Acoustic Particle Damping of Propellants Containing Ultra-Fine Aluminum

Abstract

This p aper will present work on the particle damping characteristics of several propellants containing ultra -fine aluminum powder. Typical metalized propellants produce aluminum oxide that can significantly contribute to the acoustic damping of combustion insta bilities in solid rocket motors. Some recent evidence suggests that propellants containing ultra -fine aluminum may have significantly different size distributions of aluminum oxide, which could adversely impact acoustic particle damping. In this study, f our metalized propellants were investigated varying both the size and relative concentrations of both coarse and ultra -fine aluminum. The aluminum oxide particles produced by all propellants were collected with China Lake's particle collector. Typically, two pressures were tested, 50 and 800 psi. The collected residue was analyzed by screening and sedimentation. From extensive particle analyses, the particle damping was computed that would be in a typical rocket motor using these propellants. This pape r will present both the damping and particle distributions from all propellants tested and show that propellants containing ultra -fine aluminum powder will provide less particulate damping in rocket motors.