爆轰波透射孔栅形成的高速爆燃波的结构和行为

Structure and behavior of the high-speed deflagration generated by a detonation wave passing through a perforated plate

以实验为主,研究光滑直管中乙炔氧气爆轰波透射孔栅形成的高速爆燃波结构和行为。实验以基于纹影平台的高速转鼓摄影记录孔栅下游近场内初始爆燃波的结构和发展,并以压力传感器跟踪其后继走向。研究发现,高速爆燃波是前驱激波和火焰的组合结构,随着初始压力的提升,它分别表现为紧随于前驱激波的层流和湍流燃烧火焰。入射爆轰胞格尺度小于或与孔栅扰动尺度相当时,湍流燃烧在下游近场迅速形成;层流结构的爆燃波通常无法抵制背景稀疏波而走向衰弱,而湍流燃烧结构可发生加速和向爆轰的转捩;他们之间存在一个不稳定的临界状态,高速爆燃波得以以0.5～0.6倍CJ爆轰速度传播较长距离,这一状态对应于双间断Rankine-Hugoniot关系的等容燃烧解。

An experimental investigation on the high-speed deflagration in the acetylene-oxygen mix ture was carried out in a smooth straight tube. The deflagration was generated by putting a perforated plate in the way of a self-sustained detonation wave and interrupting it. Streak schlieren photos were taken to illustrate the averaged structure of the initially transmitted deflagrations near the plate, and pressure transducers were used to trace the further development of the wave front. The high-speed deflagration wave was found to be a complex of precursor shock and flame. With the increase of the initial pressure, it varies from a laminar structure to a turbulent one, and the onset of the latter seems corresponding to the smaller or comparable cellular width of incident detonation to the disturbance scale of perforated plate. This study reveals that deflagrations with laminar structure can not stand the attenuation of background rarefaction and keeps on slowing down, whereas the turbulent one is capable of running up and transiting to a detonation wave. There is an unstable critical case between the mentioned two situations, where the deflagration can propagate for a relatively long distance at a 0. 5-0.6 times CJ detonation speed. This critical case matches the constant-volume combustion solution of the Rankine-Hugoniont relations across dual discontinuities.