Numerical Simulation And Experimental Study Of The Diesel Urea-SCR System

As the environment problem is increasingly highlight, car emissions limits of different countries are more and more strict as well. Euro IV standard of diesel engine has already been implemented, and the State IV emission standard will be carried on this year or next year, and this would make higher demands on diesel emission control. Selective catalytic reduction (SCR) technology as an efficient way to reduce NOx in the exhaust gas aftertreatment, has been adopted by more and more car manufacturers.This article introduces several kinds of common technology of diesel inside and outside purification treatment, and analyses their advantages and the existing problems respectively. Also, compares the two main technical routes (EGR+DPF and optimize combustion+SCR) to get suitable technical route for our country. Then the composition and working principle of Urea-SCR system are introduced in detail, and the key factors influencing the SCR reaction and NOx conversion efficiency are analyzed according to the mechanism of catalytic reaction.Selecting model for Urea-SCR system which is based on FLUENT software, and reactor modeling and numerical simulation of the SCR system are curried on through FLUENT software. NOx conversion rate has been studied in the different reaction temperature, time and ammonia nitrogen ratio. Then according to the model to get the best reaction condition which is almost correspond to the overall trend in literature at home and abroad.According to GB17691.2005diesel engine emission standard, ESC bench experiment and ETC simulation test are carried on for WP10engine of Weichai, and gets the original NOx emissions and NOx emissions after assembling SCR system of ESC test cycle for this type engine, and draws the NOx fuel consumption contour map of ETC simulation test(MAP). The result shows that NOx conversion rate of the two tests both reach more than70%, and the reduced emission values conform to the IV emission standards.Finally the article introduces one new test method of internal purification technology (inlet water spray), and analyses the NOx emission under different amount of water injection. The result shows the highest conversion rate can reach30%. Then it makes a comparison with the SCR technology, and analyses the advantages and existing problems of two kinds of technology.