Augmentation of the actuator-disk method for low-pressure axial flow fan simulation.

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dc.contributor.advisorOwen, Michael en_ZA
dc.contributor.advisorMuiyser, Jacquesen_ZA
dc.contributor.authorVenter, AJen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.en_ZA
dc.date.accessioned2024-02-22T15:18:37Zen_ZA
dc.date.accessioned2024-04-26T14:55:18Zen_ZA
dc.date.available2024-02-22T15:18:37Zen_ZA
dc.date.available2024-04-26T14:55:18Zen_ZA
dc.date.issued2024-02en_ZA
dc.descriptionThesis (PhD)--Stellenbosch University, 2024.en_ZA
dc.description.abstractENGLISH ABSTRACT: Actuator-disk rotor models are an invaluable simulation tool for cost-effective turbomachinery simulation. Actuator-disk models implicitly represent turbomachine rotors as momentum sources where the source term magnitude is determined from classical two-dimensional blade-element theory (BET) force calculations. Actuator-disk models accordingly require appropriate lift and drag coefficients as input to complete the force calculations. Conventional actuator-disk models utilize standard two-dimensional airfoil coefficient data, but this limits the accuracy of the models to only a small operating window where the bulk of the flow over the rotor itself is principally two-dimensional. This, consequently, limits the application of traditional actuator-disk models in industrial system analyses where complex flow environments prevail. This study considers the particular example of low-pressure axial flow fans, widely applied in thermoelectric air-cooled condenser (ACC) systems. ACCs are a key water-conservative cooling solution to the thermoelectric power industry, yet their operation is beset by inefficiencies and corresponding high operating costs. Given the scale of ACC systems, numerical investigations are forced to rely on simplified implicit fan models like actuator-disk rotor models, which provide limited approximations of actual ACC fan performance over a wide range of flow conditions. Expanding the usable window of actuator-disk axial fan models is therefore vital to providing an enhanced capacity to robustly analyse and ultimately improve ACC systems (and other industrial cooling fan systems alike). To realize this enhanced analysis capability, a new means of appropriately defining the actuator-disk model input coefficient data is required. The input coefficient data needs to appropriately reflect actual fan blade behaviour in a three-dimensional rotating context. Physical fan blade behaviour, however, has not been comprehensively investigated, and the multi-dimensional effects of rotation and blade solidity remain somewhat obscure. This study therefore sets out to define generalizable axial fan behaviour and to use the newly acquired insight to fabricate new coefficient formulations. This study constitutes a numerical analysis in which two low-pressure axial flow fans are both explicitly (full, solid rotating fan geometry) and implicitly simulated. Novel insights into generalizable aerodynamic behaviour of axial flow fans at off design operating conditions are presented and key details on the underlying phenomena are uncovered. Furthermore, this study rigorously explores the feasible potential of the actuator-disk method for axial flow fan simulation and ultimately proposes its revised coefficient formulation. The augmented actuator-disk method (AADM) is shown to more accurately simulate axial fan performance compared to existing model variants, and to resolve flow fields that are more representative of the physical case – an important feature for ACC and other industrial heat exchanger system analyses. Over a wide range of axisymmetric operating conditions (and across both considered fan types), the AADM is shown to approximate reference static pressure rise results with a maximum error of 10%, shaft power results within 8% and blade force magnitudes within 10%, thus offering a marked improvement in comprehensive accuracy relative to existing models.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Aksieskyf-rotormodelle is van onskatbare waarde as simulasie-instrument vir koste-effektiewe turbomasjinerie-simulasie. Aksieskyfmodelle word implisiet verteenwoordig deur turbomasjien-rotors as momentumbronne waar die brontermgrootte bepaal word uit die klassieke twee-dimensionele lem-element teorie (“blade-element theory” (BET)) kragberekeninge. Aksieskyfmodelle vereis dienooreenkomstig toepaslike hef- en sleepkoëffisiënte as inset om die kragberekeninge te voltooi. Konvensionele aksieskyfmodelle gebruik standaard tweedimensionele dravlak-vleuelkoëffisiëntdata, maar dit beperk die akkuraatheid van die modelle tot slegs 'n klein bedryfsvenster waar die grootste deel van die vloei oor die rotor self hoofsaaklik tweedimensioneel is. Dit beperk gevolglik die toepassing van tradisionele aksieskyfmodelle in industriële stelselontledings waar komplekse vloei-omgewings heers. Hierdie studie ondersoek die spesifieke voorbeeld van laedruk aksiaal-vloeiwaaiers, wat wyd gebruik word in termo-elektriese lugverkoelde kondensor (“air-cooled condensor” (ACC)) stelsels. ACCs is 'n belangrike waterkonserwatiewe verkoelingsoplossing vir die termo-elektriese kragbedryf, maar hul werking word belemmer deur ondoeltreffendheid en ooreenstemmende hoë bedryfskoste. Gegewe die skaal van ACC-stelsels, word numeriese ondersoeke gedwing om staat te maak op vereenvoudigde implisiete waaiermodelle soos aksieskyf-rotormodelle, wat beperkte benaderings bied van werklike ACC-waaierprestasie oor 'n wye reeks vloeitoestande. Die uitbreiding van die bruikbare venster van aksiaal waaiermodelle van die aksieskyf is dus noodsaaklik om 'n verbeterde kapasiteit te verskaf om ACC-stelsels (en ander industriële verkoelingwaaierstelsels) goed te ontleed en uiteindelik te verbeter. Om hierdie verbeterde ontledingsvermoë te verwesenlik, word 'n nuwe manier benodig om die aksieskyf-model-invoerkoëffisiëntdata toepaslik te definieer. Die insetkoëffisiëntdata moet die werklike waaierlemgedrag in 'n driedimensionele roterende konteks toepaslik weerspieël. Fisiese waaierlemgedrag is egter nie volledig ondersoek nie, en die multidimensionele effekte van rotasie en lemvastheid bly ietwat duister. Hierdie studie stel dus ten doel om veralgemeenbare aksiale waaiergedrag te definieer en om die nuutverworwe insig te gebruik om nuwe koëffisiëntformulerings te vervaardig. Hierdie studie behels 'n numeriese analise waarin twee laedruk aksiaalvloei waaiers beide eksplisiet (volle, soliede roterende waaier geometrie) en implisiet gesimuleer word. Nuwe insigte in veralgemeenbare aerodinamiese gedrag van aksiaalvloei waaiers by buite-ontwerp bedryfstoestande word aangebied en sleutelbesonderhede oor die onderliggende verskynsels word ontbloot. Verder ondersoek hierdie studie die uitvoerbare potensiaal van die aksieskyf-metode vir aksiaalvloei waaier-simulasie streng en stel uiteindelik die hersiene koëffisiëntformulering daarvan voor. Die verbeterde aksieskyf-metode (“augmented actuator-disk method” (AADM)) word gewys om aksiaal waaierprestasie meer akkuraat te simuleer in vergelyking met bestaande modelle, en om vloeivelde op te los wat meer verteenwoordigend is van die fisiese geval – 'n belangrike kenmerk vir ACC en ander industriële hitteruilerstelselontledings. Oor 'n wye reeks aksi-simmetriese bedryfstoestande (en vir beide waaiertipes wat oorweeg is), word getoon dat die AADM verwysingsstatiese drukstygingresultate benader met 'n maksimum fout van 10%, asdrywingsresultate binne 8% en lemkragwaardes binne 10%. Hierdie bied dus 'n merkbare verbetering in omvattende akkuraatheid relatief tot bestaande modelle.af_ZA
dc.description.versionDoctorateen_ZA
dc.format.extentxix, 127 pages : illustrations.en_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130364en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshAxial flowen_ZA
dc.subject.lcshActuatorsen_ZA
dc.subject.lcshHeat exchangers -- Fluid dynamicsen_ZA
dc.subject.lcshFluid dynamics -- Simulation methodsen_ZA
dc.subject.lcshUCTDen_ZA
dc.titleAugmentation of the actuator-disk method for low-pressure axial flow fan simulation.en_ZA
dc.typeThesisen_ZA
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