Analysis and modelling of rotating detonation engine refill structures

• Introduces the first analytical model of stagnation-pressure losses in the RDE fresh-gas layer. • Combines slip-line-based expansion modelling with a linearised Method of Characteristics. • Validated against high-fidelity CFD, accurately predicting inlet mass flow and front height trends. • Reveals strong performance impact of lift-induced recirculation on fresh-layer structure. This study presents a novel low-order model for the fresh gas region in Rotating Detonation Engines (RDEs), developed and verified against high-fidelity 2D computational fluid dynamics (CFD) simulations. The fresh gas model provides direct closure for the refill mechanism and can be readily implemented in other 1D or 2D RDE models. The model captures the spatially varying pressure and thermodynamic structure of the refresh layer via a linearised Method of Characteristics (MOC), accounting for the expansion process in the slip line and incorporating mass flow conservation. For the first time, the model incorporates a fully analytical treatment of stagnation pressure losses within the fresh gas layer, primarily attributed to spatial gradients within the injection region. The influence of front lift and associated fresh gas recirculation is also analysed, demonstrating a significant impact on the detonation front height and pressure gain. The model exhibits strong agreement with CFD data across multiple operating conditions, providing a practical tool for predicting spatially resolved refill conditions and enabling a more accurate prediction of post-detonation flow behavior in canonical air-breathing and rocket RDE systems compared with existing models.