Validation of Numerical Simulations for Nano-Aluminum Composite Solid Propellants

Abstract

Nano-Aluminum is of interest as an energetic additive in composite solid propellant formulations for its demonstrated ability to increase combustion efficiency and burning rate. However, due to the current cost of nanoaluminumand the safety risks associatedwith propellant testing, itmay not always be practical to spend the time and effort to mix, cast, and thoroughly evaluate the burning rate of a new formulation. To provide an alternativemethod of determining this parameter, numerical methods have been developed to predict the performance of nanoaluminum composite propellants, but these codes still require thorough validation before application. For this purpose, six propellant compositions were formulated, fully characterized, and burning rates were measured at several pressures between 34.0 and 129.3 atmospheres at room temperature, 20 C, and at an elevated temperature of 71.1 C to test the code’s ability to predict pressure-dependent burning rate and temperature sensitivity. To ensure the most accurate model possible, special emphasis was placed on characterizing the size distribution of the constituent nano-aluminum and ammonium perchlorate powders through optical diffraction or optical imaging techniques. Experimental burning rate is compared with the propellant combustion model and shows excellent agreement within 5% for a range of formulations and pressures, however, under other conditions themodel deviates by asmuch as 21%.Ananalysis of the results suggests that the current framework of the numericalmodel is unable to accurately simulate all the combustion physics of high-aluminum content propellants, and suggestions for improvements are identified.