Propulsive Performance and Heating Environment of Rotating Detonation Engine with Various Nozzles

TLDR

Geometric throats are commonly used in rocket combustors to increase pressure and specific impulse. The study measures thrust of an ethylene/gas‑oxygen rotating detonation engine with different throat geometries under vacuum backpressures of 1.1–104 kPa. The experiment tested an ethylene/gas‑oxygen rotating detonation engine with throatless and three throat‑contraction ratios (1, 2.5, 8), measuring thrust, specific impulse over a range of pressure ratios, and heat flux using heat‑resistant walls for doublet and triplet injector shapes. Combustor pressure scaled with equivalent throat mass flux, the engine achieved comparable optimum specific impulse across all backpressures, and heat flux was roughly proportional to channel mass flux.

Abstract

Geometric throats are commonly applied to rocket combustors to increase pressure and specific impulse. This paper presents the results from thrust measurements of an ethylene/gas-oxygen rotating detonation engine with various throat geometries in a vacuum chamber to simulate varied backpressure conditions in a range of 1.1–104 kPa. For the throatless case, the detonation channel area was regarded to be equivalent the throat area, and three throat-contraction ratios were tested: 1, 2.5, and 8. Results revealed that combustor pressure was approximately proportional to equivalent throat mass flux for all test cases. Specific impulse was measured for a wide range of pressure ratios, defined as the ratio of the combustor pressure to the backpressure in the vacuum chamber. The rotating detonation engine could achieve almost the same level of optimum specific impulse for each backpressure, whether or not flow was squeezed by a geometric throat. In addition, heat-flux measurements using heat-resistant material are summarized. Temporally and spatially averaged heat flux in the engine were roughly proportional to channel mass flux. Heat-resistant material wall compatibility with two injector shapes of doublet and triplet injection is also discussed.