CN104791056B - A Method for Reducing Cold Start Emissions Using Vacuum-Phase Change Insulation - Google Patents

Abstract

The invention relates to a catalytic device which utilizes vacuum-phase change heat preservation to reduce cold start emission. The device is installed on the exhaust pipe of the engine, and the catalyst carrier is wrapped with a closed cavity filled with phase-change materials so that it is in the cavity. After the engine stops, the valve switch driving device receives the signal from the electronic control unit and closes the valves on both sides of the catalytic converter. The air pump system keeps the catalytic converter in a vacuum environment to reduce the energy loss of the catalytic converter. At the same time, the phase change material is solidified during the solidification process The release of latent heat in the middle ensures that the temperature of the catalyst is high enough when the engine is restarted, shortens the time for the catalyst to reach the light-off temperature, and greatly reduces vehicle cold start emissions. After using this device to stop for 24 hours, the temperature of the catalytic converter is still maintained at 250°C. When the engine is working at a high load, the cavity is filled with air to increase its heat transfer coefficient to dissipate heat. At the same time, the phase change material absorbs heat during the melting process to ensure that the excessively high exhaust gas temperature will not deactivate the catalyst at high temperature.

Description

A Method of Using Vacuum-Phase Change Insulation to Reduce Cold Start Emissions

technical field

The invention provides a catalytic device which utilizes vacuum-phase change heat preservation to reduce cold start emission, and specifically relates to a design and control method of a novel catalytic device, which belongs to the field of internal combustion engines.

Background technique

With the rapid increase in the number of automobiles, automobile emissions have aggravated the pollution of the atmosphere and the deterioration of the environment. Automobile emissions have become the main source of urban air pollution. Reducing engine pollutant gas emissions has become one of the important issues to be solved for the continued development of internal combustion engines. The latest national standards, the country will implement the fifth phase of national motor vehicle emission standards on January 1, 2018, and Beijing will implement the fifth phase of national motor vehicle emission standards ahead of schedule on January 1, 2016. The National V standard is equivalent to the Euro V standard of the European Union. The European Union has implemented it since 2009, and its restrictions on motor vehicle emissions such as nitrogen oxides, hydrocarbons, carbon monoxide and suspended particles are more stringent. From National I to National IV, every time the standard is raised, the pollution from single vehicles will be reduced by 30% to 50%. In the emission cycle test, according to the FTP-75 test of the U.S. Environmental Protection Agency, nearly 80% of the HC and CO emissions of a gasoline engine equipped with a three-way catalytic converter are generated within the first 200s of a cold start. During the start-up phase, the exhaust gas temperature of the engine is low, and the oxygen sensor and three-way catalytic converter cannot work normally. Therefore, if measures can be taken to control the HC emission at start-up, the gasoline engine for vehicles can meet higher emission regulations.

At present, the mainstream technology for cold start emission control of gasoline vehicles is to reduce the emission of HC and CO by making the three-way catalytic converter reach the light-off temperature quickly. Increase catalyst temperature as soon as possible. However, due to the limitation of catalyst technology, the effect of the former is limited, and the content of precious metals needs to be increased, which will increase the cost of the system. Therefore, most of the research on rapid light-off of catalytic converters focuses on increasing the inlet temperature of catalytic converters as soon as possible, such as close-mounted catalytic converters, fuel heating of catalytic converters, and electric heating of catalytic converters. Close-mounted catalytic converters cannot convert HC in the first 60s after cold start; catalytic converter fuel heating requires a combustion chamber, which will generate additional emissions; catalytic converter electric heating technology is simpler in structure than fuel heating catalytic converters, but it needs to be used Catalyst temperature to reach the light-off temperature in a short time needs to consume a lot of battery power.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects of the existing engine cold start emission control device, and use the waste heat of the engine to provide a catalytic device and a control method that utilizes vacuum-phase change heat preservation to reduce cold start emissions. It can effectively reduce the exhaust gas emission when the engine is cold started.

The present invention adopts following technical scheme:

A catalytic device using vacuum-phase change heat preservation to reduce cold start emissions, characterized in that it includes an electronic control unit 5, an air pump system 4, a valve switch drive system 3, a catalyst carrier 7, a cavity 8, a phase change material 9, and a phase change material 9. The variable material 9 is arranged next to the outside of the catalyst carrier 7, and is packaged with the catalyst carrier 7 in a closed cavity, the outside of which is a cavity 8, and a pressure sensor 15 is installed in the cavity 8. The front exhaust pipe 1 and the rear exhaust The pipe 10 is equipped with a valve switch drive system 3 near the cavity 8 , and the front exhaust pipe 1 is also equipped with a temperature sensor 2 .

The method for applying the device is characterized in that the steps are as follows:

1) The device controls the opening and closing of the valve 6 according to the start signal 11 and the stop signal 12 of the engine; when the engine is running, the valve 6 remains open; when the engine starts, the electronic control unit 5 transmits the start signal 11 of the engine to the valve The switch drive system 3, the valve switch drive system 3 opens the valve 6. The temperature sensor 2 detects the temperature of the exhaust gas flowing through the front exhaust pipe 1 and transmits it to the electronic control unit 5;

When the engine is in a stopped state, the valve 6 remains closed, the cavity 8 is a vacuum cavity, and the vacuum in the cavity 8 reduces heat loss in the device;

2) When the temperature signal received by the electronic control unit 5 is greater than 800°C, the electronic control unit 5 sends an inflation signal 13 to the air pump system 4, and the air pump system 4 fills the cavity with air after receiving the inflation signal 13 until the pressure in the cavity Balanced with the external pressure; as the amount of air charged increases, the heat transfer coefficient in the cavity increases, which is conducive to the heat loss of the exhaust gas and prevents the catalyst from being deactivated at high temperature; when the temperature signal received by the electronic control unit 5 is less than 800°C, The electronic control unit 5 sends an air pumping signal 14 to the air pump system 4, and the air pump system 4 pumps air from the cavity to the outside after receiving the air pumping signal 14; as the air decreases, the heat transfer coefficient decreases and the heat loss decreases;

When the engine is stopped, the electronic control unit 5 transmits the stop signal 12 of the engine to the valve switch drive system 3, and the valve switch drive system 3 closes the valve 6. At this time, the pressure sensor 15 is used to judge whether the cavity 8 is a vacuum. If the cavity 8 is not Vacuum, the electronic control unit 5 sends an air pumping signal 14 to the air pump system 4, and the air pump system pumps air from the cavity to the outside after receiving the pumping signal 14, ensuring that the cavity 8 is a vacuum chamber in the parking state.

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.

Working principle of the present invention: the device is installed on the automobile engine exhaust pipe, wraps the catalyst carrier with a closed chamber equipped with phase change material, so that it is in the cavity with variable gas heat transfer coefficient (gas heat transfer coefficient is determined by vacuum adjustment). After the engine is stopped, close the valves on both sides of the catalytic converter so that the catalytic converter is in a vacuum environment to reduce the energy loss of the catalytic converter. At the same time, the phase change material releases latent heat during the solidification process to ensure that the catalytic converter is sufficiently high when the engine is restarted. temperature. When the engine is working at a high load, it can fill the cavity with air to increase its heat transfer coefficient and yearn for heat dissipation. At the same time, the phase change material absorbs heat during the melting process to ensure that the excessively high exhaust gas temperature will not deactivate the catalyst at high temperature. .

The beneficial effect of the invention is that, by adopting the electronically controlled vacuum-phase change heat preservation device, the temperature of the catalytic converter during the cold start of the engine is increased, the time for the catalyst to reach the light-off temperature is shortened, and the vehicle cold start emission is greatly reduced. The engine bench test shows that the temperature of the catalytic converter remains at 250°C after 24 hours of parking with this device, thereby reducing engine cold start HC emissions by more than 80%, CO emissions by more than 40%, and NOx emissions by more than 40%, so that ordinary vehicles do not Major structural changes meet Euro 4 or higher emission standards.

Description of drawings

Fig. 1 structure and working principle diagram of the present invention

In the figure: 1. Front exhaust pipe, 2. Temperature sensor, 3. Valve switch drive system, 4. Air pump system, 5. Electronic control unit, 6. Valve, 7. Catalyst carrier, 8. Cavity, 9. Phase Change material, 10, rear section exhaust pipe, 11, engine start signal, 12, engine stop signal, 13, inflation signal, 14, pumping signal, 15, pressure sensor.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the present invention will be further described:

The device mainly includes an electronic control unit 5, an air pump system 4, a valve switch drive system 3, a catalyst carrier 7, a cavity 8, and a phase change material 9, and the phase change material 9 is packaged in a closed cavity adjacent to the outside of the catalyst carrier 7. Its outer side is a cavity 8, the vacuum degree of which is adjusted by the air pump system 4 according to the inflation signal 13 and the pumping signal 14 sent by the electronic control unit 5, and the cavity 8 is equipped with a pressure sensor 15. The front section exhaust pipe 1 and the rear section The exhaust pipe 10 is equipped with a valve switch driving system 3 near the cavity 8, wherein the front exhaust pipe 1 is also equipped with a temperature sensor 2, and the driving device controls the opening and closing of the valve 6 according to the engine start signal 11 and stop signal 12 . When the engine is running, the valve 6 remains open; when the engine is stopped, the valve 6 remains closed, and the cavity 8 is a vacuum chamber.

Survey data show that more than 90% of vehicles will be restarted within 24 hours of parking, and ensuring the temperature of the engine when starting is crucial to reducing emissions when the vehicle is started. The phase change material adopts silicon-aluminum alloy material with a relatively low phase change temperature.

Using the above-mentioned automobile cold start emission adsorption device for exhaust gas adsorption is controlled according to the following steps:

1) When the engine is in a stopped state and the valve 6 is in a closed state, the vacuum in the cavity 8 can reduce the heat loss in the device. When the engine starts, the electronic control unit 5 transmits the engine start signal 11 to the valve switch drive system 3, and the valve switch drive system 3 opens the valve 6. The temperature sensor 2 detects the temperature of the exhaust gas flowing through the front exhaust pipe 1 and transmits it to the electric valve. Control unit 5.

2) When the temperature signal received by the electronic control unit 5 is greater than 800°C, the electronic control unit 5 sends an inflation signal 13 to the air pump system 4, and the air pump system 4 fills the cavity with air after receiving the inflation signal 13 until the pressure in the cavity Balance with external pressure. As the amount of air charged increases, the heat transfer coefficient in the cavity increases, which is beneficial to the heat loss of the exhaust gas and prevents the catalyst from deactivating at high temperature. When the temperature signal received by the electronic control unit 5 is less than 800°C, the electronic control unit 5 sends an air pumping signal 14 to the air pump system 4, and the air pump system 4 pumps air from the cavity to the outside after receiving the air pumping signal 14. With less air, the heat transfer coefficient decreases and heat loss decreases.

3) When the engine is stopped, the electronic control unit 5 transmits the stop signal 12 of the engine to the valve switch drive system 3, and the valve switch drive system 3 closes the valve 6. At this time, the pressure sensor 15 can be used to judge whether the cavity 8 is a vacuum. The cavity 8 is not a vacuum, the electronic control unit 5 sends an air pumping signal 14 to the air pump system 4, and the air pump system pumps air from the cavity to the outside after receiving the pumping signal 14, ensuring that the cavity 8 is a vacuum cavity in the parking state.

Claims (1)

1. A method for reducing cold-start emissions by using vacuum-phase change heat preservation, using the following device: the device includes an electronic control unit (5), an air pump system (4), a valve switch drive system (3), and a catalyst carrier (7) , a cavity (8), a phase change material (9), the phase change material (9) is arranged next to the outside of the catalyst carrier (7), and is packaged with the catalyst carrier (7) in a closed cavity, the outside of which is a cavity (8), a pressure sensor (15) is installed in the cavity (8). The front exhaust pipe (1) and the rear exhaust pipe (10) are equipped with a valve switch drive system (3) near the cavity (8), Wherein the front exhaust pipe (1) is also equipped with a temperature sensor (2); It is characterized in that the steps are as follows: 1) The device controls the opening and closing of the valve (6) according to the start signal (11) and stop signal (12) of the engine; when the engine is running, the valve (6) remains open; when the engine starts, the electronic control unit (5) ) transmits the starting signal (11) of the engine to the valve switch drive system (3), and the valve switch drive system (3) opens the valve (6); the temperature sensor (2) detects the exhaust gas flowing through the front exhaust pipe (1) The temperature is transmitted to the electric control unit (5); When the engine is in a stopped state, the valve (6) remains closed, the cavity (8) is a vacuum cavity, and the vacuum in the cavity (8) reduces the loss of heat in the device; 2) When the temperature signal received by the electronic control unit (5) is greater than 800°C, the electronic control unit (5) sends an inflation signal (13) to the air pump system (4), and the air pump system (4) receives the inflation signal (13) Fill the cavity with air until the pressure in the cavity is balanced with the external pressure; the greater the amount of air charged, the greater the heat transfer coefficient in the cavity, which is conducive to the loss of heat from the exhaust gas and prevents the catalyst from deactivating at high temperature; When the temperature signal received by the control unit (5) is less than 800°C, the electric control unit (5) sends an air pumping signal (14) to the air pump system (4), and the air pump system (4) receives the air pumping signal (14) from the air Air is pumped out of the cavity; as the air decreases, the heat transfer coefficient decreases and the heat loss decreases; When the engine is stopped, the electronic control unit (5) transmits the engine stop signal (12) to the valve switch drive system (3), and the valve switch drive system (3) closes the valve (6). At this time, the pressure sensor (15) judges Whether the cavity (8) is a vacuum, if the cavity (8) is not a vacuum, the electric control unit (5) sends an air pumping signal (14) to the air pump system (4), and the air pump system (4) receives the air pumping signal (14 ) after pumping air outwards from the cavity to ensure that the cavity (8) is a vacuum chamber in the parking state.