Investigation of Regression Rate for Htpb-Based Solid Fuel On Varying Nozzle Throat Dimensions In Ducted Rocket Applications

Abstract

Ducted rocket (DR) propulsion systems are gaining attention for their ability to enhance efficiency and performance in aerospace applications due to their efficient and controllable thrust generation. It integrates a gas generator with a ramjet engine, featuring primary and secondary combustion chambers. The combustion of solid propellant in the primary chamber produces high-pressure, high-temperature gases that are directed to the secondary chamber for reburning with atmospheric air from the duct. It provides superior specific impulse compared to conventional rockets and higher specific thrust and combustion efficiency than other ramjet designs [1]. Hydroxyl-terminated polybutadiene (HTPB) is extensively used in solid propellant rocket motors as both a fuel and binder, holding significant importance in the field of propulsion. It serves a dual role by acting as a binder for alloys and metal additives [2]. It offers superior energy density, improved temperature stability, favourable combustion characteristics, and reduced smoke emissions compared to paraffin wax. In this study, HTPB is employed as the fuel, while compressed oxygen serves as the oxidizer. The experimental results conducted by other researchers indicated that there is a decrease in combustion chamber pressure as the nozzle throat diameter increases [3]. The current research delves into the investigation of regression rates for HTPB-based solid fuel within the context of DR propulsion, with a specific focus on the effect of varying nozzle throat dimensions on regression rate. 3 sets of experiments were conducted using varying nozzle diameters of in a laboratory-scale hybrid fuel-ducted rocket, and their regression rate was analysed