| With the continuous aggravation of energy shortage and environmental pollution, liquefied petroleum gas (LPG) is widely used as an alternative fuel for automobile. All over the world the amount of the LPG vehicles has exceeded 15 million. At present the research on small-bore LPG engine of passenger car is very intensive and the related techniques has tended to be mature. However, when LPG was used on big-bore lean-burn engine many new problems were caused, such as low thermal efficiency, high emission temperature and easy to knock, etc. These problems restrict the application of LPG on commercial vehicles. Centering on the key technologies of big-bore turbocharged lean burn electronically-controlled gas mixed LPG engine, this paper carried out the following specific research work:The simulation of the engine working process has been done. The compression ratio and the distribution phase have been optimized by integrating the simulation results with the experimental data. The power performance and fuel economy have been improved by these optimization work, engine power increased by 15.6kw, gas consumption decreased by 9.1g/kw?h, exhaust temperature decreased by 43℃at the point of full load and full speed. The structure of mixer's air valve, mixer's gas valve and mixer's pressure transmission hole have been optimized to meet the requirements of air-fuel ratio adjustment and gas mixture flow control. The pressure transmission hole is the major damping element of the proportional control mixer. The structure of the pressure transmission hole has been optimized to increase the dynamic response characteristics of the mixer.Physical and mathematical model of the gas state variation and the movable elements of electric pressure regulator in fuel supply system were established. The steady state and dynamic characteristics of electric pressure regulator has been analyzed by the experimental data and the simulation results. Base on the structure and features of electric pressure regulator this paper draws a conclusion that the key factors affected the pressure control are the validity of air pressure after turbocharging and the accuracy control of pressure difference regulation force. The signal from the air pressure probe after turbocharging was filtered real-timely by Kalman filter. The signal distortion and external interference due to manifold filling and emptying process and turbocharging fluctuation has been eliminated, so the air pressure probe after turbocharging can be measured correctly. Kalman filter was used in current observation and PI control during the coil current accuracy control of voice coil motor, and the Kalman filter can eliminate the noise in the system avoid of affecting the system dynamic performance, the control performance was improved notably, so the transient output of the pressure difference regulation force of voice coil motor was ensured and the accuracy control of fuel outlet output pressure was realized.This paper presents a method of LPG engine dual spark ignition rapid lean-burning. A in-Cylinder combustion model of the LPG engine has been built with tools of 3D simulation. The impacts on in-cylinder combustion and engine performance in different ignition ways (single spark ignition and dual spark ignition) have been compared and analyzed. And it proved that the dual spark ignition can make the in-cylinder combustion more stable and fast, and this is benefit for increasing the thermal efficiency of the engine and decreasing the exhaust temperature. Knockings can be efficiently avoided at the same time,that make the improvement of compression ratio more possible. This paper do further detail research on the impact of combustion process in different ignition plug locations, ignition energy and swirl rates, which is good for establishing the theoretical base for optimization of in-cylinder combustion process. |
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