Design of an Optimized Injector for Oxygen/Hydrogen Rotating Detonation Engines

Abstract

By maintaining a continuous detonation wave the rotating detonation engine (RDE) utilizes a combustion process that is, in theory, more efficient than conventional deflagration-based systems, offering a better conversion of chemical energy to mechanical work and a smaller engine size. However, several challenges must still be overcome before RDEs can be fully integrated into practical rocket or aero-engine applications. These include the deterministic and reliable generation of stable detonation waves and the prevention of manifold-to-chamber coupling to mitigate combustion instabilities. This study focuses on designing and optimizing the RDE injection system, which plays a critical role in addressing these issues. Based on fundamental detonation physics and a literature review, requirements for RDE specific injection design are derived and two injection system concepts are identified: a variation of a triple-impinging injector and a jet-in-crossflow configuration. Additionally, the concept of a Tesla-valve-inspired flow path is found to be a promising approach for preventing backflow into the injector and decreasing chamber manifold coupling. These concepts are then parametrized, analyzed and optimized through three computational fluid dynamics (CFD) studies conducted in ANSYS Workbench. The results of the first two studies indicate that integrating a Tesla-valve-inspired flow path can improve coupling characteristics; however, its impact on reducing the backflow is limited. The third study concentrates on optimizing the injector concepts to achieve a high degree of fuel–oxidizer mixing and to characterize the shape of the injected mixture layer. Ultimately, three injector configurations are developed. These configurations are compared based on three criteria: the degree of mixing, the uniformity of the injected layer, and the potential thermal loading on the chamber walls. Since each configuration demonstrates advantageous behavior in a different area, a final selection cannot be made. However, if the described configurations will be tested experimentally, the comparison of the respective performance with the derived characteristics will provide an opportunity to analyze the relevance of the evaluation criteria for injector to the actual combustion behavior of the RDE.