Numerical Simulation of Dual Bell Nozzle for Rocket Engines

Abstract

Owing to the improved performance, several nozzle concepts have been introduced, that promises a gain in performance when compared with the conventional nozzles. As nozzle plays an important role in the improvement of the rocket engine, many have developed technologies for better operational and reliable nozzles. Altitude adapting nozzles are the most advanced technology in this field. And among them Dual Bell Nozzles have gained reasonable popularity in these days. It is shown that they gain a significant performance gain which is the result of their adaptation to the ambient pressure. Current research results presented for dual bell nozzles are mainly for understanding the flow behavior and optimizing the geometrical parameters for maximum flight performance for a range of altitude by its adaptive characteristics. In general, these altitude adapting nozzles induces less shock waves and expansion waves. Flow phenomena observed in present day experiments and numerical simulations work during different nozzle operational conditions are very much highlighted, and gained attention. Many researchers have presented the occurrence of lateral side loads but failed to explain their detailed flow mechanisms. Also, the key parameters governing fluctuations remain unknown. By its peculiar geometry with a inflection between the two nozzle, this nozzle can control flow separation corresponding to a range of Pressure Ratio. As the capturing of the flow and transition from one bell to another during startup and shutdown in Dual Bell Nozzle is not studied much, motivation for the present work is to get an understanding of the flow behaviour in Dual Bell Nozzle with highlight given to its separation phenomenon at different Pressure Ratio and holding of flow at the transition point. Being an altitude adaptive nozzle, flow separation and side loads being a major concern of such nozzle, in this way, the study can contribute to its better understanding. The comparison with the existing High Altitude nozzles will help to get the improvements obtained. Also another area which is less studied is cooling of dual bell nozzle. Cooling of Dual Bell Nozzle like any other nozzle is important for its improved performance and specific impulse. Hence all these study of flow analysis, holding at transition and cooling in Dual Bell Nozzle will cumulatively help to implement such new concepts in future launching vehicles especially for SSTO (single stage to orbit) launchers and maximizing payloads in the future launch vehicles.