狭缝内爆轰波传播模式的实验研究

An Experimental Study on Propagation Modes of Gaseous Detonation in Narrow Gap

关键词:  狭缝管  传播模式  速度震荡  速度亏损  过驱爆轰

Key words:  Narrow tube  Propagation modes  Velocity fluctuation  Detonation deficits  Overdriven detonation

摘要:

为研究狭缝内爆轰波起爆及各种传播模式的特点，实验得到了不同初始压力下(p0=10～60kPa)化学当量比的乙烯/氧气预混气体在高度1.0mm，宽度20mm狭缝内的爆轰性能。采用烟膜片记录爆轰波运行轨迹，高速摄影捕捉火焰面。结果表明:随着初始压力的降低，实验依次得到稳定爆轰模式、“结巴”爆轰模式、驰振爆轰模式和低速稳定传播模式，中间两者为不稳定模式。不稳定爆轰传播模式具有强烈的速度震荡，在一个周期内，烟膜板中周期性的出现过驱爆轰的胞格结构，随后“结巴”爆轰以单头形式与侧壁面发生碰撞并向前传播，驰振爆轰短暂熄灭。低速稳定传播速度为45%的C-J速度，烟膜板中无胞格结构出现。狭缝内爆轰波速度亏损值为10%～15%，高于大尺寸通道中的速度亏损。

Abstract:

To study initiation and propagation characteristic of detonation in a narrow gap，the gaseous detonation of stoichiometric ethylene/oxygen mixtures through a 1.0mm-height and 20mm-width narrow gap was experimentally studied with different initial pressure (p0=10～60kPa). The soot film was utilized to record the cellular structure of detonation，and the high-speed cinematography was used to capture the flame. The results show that，by decreasing the initial pressure of a given mixture，four modes of propagation could be clearly identified: stable detonation mode，‘stuttering’detonation mode，galloping detonation mode，and low-velocity stable mode. For unsteady detonation，such as‘stuttering’detonation mode and galloping detonation mode，the velocities had high fluctuation and cellular structure of overdriven detonation periodically appeared in soot film. During the next stage，the‘stuttering’detonation wave moved between the lateral walls of the rectangular channel with a sigle head mode，while galloping detonation transiently failed. For low-velocity stable mode，the average velocity was about 45% C-J value and no cellular structure appeared in soot film. The value of velocity deficits of detonation propagation appeared in narrow gap is 10%～15%，which is higher than the value of velocity deficits in large size tubes.