The present paper seeks to determine the mechanism of flame acceleration and transition to detonation when a turbulent flame preceded by a shock interacts with a single obstruction in its path, taken as a cylindrical obstacle or a wall in the present study. The problem is addressed experimentally in a mixture of propane–oxygen at sub-atmospheric conditions. The turbulent flame was generated by passing a detonation wave through a perforated plate, yielding flames with turbulent burning velocities 10 to 20 larger than the laminar values and incident shock Mach numbers ranging between 2 and 2.5. Time resolved schlieren videos recorded at approximately 100 kHz and numerical reconstruction of the flow field permitted to determine the mechanism of flame acceleration and transition to detonation. It was found to be the enhancement of the turbulent burning rate of the flame through its interaction with the shock reflection on the obstacle. The amplification of the burning rate was found to drive the flame burning velocity close to the speed of sound with respect to the fresh gases, resulting in the amplification of a shock in front of the flame. The acceleration through this regime resulted in the strengthening of this shock. Detonation was observed in regions of non-planarity of this internal shock, inherited by the irregular shape of the turbulent flame itself. Auto-ignition at early times of this process was found to be negligibly slow compared with the flow evolution time scale in the problem investigated, suggesting that the relevant time scale is primarily associated with the increase in turbulent burning rate by the interaction with reflected shocks.

本文试图确定当湍流火焰先于冲击与其路径中的单个障碍物相互作用时，火焰加速和爆炸转变为爆炸的机理，在本研究中将其作为圆柱形障碍物或壁。在低于大气压的条件下，在丙烷-氧气混合物中通过实验解决了该问题。湍流火焰是通过将爆震波穿过穿孔板而产生的，产生的火焰的湍流燃烧速度比层流值大10到20，入射冲击马赫数在2到2.5之间。时间分辨的schlieren视频以大约100 kHz的速度记录下来，并且对流场进行了数值重建，从而可以确定火焰加速和爆炸的机理。人们发现，通过与障碍物上的冲击反射相互作用，火焰的湍流燃烧速率得以提高。发现燃烧速率的增大相对于新鲜气体使火焰的燃烧速度接近于声速，从而导致火焰前的冲击的增大。通过该政权的加速导致了这种冲击的加剧。在这种内部冲击的非平面区域观察到爆震，这是由湍流火焰本身的不规则形状所继承的。与所研究问题中的流演化时间尺度相比，发现该过程早期的自燃速度可忽略不计，