Detailed numerical investigation on dynamic combustion characteristics of micro-aluminized hybrid rocket and experimental verification

The incorporation of micro-sized aluminum particles significantly enhances the energy performance of hybrid rockets. However, the evolving internal flow field during operation affects aluminum particle combustion characteristics, with underlying mechanisms remaining unclear. To investigate this phenomenon, this study performs a comprehensive numerical analysis of the dynamic combustion process in micro-aluminized hybrid rockets. A combustion model for aluminum particles is established to describe heat convection, radiation, surface reactions, gas-phase reactions, alumina condensation, and phase transitions using a Eulerian-Lagrangian approach. By coupling this particle combustion model, dynamic simulation of the internal flow field is conducted while incorporating fuel regression and nozzle erosion effects. Computational results are validated against experimental data from a firing test of a hybrid rocket containing 58% micro-sized aluminum particles, examining pressure, thrust, propellant morphology, and combustion efficiency. Furthermore, dynamic flow field properties and variations in particle temperature and composition are systematically analyzed. Simulation results indicate that the observed combustion efficiency decline during testing stems primarily from insufficient mixing of partially oxidized intermediate products with oxidizers, attributed to the post-combustion chamber volume contraction. Parametric studies for evaluating aluminum particle size effects are also presented.