天然气发动机缸内燃烧及热功转换过程的规律研究

发布时间：2018-01-28 03:41

本文关键词： 天然气发动机热功转换过程燃烧放热规律运行参数设计参数　出处：《湖南大学》2016年硕士论文　论文类型：学位论文

【摘要】：能源危机与环境污染是当前全球面临的两大挑战,发展清洁代用燃料是解决这两大难题的有效途径之一。天然气因其资源丰富、运输方便和排放污染低等优势成为汽油和柴油的理想替代物。我国天然气发动机的研究起步比较晚,对其缸内燃烧过程的研究还不够系统和完善,而发动机缸内燃烧过程的优劣以及热功转换过程的完善程度直接决定着发动机的综合性能。因此,研究天然气发动机的缸内燃烧和热功转换过程的规律对于改善天然气发动机的性能具有重要意义。本文在一台车用重型天然气发动机上开展多工况下的试验研究,通过对实测性能参数和燃烧过程参数进行对比分析,研究得出各种运行参数和设计参数对天然气发动机缸内燃烧放热规律和热功转换过程的影响,在此基础上,总结了该类型天然气发动机热功转换过程的共性规律。论文的研究结果表明:(1)全MAP下,燃烧品质指数位于1.5~3.0之间。稀薄燃烧天然气发动机的燃烧效率几乎都大于98%。50%燃烧点位置主要受点火提前角的影响,且随点火提前角的增大而提前。燃烧持续期随负荷增大呈缩短的趋势,小负荷时趋势更明显;燃烧持续期受过量空气系数的影响比较明显。50%燃烧点位置滞后于燃烧始点12~14oCA;最高爆发压力点位置滞后于50%燃烧点位置4~5oCA。(2)高压循环指示热效率受转速和负荷的影响比较明显,且转速的影响大于负荷。最佳热功转换效率对应的燃烧特征参数值:燃烧始点位于上止点前2~8oCA,50%燃烧点位置位于上止点后6~10oCA,最高爆发压力点位置位于上止点后10~15oCA,有效膨胀比为10左右。10-90%燃烧持续期对热功转换效率具有双重影响,存在一个最佳值,使得热功转换效率最大。(3)50%燃烧点位置越靠近上止点,高压循环指示比气耗越低;有效膨胀比越大,高压循环指示热效率越大,但高压循环指示热效率还受发动机转速的影响。以上总结的规律既可以为天然气发动机概念设计过程中数模阶段边界条件的取值以及关键设计参数的选择和运行参数的优化提供数据支持,另一方面也可以为改善天然气发动机的热功转换过程提供理论支撑。
[Abstract]:Energy crisis and environmental pollution are two major challenges facing the world at present. Developing clean alternative fuels is one of the effective ways to solve these two problems. Natural gas is rich in resources. The advantages of convenient transportation and low emission pollution have become the ideal substitutes for gasoline and diesel. The research of natural gas engine in China started relatively late, and the research on combustion process in cylinder is not systematic and perfect. The combustion process in the cylinder and the perfection of the thermal power conversion process directly determine the comprehensive performance of the engine. It is important to study the in-cylinder combustion and thermo-power conversion process of natural gas engine for improving the performance of natural gas engine. In this paper, an experimental study is carried out on a heavy-duty vehicle natural gas engine under various working conditions. . Through the comparison and analysis of the measured performance parameters and combustion process parameters, the effects of various operating parameters and design parameters on the combustion heat release and thermal power conversion process in the cylinder of natural gas engine are obtained. The general law of thermal power conversion process of this type of natural gas engine is summarized. The combustion quality index is between 1.5 and 3.0. The combustion efficiency of lean combustion natural gas engine is almost greater than 98.50% of the combustion point position is mainly affected by ignition advance angle. With the increase of ignition advance angle, the combustion duration is shortened with the increase of load, and the trend is more obvious at small load. The combustion duration is obviously affected by excess air coefficient. 50% of the combustion point position lags behind the combustion start point 12 ~ 14oCA; The maximum burst pressure point lags behind the combustion point position of 50%.) the indicated thermal efficiency of the high pressure cycle is obviously affected by the speed and load. And the effect of speed is greater than the load. The combustion characteristic parameter value corresponding to the optimum thermal power conversion efficiency: the combustion start point is located at 2o 8oCA 50% of the combustion point located at 610oCA after the top check point. The position of the highest burst pressure point is 1015oCA after the up-and-down point, and the effective expansion ratio is about 10. 10-90% combustion duration has double influence on the thermal power conversion efficiency, and there is an optimum value. The higher the position of 50% combustion point is, the lower the specific gas consumption of high pressure cycle is. The higher the effective expansion ratio, the greater the thermal efficiency indicated by the high pressure cycle. However, the indicated thermal efficiency of the high pressure cycle is also affected by the engine speed. The laws summarized above can be used for the selection of boundary conditions and the selection and operation of key design parameters in the numerical and analog stages of the conceptual design process of natural gas engines. Parameter optimization provides data support. On the other hand, it can provide theoretical support for improving thermal power conversion process of natural gas engine.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U464.174

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