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 lambda and ZND induction zone length Delta(l)) 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/lambda) or ZND induction zone length (D-H/Delta(l)) gives an average estimation for the highly argon diluted mixtures at the detonation limits 0.66 and 15, respectively.