Design of a centrifugal compressor impeller for micro gas turbine application

Van der Merwe, Bosman Botha (2012-12)

Thesis (MScEng)--Stellenbosch University, 2012.

Thesis

ENGLISH ABSTRACT: The use of micro gas turbines (MGTs) for the propulsion of unmanned aerial vehicles (UAVs) has become an industry standard. MGTs offer better performance vs. weight than similar sized, internal combustion engines. The front component of an MGT serves the purpose of compressing air, which is subsequently mixed with a fuel and ignited to both power the turbine which drives the compressor, and to produce thrust. Centrifugal compressors are typically used because of the high pressure ratios they deliver per stage. The purpose of this project was to design a centrifugal compressor impeller, and to devise a methodology and the tools with which to perform the aforementioned. A compressor impeller adhering to specific performance and dimensional requirements was designed. The new compressor was designed using a mean-line performance calculation code. The use of the code was vindicated through comparison with the results from a benchmark study. This comparison included mean-line, Computational Fluid Dynamic (CFD), and experimental results: the new design mean-line results were compared to the results of CFD simulations performed on the same design. The new design was optimised using an Artificial Neural Network (ANN) and Genetic Algorithm. Prior to and during optimisation, the ANN was trained using a database of sample CFD calculations. A Finite Element Analysis (FEA) was done on the optimised impeller geometry to ensure that failure would not occur during operation. According to CFD results, the final design delivered good performance at the design speed with regards to pressure ratio, efficiency, and stall margin. The mechanical stresses experienced during operation were also within limits. Experimental results showed good agreement with CFD results of the optimised impeller. Keywords: micro gas turbine, centrifugal compressor, impeller, CFD, experimental, optimisation, FEA.

AFRIKAANSE OPSOMMING: Die gebruik van mikrogasturbines vir die aandrywing van onbemande vliegtuie het ‟n standaard geword in die industrie. Mikrogasturbines bied beter werkverrigting teen gewig as binnebrandenjins van soortgelyke grote. Hierdie eienskap verseker dat mikrogasturbines as aandryfmotors vir onbemande vliegtuie uiters voordelig is. Die voorste komponent van ‟n mikrogasturbine dien om lug saam te pers, wat dan met brandstof gemeng en daarna aan die brand gesteek word om krag aan die kompressor en stukrag te voorsien. Sentrifugaalkompressors word tipies gebruik as gevolg van die hoë drukverhoudings wat hierdie komponente per stadium kan lewer. Die doel van hierdie projek was om ‟n sentrifugaalkompressor te ontwerp, en ‟n metode en die hulpmiddels te ontwikkel om laasgenoemde uit te voer. ‟n Kompressor rotor wat voldoen het aan sekere werkverrigtings en dimensionele vereistes is ontwerp. Die nuwe kompressor rotor is met behulp van 1-dimensionele werkverrigting-berekeningskode ontwerp. Die berekeningsakkuraatheid van die kode en díé van ‟n kommersiële Berekenings Vloeidinamika pakket is bevestig deur die berekende resultate te vergelyk met die van eksperimente. Die nuwe rotor is gevolglik deur middel van ‟n Kunsmatige Neurale Netwerk en Genetiese Algoritme geoptimeer. Die Kunsmatige Neurale Netwerk is voor en gedurende optimering deur Berekenings Vloeidinamika simulasies opgelei. Die meganiese sterkte van die geoptimeerde rotor is nagegaan met behulp van ‟n Eindige Element Analise. Dit is gedoen om te verseker dat die rotor nie sal faal by die bedryfspunt nie. Berekenings Vloeidinamika resultate het getoon dat die finale rotor ontwerp ‟n goeie werkverrigting lewer by die ontwerpspoed, met betrekking tot drukverhouding, bennutingsgraad, en stakingsmarge. Eksperimentele resultate het goeie ooreenstemming met die Berekenings Vloeidinamika resultate van die geoptimeerde rotor getoon. Sleutelwoorde: mikrogasturbine, sentrifigaalkompressor, rotor, Berekenings Vloeidinamika, eksperimenteel, optimering, Eindige Element Analise.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/71610
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