Effect of Aluminum on Heat Flux from a Simulated Rocket Propellant Flame

Abstract

Aluminum particles have been shown to enhance the performance in propellant systems by reacting and releasing significant chemical energy that contributes to the overall heat release. However, the heat transfer characteristics from a propellant to a target are not well understood. In this study, impinging flow geometries of a simulated propellant flame seeded with aluminum particles were investigated. Although the contribution of aluminum was the main focus of this study, inert powders of alumina-titania and yttria stabilized zirconia were also used to compare and quantify the heat flux contributions of reacting, melting, and nonmelting powders, respectively. An oxygen-acetylene torch seeded with aluminum, alumina-titania, or yttria stabilized zirconia was used to analyze the different heat transfer characteristics from each material. Copper coupons captured and quenched reacting particulates from the flame. A scanning electron microscope with energy dispersive spectroscopy and a differential scanning calorimeter were used to examine the degree of completion of aluminum oxidation. Results show that yttria stabilized zirconia experience a 1.9% increase in heat flux compared with gas-only flames. Flames seeded with alumina-titania showed an 80.2% increase in heat flux, whereas aluminum particles provide a 232.7% gain over gas-only flames. Results from the differential scanning calorimeter show that aluminum consumption percentages for flames with a 2.5 oxygen-fuel ratio are an average of 8.6% higher than those for a 1.5% oxygen-fuel ratio. The percent of aluminum consumed in the reaction generally increases with standoff distance.