Research On Combustion System And Working Process Of Lean Burn Natural Gas Engine

Resources shortage and environmental pollution are two huge problems the world faces today. After nearly30years of development, natural gas industry has entered its mature stage. Natural gas will be the most promising alternative energy of automobile in the future. Natural gas vehicles are growing rapidly in foreign countries. However, there is little study of combustion control technique of Compressed Nature Gas (CNG) engine. Especially, natural gas automobile industry is still in the initial stage in China. This paper focuses on the optimization of combustion system and control system of a heavy CNG engine from YuChai. The main content includes:The foreground and advantages of development of natural gas as an alternative energy source is introduced. The advantages and disadvantages of present natural gas engine control techniques from domestic and overseas are emphasized.Based on the experimental study of the CNG engine’s combustion system, the limited region which effected the engine’s operation is analyzed. With the pressure signal collected by the high frequency cylinder pressure sensor and HC emission data gathered by HC emission equipment. Added by lean burn’s fire criterion? using HC emission and cyclical fluctuation coefficient of the Brake Mean Effective Pressure (BMEP), the engine operating parameters on engine knock, fire, efficiency of supercharger, exhaust gas temperature under different working conditions are studied. In order to advance the operating range of the engine, the structure of the engine’s combustion system, the operating parameters and control strategy are optimized.The concept of minimum ignition energy is proposed; combustion system is optimized by the method using the minimum ignition energy; the best combustion scheme is found through the experiments.Through the research on engine operated by the best combustion parameters, the characteristic parameters of combustion engine control are also found. Through the analysis of the characteristic parameters, the factors that affect the engine power, economy, emission performance are obtained.Through the test of lean burn natural gas engine control strategy, test results show that the development of natural gas engine control strategies and optimization scheme are feasible and effective.