Droplet Characteristics in Spray Flames of Jet Fuels and Jet Fuel Surrogates

Droplet statistics of three well-studied reference jet fuels and three surrogate jet fuels with similar pre-vaporized combustion behavior are measured in a piloted spray burner using phase Doppler anemometry. The spray burner consists of a central tube of two-phase flow, resembling an open-pipe atomizer, and a surrounding hydrogen/air pilot flame to assist ignition of the liquid fuel. It is found that the droplet diameters and velocities of the reference jet fuels are quite similar, even under conditions in which their flame lift-off heights differ substantially. The droplet characteristics of the surrogate fuels are more distinct, with significant variations occurring for the droplet velocities and droplet concentrations. However, the surrogate fuel that best reproduces the droplet characteristics of the reference jet fuels is not the same as the one that best matches the average flame lift-off height. Overall, it appears that measurements of droplet characteristics are unable to answer why reference jet fuels exhibit different flame heights under various flow conditions.