The localised forced ignition and the early stages of the subsequent flame propagation in a planar turbulent methane/air jet in ambient air have been simulated using Direct Numerical Simulation (DNS) and a two-step chemical mechanism. Sixteen identical energy depositions events were simulated for four independent flow realisations at four different locations. The successful ignition and subsequent flame propagation have been found to be well correlated to the mean mixture fraction and flammability factor values of the energy deposition location. Furthermore, similarly to what has been observed in experiments, the early stages of flame development from the ignition kernel involved initial downstream convection of the kernel, followed by simultaneous radial expansion and downstream propagation and finally the upstream propagation of the flame base indicating the onset of flame stabilisation. The mixture composition and the scalar dissipation rate (SDR) values in the immediate vicinity of the ignitor have been identified to play key roles in determining the outcome of the external energy deposition, while the development of an edge flame structure propagating along the stoichiometric mixture fraction iso-surface was found to be necessary but not sufficient for the flame to propagate upstream. It has also been found that in the case of successful self-sustained burning, the edge flame was developing in low SDR regions, and that the most probable edge flame speed remains close to the theoretical laminar value irrespective of the flame development history. Finally, the mean flame speed of the edge flame elements propagating towards the nozzle exit has been found to be considerably greater than the unstrained laminar burning velocity. Thus, the edge flame, depending on its orientation with respect to the flow, is able to propagate upstream and initiate the onset of flame stabilisation.

使用直接数值模拟（DNS）和两步化学机理模拟了环境空气中平面湍流甲烷/空气射流中的局部强制点火和随后火焰传播的早期阶段。针对四个不同位置的四个独立流动实现，模拟了十六个相同的能量沉积事件。已经发现成功的点火和随后的火焰传播与能量沉积位置的平均混合物分数和可燃因子值具有良好的相关性。此外，类似于在实验中观察到的情况，从点火核产生火焰的早期阶段涉及核的初始下游对流，随后是同时发生的径向膨胀和下游传播，最后是火焰基体的上游传播，这表明火焰开始稳定。已确定点火器附近的混合物成分和标量耗散率（SDR）值在确定外部能量沉积的结果中起着关键作用，而沿化学计量混合物分数传播的边缘火焰结构的发展等值面被发现是必需的，但不足以使火焰向上游传播。还已经发现，在成功地自我维持燃烧的情况下，边缘火焰在低SDR区域中发展，并且最可能的边缘火焰速度与火焰层流历史无关地保持接近理论层流值。最后，已经发现，朝向喷嘴出口传播的边缘火焰元件的平均火焰速度明显大于未应变的层流燃烧速度。因此，边缘火焰取决于其相对于流的取向，能够向上游传播并开始火焰稳定。