A large design space multi-disciplinary optimization of a mixed flow micro gas turbine compressor stage

Ochabski, Thomas M. (2019-12)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: This thesis presents a novel method of parametrization and optimization for a large design space exploration of a micro gas turbine compressor stage. 48 free parameters were used to control the meridional channel, blade camber, and structural geometric features. The optimization focused on determining the optimal impeller meridional discharge (mixed flow) angle, αz2, for a predetermined set of constraints. The influence of key geometric features on design performance was assessed using a Pearson correlation coefficient (rp) map. Stage total-to-static pressure ratio, PR(01−4),DP , and efficiency, η(01−4),DP, were strongly influenced (| rp |> 0,4) by diffuser outlet passage height and diffuser vane wrap angle. This was due to their control of flow separation magnitude at the diffuser hub in the radial-to-axial bend. A multidisciplinary workflow was scripted to incorporate the CalculiX CrunchiX structural analysis into the NUMECA FINETM/Design3D aerodynamic optimization package. Structural feasibility constraints were placed on maximum von Mises stress, blade tip displacement, and resonance frequencies of the impeller. A three-dimensional Pareto front was constructed to assist in selection of the final design. The final design achieved a PR(01−4),DP of 4,15 and η(01−4),DP of 86,24%, at a design mass flow rate of 1,089 kg/s. Choke and stall margins of 7,4% and 11,8% were achieved at the design speed of 73 000 RPM.

AFRIKAANSE OPSOMMING: Hierdie tesis beskryf ’n nuwe metode van parametrisering en optimering vir groot ontwerpsgebiedontginning van ’n mikrogasturbine kompressor. 48 vrye parameters word vir die meridionale kanaal, lemkromming, en strukturele geometriese eienskappe gebruik. Klem word geplaas op die optimale meridionale rotorhoek, αz2, onderhevig aan ’n stel vooropgestelde beperkings. Die invloed van belangrike geometriese kenmerke word beskryf met ’n Pearson korrelasieko ¨effisi¨ent (rp) kaart. Kompressor totaal-tot-statiese drukverhouding, PR(01−4),DP , en benuttingsgraad, η(01−4),DP , word deur diffusoruitlaathoogte en diffusorvouhoek be¨ınvloed met | rp |> 0,4. Hierdie invloed was die gevolg van die hoogte en vouhoek se effek op diffusor wegbreking in die radiaaltot- aksiale draai. ’n Multidissiplinˆere Python kode is geskryf wat die CalculiX CrunchiX strukturele analise kode in die NUMECA FINETM/Design3D a¨erodinamiese analise kode inkorporeer. Strukturele uitvoerbaarheidsbeperkings is op die von Mises spanning, lem verplasing, en vibrasie toegepas. ’n drie-dimensionele Pareto grens word gebou om die finale ontwerp te kies. Die finale ontwerp het ’n PR(01−4),DP en η(01−4),DP van 4,15 en 86,24%, onderskeidelik, met ’n massavloeitempo van 1,089 kg/s. Die ontwerp het ’n smoor en staak marge van 7,4% en 11,8%, onderskeidelik, teen ’n spoed van 73 000 RPM.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107298
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