Air turbine design study for a wave energy conversion system

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dc.contributor.advisorVon Backstrom, T. W.
dc.contributor.advisorVan Niekerk, J. L.
dc.contributor.authorAckerman, Paul Henryen_ZA
dc.contributor.otherUniversity of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
dc.dateENGLISH ABSTRACT: Objectives of this study are threefold. Firstly a numerical model of the airflow through the Stellenbosch Wave Energy Converter (SWEC) is developed. Secondly a turbine and diffuser are specified and designed for operation in the SWEC. Thirdly the operation and performance of the turbine is studied under various flow conditions and for both constant and variable speed. The airflow system is modelled using Simulink (Mathworks, 2008), the results of which predict a power curve that follows experimental scale model results up to a wave height of 3m. Results from this modelling process at the design wave condition (2m) are used for specification and design of the turbine and diffuser. Turbine design is initiated by investigating turbine layout and expected performance with a non-dimensional analysis. An algorithm is written to calculate flow over the turbine stage at sections throughout the blade length to determine an estimate of performance. The turbine blade is assembled by stacking blade sections between hub and shroud. A Computational Fluid Dynamics (CFD) analysis is used to gauge the performance of the turbine under various flow conditions. The diffuser is modelled at design conditions only to limit computational time. The airflow system model overestimates performance of SWEC in wave heights larger than 3m; this overestimation is believed to stem from inaccurate estimations of added mass and damping. The results of the CFD analysis validate the turbine design assumptions at the design conditions. The constant speed turbine design approach to negate the use of expensive variable speed generators proved ineffective at off-design conditions, with stall occurring in the rotor blade row for wave heights above 3m. Poor turbine performance is predicted for wave heights of 1.5m and less. Variable speed turbine operation was modelled and improved poor performance at off-design conditions.en
dc.dateAFRIKAANSE OPSOMMING: Doelwitte van hierdie studie is drievoudig. Eerstens word 'n numeriese model van die lugvloei deur die Stellenbosch Golf Energie Omsetter (SGEO) ontwikkel. Tweedens word 'n turbine en diffusor gespesifiseer en ontwerp vir gebruik in die SGEO. Derdens word die werking van die turbine bestudeer onder verskeie vloeitoestande vir beide veranderlike en konstante spoed. Die lugvloei stelsel word gemodelleer met die gebruik van Simulink (Mathworks, 2008). Die resultate voorspel ‘n kragkurwe wat die eksperimentele skaalmodel resultate tot by ‘n golf-hoogte van 3m navolg. Resultate van hierdie modelleringsproses by die ontwerp golftoestand (2m) word gebruik vir die spesifikasie en die ontwerp van die turbine en diffusor. Turbine ontwerp word aangepak deur ‘n ondersoek van turbine uitleg en verwagte vertoning deur dimensielose analise. 'n Algoritme word geskryf om vloei oor die turbine stadium te bereken by seksies dwarsdeur die lem lengte om ‘n beraming van die vertoning te bepaal. Die turbinelem word saamgestel deur lemseksies tussen die naaf en omhulsel te stapel. ‘n Berekeningsvloeidinamika (BVD) analise word gebruik om turbine vertoning te bepaal onder verskillende vloei omstandighede. Die diffusor word gemodelleer by ontwerpstoestande slegs om berekeningstyd te beperk Die lugvloeistelsel model oorskat die vertoning van die SGEO tydens golf hoogtes groter as 3m; die oorskatting is skynbaar die gevolg van onakkurate beramings van bygevoegde massa en demping. Die resultate van die BVD analise bevestig die turbine aannames by ontwerpsomstandighede. Die konstante-spoed turbine-ontwerp benadering om die gebruik van duur veranderlike spoed kragopwekkers teen te werk is oneffektief weg van ontwerp toestande, met staking in die rotor lemry by golfhoogtes bo 3m en swak turbine vertoning vir golfhoogtes van 1.5m en minder. Veranderlike spoed turbinewerking is ondesoek en het werking weg van die ontwerppunt verbeter.af
dc.date.accessioned2010-02-22T11:51:34Zen_ZA
dc.date.accessioned2010-08-13T15:00:54Z
dc.date.available2010-02-22T11:51:34Zen_ZA
dc.date.available2010-03
dc.date.issued2010-03
dc.descriptionThesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.en_ZA
dc.format.extent124 p. : ill.
dc.identifier.urihttp://hdl.handle.net/10019.1/4270
dc.language.isoen
dc.publisherStellenbosch : University of Stellenbosch
dc.rights.holderUniversity of Stellenbosch
dc.subjectOscilating water columnen_ZA
dc.subjectStellenbosch Wave Energy Converter (SWEC)en_ZA
dc.subjectTurbine designen_ZA
dc.subjectComputational fluid dynamicsen_ZA
dc.subjectDissertations -- Mechanical engineeringen
dc.subjectTheses -- Mechanical engineeringen
dc.titleAir turbine design study for a wave energy conversion systemen_ZA
dc.typeThesis
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