CHARACTERIZATION OF SPRAY ATOMIZATION OF 3003-ALUMINUM-ALLOY DURING LINEAR SPRAY ATOMIZATION AND DEPOSITION

Linear spray atomization and deposition is an attractive technique to produce near-net-shape deposits, such as aluminum sheet and strip. In the present study, phase Doppler interferometry (PDI) was used in a ba ckscatter mode to characterize, in situ, the droplet size and velocity distributions during linear spray atomization and deposition of a 300 3 aluminum alloy. The PDI measurements were obtained along axes corres ponding to the direction parallel to the nozzle slit and to the direct ion perpendicular to the slit. The PDI results delineate the temporal and spatial distribution of the droplet size and velocity during the m etal spray. Both point and ''line'' measurements were obtained and are reported. The line measurements resulted from the integration of meas urement made along a line scan obtained in real time (i.e., not ensemb le averaged). Postrun analysis of the droplet size distribution using laser diffraction and sieving techniques is also reported. The PDI poi nt measurements revealed that droplet size and velocity distribution w ere relatively invariant with time. The line measurements of droplet v elocity showed that the droplet axial velocity exhibits a bimodal beha vior, which becomes more apparent with increasing atomizing gas pressu re, a result of droplet recirculation inside the spray chamber. In add ition, the peak in the droplet axial velocity distribution increased a s atomizing gas pressure increased. The line characterization also sho wed that the droplet size distribution became more homogeneous with in creasing gas pressure, and that the distribution characteristic diamet ers of droplets decreased consistently with increasing gas pressure. P ostrun characterization of the droplet size distribution of the entire metal spray using diffraction and sieving methods indicated that the mass (volume) median diameter D-50 and the Sauter mean diameter (SMD) D-32 decreased with increasing gas pressure in a manner consistent wit h PDI results.