Improved particle scavenging by a combination of ultrasonics and water sprays

The results of an experimental study are presented where an ultrasonic field was used to increase the scavenging of micron-scale particles by water sprays. Specifically, an ultrasonic standing wave field was set up between an ultrasonic transducer and a reflector, creating multiple pressure nodes. These nodes are locations where drops collect into what we call accretion disks. Significant increases in the scavenging coefficient were observed when these accretions disks were present. Experiments conducted in the presence of an ultrasonic standing wave field and a water spray yielded scavenging coefficients as large as 140% of those which were obtained using a spray alone. Also, experiments conducted with the ultrasonic field present, but detuned so that accretion disks did not form, showed no significant improvement over the case without ultrasonics at all. The scavenging coefficients are presented as a function of particle diameter and water flow rate.