Improving Base-Drag Corrections for Rotating Detonation Combustor Gross Thrust Measurements

One of the primary means of evaluating the total pressure ratio across a rotating detonation engine/combustor requires measuring its gross thrust output. The presence of flat aft-facing surfaces introduces base-drag forces; necessitating corrections to the measured thrust to determine the gross thrust. A finite number of static pressure measurements are taken on these surfaces, which are then numerically integrated to estimate the resulting base-drag force. This work systematically describes the methods of numerically integrating a limited number of pressure measurements at discrete locations. Sample base-drag measurements were performed on the truncated nozzle of a hydrogen/air operated rotating detonation combustor. The nozzle was instrumented with 17 pressure measurements distributed at three evenly spaced circumferential locations. An asymmetry in the pressure distribution is observed contrary to what is typically assumed in the literature. The relative impact of the edge pressure treatment is highlighted and is found to be a significant source of error in the numerical integration. The alternative means of numerical integration using a Gauss–Kronrod scheme is evaluated and compared to the standard Newton–Cotes method. Recommendations are provided to address the limitations and challenges of these types of base-drag measurements as they pertain to rotating detonation combustors.