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Atomization and Sprays

Journal of the International Institutes for Liquid Atomization and Spray Systems

ISSN for PRINT: 1045-5110

Institutional price:	$787.00
Issues per year:	8

Best Paper Award Selection - Editorial Board Site

2003, Volume13

218 pages

DOI: 10.1615/AtomizSpr.v13.i23

Issue price - $150.00

ELECTROHYDRODYNAMICS OF CHARGE INJECTION ATOMIZATION: REGIMES AND FUNDAMENTAL LIMITS

John S. Shrimpton
Department of Mechanical Engineering, Imperial College of Science, Technology & Medicine, London, United Kingdom

Andrew J. Yule
Spray Research Group (SRG), Insititute of Materials Research (IMR), School of Computing, Science and Engineering, University of Salford, Manchester, UK

ABSTRACT

The dynamics and controlling mechanisms of a charge injection electrostatic atomization method for insulating liquids have been investigated using a sharp electrode as a current source, which is placed inside the atomizer and held at a high electrical potential. The method is applicable to highly insulating liquids such as hydrocarbon oils and oil-based solutions, and potential uses of this technology include combustion systems and high-quality spray coating/deposition applications. Subcritical and supercritical flow regimes of atomizer operation are delineated by different types of electrical breakdown. The subcritical flow regime is limited by an insulation failure of the liquid hydrocarbon itself and occurs inside the atomizer. This regime, although of interest to understand the fundamental nature of the electrohydromechanics, does not produce finely atomized sprays. Atomization performance in the supercritical flow regime is characterized by the maximum spray specific charge being limited by a partial discharge in the gas outside the nozzle, around the liquid jet as it emerges from the nozzle. In this case, finely atomized sprays are possible, and with no electrical limitation on the upper flow rate limit. The maximum spray specific charge achievable in the supercritical regime has been found to increase at larger nozzle exit velocities and also for smaller orifice diameters. These two factors, combined with the increased aerodynamic shear acting on the charged liquid jet as it emerges from the orifice at higher velocities, enhances the destabilization of the charged liquid jet to produce finely atomized and well-dispersed sprays of insulating liquids.