Development And Experimental Of SCR Electronic Control System For Diesel Engine

In response to the state IV and future state V emissions regulations, it is essential to develop advanced after-treatment technology of diesel engine. SCR(selective catalytic reduction) technology, because of its low requirement of sulfur content in fuel and economic advantages, has become the mainstream route of the domestic diesel engine after-treatment technology. At the moment, the intellectual property of many SCR products on the market is in the hands of foreign companies, and the prices remain high. Therefore, it is necessary to develop SCR electronic control system with independent intellectual property rights.In this paper, an Weichai Diesel Engine WD10 is taken as the research object. The open-loop control strategy based on pulse spectrum was proposed. And the electronic control unit of SCR system was developed independently. The SCR system simulation model was established using Matlab/Simulink, and the engine bench test was carried out. The main research contents and conclusions are as follows:The selection mechanical components of SCR system was selected, and the hardware functional requirements of SCR system was analyzed. The design of the hardware circuit with Renesas V850ES/FJ3 uPD70F3380 as the core for SCR system.For the vehicle voltage fluctuation problem, a flyback switching power source was designed. A double H bridge driving circuit was designed for metering pump stepper motor. The hardware system includes the CAN communication module, the analog signal acquisition circuit, the switch driver circuit and so on.The open-loop control algorithm of SCR based on Matlab/Simulink was designed. By using the generation code toolbox to generate the C code for the uPD70F3380 microcontroller. The code was imported into the underlying driver function based on Cubesuites+. After debugging and compilation, the control strategy was downloaded to the microcontroller.On the basis of the existing experimental conditions and experimental equipment, a test bench was built. In the urea injection stability test, the stability of the injection under different air pressure was studied. Comprehensive consideration of the atomization effect and gas consumption, the constant pressure of compressed air was set to 4bar finally. And the injection volume of air pressure is modified, which improved the accuracy of injection significantly. The electronic control system of SCR was tested by ESC test. By calibrating the injection volume, the "NO_x" emission load of SCR system in ESC cycle was controlled in 3.2g/kw.h, and the leakage amount of Ammonia was 0, which could meet the limiting value of state IV emission regulations.