Simulation Analysis And Performance Experiment Of Direct Injection Low Caloric Gas Fuel Engine

Energy shortage and environmental pollution are two major problems facing humanity in the twenty-first century. In these two areas, the development of automobile and engine is suffering from the enormous challenges. So exploring the development of alternative clean fuel is the focus of study around the world currently. In this background, fuel gas with low calorific value (or low quality gas fuel) is being concerned by governments, enterprises and universities in these years. The applications of DI on low calorific value fuel for gas engine is benefit to improving volumetric efficiency and combustion, extending lean-burn limit and reducing emissions.This study was supported by National Natural Science Foundation of China (50906003). At first, the processes of gas-air mixing and combustion under various conditions are investigated by using CFD technology. The simulation results are then verified through the bench experiment. The main work and achievements are as follow:At first, the injection pressure and nozzle diameter are indentified through the study on subsonic and sonic jet in limited space. Secondly, the injection process of fuel gas will determine the flow field. So different injection strategy may results in different level of un-uniform for fuel distribution, which means that, we can meet the requirements of fuel distribution under various operation condition by changing the injection strategy The results from the study on combustion process show that:the velocity field, turbulence field and concentration field of CH4 from the process of injection determine the ignition and combustion process; injection strategy, ignition timing and excess air ratio can impact the performance of engine greatly, this paper also proved the low heat gas DI engine can extended the learn burn limit through explored the low heat engine's capability of lean burn, finally, designed and modified a low calorific valure fuel gas DI engine; through a series of experiment under different condition validated some conclusions of simulation.