Transition Process of Mach Reflection for Premixed Mixtures with Different Stability

Shock wave reflection on the wedge has garnered wide application. This paper investigated transition process of the Mach reflection of cellular detonation for premixed mixtures with different stability. Smoked foils were strategically placed at different positions to record the Mach reflection in three dimensions under varying wedge angles. The results indicated that the triple-point trajectory adheres to a transition process from the unreactive three-shock to the reactive three-shock when the Mach stem propagating along the wedge. There exists a critical Mach stem height corresponding to the transition process. For the stable premixed mixtures 2 H2+O2 +3Ar at 10 kPa and C2H2 +2.5O2 +8.17Ar at 5 kPa, critical Mach stem heights are approximately 0.81 cm and 0.74 cm, respectively. As for unstable premixed mixtures C2H2 +5N2O at 3 kPa and 5 kPa, they are about 0.99 cm and 0.71 cm, respectively. Moreover, the transition process of cellular structures on the wedge surface can be divided into three stages. The distance from the initial position of the wedge to the location where small cells first appear for unstable premixed mixtures is the shortest than that of stable premixed mixtures. This implies that the detonation instability (or mixture composition) does indeed have an impact on the transition process of the Mach reflection.