The Laboratory Characterization of Jet Fuel Vapor and Liquid

Abstract

Jet fuel (Jet A, Jet A1) was characterized using two gas chromatographic techniques. Headspace gas chromatography (HS-GC) was used to determine component partial pressures and total vapor pressures by measuring vapor densities in equilibrium with the liquid fuel. Component partial pressures and total vapor pressures were also derived from analysis of the neat jet fuel liquid by determining liquid component mole fraction and using this result with Raoult's law to calculate vapor pressure. Measurements of some of the fuel vapor samples were made at 40, 50, and 60 °C and at vapor volume-to-liquid volume (V/L) ratios of 274 and 1.2, representing, respectively, a nearly empty (2.9 kg/m3) and a half-filled (364 kg/m3) center wing tank (CWT) in a Boeing 747-100 series aircraft. The temperatures and V/L ratios were chosen to cover the range of conditions that could exist in the CWT under some aircraft operations. Measurements of other fuel vapor samples were made at the individual fuel flash point temperatures (V/L = 1.2). Characterization of the liquid fuels was done by simple injections of the neat liquids onto a temperature-programmed gas chromatograph. Results from the liquid analyses were used to calculate fuel vapor properties for comparison with the HS-GC results. Results from both characterization methods were used to predict fuel flammability by calculating fuel-to-air (F/A) mass ratios for jet fuels under different use conditions. These F/A ratio results were compared with ratios determined for the fuels at their flash points.