ID 349

EFFECT OF ELONGATIONAL FLOW BEHAVIOR AND PIGMENTATION ON LIGAMENT DISINTEGRATION AND DROP FORMATION BY MEANS OF A HIGH-SPEED ROTARY BELL ATOMIZER

 

Abstract:

High-speed rotary bell atomization is widely used in the automotive industry. It is characterized by high coating quality at short process times. In this application, ligaments are formed at the bell edge and disintegrate into droplets. Since resulting coating layer quality depends on atomization, it is essential to investigate this process. Numerous studies have dealt with the influence of material properties and application parameters on droplet size for Newtonian fluids. However, effects of elongational flow resistance and viscoelastic fluid properties on atomization have not been investigated in detail. In this study a model system is used, allowing for a variation of elongational flow behavior at essentially constant shear flow properties. The latter were determined using rotational and capillary rheometry. Elongational flow resistance was characterized using Capillary Breakup Elongational Rheometry (CaBER). Information about ligament disintegration was extracted from high-speed video recordings at the bell edge. Droplet size distribution was determined using Phase-Doppler-Anemometry (PDA). We show that increasing elongational flow resistance stabilizes ligaments towards disintegration but does not influence droplet size. Decreasing rotational speed leads to an increase of ligament length and droplet size, whereas volume flow rate hardly influences atomization results.