Experimental Investigation of a Small-Scale Oxygen-Hydrogen Rotating Detonation Rocket Combustor

Abstract

This study presents the design methodology and results from initial testing of an experimental hydrogen-oxygen rotating detonation combustor (RDC). A small-scale heat sink chamber was designed for studying rotating detonative combustion for rocket propulsion applications. Initial testing was performed to verify the design methodology. The initial tests used gaseous propellants with oxidizer-to-fuel mixture ratios between 5 and 9 and total mass flow rates between 16 and 70 g/s. During the tests pressure oscillations were observed which showed significantly higher frequencies than the expected frequency for one wave calculated with the theoretical detonation (CJ) velocity. The imaging from a high-speed camera directed upstream into the annular combustion chamber was analyzed with different post-processing methods and the results indicated 2 to 5 traveling waves, depending on the operating conditions. The multiple waves explain the high pressure oscillation frequency. For most of the cases, the calculated wave speed was around 1700 m/s and thus low compared to the theoretical detonation velocity of oxygen-hydrogen. The data indicates that for these conditions no stable detonation wave dynamics are achieved, but a rather chaotic behavior with counter-rotating waves, longitudinal thermoaocustic modes and switching wave directions. However, there are also short periods for which evenly distributed co-rotating waves were observed. For that case the wave speed exceeded 2000 m/s and reached 72% of the CJ-velocity.