Studying drop cluster and array behavior using an acousto-electric levitator

Abstract

An acousto-electric levitator is developed for studying the formation and behavior of drop clusters and arrays. The device enables us to form suspended 2-D drop clusters and arrays by using electric and acoustic fields to levitate and manipulate drops. The spacing and the size of drops can be easily controlled by varying electric and/or acoustic field intensities. Experiments have been done on single- and multi-component drops, such as octane and dodecane, which are primary materials in natural fuels. Studies are focused on the evaporation rate of each drop due to the interaction in the array. The acoustic frequency has been increased from 28 kHz to more than 150 kHz so that generation and control of smaller drops, associated with spray combustion, are possible. The formation process of clusters and arrays, and the force balance among drops are analyzed. A theoretical calculation based on the diffusion-controlled model is compared with these experimental results. This high-frequency acoustic levitator is also used to study solid particle clusters whose size is around 10 μm by using a mixture of solid particles and liquid, and then letting the liquid evaporate. [Work supported by NASA through JPL Grant No. 958722 and NASA Grant No. NAG3-2147.]