Detonation propagation limits in highly argon diluted acetylene-oxygen mixtures in channels

In this study, the velocity deficits and detonation limits of highly argon (70% and 85% vol.) diluted stoichiometric acetylene-oxygen mixtures in a small diameter circular tube (D = 36 mm) and three annular channel widths (w = 2, 4.5 and 7 mm) were investigated. The purpose is to explore the velocity behavior of stable mixture due to its different failure mechanism by investigating the scaling law between the hydraulic diameter (D_H) of the circular tube and annular channels with the characteristic length scale (i.e., cell size λ and ZND induction zone length Δ_I) of stable detonations. The experimental results suggest the detonation velocity decreases with the decreasing of initial pressure, when the initial pressure reaches a critical value corresponding the maximum velocity deficit, the detonation fails and the detonation limits are approached. The results indicate that the average maximum velocity deficit is approximately 14% of the corresponding CJ value V_CJ for the highly argon diluted mixtures in the tubes with different geometries. The scaling between the hydraulic diameter and the cell size (D_H/λ) or ZND induction zone length (D_H/Δ_I) gives an average estimation for the highly argon diluted mixtures at the detonation limits 0.66 and 15, respectively.