Modeling of the Agglomeration Phenomena in Combustion of Aluminized Composite Solid Propellant

Abstract

A theoretical model was developed in order to predict the size of agglomerates ejected from aluminized composite solid propellants. The model accounts for aspects of both mechanistic and geometric approaches. A thin mobile surface layer is assumed to dominate particle accumulation. Agglomeration number N ag expressing the ratio between ignition and accumulation times, was found to greatly affect the characteristics of agglomeration phenomena, as noted in previous works. The concept of a characteristic distance D e of the mobile surface layer was introduced, depending mostly on coarse AP particle diameter and loading. It was found to have a significant effect on the resulting agglomerate diameter. An agglomeration threshold was defined as the particle diameter equal to the mobile layer thickness. Particles smaller than this threshold have shown tendency to form large agglomerates, whereas particles with a somewhat larger diameter have demonstrated faster ignition and smaller ejected agglomerates. Model predictions for a number of propellant compositions showed good agreement with other theoretical studies as well as with experimental results.

Micro and Nano Scale Phenomena of Aluminum Agglomeration During Solid Propellant Combustion

“…Such situation together with the thickness of the packed accumulation prior to ignition dominates the actual size of the ejected agglomerates. This concept is elaborated by Yavor et al [28,30], who adjusted Gany and Caveny's model to composite propellants by adding geometrical features to it. The situation is illustrated in Fig.…”

Prediction of the Mechanical Erosion Rate Decrement for Carbon-Composite Nozzle by using the Nano-Size Additive Aluminum Particle

“…During combustion of solid propellant, a mobile liquid layer is formed at the burning fuel surface, where aluminum particle melts and agglomerates to form bigger particle [1]. A part of aluminum agglomerates gets completely oxidized either at the fluidized bed or shortly after entering the gas phase.…”

“…This unburnt aluminum does not contribute in enhancing the specific impulse and results only in two phase losses. The size of the agglomerates is determined by the quantity, diameter and ignition time of the aluminum particles [1].…”

“…However, they also result in mechanical erosion on the graphite or C-C composite nozzle wall [1]. Moreover, the…”

“…If the size of the aluminum particles is bigger than the thickness of the fluidized bed,  > , the diameter of the aggregate is represented by the following formula [1]:…”