Numerical study on slag accumulation in solid rocket motor with a new Lagrangian-Euler coupled particle computational framework

Slag accumulation is one of the key and most difficult problems in solid rocket motor (SRM) having submerged nozzles, which may cause severe ablation of insulation and even has a great influence on the interior ballistic performance. This study aims to establish a computational framework mainly based on a Lagrangian-Euler coupled particle model, which consider granular flow as a combination of smoke particle continuum phase and large particle discrete phase, to simulate two-phase flow and explore the characteristics of slag accumulation. The computational framework integrated particle injection model, Al particle combustion model and multiphase coupling model as well, and was verified by the Jet Propulsion Laboratory (JPL) nozzle numerical example. The result of the slag accumulation simulation are in good agreement with experiment data. It shows that, the slag starts to be produced after the motor is ignited, and the accumulation rate is larger at the initial time and gradually decreases. The influences of inject particle diameter in slag accumulation are explored. Discrete particles with larger peak diameter cause lower total combustion efficiency, lower conversion rate of Al, and higher slag rate. The particle size of Al₂O₃ smoke have the smallest contribution to the slag rate in the range of 1.5μm-2.5μm.