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1、耿德强：LPG汽车发动机喷雾模拟计算山东建筑大学 毕业设计题 目：LPG发动机进气过程的计算机数值模拟学 院：机电工程学院专 业：机械工程及自动化班 级：机本022学生姓名： 学生学号：2002071109指导教师： 完成日期：2006年6月16日 摘 要随着能源短缺和环境污染问题的日益突出，发动机电喷技术及清洁能源的研究备受关注，其中液化石油气(LPG)作为一种清洁的车用发动机燃料，它的应用受到各国的重视，国内外的许多研究机构都致力于车用发动机燃用LPG的研究。目前所报道的液态LPG电喷发动机几乎主要是预混合均匀燃烧方式，液态LPG经过高压喷射(15MPa) 、雾化等一系列复杂过程与空气混合
2、,形成易于燃烧的混合气。在此过程中，由于实际尺寸的限制，无论是进气管喷射还是缸内直喷都不可避免地会涉及到油束与进气管以及燃烧室壁面相撞,在碰撞面上会形成油膜,使燃油在壁面堆积。研究发现,这种燃油壁面堆积是形成HC、碳烟的主要原因,因此深入研究喷雾的撞壁过程对提高发动机的排放性能有非常重要的意义。本文根据实际的单进气道得到其网格模型，对其内部的喷射碰壁过程进行了研究。发动机进气歧管内大量的LPG喷射造成喷射的LPG与进气阀表面冲突后向进气歧管入口方向剧烈反射。据此可以预测，对于这种采用较短进气歧管结构的改装LPG汽车发动机，喷射的LPG被反射到进气歧管入口附近，并被处于进气冲程的相临气缸吸入而引
3、起发动机各缸间混合气分配不均匀是完全可能的，这不但大大影响发动机的动力性和工作稳定性，各缸空燃比控制失调也造成发动机排放恶化。因此对这种采用较短进气歧管结构的改装LPG发动机，采用适当的方法缩短LPG喷流的贯穿距离，减轻LPG在管内的反射程度，避免各缸间混合气分配不均匀现象是必要的。关键词：液化石油气；数值模拟；自由喷雾；反射 ABSTRACTThe short of energy and air pollution become two mains serious problems. The technologies of electronically controlled engine a
4、nd development for clean energy are being paid more attention. Liquefied Petroleum Gas (LPG) is clean fuel of vehicle engine; many research departments in local and foreign countries are focus on LPG-fuelled engines.It is reported that the liquid LPGs electronic- controlled injection mainly is the p
5、remix homogeneous combustion way at present, liquid LPG mix with the air after the high-pressure spray (15MPa), the atomization and a series of complex processes, then forms mixed air which easy to burn. In this process, as a result of the actual size limit, manifold injection or the direct injectio
6、n inevitably can involve to the fuel collision with the manifold as well as the wall of the combustion bowl, then can form the wallfilm on the collision surface and cause the fuel oil in the wall surface deposit. The research show that this kind of fuel oil wall surface deposition is primary cause f
7、or forming HC and the carbon smoke, therefore studies of the process of sprays collisions have the vital significance to enhance the emissions performanceObtains its grid model according to the actual single air intake, ran into a wall the process to its internal spraying to conduct the research. In
8、 the engine air admission branch pipe the massive LPG spraying creates spraying LPG and the admission valve surface conflict backward air admission branch pipe entrance direction fierce reflection. According to the above may forecast that, uses the short air admission branch pipe structure regarding
9、 this kind the re-equipping LPG motor car engine, spraying LPG is reflected to the air admission branch pipe entrance nearby, and is in the intake stroke to be near the air cylinder inspiration to cause between the engine various cylinders the mixture air to assign non-uniform is completely possible
10、, not only this affects the engine greatly the power and the work stability, various cylinders air-fuel ratio control detuning also creates the engine emissions worsening. Therefore uses the short air admission branch pipe structure to this kind the re-equipping LPG engine, uses the suitable method
11、to reduce the LPG jet the penetration distance, reduces LPG in the tube reflection degree, avoids between various cylinders the mixture air assigning the non-uniform phenomenon is necessary.Key Words : LPG；numerically simulation；spray； reflection 目 录摘要-IABSTRACT-II1. 绪论 -11.1引言-11.1.1 汽车造成的石油消耗和环境污染概况 -11.1.2 汽车清洁代用燃料-11.2 液化石油气汽车应用发展状况 -21.2.1 LPG的特性-21.2.2 我国LPG资源状况-31.2.3 LPG汽车的发展现状 -31.2.4 LPG发动机存在的问题 -51.3 本课题的主要工作内容 -51.3.1 碰壁模型 -51.3.2 在单进气道内的喷射 -61.4 本论文的主要构成 -62. 模拟计算的原理-72.1数学模型 -72.1.1 基本控制方程 -
