Numerical Analysis Of Stratified Lean Combustion For A Spray And Wall Complex Guided LPG GDI Engine

The increasingly strict fuel economy index and emissions standards make the study of clean and effecient alternative motor fuels as one of the most hot issues in the world. With the charactristic of high octane number, less harmful substances in the products of combustion etc, of all the clean fuels, liquid petroleum gas(LPG) has a very high popularization value and has become one of the most popularization value fuels of low pollution. To improve the economy, power and emission performance, instead of the mean premixed combustion, the process of the mixture formation and combustion of a lean-burn GDI engine was simulated and analysed.The processes of the mixture formation and combustion under wall guided combustion system and spray and wall complex guided combustion system were analysed by a commercial CFD software, AVL FIRE. By importing the chemical kinetic mechanisms into FIRE, the accuracy of the simulated results will be improved. Because of the long computation time and the high hardware requirements of calculating with detailed chemical kinetic mechanisms, the chemical kinetic mechanisms was reduced to one that with32components and69chemical reactions and its effectiveness was verified.Under the air-fuel ratio of40:1and60:1, the mixture formation and combustion processes of mixture formation and combustion processes were analysed under wall guided combustion system and spray and wall complex guided combustion system were analysed. The results show that it will form a rich mixture when set the injection timing at60℃ABTDC under wall guided combustion system of air-fuel ratio of40:1; the ignition advance angle has certain influence to CO and NO emissions that the CO and NO emissions will decrease with the decrease of the ignition advance angle; it will get the largest heat release rate peak, higher pressure and more work when set the ignition timing at700℃A and can obtain a better combustion and fuel consumption characteristics. Under the complex guided combustion system, it will get the same results as the wall guided combustion system except the lower CO emission. When choose the air-fuel ratio of60:1, it will get a slower combustion speed and less work under wall guided combustion system; under the complex guided combustion system, it will get a good combustion characteristic and a substantial reduction in the emissions of CO and NO compared with the air-fuel ratio of40:1when set the ignition timing at700℃A.