Superior Al90Mg10-Based Composite Fuel Grain for a Hybrid Rocket Engine

Abstract

A paraffin-based fuel coupled with a nested helical matrix structure is a low-cost, high-performing alternative for hybrid rocket engine applications. The mechanical and combustion properties of the composite fuel grain can be enhanced by replacing the conventional polymer matrix with a metal skeleton. Three-dimensional printing was used to design an Al90Mg10 skeleton embedded with the paraffin-based fuel. The combustion characteristics of the composite fuel grain, including the ignition behavior, pressure oscillations, regression rate, and combustion efficiency, were comprehensively investigated. The properties of grains with and without a secondary perforated structure were compared. The flame structure and metal burning behavior of the hybrid rocket engine were monitored by endoscopic radioluminescence imaging, and the emission spectral characteristics of the plume were analyzed simultaneously. Good flammability makes the Al90Mg10 helical skeleton a promising candidate for enhancing the combustion performance of a paraffin-based fuel grain. The combustion process with rapid ignition was relatively stable, and no additional pressure oscillation frequency was observed. The metal-based composite fuel grains had a superior regression rate to that of a paraffin-based fuel grain (up to 100% higher using the perforated skeleton). Introducing a secondary structure into the fuel grain promoted the reaction and thereby enhanced the combustion performance.