UNSTEADINESS IN EFFERVESCENT SPRAYS: A NEW EVALUATION METHOD AND THE INFLUENCE OF OPERATIONAL CONDITIONS

A new evaluation method of unsteadiness of the spray generated by an effervescent atomizer is presented. The method is based on measurements of pressure fluctuations in the atomizer mixing chamber. Measurements, made under different atomizer operational conditions, show the spray unsteadiness depends mainly on Gas-to-Liquid-Ratio (GLR). Decrease in GLR causes the spray to become more unsteady. The relation between atomizer internal two-phase flow pattern and the spray unsteadiness is elucidated by visualization of the internal twophase flow using a digital camera and the use of published two-phase flow maps. Findings of the new method are complemented and confronted with the results obtained by the use of spray unsteadiness evaluation method of Edwars & Marx.