Numerical Modeling Of Lean Burn And Experimental Study On Natural Gas Engine

As the Environmental pollution is becoming increasingly serious and Emission Regulation increasingly harsh, natural gas as a clean fuel, has become the first choice of alternative fuel for vehicle engine. By using the combustion control technology, the LNG engine not only can keep the power performance, but also reduce costs and improve engine efficiency. The LNG engine lean combustion is the preferred manner for Vehicle Engine because of its low emissions, high thermal efficiency and good economics.In this paper, a natural gas SI engine, respectively, working in condition of maximum torque and calibration in the testing by changing the spark advance angle and the air-fuel ratio,to measure and acquire cylinder pressure indicator diagram and rate of pressure rise, through the pressure indicator diagram calculated the average cylinder temperature, heat release rate and accumulate heat release which can reflect the engine performance, analyse the changes of these parameters and assess the performance of the whole engine anticipate the phenomenon of the fire loss and the reasons for the decline in power in lean combustion,at the same time the testing results and datas which can used for the three-dimensional numerical simulation.And then combined with the measured data and calculation of the working process of one-dimensional, simulated engine thermal cycle which provide accurate boundary condtion for the three-dimensional simulation.Based on three-dimensional numerical simulation model and numerical method, analyse the turbulent flow, combustion model and emission model located in cylinder, conderating the natural gas engine operating characteristics, select appropriate models and methods of calculation, the three-dimensional dymanic mesh was built to simulate the process of the intake flow, cylinder combustion and exhaust, and the sinmulation calculation was done. so as to conclude the flow and the combustion status under different crank angle, compared the simulation results and testing results to identify the deficiencies in the process of natural gas engine, to provide the theoretical basis for engine optimization.