Diesel engines have the characteristics of high torque and good fuel economy. They are widely used in commercial vehicles, engineering and agricultural machinery, fixed power units, ships and national defense equipment. However, their exhaust emissions are one of the main factors causing air pollution and smog. The emission level of my country's diesel engines is two levels different from that of developed countries such as Europe, America and Japan, which has seriously affected the technological progress and development of supporting diesel engines (vehicles). Relying on scientific research projects such as 973, this project has developed an efficient, low-cost and environmentally friendly diesel engine (vehicle) exhaust purification technology. The main invention points are as follows:
1. Design and preparation technology of efficient diesel engine (vehicle) exhaust purification catalysts. A W-Mn-Fe-based NOx selective catalytic reduction (SCR) catalyst was invented, which reduced the 50% conversion temperature of NOx to 160 degrees Celsius, improving the low-temperature reduction efficiency; the invented low-vanadium-based SCR catalyst has a NOx purification rate>90%, degradation rate in 1000 hours aging test<10%；发明的柴油氧化型催化剂(DOC)对CO和HC具有优异的氧化性能，同时还具有高的NO氧化性能；发明的催化型颗粒物捕集器(CDPF)，实现再生效率>95%。
2. Preparation technology of large size monolithic catalysts. The "vacuum coating-vacuum extraction" monolithic catalyst coating technology was invented, which solved the problem of poor production consistency of large size monolithic catalysts. The invention invented a size ceramic carrier normal temperature skin grafting and hot air humidification technology, which solved the problems that the size ceramic carrier skin grafting process requires secondary high-temperature roasting and low yield, increasing the pass rate of the carrier by 20%, and reducing production energy consumption by 40%.
3. High-precision and high-reliability urea injection control technology for NOx catalytic reduction system (SCR). Aiming at the problems of poor stability in urea injection quantity control, large emission fluctuations, lag in control, and difficulty in consistency to meet requirements in the traditional "single feedback" circuit, a "double feedback" circuit is designed to realize feedback control of NOx sensor signals and motor speed signals. The steady-state and transient injection accuracy has been doubled, and emissions have reached the fifth national standard; in view of the problem that the motor driving current is difficult to take into account various working conditions and the calorific value is large, a closed-loop control protection circuit has been designed to realize the motor's automatic adjustment of the current and reduce the calorific value., improving the reliability of the product.
4. Efficient SCR system flow field distribution and control technology. Multiple gas-liquid mixing modes are used to improve the atomization quality of urea aqueous solution, with the average spray particle size (SMD) of less than 30 microns (more than 40 microns in foreign countries); a reverse thrust one-way valve structure is used to prevent and control urea crystallization in the metering pump; Optimize the urea injection system pipelines, nozzle positions, injection angles and mixing flow fields, and evenly distribute the flow field to avoid ammonia leakage.
5. Complete machine matching technology and engineering application. The steady-state and transient calibration processes for controlling urea injection quantity for diesel engine bench and vehicle have been developed, realizing the control of NOx emissions of diesel engines under all operating conditions, forming a complete set of calibration and matching technical specifications for diesel engines and vehicle, and establishing a complete engineering application workflow and testing and evaluation methods, and establishing an SCR system matching calibration application system.
This project has obtained 19 China invention patents, 10 utility model patents, 1 U.S. invention patent, published 16 SCI papers, and formed 8 industry standards (publicity stage). It has become a major supplier to diesel engine main engine factories such as Shangchai, Weichai, Yuchai, and Xichai, with additional sales of 1.18 billion yuan. At the same time, this technology has also been promoted to Shanghai Langte Automobile Purifier Co., Ltd., forming a mass production capacity. The products produced are exported to South Korea. It provides public transportation facilities in 42 large and medium-sized cities such as Beijing and Shanghai, with a coverage rate of 85%. The complete industrial chain of diesel engine exhaust aftertreatment and purification technology established in this project has filled the gap in my country's internal combustion engine aftertreatment industry, broken the technological monopoly, and achieved huge economic and social benefits. The project results provide strong support and guarantee for the full implementation of the fourth national emission standards.