Research On The Technology Of Removing NOx From Diesel Engine

Diesel engines have gained wide application due to their high efficiency, economy, better power performance and economic performance and good work operation. Nitrogen oxide(NOx) are quite harmful to life and cause serious environmental disruption and the government have recognize the problem, the question how to purify NOx emission for diesel has become one of the hotspots. Regulations regarding automotive diesel engine emissions become more severe every year, and it is difficult to meet the requirements with only combustion improvement techniques, it is needed to add the diesel exhaust after-treatment systems. So the research of more effective and economical after-treatment systems is necessary and urgent.Now, the main technology of after-treatment system include:exhaust gas recirculation(EGR), non selective catalytic reduction(NSCR). selective non catalytic reduction(SNCR), selective catalytic reduction(SCR), non-thermal plasma, electrochemical reaction. Some references have showen that the SCR system can effectively reduce the NOx in waste gas and has been applied widely in developed countries but existed some problems such as reducing agent has low activity at lower temperature, easy to be crystallization around the nozzle and so forth. The catalyst poisoning due to higher sulphur content of China diesel oil restrict its application.The traditional system widely used to remove the NOx in the boiler, but it is difficult application on diesel for the exhaust temperature can not reach the reaction temperature. In this research, a new catalyst (mechanism) which has good activity at lower temperature and can used on diesel, was presented. Conversion mechanisms of using mechanism technology processing NOx in the diesel exhaust was induced,which can can provide the foundations for simulationg conversion mechanisms. In order to verify the practicality and the validity of the SNCR system, the bench test was performed on the R6105 engine, and researched the influence factors, include the jet of catalyst, injection mass, reaction temperature etc. On the basis of complete analysis of test results, proposed an optimizing scheme. Another part of the work in this dissertation is numerical simulation, a three-dimensional modeling was made on a full-sized diesel SNCR system by FIRE software of CFD. The result comparison between the numerical simulation and bench test in the same condition shows that they agreed well with those ofmeasured. The influence of temperature and time were thoroughly studied by numerical simulation, the simulation results might be helpful to design and optimize the SNCR system. The research in this paper has a valuable reference for the application of SNCR techniques.