环管中甲烷-氧气预混气爆轰传播机理研究[1]

Study on the Mechanism of Pre-mixed CH4-O2 Mixture Detonation Propagation in the Annular Channel

关键词:  螺旋爆轰  甲烷-氧气预混气  环形管道  三波点轨迹  烟膜

Key words:  Spinning detonation  Methane-oxygen Mixture  Annular Channel  Transverse waves trajectory  Smoked foil

摘要:

为了研究环形管内甲烷的爆轰传播机理，在内径为80 mm的管道内分别安装内径为20 mm、40 mm、60 mm的内管，形成环形管道，进行了甲烷-氧气预混气爆轰实验。将烟膜分别固定在外管的内壁以及内管的内外壁，记录环形管道通道内的三波点轨迹；同时在环管端面安设烟膜记录端面的轨迹。所记录的轨迹较混乱，这是因为横波在沿着传播方向绕着管轴旋转时不断地相互碰撞，反映出甲烷-氧气预混气是典型的不稳定预混气。明显可见当初始压力为12 kPa时，爆轰波在普通圆管内呈现双头螺旋爆轰结构，设有内部小管内径为20 mm 的环管外管内壁得到四头螺旋爆轰结构，说明其他因素不变地情况下，环形管内更容易获得自持爆轰。增大环管内管管径为60 mm，环形通道内烟膜记录中未显示任何三波点轨迹，因为此管径下，胞格尺寸过大，无法容纳于管道中。增大内管管径，外管内壁烟膜记录胞格数量增多，胞格尺寸减小，原因为当边界条件改变时，爆轰极限发生相应的变化，分子获得的初始能量多，反应速率快。

Abstract:

In order to investigate the detonation propagation mechanism of methane-oxygen in the annular channel, the experiments are conducted with pre-mixed methane-oxygen. The annular channels are designed with an outer diameter of 80mm and an inner diameter of 20mm, 40mm and 60mm respectively. Smoked foils are used to record transverse waves trajectories. In addition, the smoked foils were set on the end-on of the channel to record the detonation structure on cross section. Because the instability of Pre-mixed CH4-O2 mixture, the spinning detonation structure on the surface of the channel is not stable as this mixture is a typical unstable mixture. However, it is found that the transverse wave presents double-head structure in the original channel under 12.00kPa, while the Annular tube with inner diameter of 20mm has four-head. The reason is the annular channel is more likely to get self-sustaining detonation. When increase the diameter of the inner channel to 60mm, it is found that there is no triple point trajectory in the annular channel. The reason is the cellular structure is too larger to exist in the channel. When increase the diameter of the inner channel，it is found that the number of the cellular has increased and the cellular size has decreased. The reason is that the cellular obtained the higher initial energy and the faster reaction rate when the detonation limit has decreased.