直喷式天然气发动机不同压缩比下燃烧循环变动规律  

Effect of Compression Ratio on Cycle-by-Cycle Variations in a Direct Injection Natural Gas Engine

作　　者：郑建军[1] 黄佐华[1] 王金华[1] 王彬[1] 宁德忠[1] 张英佳[1] 

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,陕西西安710049

出　　处：《内燃机学报》2011年第2期97-104,共8页Transactions of Csice

基　　金：国家自然科学基金重点资助项目(50636040);国家重大基础研究计划资助项目(2007CB210006)

摘　　要：开展了不同压缩比下天然气直喷发动机燃烧循环变动特性研究.结果表明,低压缩比(ε=8),会出现部分燃烧循环,平均指示压力小,循环变动系数大.随着压缩比的增加,平均指示压力循环变动减小.压缩比大于12后,大负荷工况时发动机出现轻微爆燃,燃烧循环变动增加.平均指示压力反映出的燃烧循环变动比缸内最大压力反映出的循环变动效果更明显.火焰发展期、主燃烧期和燃烧持续期随压缩比增加而缩短是燃烧循环变动降低的一个重要原因.平均指示压力与火焰发展期、主燃烧期及燃烧持续期有好的相关性.火焰发展期的循环变动是天然气直喷发动机燃烧循环变动的主要原因之一.与均质混合气燃烧循环变动主要是由火焰发展期循环变动决定有所不同,缸内直喷燃烧的循环变动是由火焰发展期和燃烧后期循环变动共同作用的结果.Cycle-by-cycle variations of a direct-injection spark ignition natural gas engine under different compression ratios were investigated.The results show that there exist the partial burn cycles at low com-pression ratio,and the indicated mean effective pressure（pmi）gives a low value and the coefficient of variation of pmi（CoVpm i）gives a high value.CoVpm i decreases with the increase of compression ratio.However,when compression ratio is larger than 12,slight knock will occur at high engine load,leading to an increase in CoVpm i.Better interdependency is demonstrated between pmi and maximum cylinder pressure,while CoVpm i gives a larger value than that of maximum cylinder pressure.In addition,better interdependency also demonstrates between flame development duration and main combustion duration.Cyclic variations occur at both flame development duration and main combustion duration.Shortening in flame development duration and later combustion duration leads to the decrease of CoVpm i.Better inter-dependency presents between pmi and flame development duration and/or total combustion duration.Cyclic variations of direct-injection natural gas engine are resulted from the cyclic variations in flame development duration and main combustion duration.They are corresponding to the mixture around the spark plug and mixture stratification in the cylinder.

关 键 词：发动机 压缩比 循环变动 天然气 缸内直喷 

分 类 号：TK421.2[动力工程及工程热物理—动力机械及工程]