【作者】 胡春明；

【导师】 姚春德；

【作者基本信息】 天津大学 ， 动力机械与工程， 2006， 博士

【摘要】 人类对于自身的生存环境及空间的保护意识日益强烈,内燃机的主要发展方向已着眼于燃油消耗、排放、噪声等环保指标。高辛烷值气体燃料LPG作为替代能源被广泛地加以应用。目前面临的关键问题是在稀燃条件下提高LPG燃烧速率和火焰传播速度,以及组织燃烧室中气流运动,加强与高能点火过程的良好配合与控制,进一步促进火焰传播,从而达到提高发动机热效率和降低排放的目的。本文紧紧围绕这个关键问题创新地提出一种新的快速稀燃方法,实现高速点燃式LPG电喷发动机稳定快速稀薄燃烧。具体研究内容如下:1、研制单燃料气态LPG气道电喷系统形成LPG均质可燃混合气,开发温控LPG预热减压混合器提供压力稳定的LPG低压气源。通过LPG电喷发动机的的标定平台精确调整稀混合气的空燃比,满足发动机不同工况对混合气浓度的要求。2、研制多通道电控汽油机瞬态燃烧分析系统。该系统可以实时采集发动机燃烧压力及发动机过量空气系数、排放指标等其它相关参数,通过计算模型可以得到发动机的压力升高率、放热率和累积质量放热率、以及发动机的燃烧循环变动等参数。3、创新研制了电控高能双火花塞快速燃烧系统。系统包括新缸头(燃烧室压缩比、双火花塞位置、燃烧室内气流组织等)、两套独立的可变点火能量的高能点火系统。通过电控单元ECU及控制策略根据发动机工况的变化,提供可变的同步、异步双火花点火。双火花塞位置与燃烧室形状的配合,缩短火焰传播途径以提高火焰传播速度。以期达到快速稀燃。4、利用研制的快速燃烧系统开展了LPG快速稀燃的试验研究。在燃烧室内组织适度的涡流和滚流与双火花可变点火过程之间的配合,加快火焰传播,扩展了发动机燃烧稀限,降低发动机有害排放物的生成,同时避免爆震现象的产生。研究了LPG电喷发动机稀燃特性,以及在压缩比、点火模式、点火能量、气流运动等不同条件下的快速燃烧特性。设计了LPG电喷发动机的废气再循环系统。研究发动机在废气再循环条件下的稀燃特性、快速燃烧特性以及排放特性等。结果表明,高能同步、异步双点火快速燃烧模式相比普通单点火模式,在整个有效的EGR率范围内LPG稀燃稀限得到较大幅度地拓展。LPG发动机可以实现较高EGR率条件下的稀薄燃烧稀限。5、基于LPG快速稀薄燃烧系统的的排放特性研究结果表明,采用快速稀燃、利用EGR对NOX排放生成的“阶跃效果”可以综合控制LPG发动机有害排放物CO、HC、NOX的生成。更多还原

【Abstract】 With human being getting increasingly consciousness of environment problem, the research of internal combustion engine is focusing on environmental benefits such as fuel consumption, emissions, noise and so on. LPG as a new alternative fuel with high octane is being used broadly. Today, the key issue is enhancing flame propagation, combustion velocity, mixture flowing in cylinder and improvement and controlling enhanced ignition process for high heat efficiency and low emissions. This dissertation presents a novel solution of rapid lean-burning in a high-speed LPG engine with EFI for steady operation. The details as follows:1. A sole-fuel gaseous LPG PFI system has been developed with a thermoregulation reducer as a constant low pressure LPG resource for controlling A/F ratio precisely within required mixture concentration on a test bench in different operation conditions.2. Multi-channel transient SI engine combustion analyzer has been developed. Pressure inside cylinder,λand exhaust emissions can be measured by this analyzer. The d p/dφ, heat release ratio, MFB and thermal circulation changes are calculated through the numerical analysis.3. An electronic control rapid burning system with high-energy, duel-spark plug ignition system is developed creatively, including modified cylinder head(compression ratio, spark plug location and organization of flow motion inside cylinder), two independently adjustable high-energy-ignition system. Synchronizing and asynchronous ignition timing can be realized by ECU and control strategy according to engine operation condition. Flame core propagation is improved by enhanced ignition energy intensity in this system. To cooperate with combustion chamber and spark location, the flame propagation distance is shortened for rapid burning.4. The LPG rapid lean-burning research is carried out by using the developed system. Reasonable organization of swirl and tumble flow movement in cylinder associating with spark plug location improve flame velocity ,extend limitation of lean burn and reduce the emissions in the mean time control knock. The LPG engine with EFI performance is investigated in diverse compression rate, ignition mode, ignition energy and flow movement. EGR system of LPG engine is developed. Rapid lean-burning characteristic and emission performance is investigated in condition of EGR. The research results show that in the mode of high-energy synchronizing and asynchronous ignition, the flammability limit of LPG mixture is extended significantly comparing with normal single spark ignition mode in whole range of EGR.5. Based on above research, it can conclude that the exhaust emissions such as CO, HC and NOx can be controlled by LPG rapid lean-burning associating with EGR for NOx emission control更多还原