PREMIER (PREmixed Mixture Ignition in the End-gas Region) combustion occurs with auto-ignition in the end-gas region when the main combustion flame propagation is nearly finished. Auto-ignition is triggered by the increases in pressure and temperature induced by the main combustion flame. Similarly to engine knocking, heat is released in two stages when engines undergo this type of combustion. This pattern of heat release does not occur during normal combustion. However, engine knocking induces pressure oscillations that cause fatal damage to engines, whereas PREMIER combustion does not. The purpose of this study was to elucidate PREMIER combustion in natural gas spark-ignition engines, and differentiate the causes of knocking and PREMIER combustion. We applied combustion visualization and in-cylinder pressure analysis using a compression–expansion machine (CEM) to investigate the auto-ignition characteristics in the end-gas region of a natural gas spark-ignition engine. We occasionally observed knocking accompanied by pressure oscillations under the spark timings and initial gas conditions used to generate PREMIER combustion. No pressure oscillations were observed during normal and PREMIER combustion. Auto-ignition in the end-gas region was found to induce a secondary increase in pressure before the combustion flame reached the cylinder wall, during both knocking and PREMIER combustion. The auto-ignited flame area spread faster during knocking than during PREMIER combustion. This caused a sudden pressure difference and imbalance between the flame propagation region and the end-gas region, followed by a pressure oscillation.

当主要燃烧火焰的传播接近结束时，在尾气区域会发生自燃，从而发生PREMIER（在尾气区域进行预混混合气着火）燃烧。自燃是由主燃烧火焰引起的压力和温度的升高触发的。类似于发动机爆震，当发动机经历这种类型的燃烧时，热量会分两个阶段释放。在正常燃烧过程中不会发生这种放热模式。但是，发动机爆震会引起压力振荡，对发动机造成致命伤害，而PREMIER燃烧则不会。这项研究的目的是阐明天然气火花点火发动机中的PREMIER燃烧，并区分爆震和PREMIER燃烧的原因。我们使用压缩可视化机（CEM）进行了燃烧可视化和缸内压力分析，以研究天然气火花点火发动机的尾气区域的自动点火特性。我们偶尔会在爆震正时和用于产生PREMIER燃烧的初始气体条件下观察到爆震并伴有压力振荡。在正常和高级燃烧期间未观察到压力振荡。发现在爆震和PREMIER燃烧期间，在燃烧尾气到达气缸壁之前，最终气体区域的自燃都会引起压力的二次升高。在爆震过程中，自燃火焰区域的扩散比在PREMIER燃烧过程中更快。这导致火焰传播区域和终端气体区域之间突然出现压力差和不平衡，