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A numerical study of the electrostatic rotary bell paint spray transport region is carried out using a newly developed simulation code. Firstly, a time-accurate Navier-Stokes equation solver, utilizing the space-time conservation-element/solution-element methods, simulates the shaping air based on the known boundary and initial condition. Secondly, a particle trajectory solver, which interacts with airflow by momentum coupling, is applied to simulate the paint spray characteristics. Thirdly, an analytical solution of electrostatic field is coupled to simulate realistic electrostatic rotary bell paint sprayer. The integrated software is then applied to simulate the paint spray transport processes according to the operating conditions of interest. The numerical results show that the spray flow is very sensitive to some of the operation parameters. The transfer efficiency and the uniformity of paint distribution increase with charge-to-mass ratio and electrostatic voltage.

A better understanding is needed of the electrostatic rotating bell (ESRB) application of metallic basecoat paint to automobile exteriors in order to exploit their high transfer efficiency without compromising the coating quality. This paper presents the initial results from experimental investigation of sprays from an ESRB which is designed to apply water-borne paint. Water was used as paint surrogate for simplicity. The atomization and transport regions of the spray were investigated using laser light sheet visualizations and phase Doppler particle analyzer (PDPA). The experiments were conducted at varying levels of the three important operating parameters: liquid flow rate, shaping-air flow rate, and bellcup rotational speed. The results show that bellcup speed dominates atomization, but liquid and shaping-air flow rate settings significantly influence the spray structure. The visualization images showed that the atomization occurs in ligament breakup regime.