This paper demonstrates auto-ignition in reactants at approximately 350 K, upstream of curved H₂/air flame surfaces during flame/vortex interaction. Temperature fields were measured using laser Rayleigh scattering during head-on interactions of toroidal-vortices with stagnation flames. Repeatable ignition occurred along the ring of the vortex – slightly towards the center – when it was approximately 1 mm upstream of the wrinkled flame surface. The resultant outwardly propagating toroidal flame led to approximately twice the volumetric heat release rate over the duration of the interaction. The ignition occurred in a region of low kinetic energy dissipation rate that was farther from the flame than the region of maximum vorticity. This region was upstream of positively curved flame segments. The advective time over which the vortex transports flame-generated products to the ignition site corresponded well to the time between the beginning of the flame/vortex interaction and ignition. It therefore is hypothesized that the vortex transports HO₂ and H₂O₂ to the low-temperature, low-dissipation region wherein ignition is promoted by preferential diffusion of H due to the positively curved flame. Evidence of additional ignition pockets was found upstream of other flame wrinkles, preferentially near the highest magnitude flame curvatures. These results provide a novel test case for validating diffusion and low-temperature kinetic models, and also have potential implications for reaction rate closure models.

本文展示了在弯曲H ₂上游约350 K处反应物的自燃/火焰相互作用期间的空气火焰表面。在环形旋涡与停滞火焰的正向相互作用过程中，使用激光瑞利散射测量温度场。当它在起皱的火焰表面上游约1毫米处时，沿着涡流环可重复点火-稍微向中心-点火。在交互作用期间，最终向外传播的环形火焰导致体积放热速率的大约两倍。点火发生在动能耗散率低的区域，该区域比最大涡旋的区域离火焰更远。该区域在正向弯曲的火焰段的上游。涡流将火焰产生的产物输送到点火位置的对流时间与火焰/涡流相互作用开始和点火之间的时间非常吻合。因此，假设涡流传输HO₂和H ₂ O ₂到达低温，低耗散区域，在该区域中，由于正弯曲火焰而使H优先扩散，从而促进了点火。在其他火焰褶皱的上游发现了额外的点火袋的证据，最好是在最大的火焰曲率附近。这些结果为验证扩散和低温动力学模型提供了一个新颖的测试案例，并且对反应速率封闭模型也具有潜在的影响。