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ISSN Print: 2150-766X
ISSN Online: 2150-7678
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EVOLUTION OF ALUMINUM AGGLOMERATES MOVING IN COMBUSTION PRODUCTS OF MODEL SOLID PROPELLANT
ABSTRACT
Based on the use of special propellants that generate model monodisperse agglomerates with given size and structure during combustion, a new approach has been elaborated for reducing the uncertainty in data obtained on agglomerate evolution. The experiments with agglomerates of 400−540 μm in size and initial aluminum content 42.6 % were carried out under pressures 10−64 atm. Via direct size and weight measurements and chemical analyses of sampled particles, the following correlation for incompleteness of aluminum combustion (η) has been found: η = 2.86t−0.28P−0.20, where η = mAl/mAl0; mAl is the mass of free aluminum in sampled agglomerate and mAl0 is the initial mass of aluminum in agglomerate; t is the residence time for agglomerate in flame of burning sample (20<t<90 ms); P is the pressure (10<P<64 atm). The mass fraction (φ) of oxide accumulated on the burning agglomerate was found to increase with extent of aluminum conversion ξ = 1−η as ξ = 0.539 + 0.213ξ. The agglomerate mass also increases with ξ due to oxide accumulation on the burning agglomerate. For calculation of 1) the burning agglomerate motion law and 2) the residence time for agglomerate in the flame, the drag coefficient Cd was assumed in the form Cd = K/Re, where Re is the Reynolds number. K was determined in special experiments on panicle trajectory visualization at pressure 1 atm and found to be equal to K = 45±7 for 7<Re<9.
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