Abstract
The effects of surfactant on the evaporation, shell formation and disruptive behavior of suspended alumimum/JP-10 and boron/JP-10 slurry droplets (1300±50 μm in diameter) were studied experimentally for various surfactant concentrations and solid loadings. With experiment temperatures covering the pyrolysis temperature of the surfactant, the relationship between surfactant pyrolysis and the shell characters as well as disruptive behaviors were carefully investigated. Quantitative measurements indicated that the evaporation rate of slurry droplets was considerably lower than that of pure JP-10, with the suppression increased for higher solid loadings. With the solid loading fixed, the suppression increased for increasing surfactant concentration until, a critical concentration (0.01 to 0.02 for aluminum/JP-10 slurries, depending on the solid loading) was reached, above which the suppression remained essentially constant. Both the intensity and tendency of disruption were enhanced by the pyrolyzed surfactant, which bound the particles to form a tightly-packed shell In addition to existing disruption mechanism, in which the formation of an impermeable shell promoted by surfactant pyrolysis is the key event, an alternative disruption mechanism also may exist, probably with the attainment of the superheat of the carrier fuel liquid. Shell character and disruptive behavior with respect to different surfactant concentrations and particle sizes were also investigated. Disruption intensity was found to increase with increasing surfactant concentration. The shells formed, on slurry droplets with smaller particles were more compact and more plastic. © 1991 Combustion Institute.