Vortex generation using fin-slot structures and a submerged nozzle at a wall-injected cylinder

Abstract

The internal flows of solid rocket motors are not yet fully understood. Several cold-air flow experiments that simulated combustion gas flow with compressed gas wall injections have been conducted to observe the behavior of internal flows and acoustic phenomena. Direct visualization, however, has rarely been performed due to the non-transparency of the wall-injecting media. In this study, novel techniques were employed to visualize the internal flow of the cold-flow model of a solid rocket motor. The smoke, which was generated using a heated Ni–Cr wire, was used as a flow tracer, and a light penetrated through an acrylic nozzle. The head-end of the test model was made with a transparent acrylic window to record the visualized flow using a high-speed CCD camera. The results of the visualization at the nozzle entrance region showed the symmetric vortex tube structures and the transient behavior of the circumferential flow. The vortex tube generation mechanism was explained with reference to the inlet vortex phenomenon of an aircraft engine. Also, it was observed that the interaction between the adjacent vortex tubes created the circumferential flow.