Characterization of Liquid Sprays in the Pre-Vaporization Tube of a Small-Scaled Annular Combustor

Backlit imaging and digital in-line holography (DIH) were used to characterize fuel films and droplet formation within a pre-vaporization tube (PVT) geometry, which is characteristic of a small-scale gas turbine combustor. Non-reactive liquid water and atmospheric air sprays were investigated at conditions scaled to engine ignition. At the nominal airflow, the water failed to atomize and instead exited the PVT as a slow drip. This is consistent with ignition challenges in reactive experiments reported by others. As the airflow increased, a film developed along the PVT walls and atomized into a sparse spray at the PVT exit with measured Sauter Mean Diameters (SMDs) between 25–50 μm. These results indicate that insufficient liquid film development inhibits spray atomization, and design improvements are needed.