Characteristics Of Detonation Wave Propagation And Detonation Initiation Via Hot Jet In Bend Tubes

The application of bend tubes could effectively solve the problem of space limitation in detonation research.The present study systematically investigated the characteristics of detonation wave propagation influenced by bend wall and detonation initiation via hot jet in bend tubes by combination of experimental observation,numerical simulation and theoretical analysis.The main achievement were as follows:The Mach reflection was observed when detonation propagated through bend tubes by means of laser shadow and smoked foils,and the detonation wave would decouple and extinguish.Three propagation modes which were unstable propagation mode,transition propagation mode and stable propagation mode respectively were analyzed.The results indicated that the propagation of detonation would gradually stabilize with the increase of initial pressure and radius of curvature,and the critical condition of propagation modes of C₂H₄+3O₂ were r0/ ?=12.8 and r0/?=27.5 respectively.The Block-structured Adaptive Mesh Refinement code was adopted in the simulation study of the characteristics detonation wave propagating through bend tubes.The detailed process showed the extinguished detonation would initiated and stabilized again in unstable propagation mode,and transverse wave angle f and transition distance L were defined as the parameters of re-stabilization.The effect of curvature radius on re-stabilization was analyzed.The results showed the re-stabilization was decided by both the formation of transverse wave and the position triple point collided.The critical condition of propagation modes of 2H₂+O₂+7Ar were r0/ ?=12.1 and r0/?=27.6 respectively.The effect of bend angle and diameter on characteristics were investigated as well.The mechanism of detonation initiation by hot jet within bend tubes was studied by numerical simulation.The process was analyzed compared with straight tubes.With respected to the results,detonation could be initiated by using bend tubes with smaller curvature radius in the working conditions which the initial pressure was under the critical initiation pressure in straight ones,which indicated the bend tubes would promote detonation initiation.a high temperature and pressure area was formed within the Mach reflection structure,which could maintain the coupling of shock wave and combustion front to facilitate the formation of hemisphere detonation.And larger curvature radius would decrease the energy of the area,so detonation couldn't form.