OPTICAL CHARACTERIZATION OF CROSS-STREAM SPRAY INJECTION, WALL INTERACTION, AND MIXING IN CHANNEL AIRFLOW

The present work reports an experimental investigation on pulsed water spray impingement into cross-stream air flow in an optically accessible channel with circular cross section. Such flow configuration refers to a complex fluid dynamics system due to interaction of polydispersed droplets with the channel wall. The current study aims at gaining some insight into post-impact droplet characteristics and the in-channel mixing process following spray interaction. The spatial distribution of spray droplets across the channel cross section was visualized by application of the laser sheet imaging (LSI) technique at different axial locations. A uniformity index parameter was measured to quantify the degree of mixing. Measurement of spray droplet size distribution post-impingement and at the channel exit was achieved by the interferometric laser imaging for droplet sizing (ILIDS) technique. The impingement of the spray droplets on the channel wall was visualized by high-speed shadowgraphic imaging technique. The effect of introducing a swirler-type mixer in the channel was examined. Experiments were performed by varying the flow and injection parameters. It was found that efficient mixing of droplets after impingement is not very sensitive to moderate variations in the injection parameters though careful swirler design is important.