| As an efficient method of enhancing the transfer processes, the technology of impinging streams has taken on a wide prospect in the field of chemical engineering. The present researches on this technology are only focused on the microparticle clouds in a two-phase flow or the macroscopic gas-droplet systems, while the direct examination on a single particle or droplet is still at the beginning stage in the study. To resolve the above-mentioned question, the reliable experimental method, whose key is to acquire the controllable levitation for a single microparticle and the in-situ trace and measurement to the superficial transfer processes, is urgent and very significant to the studies in the microcosmic chemical engineering. Based on the applications of the super-gravity effect of impinging streams in the transfer processes, and breaking through the limitation of the static levitations for the present electrodynamic balances (EDB), a new experimental method of the measurements on the superficial mass transfer phenomena for a single oscillating droplet in electrodynamic super-gravity field has firstly been put forward here. In the experiments, a single 2-dodecanol microdroplet was stably levitated by an octopole double-ring EDB in a N2 gas flow and was in the oscillation confined only in the axial direction. The technology of high-speed linescan was applied to trace, record the particle oscillation, and the rate of mass transfer for the microdroplet evaporation could be examined by the technology of elastic light scattering whose precision is up to the mass level of 10-7 milligram. This experimental method will be developed into a powerful tool for the instantaneous mass transfer phenomena, which is significant to promote the researches on the microcosmic transfer processes and the aerosol science. Breaking through the static levitation theory on the particle stability in EDB (namely the Davis two-region theory) further and based on the experimental results, it has been pointed out that there must exist the particle oscillations theoretically, so much as a large-amplitude oscillation, besides the modes of being static and flying lost here. At that time, the Reynolds value of particle is larger by one order of magnitude and has been beyond the Stokes' regime, and the Davis two-region theory is no longer valid.In this study, the oscillation characteristics of a single aerosol microdroplet in EDB has thoroughly been investigated and the conclusions are as the follows:(1) The complete motion differential equation, based on Oseen's formula of the viscous drag, for an oscillating microparticle in EDB can substantially describe the steady damped oscillations driven by the electric field. The attributes of microdroplet and the operational parameters for EDBs can affect the oscillations greatly. As usual, the particle stability decreases with the increasing of ac potential Vac or the absolute value of inhomogeneous term D, but the stability increases as the increasing of ac driving frequency fac. Being the origin of inducing the particle oscillations, the inhomogeneous term in the motion equation may be regarded as one of the theoretical basis for experimental designs.(2) By solving the motion differential equation numerically, the trajectories of particle oscillations can be obtained. The theoretical results have firstly predicted the existence of the particle oscillations and their characteristics, especially of the large-amplitude oscillation, which is in excellent agreement to the experimental observations.(3) By simulating the particle trajectories, a three-region zoning ((,() diagram, other than the Davis two-region theory, for particle oscillations in EDB has been delineated. A transitional region between the stable and unstable regions defined by Davis has firstly been obtained theoretically. In this region, though the particle has been over the springpoint, the particle can still be kept in a steady damped oscillation but not flying lost predicted by the Davis theory. The validity for the...
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