Direct observation of two phase flow generated by an alumina seeded grain in high aspect ratio channels

Abstract

Adding appropriate amounts of aluminum to solid rocket propellant improves energy performance by increasing both the specific impulse and propellant energy density. However, as the propellant combusts, the aluminum is oxidized into alumina (Al2O3) which tends to agglomerate into relatively large molten droplets under the right flow conditions, and may cause significant two-phase flow losses, potentially catastrophic nozzle erosion, and a potentially increased burn rate as a result of erosive burning. Significant research has been conducted regarding agglomerate formation at the propellant surface and agglomerate impact on nozzle erosion, but little is known about agglomerate behavior within high aspect ratio regions of advanced propellant grain designs and how this behavior affects flow through the combustion chamber and impacts erosive burning. An experiment was designed to image agglomerate behavior within these regions. The experimental method was validated using an inert calibration grain containing known alumina particulates. The primary goal of this thesis was to establish a working experimental setup and method that can be used to evaluate agglomerate flow for actual propellant samples.