Spray characteristics and flow topologies of high shear injector at high primary swirl

Abstract

In this paper, we present detailed experimental measurements and analysis on the spray-flow interaction emerging from a newly designed high shear injector. The injector consists of a series of radial/axial entry air swirler with interchangeable flare at the exit and the fuel nozzle mounted concentric to the swirlers. The geometrical parameters concerning the swirl configuration are geometrical swirl number (SNPrim), airflow split ratio(γ), area ratio(Δ), flare angle(θ) and relative flow orientation of primary and secondary swirlers (co and counter-rotation). The time-resolved particle image velocimetry is employed to capture the spray flow field topology. The radial (W/Df) and axial (L/Df) expansion of the recirculation zone are explored with respect to the near field swirl number (SN5). The flow from the present injector indicates a negligible change in the radial expansion (W/Df) of the recirculation zone on switching the relative swirl orientation from counter to co-rotation configuration. The radial dispersion of spray illustrates nearly linear relationship with the size of the recirculation zone, whereas the droplet size distribution is insensitive across the test cases. Furthermore, the spray patternation and droplet size across all the cases indicate that a change in spray cone angle could be achieved without much deteriorating the circumferential uniformity and droplet size distribution. Finally, proper orthogonal decomposition (POD) analysis reveals that with radial expansion of recirculation zone, the peak amplitude shifts to lower frequencies and the turbulent kinetic energy contribution to flow of the different spatial coherent structures change accordingly.