混气活性对爆震波在突扩段传播特性的影响研究

Effects of Mixture Detonability on Detonation Transmission Through Abrupt Expansion

关键词:  爆震波  突扩段  混气活性  传播特性  化学反应动力学  爆震波动力学参数

Key words:  Detonation wave  Abrupt expansion  Mixture detonability  Transmission characteristics  Chemical kinetics  Detonation dynamic parameter

摘要:

为研究爆震波经过突扩段的传播特性，实验采用低活性混气C2H2+2.5O₂+70%Ar和高活性混气C2H2+2.5O₂，测量了爆震波在扩张比为1.34的圆管间传播的速度变化，并运用化学反应动力学分析爆震波动力学参数。结果表明:爆震波在小管出口的速度至多降至0.6倍的Chapman-Jouguet爆震波速。高活性混气触发的爆震波的成功传播是由于在大管产生局部爆炸，随后形成了过驱爆震波。相应地，低活性混气触发的爆震波不会形成过驱爆震波，且波速的波动范围较小。当预混气体压力小于爆震波从小管向大管成功传播的最低压力时，低活性混气触发的爆震波更快地衰减为爆燃波。通过化学反应动力学分析可知，高活性混气的爆震波稳定性参数较高，更容易形成局部爆炸。在最低压力处两种混气的爆震波诱导区长度接近0.8mm，管径与胞格宽度之比接近于1，因此爆震波在圆管中传播的准则可以用于预估爆震波在扩张比为1.34的圆管内能否成功传播。

Abstract:

To study the detonation transmission characteristics through abrupt expansion，the variations of detonation velocity were measured when the detonation transmitted in the round tubes with the expansion ratio of 1.34 in the low detonability C2H2+2.5O₂+70%Ar mixture and high detonability C2H2+2.5O₂ mixture. The detonation dynamic parameters were also analyzed by the chemical kinetic model. The results indicate that the detonation velocity decreases up to 0.6 times of Chapman-Jouguet detonation velocity at the exit of the small tube. For the high detonability mixture，the detonation transmits to the big tube successfully due to the local explosion in the big tube with subsequent overdriven detonation initiation. For the low detonability mixture，the overdriven detonation is not observed when the detonation transmits into the big tube，and the fluctuation in the velocity is small. When the initial pressure is lower than the minimum pressure that the detonation can transmit to the big tube，the detonation decays to the deflagration faster in the low detonability mixture. It indicates from the chemical kinetic analysis that the stability parameter in the high detonability mixture is higher，thus it is easy to generate the local explosion. When the initial pressure equals to the minimum pressure，the induction zone lengths are about 0.8mm in both mixtures，and the ratio of the tube diameter to the cell width approaches 1，therefore the criterion for the transmission in round tube can be used to estimate whether the detonation transmission is successful through tubes with the expansion ratio of 1.34.