The numerical model of diesel engine fueled with pilot-ignited directly-injected natural gas is built, and the influence of natural gas injection timing on the combustion process is studied using CFD software. And obtained the following conclusions, as the delay of natural gas injection timing, the maximum of the mean pressure and mean temperature decrease gradually and the timings for the maximum value increase. With every delay of 5 °CA of the injection, the mean pressure reduces by about 16%.As the delay of injection timing, the delay of the timing of the high temperature and the range decrease for the high temperature region, and this is beneficial for the emission of NO, but not conducive to the emission of HC、CO and PM

In this study, an environmental comparison of hybrid, fuel cell and gasoline passenger vehicles is performed with the application of life cycle assessment (LCA) methodology. Unlike in a classic LCA, the vehicle cycle and fuel cycle of vehicles have both been modeled to cover vehicles with the full life time.According to the assumptions, the total energy consumption of the hybrid and fuel cell vehicles are respectively 27% and 37% lower than that of the gasoline vehicle. The GHG emission of the hybrid and fuel cell vehicles are respectively 27% and 44% lower than that of the gasoline vehicle. The results of the study show that the FCV is the one that presents the lower LCA energy consumption and GHG emission compared with the HEV.