The effect of shaping air on breakup of liquid column by bell-cup atomizer

M. Daikoku, T. Asakawa, S. Tamakuma, K. Sato, R. Sakabe, T. Inamura, S. Amemiya, T. Soma, T. Katayama, Y. Saito, Y. Matsushita, H. Aoki, J. Fukuno

Research output: Contribution to conferencePaperpeer-review

Abstract

The objective of this study was to reveal the characteristics of shaping air (SA) induced atomization of liquid filaments generated at the edge of a rotating bell cup used in spray painting equipment. A single nozzle generating a liquid column was substituted for the rotating cup generating the liquid filament. A high-speed lateral air flow was introduced from the side to locally impinge on the liquid column and the resulting atomization characteristics were investigated to determine the conditions that give rise to the coarse droplets called “ghosts” in automobile spray painting. It was found that the spray angle of the atomized stream from the liquid column increased with increasing air flow velocity. In addition, the air flow velocity required to cause a transition from a deflected liquid column to a spray increased with increasing liquid flow rate. The velocity of the generated droplets increased immediately after mixing with the SA. Variations in the droplet size were also observed; the fraction of smaller droplets increased and the Sauter mean diameter decreased with increasing air flow velocity. The patterns of liquid column breakup were also classified using dimensionless parameters; the larger the Reynolds number for the liquid column/filament, the larger the Weber number for the flow when breakup occurred. Using these dimensionless parameters, the breakup behavior associated with the single nozzle and the rotating bell cup were compared. For a Weber number of 47-52, a liquid film was generated from the liquid filament/column, and the film then broke up into droplets. Flows with the same Weber numbers underwent the same breakup process.

Original languageEnglish
Publication statusPublished - 2015
Event13th International Conference on Liquid Atomization and Spray Systems, ICLASS 2015 - Tainan, Taiwan, Province of China
Duration: 2015 Aug 232015 Aug 27

Conference

Conference13th International Conference on Liquid Atomization and Spray Systems, ICLASS 2015
CountryTaiwan, Province of China
CityTainan
Period15/8/2315/8/27

Keywords

  • Bell-cup atomizer
  • Breakup behavior
  • Liquid filament/column
  • Shaping air

ASJC Scopus subject areas

  • Surfaces, Coatings and Films

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