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ABSTRACT
Soot shell standoff ratios in reduced-gravity droplet combustion are investigated analytically. Analysis of energy conservation shows that temperature gradients between the droplet and a flame, which influence thermophoretic soot transport, are affected by variations in specific heats as well as fuel pyrolysis. Analyses suggest the onset of fuel pyrolysis can be abrupt, leading to local increases in temperature gradients. These temperature gradient changes can be large enough to influence soot shell formation. Estimates indicate that soot shell standoff ratios will increase as droplets decrease in size, which is in agreement with available experimental results for combustion of n-heptane droplets in reduced gravity.
Acknowledgments
The financial support of the NASA Microgravity Combustion Program is gratefully acknowledged. The Technical Monitor was Dr. D. L. Dietrich. Appreciation is also expressed to Prof. F. A. Williams and Prof. P. L. Garcia-Ybarra for their contributions.