Presented herein is a fundamental study of laser ignition of methane/air mixtures at temperatures and pressures representative of an internal combustion engine. An Nd:YAG laser operating at λ = 1064 nm was used to ignite methane/air mixtures at equivalence ratios of 0.4 ≤ Φ ≤ 1 in a Rapid Compression Machine (RCM). Experiments were conducted to study the lean limit, minimum spark energy (MSE), and minimum ignition energy (MIE). The results show that laser ignition exhibits a stochastic behavior which must be interpreted statistically. A 90% probability of occurrence was used to evaluate the MSE and MIE, which resulted in MSE₉₀ =2.3 mJ and MIE₉₀ =7.2 mJ at an equivalence ratio Φ = 0.4 at compressed pressure and temperature of P_comp = 29 bar and T_comp = 750 K, respectively. The lean limit was characterized based on the fraction of chemical energy converted into thermal energy, which was determined by calculating the apparent rate of heat release as derived from RCM high speed pressure data. A lean limit for 90% chemical energy conversion was found to correspond to an equivalence ratio of 0.47 (T_comp = 782 K). Schlieren photography was employed as a diagnostics tool to visualize the flame initiation and propagation inside the RCM.

本文提出的是在代表内燃机的温度和压力下对甲烷/空气混合物进行激光点火的基础研究。使用Nd：YAG在激光器工作λ  = 1064nm的以0.4≤当量比被用来点燃甲烷/空气混合物Φ在快速压缩机（RCM）≤1。进行实验以研究稀薄极限，最小火花能量（MSE）和最小点火能量（MIE）。结果表明，激光点火具有随机行为，必须进行统计学解释。90％的发生概率用于评估MSE和MIE，当等价比Φ时，MSE ₉₀ = 2.3 mJ和MIE ₉₀ = 7.2 mJ 在压缩压力和温度分别为P _comp  = 29 bar和T _comp  = 750 K时= = 0.4 。稀薄极限是根据转化为热能的化学能的分数来表征的，化学能的分数是通过计算根据RCM高速压力数据得出的表观放热率来确定的。发现90％化学能转化的稀薄极限对应于0.47的当量比（T _comp  = 782 K）。Schlieren摄影被用作诊断工具，以可视化火焰在RCM内部的萌生和传播。