Dual Diverging Annular Rocket Nozzle (Focusing Flow Separation and Minimizing Overexpansion)

Nozzle is a device designed to control the rate of flow, speed, direction, mass, shape, and the pressure of the stream that exhaust from them. Nozzles come in a variety of shapes and sizes depending on the mission of the rocket. This is very important for the understanding of the performance characteristics of rocket. The increasing demand for higher performance in rocket launches promotes the development of nozzles with higher performance, which is basically achieved by increasing the expansion ratio. However, this may lead to flow separation due to altitude variations and thus resulting in asymmetric forces, so-called side-loads, which may present life-limiting constraints on both the nozzle itself and other engine components. By the proper geometrical design of the nozzle, the exhaust of the propellant gases will be regulated in such a way that maximum effective rocket velocity can be reached without flow separation. Convergent divergent nozzle is the most commonly used nozzle. The present paper presents a comprehensive, review of supersonic flow separation in internal rocket nozzle due to altitude variations and hence a different method of separation control has been suggested by redesigning the bell-shaped rocket nozzle. In this work a comprehensive simulation of a flow in a typical supersonic converging-diverging bell shaped rocket nozzle has been reported. In the respective nozzle, flow suddenly contracts at a certain point and then expands after throat. All the simulation endeavors have been carried out by ANSYS FLUENT. The simulations have been conducted in 3D domains to provide better comparative platform. Also, a comprehensive simulation of a flow in the proposed supersonic converging-diverging bell shaped rocket nozzle has been conducted. Furthermore, comparison between CFD modeling results and corresponding available measured data has been presented.