Effect of perforated plate with high blockage rate on detonation re-initiation in H2–O2-Ar mixture. (18th June 2021) - Zhang, Zhi
Abstract: An experimental investigation was performed to study the pressure limits and mechanism of the detonation re-initiation behind the perforated plate with various thicknesses and hole diameters in H2 –O2 -Ar mixture by schlieren and soot track measurement. The Chapman-Jouguet (CJ) detonation and overdriven detonation were used to collide with the perforated plate. For the CJ detonation transmission, the detonation re-initiation distance is larger than 3.9 times the tube hydraulic diameter. Both the thickness and the hole size have significant effects on the critical pressure and the re-initiation distance. The ratios of the hole hydraulic diameter and the critical cell size ( d H / λ c ) are less than 1. The cellular structure can be observed near the perforated plate on the smoked foils due to the collision of the arc-sharp shock waves via multi-jet structure. For the overdriven detonation transmission, the detonation can be re-initiated quickly, and the re-initiation distances are all less than twice the tube hydraulic diameter. The re-initiation distance increases with the hole size while the thickness has little effect on the re-initiation distance. The "abrupt" mode of the detonation re-initiation is transformed into the "gradual" mode with the increase of the initial pressure. The pressure limit of the re-initiation mode transformation also increases with the decrease of the hole size. Two mechanisms of the multi-jet initiation: rapid turbulent mixing initiation and the induction by the collisions of transverse waves were verified experimentally, corresponding to the "abrupt" and "gradual" modes, respectively. The critical condition of detonation propagation can be quantified as d H /λ ∗ > 3.37 and 3.77 for the 3 mm-hole and 2 mm-hole perforated plates, respectively, where d H is the hydraulic diameter and λ is the detonation cell size. Highlights: The overdriven detonation diffraction around the perforated plate was studied. The critical pressure was determined by various thicknesses and hole sizes. The cellular structure appeared near the plate due to the shock wave collisions. Two mechanisms of detonation re-initiation were focused.