System and method for reducing cold start emission of engine by adopting phase change heat reservoir

Abstract

The invention relates to a system for reducing cold start emission of an engine by adopting heat of a phase change storage device, which comprises a warming-up part device and an accelerating catalytic converter ignition part device which are connected in series. According to the system, a catalyst carrier and a snakelike cooling liquid water pipe are wrapped by a closed cavity filled with a phase change material, so that the catalyst carrier and the snakelike cooling liquid water pipe are positioned in a cavity with a variable gas heat transfer coefficient (the gas heat transfer coefficient is adjusted by vacuum degree). When the engine works in a high-load mode, the phase change heat storage device recovers and stores waste heat of waste gas exhausted by the engine. After the engine stops, all valves at gas and liquid inlets and outlets of the catalytic converter and the warming device are closed, so that the catalytic converter and the warming device are in a vacuum environment to reduce energy loss of the phase-change material, and when the engine is cold-started again, the phase-change material releases latent heat in the solidification process, so that the energy loss is reduced. And the temperature of the catalytic converter and the cooling liquid is ensured to be high enough when the engine is started. Waste heat of waste gas exhausted by the engine is utilized, the temperature of the catalytic converter and the temperature of cooling liquid during cold start of the engine are increased, the time for a catalyst to reach the ignition temperature is shortened, the combustion environment of cold start of the engine is improved, and oil consumption and emission of cold start of a vehicle are greatly reduced.

Description

Technical Field

[0001] The present invention provides a system and a control method for reducing engine cold start emissions by using a phase change heat storage device, and specifically relates to a system and a control method for reducing engine cold start emissions by using a phase change heat storage device, and belongs to the field of internal combustion engines. Background Art

[0002] Due to the impact of engine-powered automobile emissions on atmospheric pollution and global energy issues, energy conservation and emission reduction have become important research directions for automobile engines. At present, the key technologies for energy conservation are to improve the combustion efficiency of the engine and the recovery and utilization of the engine's waste heat, and the main measure for emission reduction is to reduce emissions during engine startup. According to the FTP-75 test of the US Environmental Protection Agency, nearly 80% of HC and CO emissions from gasoline engines equipped with three-way catalytic converters are generated within the first 200 seconds of cold start, especially in winter. The reason is that during the cold start stage, the coolant temperature is low, the fuel is not fully burned, and the engine exhaust temperature is low at this time, so the oxygen sensor and three-way catalytic converter cannot work properly. Therefore, taking measures to improve the combustion of the engine during cold start and improve the conversion efficiency of the three-way catalytic converter during cold start is of great significance to energy conservation and emission reduction.

[0003] Starting warm-up can improve the combustion of cold-start engines. However, the starting warm-up technology currently studied at home and abroad usually heats the coolant through an electric heater, which has a large power demand for the heater and high power consumption. The heater uses the direct current of the car battery, and the battery charging is also converted from the fuel consumed by the engine, which not only reduces the conversion efficiency, but also causes fuel waste. The mainstream technology for cold-start emission control of gasoline vehicles is to reduce HC and CO emissions by making the three-way catalytic converter quickly reach the ignition temperature. The main method for studying the rapid ignition of the catalyst is to reduce the ignition temperature of the catalyst and increase the catalyst temperature as soon as possible. However, due to the limitations of catalyst technology, the effect of the former is limited, and it is also necessary to increase the content of precious metals, which will increase the system cost. Therefore, the research on the rapid ignition of the catalyst is more focused on increasing the catalyst inlet temperature as soon as possible, such as close-mounted catalysts, catalyst fuel heating, and catalyst electric heating. However, the nearby catalyst cannot convert HC within the first 60 seconds after cold start; catalyst fuel heating requires a combustion chamber, which will produce additional emissions; catalyst electric heating technology is simpler in structure than fuel heating catalyst, but it consumes a lot of battery power to make the catalyst temperature reach the ignition temperature in a short time.

[0004] The present invention uses a phase change heat storage device to recover the waste heat of the exhaust gas discharged by the engine, which is used to improve the combustion temperature environment of the engine during the cold start stage and accelerate the ignition temperature of the catalytic converter. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the existing engine cold start, utilize the waste heat of the engine, and provide a system and control method for reducing engine cold start emissions using a phase change heat storage device. The system can effectively improve the combustion temperature environment of the engine, accelerate the ignition temperature of the three-way catalytic converter, and reduce the exhaust emissions during engine cold start.

[0006] The present invention adopts the following technical solution: The system adopts a phase change heat storage device to reduce the cold start emission of the engine. The system includes a warm-up device and a catalytic converter ignition acceleration device. The characteristics are as follows: the phase change material 9 is arranged next to the catalyst carrier 7 and the outer side of the serpentine coolant water pipe, and the catalytic converter 24 and the warm-up device 25 are respectively placed in the cavity 8 and the cavity 23, and the pressure sensor 15 and the pressure sensor 22 are installed in the cavity 8 and the cavity 23. Electronic valves are installed at the gas and liquid inlet and outlet of the two parts of the device, which are electronic gas valve 3, electronic gas valve 19, electronic gas valve 20, electronic gas valve 6, electronic liquid valve 18, and electronic three-way liquid valve 17. The exhaust temperature sensor 2 and the coolant temperature sensor 16 are installed at the front exhaust pipe 1 and the engine cylinder head coolant outlet. The control unit 5 receives and processes the signals of the engine and each valve and temperature sensor.

[0007] The method of applying the system as described above is characterized by the following steps: When the engine is in the parking state, the heating branches of the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, the electronic liquid valve 18, the electronic gas valve 6, and the electronic three-way liquid valve 17 are all in the closed state, and the vacuum in the cavity 8 can reduce the heat loss in the device. When the engine is started, the electronic control unit 5 transmits the engine start signal 11 to the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, the electronic gas valve 6, the electronic liquid valve 18, and the electronic three-way liquid valve 17, and the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, and the electronic gas valve 6 are opened, the exhaust passage is unblocked, the electronic liquid valve 18 is opened, and the electronic three-way liquid valve 17 is connected to the heating branch. The exhaust temperature sensor 2 and the coolant temperature sensor 16 respectively detect the exhaust temperature and the coolant temperature flowing through the front exhaust pipe 1 and the engine cylinder head coolant outlet and transmit them to the electronic control unit 5.

[0008] When the exhaust temperature signal received by the electronic control unit 5 is greater than 800°C, the electronic control unit 5 sends a charging signal 13 to the air pump system 4. After receiving the charging signal 13, the air pump system 4 fills the cavity with air until the pressure in the cavity is balanced with the external pressure. As the amount of air filled increases, the heat transfer coefficient in the cavity increases, which is conducive to the loss of exhaust gas heat and prevents the catalyst from being deactivated at high temperature. When the exhaust temperature signal received by the electronic control unit 5 is less than 800°C, the electronic control unit 5 sends a pumping signal 14 to the air pump system 4. After receiving the pumping signal 14, the air pump system 4 pumps air out of the cavity. As the air decreases, the heat transfer coefficient decreases, and the heat loss decreases. When the coolant temperature signal received by the electronic control unit 5 is higher than the pre-set temperature limit, the electronic control unit 5 controls the electronic three-way liquid valve 17 to close the heating channel through the warm-up device, connect the normal circulation channel of the coolant, end the warm-up process, and the cooling system returns to normal. The electronic liquid valve 18 remains open (to prevent the water in the serpentine coolant water pipe from being heated and vaporized to form high pressure). When the engine is operating normally, the high-temperature exhaust heats the phase change material in the warm-up device. Through the phase change process of the phase change material, the exhaust waste heat is absorbed, and the warm-up device is in a heat storage condition.

[0009] 3) When the engine is stopped, the electronic control unit 5 controls the electronic valve 3, the electronic valve 18 and the electronic three-way valve 6 to close according to the engine stop signal 12. At this time, the pressure sensor 15 is used to determine whether the cavity 8 is a vacuum. If the cavity 8 is not a vacuum, the electronic control unit 5 sends a pumping signal 14 to the air pump system 4. After receiving the pumping signal 14, the air pump system 4 pumps air from the cavity to the outside to ensure that the cavity 8 is a vacuum cavity in the parking state; the pressure sensor 22 determines whether the cavity 23 is a vacuum. If the cavity 23 is not a vacuum, the electronic control unit 5 sends a pumping signal to the air pump system 21. After receiving the pumping signal, the air pump system 21 pumps air from the cavity to the outside to ensure that the cavity 23 is a vacuum cavity.

[0010] The phase change material mentioned in this device is a silicon-aluminum alloy material, and the phase change material absorbs or releases a large amount of latent heat during the phase change process.

[0011] The working principle of the present invention is as follows: the device is installed on the exhaust pipe of the automobile engine, and the catalyst carrier and the serpentine coolant water pipe are wrapped with a closed cavity filled with phase change material, so that they are in a cavity with a variable gas heat transfer coefficient (the gas heat transfer coefficient is adjusted by the vacuum degree). After the engine is stopped, the valves at all gas and liquid inlets and outlets of the catalytic converter and the warm-up device are ensured to be in a vacuum environment to reduce the energy loss of the phase change material. At the same time, the phase change material releases latent heat during the solidification process, ensuring that the catalytic converter and the coolant are at a sufficiently high temperature when the engine is started again.

[0012] The beneficial effect of the present invention is that by adopting a phase change heat storage device, the waste heat of the exhaust gas discharged by the engine is recovered, the temperature of the catalytic converter and the coolant during the cold start of the engine is increased, the time for the catalyst to reach the ignition temperature is shortened, the combustion environment of the engine cold start is improved, and the fuel consumption and emissions of the vehicle cold start are greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The structure and working principle diagram of the present invention In the figure: 1. front exhaust pipe, 2. exhaust temperature sensor, 3. electronic air valve, 4. air pump system, 5. electronic control unit, 6. electronic three-way air valve, 7. catalyst carrier, 8. cavity, 9. phase change material, 10. rear exhaust pipe, 11. engine start signal, 12. engine stop signal, 13. charging signal, 14. exhaust signal, 15. pressure sensor, 16. coolant temperature sensor, 17. electronic three-way liquid valve, 18. electronic liquid valve, 19. electronic air valve, 20. electronic air valve, 21. air pump system, 22. pressure sensor, 23. cavity, 24. catalytic converter, 25 warm-up device DETAILED DESCRIPTION

[0014] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments: A system using a phase change heat storage device to reduce engine cold start emissions, the system includes a warm-up device and a catalytic converter ignition acceleration device, characterized in that: the phase change material 9 is arranged next to the catalyst carrier 7 and the outer side of the serpentine coolant water pipe, and the catalytic converter 24 and the warm-up device 25 are respectively placed in the cavity 8 and the cavity 23, the pressure sensor 15 and the pressure sensor 22 are installed in the cavity 8 and the cavity 23, the gas and liquid inlet and outlet of the two parts of the device are both installed with electronic valves, which are electronic gas valve 3, electronic gas valve 19, electronic gas valve 20, electronic three-way gas valve 6, electronic liquid valve 18, and electronic three-way liquid valve 17, and the front exhaust pipe 1 and the engine cylinder head coolant outlet are equipped with exhaust temperature sensor 2 and coolant temperature sensor 16. The control unit 5 receives and processes the signals of the engine and each valve and temperature sensor.

[0015] Survey data shows that more than 90% of vehicles will be restarted within 24 hours of parking. Ensuring the temperature of the engine when starting is crucial to reducing emissions when the vehicle starts.

[0016] The use of the phase change heat storage device as described above to reduce engine cold start emissions is controlled according to the following steps: 1) When the engine is in the parking state, the heating branches of the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, the electronic liquid valve 18, the electronic gas valve 6, and the electronic three-way liquid valve 17 are all in the closed state, and the vacuum in the cavity 8 can reduce the heat loss in the device. When the engine is started, the electronic control unit 5 transmits the engine start signal 11 to the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, the electronic gas valve 6, the electronic liquid valve 18, and the electronic three-way liquid valve 17, and the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, and the electronic gas valve 6 are opened, the exhaust passage is unblocked, the electronic liquid valve 18 is opened, and the electronic three-way liquid valve 17 is connected to the heating branch. The exhaust temperature sensor 2 and the coolant temperature sensor 16 respectively detect the exhaust temperature and the coolant temperature flowing through the front exhaust pipe 1 and the engine cylinder head coolant outlet and transmit them to the electronic control unit 5.

[0017] 2) When the exhaust temperature signal received by the electronic control unit 5 is greater than 800°C, the electronic control unit 5 sends a charging signal 13 to the air pump system 4. After receiving the charging signal 13, the air pump system 4 fills the cavity with air until the pressure in the cavity is balanced with the external pressure. As the amount of air filled increases, the heat transfer coefficient in the cavity increases, which is conducive to the loss of exhaust heat and prevents the catalyst from being deactivated at high temperature. When the exhaust temperature signal received by the electronic control unit 5 is less than 800°C, the electronic control unit 5 sends a pumping signal 14 to the air pump system 4. After receiving the pumping signal 14, the air pump system 4 pumps air out of the cavity. As the air decreases, the heat transfer coefficient decreases, and the heat loss decreases. When the coolant temperature signal received by the electronic control unit 5 is higher than the pre-set temperature limit, the electronic control unit 5 controls the electronic three-way liquid valve 17 to close the heating channel through the warm-up device, connect the normal circulation channel of the coolant, end the warm-up process, and the cooling system returns to normal. The electronic liquid valve 18 remains open (to prevent the water in the serpentine coolant water pipe from being heated and vaporized to form high pressure). When the engine is operating normally, the high-temperature exhaust heats the phase change material in the warm-up device. Through the phase change process of the phase change material, the exhaust waste heat is absorbed, and the warm-up device is in a heat storage condition.

[0018] 3) When the engine is stopped, the electronic control unit 5 controls the electronic valve 3, the electronic valve 18 and the electronic three-way valve 6 to close according to the engine stop signal 12. At this time, the pressure sensor 15 is used to determine whether the cavity 8 is a vacuum. If the cavity 8 is not a vacuum, the electronic control unit 5 sends a pumping signal 14 to the air pump system 4. After receiving the pumping signal 14, the air pump system 4 pumps air from the cavity to the outside to ensure that the cavity 8 is a vacuum cavity in the parking state; the pressure sensor 22 determines whether the cavity 23 is a vacuum. If the cavity 23 is not a vacuum, the electronic control unit 5 sends a pumping signal to the air pump system 21. After receiving the pumping signal, the air pump system 21 pumps air from the cavity to the outside to ensure that the cavity 23 is a vacuum cavity.

Claims

1. A system for reducing engine cold start emissions using a phase change heat storage device, the system includes a warm-up device and a catalytic converter ignition acceleration device, characterized in that: The phase change material 9 is arranged next to the catalyst carrier 7 and the outer side of the serpentine coolant water pipe, and the catalytic converter 24 and the warm-up device 25 are placed in the cavity 8 and the cavity 23 respectively. The pressure sensor 15 and the pressure sensor 22 are installed in the cavity 8 and the cavity 23. The gas and liquid inlet and outlet of the two parts of the device are equipped with electronic valves, which are electronic gas valve 3, electronic gas valve 19, electronic gas valve 20, electronic gas valve 6, electronic liquid valve 18, and electronic three-way liquid valve 17. The exhaust temperature sensor 2 and the coolant temperature sensor 16 are installed at the front exhaust pipe 1 and the engine cylinder head coolant outlet. The control unit 5 receives and processes the signals of the engine and each valve and temperature sensor. A method for applying the system as described above, characterized in that The steps are as follows: (1) When the engine is in the parking state, the heating branches of the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, the electronic liquid valve 18, the electronic gas valve 6, and the electronic three-way liquid valve 17 are all in the closed state, and the vacuum in the cavity 8 can reduce the heat loss in the device. When the engine is started, the electronic control unit 5 transmits the engine start signal 11 to the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, the electronic gas valve 6, the electronic liquid valve 18, and the electronic three-way liquid valve 17, and the electronic gas valve 3, the electronic gas valve 19, the electronic gas valve 20, and the electronic gas valve 6 are opened, the exhaust passage is unblocked, the electronic liquid valve 18 is opened, and the electronic three-way liquid valve 17 is connected to the heating branch. The exhaust temperature sensor 2 and the coolant temperature sensor 16 respectively detect the exhaust temperature and the coolant temperature flowing through the front exhaust pipe 1 and the engine cylinder head coolant outlet and transmit them to the electronic control unit 5. (2) When the exhaust temperature signal received by the electronic control unit 5 is greater than 800°C, the electronic control unit 5 sends a charging signal 13 to the air pump system 4. After receiving the charging signal 13, the air pump system 4 fills the cavity with air until the pressure in the cavity is balanced with the external pressure. As the amount of air filled increases, the heat transfer coefficient in the cavity increases, which is conducive to the dissipation of exhaust gas heat and prevents the catalyst from being deactivated at high temperature. When the exhaust temperature signal received by the electronic control unit 5 is less than 800°C, the electronic control unit 5 sends a pumping signal 14 to the air pump system 4. After receiving the pumping signal 14, the air pump system 4 pumps air out of the cavity. As the amount of air decreases, the heat transfer coefficient decreases, and the heat loss decreases. When the coolant temperature signal received by the electronic control unit 5 is higher than the pre-set temperature limit, the electronic control unit 5 controls the electronic three-way liquid valve 17 to close the heating channel through the warm-up device, connect the normal circulation channel of the coolant, end the warm-up process, and the cooling system returns to normal. The electronic liquid valve 18 remains open (to prevent the water in the serpentine coolant water pipe from being heated and vaporized to form high pressure). When the engine is working normally, the high-temperature exhaust heats the phase change material in the warm-up device, and the phase change process of the phase change material absorbs the exhaust waste heat, and the warm-up device is in a heat storage state. 3) When the engine stops, the electronic control unit 5 controls the electronic valve 3, the electronic valve 18 and the electronic three-way valve 6 to close according to the engine stop signal 12. At this time, the pressure sensor 15 determines whether the cavity 8 is a vacuum. If the cavity 8 is not a vacuum, the electronic control unit 5 sends a pumping signal 14 to the air pump system 4. After receiving the pumping signal 14, the air pump system 4 pumps air from the cavity to the outside to ensure that the cavity 8 is a vacuum cavity in the parking state; the pressure sensor 22 determines whether the cavity 23 is a vacuum. If the cavity 23 is not a vacuum, the electronic control unit 5 sends a pumping signal to the air pump system 21. After receiving the pumping signal, the air pump system 21 pumps air from the cavity to the outside to ensure that the cavity 23 is a vacuum cavity.

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