Investigation on burning behaviors of aluminum agglomerates in solid rocket motor with detailed combustion model

Solid rocket motor has been widely used in space exploration because of its advantages such as high energy density, compact structure and fast response etc., in which aluminum powder is commonly employed as a fuel additive to facilitate density and specific impulse. Evolution process of aluminum particles in solid rocket motor is significantly complicated. To characterize the detailed burning behaviors of aluminum agglomerates in solid rocket motor, this study develops a computational framework, in which propellant combustion model, agglomeration and burning models of aluminum particles are integrated into multiphase flow approach. The model was gradually validated by experimental results. States of single particle and particle clouds in solid rocket motor were analyzed, and the influences of agglomerate size, coarse-to-fine ratio of ammonium perchlorate and pressure on combustion properties of aluminum particles and specific impulse were examined. Results show that the highest and average temperatures in combustion chamber are 3300 and 3100 K, respectively. The agglomerates with diameter less 60 μm can achieve complete combustion at 10 mm away from burning surface, whereas agglomerates with larger size injected from the latter half chamber account for greater proportion in incompletely consumed aluminum particles at nozzle outlet. Larger agglomerate size at burning surface leads to greater particle size distribution in the entire space of solid rocket motor. The combustion efficiency and specific impulse increase with reducing size of agglomerates, and coarse-to-fine ratio of ammonium perchlorate away from critical value, and increase of pressure.