Isolating gasdynamic and chemical effects on the detonation cellular structure: A combined experimental and computational study

The dependence of detonation cell regularity on mixture gasdynamic and chemical kinetic properties are investigated through hydrogen-oxygen detonations with different diluent and ozone addition. A total of seven mixtures are specifically designed such that the post-shock specific heat ratio γVN, representing the gasdynamic effect, and the effective activation energy ϵi, representing the chemistry effect, can be varied independently among these mixtures. Both experiments and two-dimensional (2D) Navier-Stokes simulations are performed. For the ranges of γVN and ϵi considered, γVN is found to moderately affect cell regularity. For mixtures of relatively large γVN (≥1.3), detonation cells become slightly irregular with decreasing γVN. A clear increase in cell irregularity is found when γVN is small (<1.3). In contrast, the impact of ϵi on cell regularity is more notable: mixtures of large ϵi produce significantly more irregular cells, corresponding to frequent appearances of transverse detonation structures that dominate the global burning behavior. Finally, ozone is qualitatively and quantitatively shown to regulate the detonation structures in both simulations and experiments tested in this study, and results suggest that trace additives that alter the ϵi of a mixture can likely be used to tune the mixture for a desired regularity.