电控LPG发动机稀薄燃烧技术研究

【作者】 郭辉；

【导师】 张振东；

【作者基本信息】 上海理工大学 ， 机械设计及理论， 2005， 硕士

【摘要】 能源结构的合理配置是社会健康发展的必要条件,而在我国,汽车每年约消耗我国汽油总产量的80%,柴油总产量的20%,因此汽车工业的能源消耗很大程度上决定了我国的能源结构。在全球范围内,世界能源消费总量始终保持增长趋势。因此,随着石油资源的日益枯竭,尽可能提高能源利用率已是我国重要的能源政策。同时,汽车尾气排放又是大气污染的主要来源之一,在大中型城市中,车辆尾气排放已经名列各类污染的首位,降低车辆排放、保护我们赖以生存的环境更是一个刻不容缓的问题。液化石油气(LPG)作为汽车发动机的代用燃料在降低排放污染和解决能源短缺等方面均具有巨大的优越性,各国政府和汽车研发机构都投入了大量的人力物力,并做出了相当大的成果。特别是近年来在大城市应用的比例逐渐加大,成为城市降低汽车尾气排放的首选方案之一。但是就燃烧优化而言,目前LPG气体燃料发动机尚未发挥其潜在的优势。一方面由于采用当量混合比附近的混合气工作,使热效率低,如果能以稀混合气工作,可以大幅提高循环热效率,降低燃料消耗率;另一方面,发动机排气中的有害成分与混合气的浓度有密切关系,当前LPG气体燃料发动机所使用的混合比正是排放高的范围,如果以稀的混合气工作,还可以得到更低的排放指标。因此,稀薄燃烧技术成为LPG气体发动机的一个重要研究方向。本文对电控LPG发动机的稀薄燃烧技术进行了研究。文章分析了LPG发动机的发展水平和现状,并在论述稀燃机理、分析稀限影响因素以及确定稀限判定方案之后,制取并优化了电控LPG稀燃发动机的稀燃控制MAP,利用发动机台架试验,与原LPG发动机在整机性能方面作了全面的对比与分析。本文主要内容包括:1.设计了电控LPG发动机稀燃控制系统的软硬件,该系统可对发动机的供气量、点火提前角进行实时控制和调节。2.利用所设计的控制系统,分析研究了电控LPG发动机的稀燃界限及其影响因素,并得到了电控LPG发动机稀燃系统的控制脉谱。3.从硬件和软件两方面对控制系统进行了抗干扰设计,解决了控制系统的干扰问题,并实现了控制系统的稳定运行。4.发动机台架实验结果表明,所设计的电控LPG稀燃发动机不但可以接近原机的动力性,还能具有出色的燃料经济性和排放特性。更多还原

【Abstract】 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.更多还原