Surrogate Fuel Development Based on Droplet Combustion: Comparison of Multi-Component Mixtures with an Aviation Fuel

Abstract

This study examines the extent to which three and four component mixtures can replicate the burning characteristics of an aviation fuel, Jet-A (designated by the Air Force as “POSF4658”). The three component mixture (n-decane/iso-octane/toluene with a molar ratio 42.67/33.02/24.31) was previously developed to match the derived cetane number and H/C ratio of Jet-A, whereas the four component mixture (n-dodecane/iso-octane/1,3,5trimethylbenzene/n-propylbenzene with a molar ratio 40.41/29.48/7.28/22.83) had been proposed based on a refinement that further matched Jet-A’s molecular weight and threshold sooting index. The approach taken in this paper is that the extent to which a proposed blend may be a useful surrogate could in part be based on the extent to which the surrogate would replicate certain features of the base case for liquid combustion, namely spherical symmetry. Accordingly, in this paper experiments were carried out in an environment that minimizes convection and thereby promotes spherical flame symmetry in the droplet burning process. The initial droplet diameters were fixed at 0.56±0.04 mm. Droplet combustion “targets” measured included the evolution of the droplet, flame and soot shell diameters. Results suggest that the four component mixture better replicates Jet-A’s these targets than does the three component blend.