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Ultrasound‐modulated two‐fluid atomization of a water jet
Author(s) -
Tsai Shirley C.,
Childs Paul,
Luu Patrick
Publication year - 1996
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690421206
Subject(s) - drop (telecommunication) , capillary action , amplitude , capillary wave , wavelength , mechanics , ultrasonic sensor , chemistry , ultrasound , coaxial , volumetric flow rate , optics , analytical chemistry (journal) , materials science , acoustics , physics , chromatography , composite material , surface wave , telecommunications , electrical engineering , computer science , engineering
A new spray technique, called ultrasound‐modulated two‐fluid (UMTF) atomization, is based on resonance between the liquid capillary waves generated by ultrasound and those generated by high‐velocity air. The capillary waves generated by ultrasound on the cone of liquid film issuing from a coaxial two‐fluid atomizer are magnified in amplitude by air blowing around them. Atomization occurs when the amplitude of the capillary waves is too great to maintain wave stability, and the resulting drop sizes are determined by the frequency of the ultrasound. Calculations of the relative amplitude growth for the capillary waves of various wavelengths yield predictions that agree remarkably well with experimental results of drop size and size distribution. Specifically, uniform drops with diameter determined by the third harmonic frequency of the ultrasound are obtained in UMTF atomization at high air velocity and large air‐to‐water mass ratio. In contrast, drop‐size distributions with multiple peaks are obtained in UMTF atomization at low air velocity and small air‐to‐water mass ratio. The use of air also allows the liquid jet to atomize at ultrasonic power levels below and liquid flow rates above the threshold values for ultrasonic atomization without air. These new findings provide not only direct evidence of the capillary wave mechanism but also a means of controlling drop size and size distribution in two‐fluid atomization.