The propagation speed of an auto-ignitive dimethyl-ether (DME)/air mixture at elevated pressures and subjected to monochromatic temperature oscillations is numerically evaluated in a one-dimensional statistically stationary configuration using fully resolved numerical simulations with reduced kinetics and transport. Two sets of conditions with temperatures within and slightly above the negative temperature coefficient (NTC) regime are simulated to investigate the fundamental aspects of auto-ignition and flame propagation along with the transition from auto-ignitive deflagration to spontaneous propagation regimes under thermal stratification. Contrary to the standard laminar flame speed, the steady propagation speed of an auto-ignitive front is observed to scale proportionally to its level of upstream reactivity. It is shown that this interdependence is primarily influenced by the characteristic residence time and the homogeneous auto-ignition delay. Furthermore, the unsteady reaction front in either of the two cases responds distinctly to the imposed stratification. Specifically, the results in both cases show that the dynamic flame response depends on the mean temperature at the flame base T_b and the time-scale of thermal stratification. It is also found that, based on T_b and the propensity of the mixture to two-stage chemistry, the instantaneous peak propagation speed and the overall time taken to achieve that speed differs considerably. A displacement speed analysis is carried out to elucidate the underlying combustion modes that are responsible for such a variation in flame response.

使用完全解析的数值模拟（具有降低的动力学和传输），在一维统计固定配置中对自燃二甲醚（DME）/空气混合物在升高的压力下并经受单色温度振荡的传播速度进行了数值评估。模拟了两组温度在负温度系数（NTC）范围内并略高于负温度系数（NTC）范围的条件，以研究自动点火和火焰传播的基本方面，以及在热分层条件下从自点火爆燃过渡到自发传播状态的过程。与标准层流火焰速度相反，观察到自燃前沿的稳定传播速度与其上游反应性水平成正比。结果表明，这种相互依赖性主要受特征停留时间和均匀自燃延迟的影响。此外，在两种情况中的任何一种情况下，不稳定的反应前沿对所施加的分层都有明显的反应。具体而言，两种情况下的结果均表明动态火焰响应取决于火焰底部的平均温度T _b和热分层的时间尺度。还发现，基于T _b和混合物对两阶段化学物的倾向，瞬时峰值传播速度和达到该速度所花费的总时间明显不同。进行了位移速度分析，以阐明导致火焰响应发生这种变化的潜在燃烧模式。