Experimental Characterization of a Two-Phase Flowfield in a Solid Rocket Motor Model

摘要

In solid propellant rocket motors incorporating a submerged nozzle, liquid alumina residues of the combustion can be entrapped in the cavity formed by the casing and the nozzle integration part. This continuous entrapment leads to an accumulation of slag, resulting in a considerable mass at the end of the booster operation. Various aspects of the slag accumulation are experimentally investigated using a simplified cold-gas model. The main focus is on the characterization of the internal flowfield by a new two-phase particle image velocimetry method in a representative cold-gas, two-phase flow configuration. The technique is based on a two-color YAG laser and phase separation methodology using fluorescent dyes. This approach permits the simultaneous separation of the images of the two phases by optical means. This new method opens a new dimension of experimental capabilities and two-phase numerical code validation. The investigation reveals two droplet-entrapment mechanisms for small and large droplets, respectively. Small droplets tend to follow approximately the gas flow and are therefore transported to the recirculation zone within the cavity and contribute to the accumulation. Large droplets follow a ballistic trajectory and can therefore be entrapped by the cavity due to their inertia. This also increases the amount of accumulated liquid in the slag pool.