EXPERIMENTAL AND THEORETICAL-STUDY OF SPRAYS PRODUCED BY ULTRASONIC ATOMIZERS

The atomisation of liquids by means of low-frequency ultrasonic atomis ers results from unstable surface waves generated on the free surface of a thin liquid film. These unstable waves are obtained from the tuni ng of the amplitude and the frequency of an imposed oscillation. The t hin liquid film develops as the liquid spreads over the atomising surf ace of the atomiser. This paper focuses on a systematic experimental a nalysis of the sprays produced by low-frequency ultrasonic atomisers. The thickness of the liquid film was measured and its effects on the d rop diameter were studied to ether with the effects of both the liquid 's physical properties and the ultrasonic atomiser's characteristics. The relationship between the mean drop diameter and the surface wave w avelength was accurately determined and introduced into a mathematical approach based on the maximum entropy formalism to predict the drop s ize distribution of the spray. Within the range nf working conditions tested the application of this formalism is successful and provides a procedure for the prediction of spray drop size distributions from cal culations only.