Development Of Selective Catalytic Reduction(DOC/POC/SCR) Technology For Vehicle Diesel Engine

In recent years,haze has become the focus of attention to air quality,There are divergent views on the causes of this phenomenon.But,with the rapid growth of China's car ownership,the pollutants of automobile exhaust become a major cause of air pollution,Heavy-duty diesel engine exhaust pollution is more serious,among them,particulate matter and nitrogen oxides are the main pollutants.In order to alleviate the air pollution,our government sequentially enact strict automobile exhaust emission regulations,at present,the national emission standard is country ?.In this paper,through the study of exhaust aftertreatment system to achieve the existing high pressure common rail diesel engine upgrade country ? transformation.This paper frist using YC4F115-40 high pressure common rail engine for the bench test,For the engine bench test without adding any exhaust gas aftertreatment systems,The emission concentration of pollutants in exhaust gas was measured using a five-component exhaust gas analyzer,Especially the NOx emission concentration;Then,Add the traditional urea SCR system to measure the emission concentration of pollutants in exhaust gas again under the same operating conditions,compare and drawing the NOx emission concentration with the exhaust temperature curve,simulating the urea SCR system by FIRE——a CFD software,verifying the reducing effectiveness of 32.5% urea aqueous solution for NOx at the reaction cycle.The test results show that the emission concentration of NOx is stable below 260 ppm after purification,only to meet the country ? emission standards.This paper found that the urea aqueous solution had the phenomenon of crystallization and freezing at low temperature through the research of the traditional urea SCR aftertreatment system.Because of these,we developed a new reducing agent 40% methylamine aqueous solution and use vanadium-based catalyst methylamine SCR system,measurementing the NOx emission concentration with the exhaust temperature curve by bench scale test.Eventually,the NOx emission concentration can be reduced to about 300 ppm and NOx conversion rate can reach about 75%,and the market mainstream urea SCR system is not very different.In order to complete the retrofitting of high pressure common rail diesel engine upgrade country ? emission standards,this paper has developed a aftertreatment system of DOC + POC + methylamine SCR combination,To install the system of diesel engine carried out a series of engine bench test,and mapped the NOx emission concentration changes with the temperature curve and NOx conversion rate curve.the NOx emission concentration can be stable at the below 180 ppm and the NOx conversion rate can reach about 85% and the NOx emission concentration is around 1.9 g / Kw.h measured by ESC cycle test conditions,it has reached the current national requirements of the country ? emission levels,the aftertreatment system has real significance for the retrofitting of high pressure common rail diesel engine upgrade country ? emission standards.