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ICLASS 94<br>Proceedings of the Sixth International Conference on Liquid Atomization and Spray Systems

ISBN:
978-1-56700-019-1 (Print)
978-1-56700-445-5 (Online)

ATOMIZATION OF WATER BASED METALLIC PAINT BY MEANS OF ELECTROSTATION ROTARY ATOMIZERS

Klaus Bauckhage
Chemical Engineering Department, University of Bremen, Bremen, Germany

Gunther Schulte
Chemical Engineering Department, University of Bremen, Bremen, Germany

T. Scholz
Universitat Bremen Bremen, Germany

Abstract

Investigations were made on the atomization characteristic of a commercial electrostatic high-speed rotary atomizer. The fluid atomized was a waterborne metallic paint used in automotive coating processes. Methods employed were Laser Light Sheet (LLS) technique for qualitative hydrodynamic studies in the spray cone, Diffraction Spectra Metry (DSM) for integral particle size distributions and Short Spark Photography (SSP) for determining the current atomization mode at the bells edge of the atomizer. The atomizer operation parameters varied were the paint volume flow (100 and 200 ml/min), the bells circumferential speed (75-186 m/s) and applied high voltage (0, 20, 40, 80 kV). Furthermore three geometrical different bell types were tested, one with serrations and two without ones. The LLS-method showed unexpected axial zones of recirculating drops on one hand and a radial swirl on the other. It was observed that these vortices were influenced by the shaping-air volume flow. Different mean drop sizes were found for the three bells and for different paint volume flows. The small dispersion of the drop size distributions leads to the supposition that all the bells worked in ligament atomization mode. This was supported by the results of the Short Spark photographs taken. Increasing applied high voltage leads to smaller drop sizes.