Burning rate of solid propellants containing micro-nanometric fuel blends

Abstract

Consulta en la Biblioteca ETSI Industriales (Riunet)

[EN] The use of aluminized solid propellants produces the presence of multiphase flow into engines that leads to performance losses. This implies a decrease of the real performance parameters with respect to the theoretical values that could be obtained. Modifications on the propellant formulation may allow obtaining an optimal solution in which performance parameters are increased with minimal loss. In order to do so, a change that can be done is to act on the size of the particles that compose the propellant avoiding the need of changing its global configuration. The modifications have been done on the size of the metal and the oxidizer and the objective of this work has been to observe the effect of the use of fine AP in mixed nano-microaluminum formulations. For every propellant, a study of the burning rate has been done to reveal the impact of the named modifications. The choice of the propellant formulations derives from precedent results obtained for an optimal composition with 3% content of nAl. Using this configuration as the starting point, the experimental campaign conducted in the Space-Propulsion Laboratory of Politecnico di Milano (SPLab) consisted of six different AP/HTPB/Al based composite propellants where the global configuration remained constant (68%AP/18%HTPB/14%Al). The microstructure of the propellants has been changed remaining unchanged these mass fractions looking at pocket composition and resulting effect. This implies variations in the granulometry of both the oxidizer and the metal. Standardized optical and digital techniques have been used to measure the burning rate at different pressures. From the final analysis of the experimental results emerges that mixed nano-microaluminum formulations increased burning rate in comparison with traditional μAl configurations. In addition, the use of fine AP in these mixed formulations did not have a significant impact on burning rate except for an increase for the highest concentrations of fAP. The combination of thermodynamic with experimental results regarding fAP introduction in nano-microaluminum formulations allows demonstrating the dependence of burning rate with flame temperature of the pocket and composition.