Spray Characteristics of Standard and Alternative Aviation Fuels at Cold-start Conditions

The spray characteristics of standard and alternative aviation fuels created by a hybrid pressure-swirl airblast (HPSA) atomizer were investigated at conditions corresponding to engine cold start for an aviation gas turbine. Drop size and drop velocity of sprays from three different fuels, Jet-A (A-2), JP-5 (A-3), and a JP-5/farnesane blend (C-3) were investigated using a phase Doppler anemometry. The spatially resolved drop measurements were obtained at three axial locations downstream of the swirler exit plane and up to 30 mm in the radial direction from the spray centerline. Smaller D10, D32, and MMD were observed when increasing the pressure drop across the atomizer swirler (ΔP/P). Increasing ΔP/P also increased the mean axial velocity. No definitive trend was observed with viscosity on drop size, while liquid–gas surface tension showed a weak correlation with drop size due to its small variation in value among fuels. The spray unsteadiness was examined using interparticle arrival time distribution functions. A semi-empirical model was also developed using a phenomenological three-step model for the atomization process of the HPSA atomizer and was used to predict drop-size values at engine cold-start conditions in this work and near lean blowout conditions presented in earlier work.