Liquid Atomization Using a Rotary Bell Cup Atomizer

Abstract

This present study investigates liquid flow patterns on the inner surface of a rotary bell cup atomizer and the effect of these flow patterns on the breakup patterns at the edge of the rotary bell cup. It also estimates the atomization characteristics based on the diameter of liquid ligaments issuing from the cup edge. The cup had an outer diameter of 70 mm and the following experimental conditions were used: rotational speed N = 1,000 to 50,000 rpm and liquid flow rate Q = 50 to 300 mL/min. Classification of the breakup pattern at the cup edge revealed that, irrespective of the flow rate, several liquid ligaments were produced at low rotational speeds and fine ligaments, which cause Rayleigh breakup, were generated at high rotational speeds. Classification of the liquid flow pattern on the cup surface revealed that the liquid film on the surface was a smooth film at low rotational speeds and a radial streak film or a partial dry film at high rotational speeds. Good atomization characteristics are expected since the radial streak film and the partial dry film cause fine ligament breakup at the cup edge. It was also demonstrated that the mean droplet size for Rayleigh breakup, which generates uniform droplets, can be effectively estimated by calculations based on the diameter of the ligaments that form on the cup edge.

Keywords

• rotary atomizer
• ultra hi-speed
• groove
• breakup pattern
• flow pattern
• atomization characteristics
• ligament diameter