Study On Influence Of Pipe Layout And Exhaust Condition To Diesel Engine SCR

Along with the implement of State Emission Stage IV standard,almost all of the heavy duty diesel vehicles of Stage IV selling in the market takes the selective catalytic reduction(SCR)solution,and lots of research has been done on SCR technology.In this paper,the influence of several boundary conditions on performance of SCR system has been studied,which include raw emission,pipe layout,exhaust condition,nozzle style,quantity of injection holes,the angle of injection,the Map of urea supply and so on.Several conclusions has been made as followed: the NOx raw emissions of China IV diesel engine with SCR technology are analyzed and low temperature operation conditions below 200? has been found in several engines.This problem need to be solved by heat management technic.An engine test bench for SCR system study has been built up.It was found that nozzle installation at elbow and installation of mixer benefits decomposition of urea solution.Based on the optimized pipe layout,the left experiment study has been conducted.It was found that at 200~210?,although the rate of both urea decomposition and reaction on catalyst are relatively low,the urea decomposition doesn't restrict the conversion efficiency of whole SCR system.At 260~350?,the rate of reduction reaction on catalyst are high enough,but the rate of urea decomposition is relatively low.So urea decomposition restricts the conversion efficiency of whole SCR system.