Abstract A TRAnsparent cylindrical (TRAC) shock tube test section has been developed to explore the ignition structure behind reflected shockwaves via simultaneous lateral and endwall high-speed imaging using three fuel/oxidizer mixtures: 0.1% n-C7H16/1.10% O2/4.14% N2/94.66% Ar, 0.1% iC8H18/1.25% O2/4.69% N2/93.96% Ar, and 5% CH4/10% O2/85% CO2. During mild ignition, the first exothermic centers were located outside of the observable test section. It is shown that with increasing temperature the far-wall ignition events move closer to the endwall, until a strong ignition is achieved. The temperature gradients that promote mild ignition were quantified and were found to have a slight dependence on fuel with the RMS temperature gradients being 0.80% for n-heptane and 1.07% for isooctane. The impact of temperature gradients on metrics used to improve kinetic models, such as species time histories, is noteworthy. From this temperature gradient, an experimental correlation is provided to estimate the transition temperature from mild to strong ignition for a mixture. The effect of diagnostic location in non-homogeneous reactions is quantified in reference to ignition delay. The unique and insightful perspective on the ignition process under heavy shock bifurcation is also discussed.

中文翻译：

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通过使用透明圆柱形测试部分同时进行横向和端壁高速成像探测反射冲击引发的点火

摘要 使用三种燃料/氧化剂混合物：0.1% n-C7H16/1.10% O2/4.14%，通过同时横向和端壁高速成像，开发了透明圆柱 (TRAC) 激波管测试部分，以探索反射激波背后的点火结构。 N2/94.66% Ar、0.1% iC8H18/1.25% O2/4.69% N2/93.96% Ar 和 5% CH4/10% O2/85% CO2。在温和点火期间，第一个放热中心位于可观察的测试部分之外。结果表明，随着温度升高，远壁点火事件靠近端壁，直到实现强烈点火。促进温和点火的温度梯度被量化，发现对燃料有轻微的依赖性，正庚烷的 RMS 温度梯度为 0.80%，异辛烷为 1.07%。温度梯度对用于改进动力学模型的指标（例如物种时间历程）的影响值得注意。从这个温度梯度，提供了一个实验相关性来估计混合物从轻度到强点火的转变温度。非均相反应中诊断位置的影响参考点火延迟进行量化。还讨论了重激波分岔下点火过程的独特而深刻的观点。