Droplet vaporization for conventional and alternative jet fuels at realistic temperature conditions: Systematic measurements and numerical modeling

Abstract The desired reduction of fossil fuel consumption of the aviation sector requires the introduction of alternative jet fuels from renewable sources. A major hurdle for their introduction is the cost-intensive assessment of fuel effects on combustion performance, which relies on fuel-dependent processes such as atomization, vaporization and chemical reaction. The present work describes results from a newly designed experiment that provides accurate measurements of vaporization of free-falling droplets of realistic size (D ≈ 80 µm) in a vertical laminar flow with temperatures typical of technical combustors. Measurements are performed for a set of systematically chosen conventional and alternative multi-component jet fuels for which detailed compositions are available, and for three single species. The results show that the differences of their vaporization can be accurately resolved and related to physical properties. In particular, it is found that the effect of fuel boiling point on vaporization is largest for ambient gas temperatures T∞ below  ≈ 1000 K, whereas for higher T∞ the influence of heat of vaporization is dominant. The well-defined boundary conditions of the experiment further enable a numerical simulation of the ambient flow and the droplet vaporization, where the latter uses a multi-component vaporization model based on a continuous thermodynamic representation of chemical species. Comparisons to measurements show that the present model accurately predicts the temporal evolution of droplet diameters and fuel-dependent effects on vaporization.