Effect of the Precessing Vortex Core on Primary Atomization

Abstract

The present work is focused on the airblast atomization in a gas turbine model combustor. Swirl flows in such combustion chambers form an inner recirculation zone that can develop a precessing vortex core. This instability affects the velocity field at the exit of the nozzle, where the fuel is atomized. The influence of the precessing vortex core on the airblast atomization is examined in this work. The flow field in the combustion chamber is examined under reacting and non-reacting conditions. The velocity amplitudes under reacting conditions are more than twice as high compared to non-reacting conditions. The influence of the precessing vortex core on the airblast atomization process is examined in detail at an atomization test rig with a perspex nozzle. High speed shadowgraphy and POD analysis have been performed of the liquid film on the prefilmer as well as on the ligaments formed at the atomizing edge. It was observed that although the PVC does affect the liquid film flow of the prefilming surface, it does not affect the breakup into ligaments, i. e. primary atomization.

Numerical study on pre-film atomization mechanism and characteristics by a coaxial swirl injector

“…Rizk and Lefebvre 2 and other scholars have found that an increase in liquid-film thickness leads to an increase of droplet average diameter. Müller et al., 3 Gepperth et al., 4 and Bärow et al., 5 however, pointed out that the change of film thickness has no effect on the droplet size because of the decomposition and coupling of the atomized edge film during film decomposition. These two different points of view are worth more work to explore and find the truth.…”