Development And Experiment On Electronic Control System Of SCR For Diesel Engine

Recently, with the rapid growth of China's automobile industry, it brings people much convenience, while its impact on the environment is becoming serious. The automobile exhuast constructs a serious threat to people's health and safety. The industry faces a great challenge.NOx are the main emissions of diesel and cannot be effectively solved. It can not meet the requirements of increasing stringent emissions regulations. We must rely on exhaust after-treatment technology. In all technology routes to reduce NOx emissions two methods are concluded:one is reducing NOx emissions with SCR(Selective Catalytic Reduction) technology on the basis of combusion optimization for diesel engines to reduce PM, and the other to debase NOx emissions with EGR(Exhaust Gas Recirculation) and PM with DPF. To meet good fuel economy, Euro IV and V emission regulations, domestic and international research focus on SCR technology. SCR technology will become the most effective measure in reducing automobile exhaust.The paper first introduces composition and work principle of SCR control system. Then gives the open-loop control strategy, that is, the basic injection amount of urea is calculated according to engine speed and load to search the steady-state MAP and add the compensation of catalyst temperature and NH3 slip model. The control strategy descripts the urea inject calculation, correct model base on catalyst temperature and NH3 slip in detail.In this study, SCR electronic control system was built and hardware and software design of DCU was completed, including choice of microprocessor, sensor signal acquisition, driver of urea pump, nozzles and heating valve, and CAN communication interface design. In software program, the urea injection control system is divided into five stages (standby, no pressure control, pressure control, pressure reduction and afterrun) to meet precise measurement of urea.Finally, NOx emission experiment was executed on engine with SCR electronic control system. The result shows that SCR electric control system has a significant effect on reduction of NOx emission. In summary, this study has reference value to development commercial diesel engine whic can satisfy Chinaâ…£emission limits, and has realistic social meaning to China for reducing commercial automobile diesel engine emissions and air pollution.