Subatmospheric Extinction of Opposed-Jet Diffusion Flames of Jet Fuel and Its Surrogates

Abstract

In this experimental study, the pressure dependence of the extinction strain rate of flames of jet fuel and other hydrocarbons was measured and quantified. Laminar nonpremixed opposed jet flames of fuel/nitrogen mixtures versus oxygen-enriched air were progressively strained to extinction by lowering pressure over the pressure range 0.1 to 0.68 atm. The fuels investigated were methane, ethylene, jet-A, n-decane, 1,2,4-trimethyl benzene, and blends of n-decane and 1,2,4-trimethyl benzene. All liquid fuels were vaporized and diluted to a mass fraction of 21.5% in nitrogen gas; the gaseous fuels were not diluted. The oxidizer was a 50-50% molar mixture of oxygen and nitrogen. The global strain rate at extinction was seen to monotonically increase with pressure in the sub-atmospheric pressure range explored. Overall reaction orders calculated from density-weighted extinction strain rates were between 1.3 and 2.0. Jet-A flames were extinguished at conditions similar to those for the decane/trimethyl benzene blends, indicating that these blends can serve as a surrogate for Jet-A.