Research On Optimization Of Structural Parameters Of Selective Catalytic Reduction (SCR) System For China 6 Heavy Diesel Engine

Diesel engines have the characteristics of strong power,easy maintenance,etc.,and are widely used in various aspects.With the increase in the number of diesel engines in construction machinery,the total amount of pollutants also increases,especially the rapid increase of nitrogen oxides(NOx).The article mainly focuses on how to reduce NOx emissions.It conducts experiments and comparisons for straight-through catalytic converters,U-shaped catalytic converters and dual SCR catalytic converters,and then continues to study the impact of injection angle and coating thickness on SCR performance,and compares it with single SCR The system comparison highlights the superiority of dual SCR and lays a foundation for the application of dual SCR catalysts.The article describes the development history of internal combustion engines,reveals the main pollutant sources and control methods of internal combustion engines,the content of European and domestic heavy-duty diesel engine emission regulations,and compares the differences in emission limits at various stages,and analyzes the current mainstream diesel engine aftertreatment systems technology.A comparative test was carried out for the straight-through catalytic converter,the U-shaped catalytic converter and the dual SCR system catalytic converter.The SCR with better performance was selected from the three aspects of engine power,back pressure and conversion efficiency as the prototype for further structural optimization.Due to the limited space reserved for the entire vehicle,the optimized SCR catalyst prototype was used to study the impact on SCR performance from parameters such as length,spray angle,and coating thickness.The results show that the longer the length of the SCR catalyst and the increase of the coating thickness,the conversion efficiency and back pressure will be inversely proportional to a certain extent.Under high temperature conditions,the smaller the injection angle,the lower the conversion efficiency.The optimized catalytic converter was tested on a bench.The test results show that it meets the national standard under the conditions of WHTC and WHSC test cycles.Finally,compared with a single SCR system,engine power,back pressure and conversion efficiency are used as evaluation criteria.The results show that the superior performance of the dual-SCR system is more suitable for heavy-duty diesel engines.The research on the dual-SCR system is also a basis for future catalyst optimization and improvement.