A systematic study relying on Direct Numerical Simulations (DNS) of premixed hydrogen-air mixtures has been performed to investigate the hotspot ignition characteristics and ignition probability under turbulent conditions. An ignition diagram is first obtained under laminar conditions by a parametric study. The impact of turbulence intensity on ignition delays and ignition probability is then quantified in a statistically-significant manner by repeating a large number of independent DNS realizations. By tracking in a Lagrangian frame the ignition spot, the balance between heat diffusion and heat of chemical reaction is observed as function of time. The evolution of each chemical species and radicals at the ignition spot is checked and the mechanism leading to ignition or misfire are analyzed. It is observed that successful ignition is mostly connected to a sufficient build-up of a HO2 pool, ultimately initiating production of OH. Turbulence always delays ignition, and ignition probability goes to zero at sufficiently high turbulence intensity when keeping temperature and size of the initial hotspot constant.

中文翻译：

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均质氢-空气预混物中热点诱导点火的直接数值模拟和点火点跟踪

已经进行了依赖于预混氢-空气混合物的直接数值模拟 (DNS) 的系统研究，以研究湍流条件下的热点点火特性和点火概率。首先通过参数研究在层流条件下获得点火图。然后通过重复大量独立的 DNS 实现，以具有统计意义的方式量化湍流强度对点火延迟和点火概率的影响。通过在拉格朗日坐标系中追踪点火点，热扩散和化学反应热之间的平衡被观察为时间的函数。检查点火点处每种化学物质和自由基的演变，并分析导致点火或失火的机制。据观察，成功点火主要与足够的 HO2 池积聚有关，最终开始产生 OH。湍流总是会延迟点火，并且在保持初始热点的温度和大小不变的情况下，在足够高的湍流强度下，点火概率为零。