Computational and Experimental Investigation of a Spray Rig for Airborne Icing Tankers

Computational and experimental investigations were conducted to evaluate the performance of a spray rig for airborne icing tanker applications. Tests were performed at the Wichita State University (WSU) 7-ft x 10-ft wind tunnel facility to assess the effects of spray nozzle number density, pattern and spacing on spray cloud plume size and uniformity. Air-atomizing multi-jet nozzles and vortex generators were incorporated into the spray rig design to enhance cloud size and uniformity. Computational fluid dynamics (CFD) analyses were conducted prior to the wind tunnel tests to evaluate the effects of vortex generators and nozzle support structure on spray cloud droplet dispersal. FAR Part 25 Appendix C and SLD spray cloud conditions were generated with a computer controlled spray system developed at WSU. Spray plume sizes were documented at an airspeed of 155 mph using a laser sheet imaging (LSI) technique. Spray cloud liquid water content (LWC) was measured with a CSIRO-King probe installed at the diffuser section of the tunnel. Three nozzle arrangements with 7, 11 and 12 nozzles placed within a circle of 24-in radius were investigated. Spray plume sizes measured at a location 10.5-ft downstream of the nozzles were approximately 5-ft in diameter for all three nozzle arrangements tested. The 11-nozzle spray rig tested provided the best overall cloud uniformity. Spray cloud LWC for the 11nozzle spray rig was 0.13 g/m 3 for a cloud median volumetric diameter (MVD) of 40 microns, and 0.47 g/m 3 for a cloud MVD of 50 microns. For large droplet spray clouds, the LWC varied from 1.20 to 1.50 g/m 3 as the cloud MVD was increased from 100 to 160 microns.