Ultrasound-modulated twin-fluid jet atomization

We have observed a new resonance phenomenon 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 twin-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. Specifically, single-peak frequency plots with the peak frequency occurring at drop diameter determined by the third harmonic frequency of the ultrasound can be obtained by tuning air velocity. We have also found that with the use of air, jet atomizes at ultrasonic power levels below and liquid flow rates above the threshold values for ultrasonic atomization without air. In addition, 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 twin-fluid atomization