| Thanks to the rapid development of Chinese economy,the motor vehicle industry is developing speedily.However,the frequent appearance of fog and haze,it reminds us of the importance of energy saving and green travel.The nature of the extended-range electric vehicle is electric vehicle,the promotion process device is composed of engine and motor,the engine is in the most economical operating point for battery powered "extended range".For the purpose of dropping the cost,making the extended-range electric vehicle structure more compact and simpler,this paper proposed the idea that two-stroke engine is used in the extended-range electric vehicle.We used the liquid LPG for fuel,so that the electric car can be very good control of costs,and cut down the emission of the engine.As everyone knows that the combustion process involves the ignition and combustion phase.The fire is burning in the process of preparing stage,regardless of autoignition or ignition on fire,the formation of flames is a typical phenomenon under the control of the combustion chemical kinetic.So this paper conducted the research for the chemical kinetic mechanism of LPG/Air combustion.Although the detailed chemical kinetic mechanism can improve the accuracy of the calculation,it will cause the problem of rigidity calculation,and lower the computational efficiency.As such,in the third part,by using sensitivity analysis method of the simplified chemical kinetic model of LPG with chemical mechanism is simplified as applied to high temperature oxidation conditions including 27 species and 34 reactions,and the simplified model was proved effectively.In this paper,the processes of the mixture formation and combustion with the simplified mechanism of LPG for two-stroke direct engine were analysed by a commercial CFD software,AVL FIRE.For the crankcase scavenged two-stroke direct engine model,simulated the processes of homogeneous mixture formation and combustion.The results of numerical analysis show that,when the injection timing is later than the ending point of 15 o CA,the fuel will not flow away from the exhaust,and it is easy to formation of homogeneous mixture before TDC.The combustion process is researched by selecting different ignition advance angles.The results of numerical analysis show that,When the ignition timing is at the BTDC25oCA,combustion pressure peak and the maximum of heat release rate are the highest,the corresponding phase angle near the ATDC 5~15oCA,external effective work is best,too.In addition,the research group put forward a new curved surface guide inlet scavenged LPG two-stroke direct engine structure.It was simulated partial load of stratified lean combustion numerical.The results of numerical analysis show that,when the LPG is injected into the cylinder with the pressure of 5Mpa,the injection timing is BTDC 60oCA,good stratified mixture can be formed.By comparing the combustion processes and characteristics of different positions of the spark plug and different ignition timing,the results of numerical analysis show that,the maximum explosion pressure is greater,the maximum of heat release rate is higher and fuel consumption characteristics are better when the spark plug is set the top of the cylinder. |
