Numerical analysis and parameter optimization of ultra-fine air-blast atomizers for rotating detonation engines

Abstract While air-blast atomizers have been extensively studied in conventional combustion systems, systematic investigations under RDE-relevant geometric configurations and parametric optimization of multiple coupled factors remain scarce. In a rotating detonation engine (RDE), liquid fuel must be injected, atomized, mixed with oxidizer, and then detonated within an extremely short residence time. The quality of fuel atomization directly affects the formation and stable propagation of detonation waves. Among various atomization methods, the air-blast atomizer is widely used due to its good atomization performance and structural simplicity. Many factors influence the atomization performance of an air-blast atomizer. The structural parameters of the nozzle mainly include the diameter of the nozzle air passage, the injection angle, and the fuel (diesel) supply rate. In this study, the effects of these three parameters on the Sauter mean diameter (SMD) of the fuel spray, a key indicator of atomization quality, are investigated using a single-factor method. Subsequently, an orthogonal experimental design is carried out to determine the primary and secondary order of the influence of the three factors on the droplet SMD. Based on the SMD as the evaluation index, the optimal combination of the three parameters is obtained. The present results provide parametric trends and design guidelines for the geometric optimization of air-blast atomizers intended for RDE applications. Although the simulations are performed under simplified room-temperature conditions, the observed qualitative trends are governed by the primary breakup mechanisms that are relevant to actual RDE operation, and thus offer valuable directional guidance for injector design. Since elevated temperatures in actual RDE combustors reduce fuel surface tension and viscosity, the SMD values obtained under the present cold-flow conditions represent a conservative estimate of the atomization performance; the actual atomization in hot RDE environments is expected to be at least as good as, or better than, the present predictions. These findings serve as a foundation for future experimental validation and coupled simulations under more representative conditions.