STRUCTURE AND SOOT PROPERTIES OF NONBUOYANT ETHYLENE AIR LAMINAR JET DIFFUSION FLAMES/

The structure and soot properties of round, soot-emitting, nonbuoyant, laminar jet diffusion Blames are described, based on long-duration (1 75-230-s) experiments at microgravity carried out on orbit in the Spac e Shuttle Columbia. Experimental conditions included ethylene-fueled f lames burning in still air at nominal pressures of 50 and 100 kPa and an ambient temperature of 300 K with luminous flame lengths of 49-64 m m. Measurements included luminous flame shapes using color video imagi ng, soot concentration (volume fraction) distributions using deconvolu ted laser extinction imaging, soot temperature distributions using dec onvoluted multiline emission imaging, gas temperature distributions at fuel-lean (plume) conditions using thermocouple probes, soot structur e distributions using thermophoretic sampling and analysis by transmis sion electron microscopy, and flame radiation using a radiometer. The present Barnes were larger, and emitted soot more readily, than compar able flames observed during ground-based microgravity experiments due to closer approach to steady conditions resulting from the longer test times and the reduced gravitational disturbances of the space-based e xperiments.