Morphology and concentration of smoke from fluorinated ethylene propylene wire insulation in microgravity under forced airflow.

The production of smoke particles from the jet bursting flame caused by overheating fluorinated ethylene propylene (FEP) wire insulations was investigated. Experiments examining the morphology and volume fraction of the fractal smoke particle aggregates with forced airflow were conducted in a 3.5s drop tower. Gravity level and forced flow were shown to have significant hydrodynamic effects on the pathlines and fractal aggregation of the smoke particles, thus the residence time-dependent flame shape, particle size and concentration have obvious changes. For cases in still air, compared with normal gravity, the jet flame in microgravity has a spherical shape, the mean primary particle and aggregate gyration radius are bigger due to longer residence time, but the fractal dimension maintains at about 1.79, similar to that in the normal gravity level; the calculated smoke volume fraction is also bigger. For cases with force flow in microgravity, the mean primary particle diameter, the mean aggregate gyration radius, and soot volume fraction all decrease with increasing forced flow due to decreasing residence time.