The effect of a crossover diffuser configuration on the performance of a mixed flow compressor stage for a micro gas turbine engine.

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dc.contributor.advisorVan der Spuy, SJen_ZA
dc.contributor.authorVan Eck, Hen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.en_ZA
dc.date.accessioned2023-11-22T15:09:31Zen_ZA
dc.date.accessioned2024-01-08T20:57:02Zen_ZA
dc.date.available2023-11-22T15:09:31Zen_ZA
dc.date.available2024-01-08T20:57:02Zen_ZA
dc.date.issued2023-11en_ZA
dc.descriptionThesis (PhD)--Stellenbosch University, 2023.en_ZA
dc.description.abstractENGLISH ABSTRACT: Mixed flow compressor configurations have become increasingly popular for use in Micro Gas Turbine (MGT) engines. Mixed flow configurations have the advantage of smaller frontal areas while still attaining high pressure ratios from a single stage configuration. The performance of these compressors is largely influenced by the performance of the diffuser, which in turn is limited by inherent geometric restrictions. Research has shown that, compared to legacy diffuser configurations, crossover diffusers provide superior performance in such cases. It does however suffer from inferior operating ranges. This study investigates various crossover diffuser configurations aimed at expanding the operating range and increasing the performance of a mixed flow compressor stage of a MGT engine. To this end, three baseline test compressors, featuring single vane crossover diffusers, are designed using the MATLAB® based 1D Application (App) V2.0. The baseline compressors cover a wide range of design mass flow rates, rotational velocities, and impeller meridional exit angles (mixed flow angles). To evaluate the effect of diffuser configuration on compressor performance, the diffuser configurations of the baseline compressors aremodified, with the achieved performance being compared to that of the baseline configuration. Preliminary performance prediction results for all designs are provided by the 1D App V2.0, which is based on mean line loss model theory. These results are validated using NUMECA/Fine™ Turbo CFD software. Diffuser modifications include various unique single and tandem vane crossover diffuser configurations. A splitter vane configuration provides a marked increase in choke margin, albeit at a slightly reduced stall margin. A relative choke margin increase of up to 106% is observed. Tandem vane configuration evaluations include the investigation of relative vane length, as well as tangential shift of the second vane row relative to the first. A 75% relative tangential shift tandem configuration provides the best overall performance results, regardless of relative vane length. A tandem vane configuration with a reduced first vane row number (half) is proposed. It provides a relative choke margin increase of up to 155% compared to the baseline configuration. As a final validation, the findings of this study are tested on a real-world application. A compressor upgrade is proposed for the CAT250TJ – Gen1 MGT engine. A baseline single vane crossover diffuser and four additional modified vaned diffuser configurations are presented. An on-engine evaluation is conducted using GasTurb™ gas turbine modelling software. The baseline configuration provides a 10.74% static thrust increase compared to the Gen1 configuration at maximum operating conditions. Compared to the Gen1 configuration, a reduced first vane row number diffuser configuration display a design point performance increase of 7.18% and 6.27% for total-to-total efficiency and pressure ratio respectively. An operating margin increase of 9.8% compared to the baseline crossover diffuser is also achieved.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Gemengde vloei kompressor konfigurasies word toenemend meer gewild vir gebruik in mikro gasturbine (MGT) enjins. Die voordeel van gemengde vloei konfigurasies is kleiner frontale oppervlaktes terwyl hoë druk verhoudings steeds haalbaar is in enkel stadium konfigurasies. Die werkverrigting van hierdie kompressors word grootliks bepaal deur die werkverrigting van die diffusor, wat verder beperk word deur inherente geometriese beperkings. Navorsing toon dat oorgangsdiffusors beter werkverrigting toon as tradisionele diffusor konfigurasies, alhoewel dit gepaart gaan met ‘n laer operasionele band. Hierdie studie ondersoek verskeie oorgangsdiffusor konfigurasies met die oog op die uitbreiding van die operasionele band en verbetering van die werksverrigting van ‘n MGT gemengde vloei kompressor stadium. Drie basislyn toetskompressors word daarom ontwerp, elk toegerus met ‘n enkel-lem oorgangsdiffusor. Hierdie toetskompressors is ontwerp met die hulp van die MATLAB® gebasseerde 1D Toepassing (Toep) V2.0. Hulle dek ‘n wye verskeidenheid ontwerps snelhede, massavloeitempos en meridionale uitlaat hoeke (gemengde vloei hoeke). Om die effek van diffusor konfigurasie op kompressor werksverrigting te evalueer word die diffusor konfigurasie ontwerpe van die basislyn kompressors gemodifiseer. Die werkverrigting resultate van hierdie gemodifiseerde konfigurasies word dan met die basislyn konfigurasie vergelyk. Aanvanklik voorspelde werksverrigting resultate word verskaf deur die 1D Toep V2.0, wat gebasseer is op een dimensionele (1D) vloei en verlies modelle. Alle 1D Toep V2.0 ontwerpe word geverifieer met NUMECA/Fine™ Turbo berekenings vloeimeganika (BVM) sagteware. Diffusor modifikasies sluit verskeie unieke enkel- en tandemlem oorgansdiffusor konfigurasies in. ‘n Verdeellem konfigurasie lei tot ‘n beduidende toename in wurgingsmarge, alhoewel ‘n klein afname in staakmarge waargeneem word. ‘n Relatiewe wurgingsmarge toename van tot 106% word waargeneem. Tandem lem konfigurasie evaluasies sluit in die effek van relatiewe lem lengte en ‘n tangentionale skuif van die tweede lem ry relatief tot die eerste ry. ‘n 75% reltiewe tangensionale skuif tandem lem konfigurasie verkaf die beste resultate, ongeag die relatiewe lem lengte. ‘n Tandem lem konfigurasie met ‘n verminderde voorste ry lemnommer (helfde) word voorgestel. Hierdie konfigurasie lei tot ‘n maksimum 155% relatiewe wurgingsmarge toename vergeleke met die basislyn konfigurasie. As ‘n finale validasie, word die bevindings van hierdie studie op ‘n regte-wêreld toepassing getoets. ‘n Kompressor opgradering word voorgestel vir die CAT250TJ – Gen1 MGT enjin. ‘n Basislyn enkellem oorgangsdiffusor en vier additioneel gemodifiseerde oorgangsdiffusor konfigurasies word aangebied. ‘n In-enjin evaluasie word gedoen met behulp van GasTurb™ gasturbine modellerings sagteware. Die Gen1 konfigurasie toon ‘n 10.74% toename in statiese stukrag by maksimum operasionele toestande wanneer dit vergelyk word met die basislyn konfigurasie. In vergelyking met die Gen1 konfigurasie, toon ‘n verminderde voorste ry lemnommer konfigurasie ‘n ontwerpspunt werksverrigting toename van 7.18% en 6.27% onderskeidelik vir total-tot-totale effektiwiteit en drukverhouding. Vergeleke met die basislyn konfigurasie, word ‘n operasionele marge toename van 9.8% behaal.af_ZA
dc.description.versionDoctorateen_ZA
dc.format.extentxxv, 186 pages : illustrationsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/129060en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshAxial flow compressorsen_ZA
dc.subject.lcshGas-turbine industryen_ZA
dc.subject.lcshStalling (Aerodynamics)en_ZA
dc.subject.lcshDiffusers -- Aerodynamicsen_ZA
dc.subject.lcshBladesen_ZA
dc.titleThe effect of a crossover diffuser configuration on the performance of a mixed flow compressor stage for a micro gas turbine engine.en_ZA
dc.typeThesisen_ZA
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