The Simulation On The Performance Of Turbocharged Diesel Engine With High Pressure EGR System

With the development of diesel technology and increasingly stringent emission regulations,the focus of diesel research has been transferred from economy and power to not only economy and power but also emissions.EGR technology,as a very effective measure to reduce NO_x emission,has been used as a relatively mature technology applying on diesel engine in foreign countries.However,domestic researches are mostly in the research stage,which is far from the practical application.Therefore,a detailed study on ship diesel engine EGR has great practical significance.This thesis established the high pressure EGR system and the low pressure EGR system.The biggest EGR rate is studied under different load on EGR system,obtaining the influence of EGR rate on diesel engine performance parameters.The simulation result of the high and the low pressure EGR system showed that:the fuel consumption rate of high pressure EGR system was lower with the same NO_x emission,which proved that the high pressure EGR system had better ability to reduce NO_x emission.The analysis and optimization of performance and NO_x emission had been done in this thesis.High pressure EGR system can affect the performance of the turbocharger,and the largest EGR rate is limited by the turbocharger performance.By optimizing of compressor in high pressure EGR system,the operating condition of compressor was ensured to run away from surge line.Upon the study of the influence that fuel injection angle,Miller time and EGR cooling temperature have on the diesel engine's economy and NO_x emission,the following results was discovered.Advancing the fuel injection timing could improve the economy,but would increase the NO_x emission;the Miller timing delay could improve the economy,but had adverse effects on reducing NO_x emission;reducing the EGR cooling temperature could improve the economy,simultaneously reduce the NO_x emission.This thesis confirmed the new injection advancing angle and intake valve closing time of different load.After the optimization,the specific fuel consumption of 100%,75%and 50%load was increased by 0.47%,2.4%and 1.8%compared with the original machine,and the NO_x emission respectively was decreased to 2.94 g/kW·h,1.78 g/kW-h and 1.70 g/kW·h,realizing the balance of fuel consumption and NO_x emission.This thesis had carried on the simulation research on the performance of high supercharged EGR diesel engine,it mainly studied the influence of EGR system on economy and emissions and analyzed the influence of the EGR cooling temperature,the fuel injection timing and the Miller timing on the NO_x emission and specific fuel consumption.The research results could provide a reference to reduce NO_x emission of a turbocharged diesel engine with EGR technology.