Gasoline spark ignition (SI) – Controlled auto-ignition (CAI) hybrid combustion had previously been shown to expanding the operational range of high-efficiency low-temperature combustion and reducing fuel consumption. However, the spark ignition became ineffective when the mixture became highly diluted and the large cyclic variation and even misfire would occur. To achieve high-efficiency combustion in extended engine operational range and overcome the limitation of SI-CAI hybrid combustion, Micro Flame Ignition (MFI) was proposed and researched as a mean to providing multiple auto-ignition sites to initiate the combustion process of the diluted mixture. In this research, both engine experiments and Computational Fluid Dynamics (CFD) simulations were carried out to study the MFI combustion and SI-CAI hybrid combustion in a single-cylinder optical engine. Compared to the SI-CAI hybrid combustion, the flame propagation in MFI hybrid combustion was initiated by a large number of reaction fronts produced by the DME auto-ignition at multiple sites. MFI was found to deliver substantially more heat and ignition energy to the premixed mixture than the single spark ignition, enabling much faster initial heat release. However, the flame front expansion speed of MFI hybrid combustion dropped significantly to a similar value to that of the SI-CAI case because of the slower flame speed of diluted gasoline mixture. The MFI combustion exhibited three phases of autoignition stage, flame propagation stage and fast heat release stage. It is characterized by a higher peak heat release rate and shorter duration of the main combustion than those of the SI-CAI combustion. Besides, the use of spark ignition in the MFI operation promoted the autoignition of DME, leading to a shorter combustion duration and faster combustion than the MFI combustion without spark ignition. As a result, the spark assisted MFI strategy could be used to control the combustion phasing and optimize the MFI combustion process.

汽油火花点火（SI）–受控自燃（CAI）混合燃烧先前已显示出扩大了高效低温燃烧的运行范围并减少了燃料消耗。但是，当混合物高度稀释后，火花点火将失效，并且会发生较大的循环变化，甚至失火。为了在扩展的发动机工作范围内实现高效燃烧并克服SI-CAI混合燃烧的局限性，提出并研究了微火焰点火（MFI），以提供多个自燃点来启动稀释液的燃烧过程混合物。在这项研究中 进行了发动机实验和计算流体动力学（CFD）模拟，以研究单缸光学发动机中的MFI燃烧和SI-CAI混合燃烧。与SI-CAI混合燃烧相比，MFI混合燃烧中的火焰传播是由DME自燃在多个位置产生的大量反应前沿引发的。发现MFI比单火花点火向预混混合物传递的热量和点火能量大得多，从而可以更快地释放初始热量。但是，由于稀释汽油混合物的火焰速度较慢，MFI混合燃烧的火焰前沿膨胀速度显着下降至与SI-CAI情况相似的值。MFI燃烧表现出自燃阶段的三个阶段，火焰传播阶段和快速放热阶段。与SI-CAI燃烧相比，它具有更高的峰值放热率和更短的主燃烧持续时间。此外，在MFI操作中使用火花点火可促进DME的自燃，与没有火花点火的MFI燃烧相比，燃烧时间更短，燃烧更快。结果，火花辅助MFI策略可用于控制燃烧定相并优化MFI燃烧过程。与没有火花点火的MFI燃烧相比，燃烧时间更短，燃烧更快。结果，火花辅助MFI策略可用于控制燃烧定相并优化MFI燃烧过程。与没有火花点火的MFI燃烧相比，燃烧时间更短，燃烧更快。结果，火花辅助MFI策略可用于控制燃烧定相并优化MFI燃烧过程。