Numerical Simulation Research On Combustion Characteristic And Emission Behavior Of Diesel Engine With High-pressured Common Rail System

Energy crisis and environmental pollution pushes the rapid development of automobile new technology.The usage of electronic control technology in automobiles and internal combustion engines make the power,efficiency and emission behavior of internal combustion engines to be improved.Especially in order to comply with the gradually strict emission control regulations,the high-pressured common rail system is taken by more and more people for its outstanding fuel injection function.It can realize the flexible adjustment in injection pressure,fuel charge,injection timing and fuel inject rate curve,which can make the diesel engine work in the optimum condition within maximum limit.Therefore,it has theoretical significance and the applied value to research the matching technique between high-pressured common rail system and diesel engine.At first,On the basis of the basic structure and the work principle of high-pressured common rail injector with solenoid valve,this article build the simulation model of common rail injector by HYDSIM which is a large-scale hydraulic pressure simulation software developed by AVL Corporation.The test bench of common injector system was built,by which the article has made sure the validity and the precision of the simulation model from fuel inject rate curve and fuel charge.Further,the simulation model of the diesel engine combustion chamber was built by FIRE which is a large-scale CFD calculated software developed by AVL Corporation.On the basis of the injection characteristics of different injection pressures which are gained by the simulation model of the common rail injector,the article has calculated the combustion performance and the emission behaviors at different injection pressures.The results by simulation indicate:As the injection pressure in the common rail system increases,the inject rate rises,and atomization of the fuel is better,which not only make the combustion speed up,but also make the end of the combustion approach the top dead center.As a result,the mean combustion pressure and the mean combustion temperature rise.This is advantageous in raising diesel engine's combustion thermal efficiency and improving the work capacity.Moreover,if the injection pressure in the common rail system increase,the combustion timing and the heat release rate centroid is advanced,the maximum heat release rate increases,the combustion duration reduces,which is advantageous in improving diesel engine's combustion status,raising the utilization efficiency of fuel and improving the engine's overall performance.If the injection pressure increases and the other parameters are not varied,the partial maximum temperature in the air cylinder increases,the generating area of nitrogen oxide is bigger and the generating rate of nitrogen oxide quickens,the total quantity of nitrogen oxide increases.With the reduction of the injection pressure,the injection duration is longer,the atomization of fuel is inferior, the total quantity of dry soot increases.In conclusion,by the simulation research of the high-pressured common rail systems,this article provides a good theoretical basis for the further development and the performance optimization of the diesel engines with the high-pressured common rail systems.It has certain theoretical significance and the applied value.