Side Loads in Dual Bell Nozzles, Part II: Design Parameters

Kurzfassung

The contour inflection of the dual bell nozzle forces the flow to a symmetrical and controlled separation under sea level conditions. At a certain altitude, the transition to high altitude mode takes place: the flow attaches rapidly the nozzle extension wall down to the exit plane. During this transition, the separation point moves in the extension generating potential high side load peaks due to its asymmetrical position. A campaign of cold flow tests has been conducted to evaluate the generation of side load. The phenomenology during each phase of the flow has been presented in the first part of this work. The influence of the various geometrical parameters on flow behavior and side load generation is investigated in this study. The extension length is shown to be the critical parameter for flow stability, transition duration and side load generation. A trade off has to be found for the optimization of the dual bell concept to rocket applications.