中文摘要：

针对汽油机在稀燃时循环变动高的问题，在一台加装了氢气喷射系统的发动机上就进气混氢对稀燃汽油机循环变动及稀燃极限的影响进行了试验研究。发动机在1400r／min的条件下，首先选择3％和6％两种不同的进气混氢体积分数，在不同过量空气系数条件下就混氢对汽油机循环变动的影响进行了研究。之后，在1％、3％和4．5％三种进气混氢分数条件下研究了混氢对汽油机稀燃极限的影响。研究结果表明，进气混氢有利于减少汽油机火焰发展期及快速燃烧持续期并降低稀燃时汽油机的循环变动；相同混氢分数条件下，发动机峰值压力的循环变动系数随过量空气系数的加大先增加后减小；混氢后发动机稀燃极限所对应的过量空气系数由原机的1．45升高至混氢体积分数为4．5％时的2．45。

英文摘要：

To decrease cyclic variations of gasoline engine at lean conditions, this paper investigated the effect of hydrogen addition on cyclic variations and lean burn limit of a spark ignition engine. Experiment was conducted on a gasoline engine equipped with a hydrogen injection system. The engine runs at 1 400 r/min, 3% and 6% hydrogen volume fractions are selected to study the effect of hydrogen enrichment on engine cyclic variations. Meanwhile, hydrogen volume fractions 1%, 3% and 4.5% are used to investigate the effect of hydrogen addition on lean burn limit of the gasoline engine. The test results demonstrate that the cyclic variations in indicated mean effective pressure, flame development duration and flame propagation duration were decreased under hydrogen enrichment. For a specific hydrogen fraction, the coefficient of variation in peak cylinder pressure shows an increasing and then decreasing trend with the increase of excess air ratio. The corresponding excess air ratio to lean burn limit extends from 1.45 of the original engine to 2.45 of 4.5% hydrogen-enriched engine.