两种不同气体中的高速爆燃波及其向爆轰的转变

High-speed Deflagration and Its Transition to Detonation in Two Different Gaseous Mixtures

对2C2H2+5O2及2C2H2+5O2+80%Ar两种可燃混合气体中的高速爆燃波及其向爆轰的转变过程进行实验研究。高速爆燃波由孔栅干涉爆轰波的方法直接生成,观测手段则以高速转鼓摄影获取孔栅近场流场x-t纹影图,以传感器追踪波面的后继发展。研究发现,两种气体中的爆燃波具有迥异的特性。前者燃烧波面在较低初压条件下为层流结构,而较高初压下为湍流结构,向爆轰转变点可以延伸至下游较长距离;后者在不同初压条件下燃烧波面无明显差异,爆轰的再次形成只能在孔栅下游近场内建立。两种气体中高速爆燃波的维持和爆轰转变过程均非纯粹激波压缩所致,湍流输运在其中起着必不可少的作用。分析显示,激波压缩效应对纯氧炔气体的高速爆燃和DDT贡献较小,湍流输运占主导地位;而氩气稀释气体较为稳定,缺乏自行衍生剧烈湍流燃烧的能力,因而激波压缩和外界扰动对其高速爆燃传播和爆轰转变起十分重要的作用。

This paper presents an experimental study of high-speed deflagration waves and their transition to detonation in an acetylene-oxygen mixture （2C2 H2 ＋ 5O2） and its diluted mixture with 80% argon. High-speed deflagration waves were generated directly by interrupting a self-sustained detonation wave through a perforated plate, x--t streak schlieren photos of flow field near the perforated plate were taken by high-speed rotating-drum photography, and transducers were used to trace the further development of the deflagration wave fronts. It was found that these two mixtures carry different characteristics. With the increase of initial pressure, the deflagration waves in the pure mixture vary from a laminar structure to a turbulent one, and the detonation re-ignition needs a quite long distance. While in the diluted mixture the deflagration waves keep similar structures and detonation re-ignition only occurs nearby the perforated plate. Shock compression and turbulence transport both play important role in deflagration propagation, where the latter effect is usually indispensable. This study suggests that the turbulence transport counts for the dominant mechanism in the propagation of high-speed deflagration and its DDT in the pure mixture, while the argon-diluted mixture is more stable and lacks of the ability of developing violent turbulent combustion by itself, which results in the remarkable dependence on shock compression and additional disturbances above high-speed deflagration and the transition processes.