Numerical Simulation Of Gas-solid Flow In Solid Rocket Motor

Modern solid rocket motor usually uses aluminum propellant to improve the capability and restrain the unstable combustion. Alumina particles and the gas will form the typical two-phase flow. Two-phase flow affects the motor character. Particles with high speed maybe erode the walls of motor and nozzle. Recently, flush type nozzle is employed in many large solid rocket motors. Larger solid particles generated by aluminum propellant can't enter the nozzle and deposit in the cavity at the back wall of the flush type nozzle, which results in the so-called slag and causes the propellant energy loss and increases passive weight of the motor.In numerical simulation of two-phase flow, there are two approaches (Lagrangian approach and Eulerian approach) typically used for modeling fluid-solid flows. The former treats the fluid phase as continuous phase and the solid phase as dispersed phase and predicts the particle trajectories in the fluid phase as the results of forces acting on particles. The latter treats the solid as a certain kind of continuum and solves two continuum equations for both fluid and solid phase. Base on the advantages and disadvantages of the two approaches, we simulate the two-phase flow in solid rocket motor with these two approaches, and discuss the flow from different aspects. Then simulate the classic examples in the references with the Lagrangian approach and Mixture approach (Eulerian approach) in the big CFD software FLUENT, and compare with the result in the references. At last, we simulate the two-phase flow in some flush type nozzle with the two approaches.The conclusions from the calculation are as follows:1. Lagrangian approach cannot model the solid phase with complex experiences, like evaporation or coagulation, the deposition or washes out, and may clearly see the particle trajectories. It also cannot produce the continual particle speed and the density spatial distribution.