Effect of reflection wall distance and supply conditions on reflective shuttling detonation combustor

In a reflective shuttling detonation combustor (RSDC), detonation waves propagate between the two reflection walls of a thin combustion chamber. As the chamber is two-dimensional and does not have any curvature, optical and pressure measurements can be conducted simultaneously. In this study, pressure measurements as well as self-luminous and schlieren visualizations were performed using a chamber with a reflection wall distance of 90 mm with ethylene and oxygen. Consequently, the detonation wave number increased from 2 to 5 following the total mass flux, indicating that the wave number depended on the reflection wall distance because the maximum wave number increased with increasing distance. In addition, although the reflection wall distance was varied, the mode transition, in which the wave number increased from 1 to 2, 2 to 3, and 3 to 4, occurred at similar values to the critical value at which the maximum mixture fill height was non-dimensionalized by the cell size. The dimensionless detonation wave propagation distance, that is, the reflection wall distance divided by the wave number and maximum mixture fill height, was 3.0 ± 0.3, which is almost the same as that of the previous 45 mm combustor. Additionally, when the ratio of the reflective wall distance to the wave number is the same, the dimensionless quantities match, except in a few cases. Comparing the model results with the schlieren results, different trends were caused by non-ideal phenomena arising from the supply conditions, such as the equivalence ratio and the relationship between the plenum pressure and combustion pressure.