Numerical Study on Pyrolysis and Combustion Characteristics of Grain in Solid Fuel Ramjets

The solid fuel ramjet (SFRJ) is attracting attention due to its advantages, including high specific impulse, relative design simplicity, and improved combustion stability.This study investigates solid fuel pyrolysis and combustion using a commercial computational fluid dynamics program.Various reaction models and pyrolysis boundary conditions were evaluated, and the simulation results were compared against experimental data from the literature.Additionally, the effects of different air inlet mass flow rates and temperatures were examined using the reaction model and boundary condition that provided the best match with experimental data.Simulations were performed using the eddy dissipation model (EDM) and non-premixed combustion model (NPCM) under the assumption of complete fuel decomposition, applying mass flow inlet and wall+source conditions.The results indicated that the NPCM, particularly when coupled with the wall+source boundary condition, closely matched experimental data, yielding mean relative errors of 1.9% for outer boundary regions and 9.8% for temperatures.Parametric simulations further revealed a higher CO mass fraction in the premixed region and a subsequent rise in CO 2 mass fraction downstream as combustion progressed.These findings provide valuable insights for optimizing the design and performance of solid fuel ramjets, particularly in terms of enhancing fuel efficiency and combustion stability.