Electronically Controlled Lpg Engine Lean-burn Technology Research

Optimal energy structure is the essential condition for the society to develop healthily. At home, 80 percent of the gasoline productions and 20 percent of the diesel productions are consumed by the vehicle industry every year. In the world, the total energy consumed by the entire world has been increasing. With the petroleum gradually exhausted, it has been an important energy policy of our country to improve the utilization efficiency of the energy. Meanwhile, the exhaust emission of vehicle is one of the most serious headstreams of air pollution. In large cities, the vehicles exhaust emission has been the arch criminal among all the contaminations. Nowadays, there is no time to delay to decrease the vehicles exhaust emission and to protect the environment which the mankind depends on.As one kind of alternative fuel, Liquefied Petroleum Gas (LPG) has its large advantages in decreasing the vehicles exhaust emission and solving the problem of lacking energy. In recent years, lots of research and development working has been done on LPG vehicles (LPGV) by the governments and vehicle research and development departs. But as for burning optimization, many potential advantages of the LPG engines at present have not been developed yet. On the one hand, as the mixing ratio of LPG engines is nearby the stoichiometric ratio, its thermal efficiency is very low.If it works under the lean burning mode, the circulation stoichiometric ratio will rise,while the fuel consumption ratio will be decreased. Additional, as there is a close relation between the objectionable constituent of engine exhaust and the mixture strength, while the mixing ratio of LPG engine currently is just about the range within which the exhaust emissions are very high, if it works under the lean burning mode, the emission indices will be lower. Therefore, lean burn technology has become one of the most important research directions on LPG engine.Under the supporting of Shanghai Municipal Education Commission Development Fund, the lean burn technology on an electronic controlled LPG engine is researched. In this paper, firstly, lean burn mechanism is discussed; then the influencing factors, the engine structure and running parameters, on lean limit are analyzed and a simple and precise judgment to select the lean limit is defined; and then the control parameter map for lean burn is got through experiments and optimized by the aid of computer; at last, the testing of the lean burn LPG engine is performed.From the testing, the following conclusions are drawn: 1. The software and hardware system for the electric controlled LPG lean burn engine, designed by us, works well enough to control and adjust the LPG quantity injected and the ignition advance angle;2. The lean limit falls down when engine speed is decreased, while it will be broaden when the engine load is increased, the compression ratio is bigger, the ignition advance angle is reasonable, and spark-plug gap is wider but permitted by ignition energy;3. In the control system, a MCS-80C196KC single chip microprocessor is used as the electronic control unit (ECU) to process sensor signals and control the actuators to adjust the LPG quantity injected and the ignition time. And the interference problem, which bothers the control system, is also solved.4. Lean burn LPG technology with electronic control is feasible for vehicles to realize low emissions and improve fuel economy.