Stable Hydrocarbon Diffusion Flames in a Weightless Environment

Abstract

An experimental investigation of stable laminar ethylene and propylene diffusion flames burning on a nozzle in weightlessness was performed at the NASA-Lewis 2.2 Second Drop Tower. For a range of low flow conditions, visual evidence indicated that the flames reaction zone was burning over a wide range of combustion rates; however, for the purposes of correlating flame length the stoichiometric burning rate appeared adequate. It was found that if Re is the ambient pure fuel Reynolds number based on nozzle radius, Sc is the ambient pure fuel Schmidt number, and c, is the mole fraction of fuel burning stoichiometrically in air, the ratio of flame length to nozzle radius was predicted and experimentally verified to be proportional to Sc^1/2 Re ln^1/2 (1/(1−c₈)).