Ignition of fuel-lean premixed methane-air flow was investigated using single-pulse laser-induced spark (SPLIS) and dual-pulse laser-induced spark (DPLIS). Ignition enhancement was quantified with ignition probability in flow speeds and equivalence ratios of 3.75 m/s–12.5 m/s and 0.53–0.57, respectively. The range of total laser pulse energy per ignition event was 20–30 mJ. For DPLIS, the energy per pulse was half of the total energy and the time interval between pulses varied from 10 ns to 100 ns where pulse-to-pulse coupling increased the spark surface area. Broadband chemiluminescence within the visible wavelength region was used to determine ignition of the combustible mixture. The ignition probability increased with velocity for both SPLIS and DPLIS as more fuel-oxidizer mixture was exposed to the ignition source. For a fixed total energy, ignition probability was higher for DPLIS than SPLIS particularly as the equivalence ratio was increased. Depending on the flow velocity, a change in the total energy determined whether SPLIS or DPLIS had a higher ignition probability at a given flow velocity. The study showed that using DPLIS to ignite fuel-lean combustible mixtures can enhance ignition compared to SPLIS particularly at low total laser energy and high-speed flow conditions.

点火使用单脉冲激光诱导火花（SPLIS）和双脉冲激光诱导火花（DPLIS）燃料贫油预混甲烷-空气流的影响。点火增强通过流速和等效比分别为3.75 m / s–12.5 m / s和0.53–0.57的点燃概率进行量化。每个点火事件的总激光脉冲能量范围为20–30 mJ。对于DPLIS，每个脉冲的能量为总能量的一半，脉冲之间的时间间隔从10 ns到100 ns不等，其中脉冲间耦合增加了火花表面积。可见光波长内的宽带化学发光区域用于确定可燃混合物的着火。SPLIS和DPLIS的点火概率随速度增加而增加，因为更多的燃料-氧化剂混合物暴露于点火源。对于固定的总能量，DPLIS的点火概率高于SPLIS，尤其是当当量比增加时。取决于流速，总能量的变化确定了SPLIS或DPLIS在给定流速下是否具有较高的点火概率。研究表明，与SPLIS相比，使用DPLIS点燃贫燃料的可燃混合物可以增强点火，特别是在低总激光能量和高速流动条件下。