Investigation of Solid-Fuel, Dual-Mode Combustion Ramjets

An investigation was conducted to determine the feasibility of using a solid-fuel, dual-combustion mode ramjet (DMRJ) for hypersonic vehicles (e.g., tactical missiles) operating at a design point of Mach 6 and an altitude of 24.4 km. The analysis showed that, with a supersonic combustion efficiency of 90%, the DMRJ can exceed the performance of the solid-fuel ramjet (SFRJ) by as much as 20% at near stoichiometric fuel-to-air ratios, neglecting heat and wall shear losses in the supersonic combustor. It also seems that the combustion efficiency must be greater than 70% in order for the DMRJ to outperform the conventional SFRJ at the chosen design point. Chemical kinetics considerations revealed that the dual-mode configuration enables the efficient use of solid hydrocarbon fuels due to the existence of highly reactive species in the supersonic combustor, after the completion of the initial slow reaction stages in the subsonic gas generator. Preliminary laboratory tests demonstrated the operation of such a DMRJ system, including the establishment of sustained combustion in the supersonic chamber.