Supersonic Combustion and Flow Evolution in Dual-Combustion Ramjet Engine

Abstract

This work presents a numerical investigation of supersonic combustion dynamics and flow evolution in a dualcombustion ramjet (DCR) engine. Two series of parametric numerical experiments were conducted for the DCR combustor configuration by varying the length of the constant-area section LC and the divergence angle θ of the expansion section. The operating conditions were selected to mimic realistic flight scenarios. Two distinct combustion modes were identified, based on the occurrence of thermal choking. To analyze the combustion characteristics of these modes, chemical explosive mode analysis was performed, along with an evaluation of the Damköhler number. In the thermally choked combustion mode, both pressure and temperature were significantly elevated compared to the supersonic shear-layer combustion mode. This increase is attributed to the coupling between pressure and heat release, which enhances combustion efficiency. A thermal throat forms at the end of the constant-area section, while the divergent section functions as a supersonic nozzle. The exit Mach number in thermally choked cases is higher than its counterpart in supersonic shear-layer mode cases. An optimal geometric combination of the constant-area and expansion sections significantly improves the propulsion performance of the DCR engine.