Experimental observations of gaseous cellular detonation reflection

When propagating in an annular combustion chamber, the detonation wave reflects under the effect of wall curvature. In order to comprehend the reflection mechanism, a high-speed, high-resolution schlieren imaging system is used to capture the transient reflection structure. Smoked foil is used to record cellular patterns as an additional technique to visualize the reflection process. Two-dimensional numerical simulations are used for further illustration. Mach reflection, regular reflection, and Mach-to-regular reflection occur on the 30 degrees degrees wedge, 45 degrees degrees wedge, and semicylindrical concave, respectively. Regardless of the reflection type, incident transverse waves (ITWs) deviate toward the center of the reflector due to the influence of the nonuniform state of the gas within the range swept by the reflected bow shock. The deflected ITWs reflect on the wedge surface, forming reverse transverse waves (RTWs). These two sets of waves intersect with each other, creating a regular rhombic pattern, which is observed for the first time in detonation reflection experiments. In Mach reflection, the RTWs move along the Mach stem and accumulate at the triple point, leading to more transverse waves than those in a normal planar detonation wave. The secondary compression effect caused by the RTWs promotes chemical reactions, which in turn leads to an overdriven detonation wave at the Mach stem. However, in regular reflection, due to the absence of the triple point, the RTWs can be successfully transmitted to the bow shock and therefore will not produce overdriven detonation.