The Simulation And Experimental Of Urea SCR Mixer Of Diesel Engine

With the awareness of environmental protection strengthening gradually around the world,the emission standards for engines have also been tightened.At present,one of the main methods for reducing emissions is the SCR(Selective Catalytic Reduction technology).The mixer is an important part of the SCR system.Therefore,it is of great theoretical value and practical significance to study the mixer in SCR system to reduce the emission level of diesel engine.Based on the theoretical method,this paper introduces the composition and working principle of SCR system.Combined with the research status of SCR system at home and abroad at this stage,the factors affecting the catalytic efficiency of the system are described.Afterwards,the three-dimensional software Catia is used to design an SCR system with different blade type mixers.Under the same working conditions,CFD simulations are performed on different shapes of mixers in the exhaust pipe section.And the mixers with better performance are selected from two aspects of flow field changes and pressure field changes for the following experimental research.During the test,the working characteristics of the Diesel Oxidation Catalyst are studied and the overall system's emission effects are explored.And the test results with the simulated pressure drop results are compared to ensure the consistency of test and simulation results.Finally,three different types of emission tests including ESC,ETC and WHTC were used to test the performance and practicality of the system.This paper mainly describes the following conclusion.During the test,it is found that when the temperature increases to 220?,the outlet temperature of the DOC system begins to be greater than the exhaust temperature of the engine.At this temperature,the DOC system can effectively perform its transformation and ensure the efficient operation of the SCR system.With the addition of the DOC+DPF+SCR system,engine exhaust emissions have been greatly improved compared to the original engine emission levels,and significantly reduced the emission levels of pollutants such as THC,CO,PM,and NOx.Meanwhile,the efficiency of the SCR system after adding the mixer is increased by 5.5%-8.0%.