Gas Engine Combustion Simulation And Experimental Study

The research of alternative fuels has received renewed interest in recent years for the stringent emission regulations. Coal-bed gas is becoming a major research aspect because of its low pollution and abundant deposit in many countries.With the appearance of numerical simulation and the application of CFD tools, it brought a new way to the development of internal combustion engine. The flow, combustion and emission characteristics of a spark ignition engine fuelled with coal-bed gas, made in Weichai Power Co. Ltd, was investigated; and the exhaust temperature and gas consumption were recorded in experiment under different ignition advance angle and coefficient of excess air.First, the optimal design of intake system was carried out. The flow equality, flow resistance and power of engine were contrasted among three different proposals in this paper. The optimized intake system was designed through analyzing the calculation results. Furthermore, the flow characteristics inside the engine cylinder was investigated. For this, complete caculations of the intake and compresstion strokes were performed and the ensemble-averaged velocity and turbulence flow fields obtaind in detail.The basic law of flow coefficient, swirl rate, differential pressure and mass flow was found with different valve diameter ( 90mm,92mm and 95mm). The result showed that flow field with the valve diameter of 95mm is more favorable for the combustion process and its flow coefficient is the highest.The effect of the different combustion chamber, ignition advance angle and lamda to the combustion and emission level were compared. The result showed the calculated in-cylinder mean pressure and in-cylinder mean temperature decline with the delay of ignition advance angle. The same trend was investigated with the increase of lamda. In the aspect of exhaust emission, the amount of NO emission declined with the increase of lamda. Because the viscosity of the mixture was reduced, the combustion delay period and main combustion period grew, and the flame propagating speed slowed. Then the heat release rate, cylinder main pressure and temperature declined.Moreover, the chose of electric control system was shown. Meanwhile, the calibration on the coefficient of excess air and volume efficiency was carried out. The exhaust temperature and gas consumption rate were analyzed with different coefficient of excess air and spark advance angle.