-Condensing heat exchanger; 6-Gas-water separator; 7-First temperature sensor; 8-Fourth three-way valve; 9-Gas flow meter; 10-Blower; 11-Gas injection device; 12-Second temperature sensor; 13-Radiator; 14-Evaporative heat exchanger; 15-Cooling water pump; 16-Third temperature sensor; 17-First three-way valve; 18-Second three-way valve; 19-Fifth three-way valve; 20-CO2 compressor; 21-Vehicle air conditioner; 22-Third three-way valve; 23-Expansion valve. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1 As shown, a waste heat utilization system for a fuel cell engine based on a CO2 heat pump includes an intake and exhaust system for a fuel cell engine with an air compressor and an expander, a cooling system for a fuel cell engine with waste heat recovery, and a waste heat utilization system for a fuel cell engine based on a CO2 heat pump. The intake and exhaust system for the fuel cell engine includes an air filter 1, an air compressor 2, an intercooler 3, a fuel cell stack 4, a condenser heat exchanger 5, a first three-way valve 17, a second three-way valve 18, a gas-water separator 6, a first temperature sensor 7, a fourth three-way valve 8, a gas flow meter 9, a blower 10, and a gas injection device 11. The air compressor 2 has a built-in expander, and the air filter is installed on the air compressor.

[0024] Air compressor 2 is connected to intercooler 3, intercooler 3 is connected to the air inlet of fuel cell stack 4, and the air outlet of fuel cell stack 4 is connected to intercooler 3 and condenser heat exchanger 5 through first three-way valve 17. Intercooler 3 and condenser heat exchanger 5 are then connected back to air compressor 2 through second three-way valve 18. Air compressor 2 is connected to gas-water separator 6, gas-water separator 6 is connected to fourth three-way valve 8 through gas pipeline 1, first temperature sensor 7 is installed on gas pipeline 1, fourth three-way valve 8 is connected to blower 10 through gas pipeline 2, gas flow meter 9 is installed on gas pipeline 2, and blower 10 is connected to gas injection device 11.

[0025] The air-water separator 6 is used to separate excess water from the exhaust pipe, preventing water from being sprayed onto the surface of the radiator 13 and causing the entire vehicle to be in a humid environment.

[0026] A fourth three-way valve 8 was added at the rear end of the blower 10 near the air-water separator 6. The fourth three-way valve 8 is mainly used to control the amount of exhaust gas sprayed onto the surface of the radiator 13 core.

[0027] The fuel cell engine's intake and exhaust systems are connected to the fuel cell waste heat recovery system via a condenser heat exchanger 5. The fuel cell waste heat recovery system includes a CO2 compressor 20, an evaporator heat exchanger 14, a vehicle air conditioner 21, a third three-way valve 22, and an expansion valve 23. The evaporator heat exchanger 14 is connected to the CO2 compressor 20. The CO2 compressor 20 is connected to the condenser heat exchanger 5 via a fifth three-way valve 19. The vehicle air conditioner 21 is connected to both the third three-way valve 22 and the fifth three-way valve 19. The fifth three-way valve 19 is connected to the outlet of the CO2 compressor 20, and the inlet of the CO2 compressor 20 is connected to the evaporator heat exchanger 14. The fifth three-way valve 19 is connected to the condenser heat exchanger 5, the condenser heat exchanger 5 is connected to the third three-way valve 22, the third three-way valve 22 is connected to the expansion valve 23, and the expansion valve 23 is connected back to the evaporator heat exchanger 14. The vehicle uses the waste heat from the vehicle air conditioner 21 to heat the cab, or uses the waste heat from the condenser heat exchanger 5 to heat the exhaust gases, thus achieving waste heat recovery and utilization across the entire temperature range.

[0028] The fuel cell waste heat recovery system is connected to the fuel cell engine cooling system via an evaporative heat exchanger 14. The fuel cell engine cooling system includes a cooling water pump 15, a radiator 13, a second temperature sensor 12, and a third temperature sensor 16. The cooling water pump 15 is connected to the fuel cell stack 4 and the evaporative heat exchanger 14, and the evaporative heat exchanger 14 is connected to the radiator 13. The inlet of the cooling water pump 15 is connected to the coolant outlet of the fuel cell stack 4 via a water pipe, and the third temperature sensor 16 is installed on the water pipe. The outlet of the cooling water pump 15 is connected to the radiator 13, and the radiator 13 is connected to the coolant inlet of the fuel cell stack 4 via a water pipe, and the second temperature sensor 12 is installed on the water pipe.

[0029] Evaporative heat exchanger 14 is mainly used to absorb the heat carried out by the heat dissipation system of fuel cell engine, so as to realize the utilization of the engine's waste heat.

[0030] The fifth three-way valve 19, controlled by the heating demand signal of the vehicle air conditioning 21, connects the vehicle air conditioning 21 when the vehicle needs air conditioning heating, and uses the waste heat of the vehicle air conditioning 21 to heat the cab; when the vehicle does not need air conditioning heating, the fifth three-way valve 19 connects the condenser heat exchanger 5, and uses the waste heat of the condenser heat exchanger 5 to heat the exhaust gas, and the waste heat is recovered and utilized by the air compressor 2 with expander in the intake and exhaust system of the fuel cell engine.

[0031] An air compressor 2 with an expander is connected to a fuel cell waste heat utilization system of a CO2 heat pump via an evaporative heat exchanger 14, thereby realizing the utilization and recovery of waste heat from fuel cell engine exhaust gas and fuel cell engine cooling system, and cooling the exhaust gas to 10°C. Furthermore, the exhaust gas passing through the expander can be used to increase the heat dissipation capacity of the cooling system.

[0032] The dual-jet system has multiple gas injection devices 11 installed on the surface of the radiator core. The gas injection devices 11 are close to the surface of the radiator 13. The gas injection devices 11 spray low-temperature exhaust gas onto the surface of the radiator 13, thereby reducing the gas problem around the radiator 13, thereby increasing the gas-liquid temperature difference of the radiator 13, and thus increasing the heat dissipation of the radiator 13.

[0033] A control method for a waste heat recovery system of a fuel cell engine based on a CO2 heat pump includes the following steps:

[0034] 1. When the fuel cell engine starts, it obtains the vehicle control braking signal and determines the connection direction of the fifth three-way valve in the fuel cell waste heat utilization system based on the braking signal.

[0035] 2. When the vehicle's air conditioning system requests heating, the fifth three-way valve connects the vehicle's air conditioning system, using the waste heat from the vehicle's air conditioning system to heat the driver's cab.

[0036] 3. When the vehicle's air conditioning does not request heating, the fifth three-way valve connects to the condenser heat exchanger, using the waste heat from the condenser heat exchanger to heat the exhaust gas, and then recovering the waste heat through the air compressor with an expander in the intake and exhaust system of the fuel cell engine.

[0037] When the fuel cell engine starts, the real-time ambient temperature Th and exhaust gas temperature Tp of the system are obtained through temperature sensors.

[0038] If Th≥2*Tp, the gas injection device 11 for the low-temperature exhaust gas of the fuel cell is connected to the blower 10, and the exhaust gas is injected onto the core of the radiator 13 to increase the heat dissipation capacity of the radiator 13.

[0039] If Th < 2*Tp, the gas injection device 11 for the low-temperature exhaust gas of the fuel cell is closed in the direction of the blower 10, and the exhaust gas is directly discharged.

[0040] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0041] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A waste heat recovery system for a fuel cell engine based on a CO2 heat pump, characterized in that, The system includes a fuel cell engine intake and exhaust system, a fuel cell engine cooling system, and a fuel cell waste heat recovery system. The fuel cell engine intake and exhaust system is equipped with an air compressor, a fuel cell stack, and a condenser heat exchanger. The air compressor has a built-in expander. The fuel cell engine intake and exhaust system is connected to the fuel cell waste heat recovery system through the condenser heat exchanger. The fuel cell waste heat recovery system is equipped with a CO2 compressor and an evaporator heat exchanger. The evaporator heat exchanger is connected to the CO2 compressor. The CO2 compressor is connected to the condenser heat exchanger through a fifth three-way valve. The fuel cell waste heat recovery system is connected to the fuel cell engine cooling system through the evaporator heat exchanger. The fuel cell engine cooling system is equipped with a cooling water pump and a radiator. The cooling water pump is connected to the fuel cell stack and the evaporator heat exchanger. The evaporator heat exchanger is connected to the radiator.

2. The waste heat recovery system for a fuel cell engine based on a CO2 heat pump according to claim 1, characterized in that, The fuel cell engine intake and exhaust system also includes an air filter, an intercooler, a first three-way valve, a second three-way valve, a gas-water separator, a first temperature sensor, a fourth three-way valve, a gas flow meter, a blower, and a gas injection device. The air filter is installed on the air compressor, which is connected to the intercooler. The intercooler is connected to the air inlet of the fuel cell stack. The air outlet of the fuel cell stack is connected to the intercooler and the condenser heat exchanger via the first three-way valve. The intercooler and the condenser heat exchanger are then connected back to the air compressor via the second three-way valve. The air compressor is connected to the gas-water separator, which is connected to the fourth three-way valve via gas pipeline one. The first temperature sensor is installed on gas pipeline one. The fourth three-way valve is connected to the blower via gas pipeline two. A gas flow meter is installed on gas pipeline two. The blower is connected to the gas injection device.

3. The waste heat recovery system for a fuel cell engine based on a CO2 heat pump according to claim 2, characterized in that, The gas injection device is located near the surface of the radiator, and the gas injection device injects low-temperature exhaust gas onto the surface of the radiator.

4. The waste heat recovery system for a fuel cell engine based on a CO2 heat pump according to claim 1, characterized in that, The fuel cell waste heat utilization system also includes a vehicle air conditioner, a third three-way valve, and an expansion valve. The vehicle air conditioner is connected to the third three-way valve and the fifth three-way valve. The fifth three-way valve is connected to the outlet of the CO2 compressor. The inlet of the CO2 compressor is connected to the evaporator heat exchanger. The fifth three-way valve is connected to the condenser heat exchanger. The condenser heat exchanger is connected to the third three-way valve. The third three-way valve is connected to the expansion valve. The expansion valve is connected back to the evaporator heat exchanger. The vehicle air conditioner uses the waste heat for heating the cab, or uses the waste heat through the condenser heat exchanger to heat the exhaust gas.

5. The waste heat recovery system for a fuel cell engine based on a CO2 heat pump according to claim 1, characterized in that, The fuel cell engine cooling system is also equipped with a second temperature sensor and a third temperature sensor. The inlet of the cooling water pump is connected to the coolant outlet of the fuel cell stack through a water pipe. The third temperature sensor is installed on the water pipe. The outlet of the cooling water pump is connected to the radiator. The radiator is connected to the coolant inlet of the fuel cell stack through a water pipe. The second temperature sensor is installed on the water pipe.

6. The control method for a waste heat recovery system of a fuel cell engine based on a CO2 heat pump according to any one of claims 1-5, characterized in that, Includes the following steps: S1. When the fuel cell engine starts, the vehicle control braking signal is obtained, and the connection direction of the fifth three-way valve in the fuel cell waste heat utilization system based on the braking signal is determined. S2. When the vehicle air conditioning system requests heating, the fifth three-way valve turns on the vehicle air conditioning system and uses the waste heat of the vehicle air conditioning system to heat the cab. S3. When the vehicle's air conditioning does not request heating, the fifth three-way valve connects to the condenser heat exchanger, using the waste heat from the condenser heat exchanger to heat the exhaust gas, and then recovering the waste heat through the air compressor with an expander in the fuel cell engine's intake and exhaust system.

7. The control method for a waste heat recovery system of a fuel cell engine based on a CO2 heat pump according to claim 6, characterized in that, In step S1, when the fuel cell engine starts, the real-time ambient temperature Th and exhaust gas temperature Tp of the system are obtained. If Th≥2*Tp, the gas injection device for the low-temperature exhaust gas of the fuel cell is turned on towards the blower, and the exhaust gas is injected onto the radiator core. If Th < 2*Tp, the gas injection device for the low-temperature exhaust gas of the fuel cell is shut off towards the blower, and the exhaust gas is directly discharged.

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