Near-field spray characterization of a high-viscosity alternative jet fuel blend C-3 using a flow blurring injector

Abstract

Efficient and clean combustion of jet fuels highly relies on their spray characteristics. Prior studies have shown that the flow blurring (FB) injector developed in the recent decade could generate fine sprays at the injector’s immediate exit rather than a jet core of conventional fuel nozzles. The current study experimentally investigates spray characteristics of a viscous renewable jet fuel, C-3, using FB atomization. The effect of Air-to-Liquid Mass Ratio (ALR) across the injector is investigated. Results show the stable and fine FB sprays are obtained at ALRs of 1.0–2.5 for the high viscosity fuel. Cumulative droplet size distribution and Sauter Mean Diameter (SMD) obtained using high-spatial-resolution Shadowgraph imaging technique (SIT) reveal the fine atomization is rapidly accomplished at approximate 1.67–2.67 D downstream the injector exit with the diameter D of 1.5 mm for all the ALRs. The spray velocity measurements using Particle Image Velocimetry (PIV), the SMD by SIT, and Weber number estimate consistently show rigorous secondary droplet disintegration at spray periphery. Estimation of Weber and Ohnesorge numbers suggests that oscillatory deformation is dominant at the spray center across the effective ALRs, and droplets at higher ALR and spray periphery experience more vibrant breakup modes such as bag, bag-stamen or multi-mode. The results quantitatively demonstrate that the FB injector can generate ultra-fine and stable sprays for the viscous bio-jet fuel C-3, suggesting the potential use of this fuel injector for renewable jet fuels regardless of high viscosity to achieve stable, complete, and premixed combustion with ultra-low emissions.