Mathematical and numerical analysis of electrospraying electrodynamics

[摘要] ENGLISH ABSTRACT: The electrodynamics of arbitrary, point-to-plane electrospraying geometries,were investigated in this research both analytically and numerically. Electrosprayingis the process during which particles of sizes in the nanometre rangeare simultaneously generated and charged by means of an applied electrostaticfield. A high electrostatic potential is applied to a conductive capillary needle,which overcomes the force exerted by the liquid surface tension. One of theprimary limitations of this process are corona discharges. The effect of coronadischarges have not been studied quantitatively, even though it is frequentlyreported in the electrospraying literature.The main objective of this research was to understand the corona dischargethresholds associated with electrospraying. Previously, only one theoretical,and two empirical investigations studied this phenomenon, over a time periodof approximately forty years. It was clear that by better understanding thesethresholds, electrospraying could be applied much more effectively.A corona discharge threshold model is proposed, using either a numericalor analytical model for the calculation of polarization fields. When comparedwith the experimental results of other researchers, both these two models haveaverage relative percentage errors of approximately 15%. These are the firstmodels proposed in the literature for the calculation of electrospraying coronathresholds. A new method to determine surface tension using electrosprayingis described theoretically. In addition to this method, the calculation of coronadischarge thresholds have various applications. For example, the dynamics ofelectrostatic ion thrusters are much better described, powder production bymeans of electrospraying can be optimised, and pattern generation using pulsedelectrospraying cone-jets can be optimised as well.

[发布机构] Stellenbosch University