Thesis (MEng) -- Stellenbosch University, 2014 / ENGLISH ABSTRACT: The electrodynamics of arbitrary, point-to-plane electrospraying geometries,
were investigated in this research both analytically and numerically. Electrospraying
is the process during which particles of sizes in the nanometre range
are simultaneously generated and charged by means of an applied electrostatic
field. A high electrostatic potential is applied to a conductive capillary needle,
which overcomes the force exerted by the liquid surface tension. One of the
primary limitations of this process are corona discharges. The effect of corona
discharges have not been studied quantitatively, even though it is frequently
reported in the electrospraying literature.
The main objective of this research was to understand the corona discharge
thresholds associated with electrospraying. Previously, only one theoretical,
and two empirical investigations studied this phenomenon, over a time period
of approximately forty years. It was clear that by better understanding these
thresholds, electrospraying could be applied much more effectively.
A corona discharge threshold model is proposed, using either a numerical
or analytical model for the calculation of polarization fields. When compared
with the experimental results of other researchers, both these two models have
average relative percentage errors of approximately 15%. These are the first
models proposed in the literature for the calculation of electrospraying corona
thresholds. A new method to determine surface tension using electrospraying
is described theoretically. In addition to this method, the calculation of corona
discharge thresholds have various applications. For example, the dynamics of
electrostatic ion thrusters are much better described, powder production by
means of electrospraying can be optimised, and pattern generation using pulsed
electrospraying cone-jets can be optimised as well. / AFRIKAANSE OPSOMMING: Die elektrodinamika van arbitrêre, punt-tot-vlak elektrosproei geometrieë was
beide analities en numeries ondersoek in hierdie tesis. Dit is die proses waartydens
nanodeeltjies gelyktydig gegenereer en elektrostaties gelaai word. Deur 'n
hoë elektriese potensiaal aan te lê tot 'n geleidende kapillêr, is dit moontlik om
die krag van die oppervlakte spanning te oorkom. Een van die primêre beperkings
van elektrosproei is corona ontladings. Die effek van corona ontladings
was nog nie kwantitatief bestudeer nie, selfs al word dit dikwels rapporteer in
die elektrosproei literatuur. Die primêre doel van hierdie navorsing was om die
corona ontlading drempels te verstaan wat geassosieer word met elektrosproei.
In die verlede was daar nog net een teoretiese, en twee empiriese ondersoeke
gewees wat hierdie verskynsel bestuur het, oor 'n tydperk van ongeveer veertig
jaar. Dit was duidelik dat deur 'n beter begrip te hê van hierdie elektrosproei
drempels, kan hierdie proses baie meer doeltreffend toegepas word.
In hierdie tesis word 'n corona ontlading drempel model voorgestel, wat
gebruik maak van 'n analitiese of numeriese model om die polarisasie velde te
bereken. Wanneer vergelyk met die resultate van ander navorsers, het beide die
modelle 'n gemiddelde relatiewe persentasie fout van ongeveer 15%. Hierdie is
die eerste modelle wat voorgestel word vir die berekening van corona ontlading
drempels. Deur gebruik te maak van elektrosproei, word 'n nuwe metode ook
voorgestel om die oppervlakte spanning te bereken. In byvoeging tot hierdie,
het die berekening van corona ontlading drempels vele ander toepassings. As
'n voorbeeld, die dinamika van elektrostatiese ioon stuwers word beter beskryf,
en poeier produksie deur middel van elektrosproei kan optimeer word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/95529 |
| Date | 12 1900 |
| Creators | Pieterse, Cornelius Louwrens |
| Contributors | Perold, Willem J., Papka, Paul, Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | viii, 89 p. : ill. |
| Rights | Stellenbosch University |
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