Disruptive Burning of Aluminum/arbon Slurry Droplets

Abstract

The disruptive combustion of probe-supported and free-falling Al/C/JP-lO slurry droplets (200 to IOOO,um in diameter) was investigated experimentally. The disruption processes and disruption times were analyzed using backlit or natural-light film records taken with a high-speed motion picture camera. Parametric studies were conducted to investigate the influence of the relative proportions of aluminum and carbon in the solids and of surfactant and stabilizing additive levels; and disruption times were quantified with respect to droplet diameter, total solids loading. ambient gas temperature, and oxygen mole fraction. Slurry composition parameters were found to affect the type and strength of the observed disruptive phenomena presumably by altering the porosity and plasticity of the surface shells of solids formed during the early stages of gasification.

Metal Slurry Droplet and Spray Combustion

“…Increasing the gas temperature results in faster heating of the dry particle, and so shorter ignition times, as shown in Figure 3.7(b) While no direct comparison of results is possible with available experimental data, the Wong and Turns [111,112] studies, show similar trends for the ignition times. Figure 3.8(c) shows the effect of changing the initial Reynolds number, for a fixed 4ý = 0.4.…”

“…The manner of liquid vaporization depends upon the permeability, the effective pore radius, the strength of the shell and, depending upon these, several models exist [refer to High-molecular-weight organic dispersing agents are often added to liquid fuel to stabilize the slurries. These additives may pyrolize as the dry outer surface of the shell gets heated to temperatures larger than the liquid fuel boiling point, thus making the shell impervious [19,112]. Also, the pore spaces between the metal particles could be physically filled by addition of submicron particles, e.g., -0.35 pm carbon particles in a slurry droplet consisting of 4 pm aluminum particles, as in the work of Wong and Turns [112].…”

“…As the environment oxygen content is increased, the disruption is seen to occur earlier, largely because of the increased diffusion-flame temperature. The disruptive combustion of A/C/JP-10 slurry droplets is studied experimentally by Wong and Turns [112].…”

“…These additives may pyrolize as the dry outer surface of the shell gets heated to temperatures larger than the liquid fuel boiling point, thus making the shell impervious [19,112]. Also, the pore spaces between the metal particles could be physically filled by addition of submicron particles, e.g., -0.35 pm carbon particles in a slurry droplet consisting of 4 pm aluminum particles, as in the work of Wong and Turns [112]. If the shell is impervious to the gases and liquid flow, then the droplet heating shall result in nucleation inside the shell.…”

“…Combustion of metal-based slurries has been studied [5,6,7,68,95,98,111,112] for potential development of high energy density fuels for air breathing propulsion systems as ramjets. Additionally, coal-based slurries have been studied [32,84,93,94] for burning coal in liquid fueled combustors, and calcium-based slurries for reducing SO 2 emissions [63] from coal fueled power plants.…”