Experimental Study On The Propagation And Failure Mechanism Of Detonation Wave In A Rough Tube

Combustible gas is widely used in the fields of petrochemical,mining,gas supply and etc.The investigation of propagation of detonation waves in rough tubes is considerably significant on explosion prevention and suppression.In this study,velocity measurement(Optical fiber and high-speed photography measurement)and smoking foil technique were used to study the detonation propagation and failure mechanism of detonation wave in rough tubes.By using spirals to produce roughness in annular and circular pipes,the roughness effects on the stability of detonation wave and frontal structures were studied.The results of this study are as follows.(1)In the smooth tube,the detonation propagation limit remains about 80%V_CJ.In rough tubes with spirals,the detonation velocity basically varies from V_CJ to 40%V_CJ,and the detonation fails when velocity is below 40%V_CJ.It shows that,on one hand the roughness has a baffling effect on detonation propagation and thus reduce the velocity;on the other hand,it extent the propagation limit of detonation waves.The study also found that,when a high proportion of argon-diluted premixed gas is used,a sudden drop of velocity exists with the reduction of initial pressure,indicating that the quasi-detonation changes into low-velocity deflagration.As the roughness increases,the initial pressure of the velocity discontinuity increases simultaneously.(2)In order to study the phenomenon of the sudden drop in velocity during the transition process of quasi-detonation into the low-velocity deflagration,smoked foils are used to record the change of cellular cell patterns.As the initial pressure decreases,the detonation front detonation changes from stable regular multi-head structure to single-head.When the detonation fails,the single head detonation disappears.The experimental results also suggest that the sudden drop in velocity occurs when d/??1.(3)The experimental results show that,with same initial condition,the baffling effect on the detonation wave generated by the obstacles in the annular tube are more intense than that in the circular tube by producing a lower detonation velocity in the annular tube.Velocity discontinuity also exists in annular detonation when quasi-detonation changes into a low-speed deflagration.As the roughness increases,the initial pressure of the velocity discontinuity increases simultaneously.The smoke foils also show that with same initial condition,the cellular cell of the annular detonation presents higher instabilities than of the circular detonation.The initial pressure required to achieve a steady propagation is higher than that of the circular detonation.