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

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.

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