Investigation of the Effect of Atomizing Air-to-Liquid Mass Ratio on Spray Dynamics for a Novel Injector Design

Abstract

The present study investigates the effect of the atomizing air-to-liquid mass ratio (ALR) on the spray stability and near-field spray properties of a recently developed transparent novel twin-fluid injector. It involves primary atomization by bubble-bursting and secondary atomization by shear layer instabilities. A previous design integrated swirling flows and successfully enhanced secondary atomization. This design resulted in clean, compact lean-premixed combustion of distinct fuels, potentially enabling small-core fuel-flexible combustors. The current design enhances the primary atomization that leads to fine droplets immediately at the injector exit, rather than the typical liquid jet-core from a conventional air-blast atomizer. The effect of injector on the near-field spray characteristics and dynamics were quantitatively investigated using high-speed laser-driven shadowgraph imaging for ALR of 1.25 to 2.00. Results show that at all the tested ALRs, stable and finely atomized sprays were achieved. Increase in ALR resulted in finer sprays. An optimum ALR of 1.75 was suggested based on the droplet size distribution and stability for future application of the injector’s optimal range of operation in liquid-fueled gas turbine engines that can be expected to have high stability and fuel flexibility.