Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: A measurement device was developed to accurately determine the pneumatic
power performance of an Oscillating Water Column (OWC) model in a wave
flume. The analysis of the pneumatic power is significant due to the wave-topneumatic
energy being the primary energy conversion process and where the
most energy losses can be expected. The aim of the research study is to address
the accurate pneumatic power measurement of unsteady and bidirectional airflow
in OWC model experiments.
The two fundamental measurements required for the pneumatic power
measurement are the pressure difference over an orifice on the OWC model and
the volumetric flow rate of air through the outlet. The designed, constructed and
assembled measurement device comprised of a venturi flow meter, containing a
hot-film anemometer, which could measure the pressure drop and the volumetric
flow rate in one device. The assembled pneumatic power measurement device
was calibrated in a vertical wind tunnel at steady state. The results from the
calibration tests showed that the volumetric flow rate measurements from the
pneumatic power measurement device was accurate to within 3 % of the wind
tunnel’s readings. The pneumatic power measurement device was incorporated
onto a constructed Perspex physical model of a simple OWC device. This
assembled system was used as the test unit in the wave flume at Stellenbosch
University (SUN).
The results from the experimental tests underwent comparative analysis with
three analytical OWC air-flow models which were simulated as three scenarios
using Matlab Simulink. These results showed that the measurement device has the
ability to measure the pneumatic power but there is difficulty in modelling the
complex air-flow system of the OWC device. This results in varying levels of
agreement between the experimental and simulated pneumatic power results. The research study has revealed that there is difficulty in designing an accurate
device for a wide range of test parameters due to the variance in output values.
The unsteady and bidirectional nature of the air flow is also difficult to accurately
simulate using a one-dimensional analytical model. Recommendations for further
investigation are for CFD systems to be used for the analysis of the air-flow in an
OWC system and to be used to validate future pneumatic power measurement
devices. / AFRIKAANSE OPSOMMING: ‘n Meetinstrument was ontwikkel om die pneumatiese kraglewering van ‘n model
van die Ossillerende Water Kolom (OWK) golfenergie omsetter in ‘n golf tenk
akkuraat te meet. Dit is belangrik om die omskakeling van golf na pneumatiese
energie te analiseer siende dat die grootste energieverlies in dié proses plaasvind.
Die doel van hierdie navorsingsprojek was om die akkurate pneumatiese
kragmeting van variërende en twee-rigting vloei van lug in ‘n OWK model na te
vors.
Die twee fundamentele metings wat benodig word vir die pneumatiese
kragbepaling is die drukverskil oor die vloei vernouing en die volumetriese
vloeitempo van lug deur die uitlaat van die toetstoestel. Die spesiaal ontwerpte
meettoestel wat gebruik is in die eksperiment het bestaan uit ‘n venturi vloeimeter
wat ‘n verhitte-film anemometer bevat het wat die drukverandering en die
volumetriese vloeitempo kan meet in ‘n enkele instrument. Die pneumatiese
kragmeting was gekalibreer in ‘n vertikale windtonnel waarin ‘n konstante vloei
tempo geïnduseer was. Die kalibrasieproses het bevestig dat die meettoestel
metings lewer met ‘n fout van minder as 3 % wanneer dit vergelyk word met die
bekende konstante vloei tempo soos bepaal in die windtonnel. ‘n Fisiese model
van ‘n vereenvoudigde OWK golfenergie omsetter was ontwerp en gebou uit
Perspex om as toetstoestel te gebruik vir die evaluering van die ontwerpte
pneumatiese kraglewering meettoestel. Die toetse was uitgevoer in ‘n golftenk by
die Universiteit Stellenbosch (SUN).
The toetsresultate was vergelyk met drie ander OWK lugvloei modelle wat
gesimuleer was deur om die analitiese modelle op te stel en te simuleer in Matlab
Simulink. Die vergelyking van modellering resultate het gewys dat die meettoestel
die vermoë het om pneumatiese krag te meet. Daar was wel komplikasies met die
modellering van die komplekse lugvloei in die OWK toestel, die resultate het geen
definitiewe ooreenstemming gewys tussen die eksperimentele en gesimuleerde
pneumatiese krag resultate nie. Die navorsingsprojek het gewys dat daar komplikasies is om ‘n enkel toestel te
ontwerp wat oor ‘n wye bereik kan meet weens die variasie van die verskillende
parameters. Die variërende en twee-rigting lugvloei is ook moeilik om akkuraat te
simuleer met ‘n een-dimensionele analitiese simulasie model. Aanbevelings vir
verdere navorsing sluit in om die lugvloei in die OWK stelsel te modelleer en te
analiseer in ‘n drie-dimensionele model om die lesings van ‘n pneumatiese krag
meettoestel te bevestig.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86662 |
| Date | 04 1900 |
| Creators | Kooverji, Bavesh |
| Contributors | Van Niekerk, J. L., Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xv, 113 p. : ill. |
| Rights | Stellenbosch University |
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