Design of a centrifugal compressor for application in micro gas turbines

De Villiers, Lodewyk Christoffel Barend (2014-12)

Thesis (MEng)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: This thesis details the methodology for developing a centrifugal compressor for application in a Micro Gas Turbine (MGT). This research forms part of a larger project, namely project Ballast, initiated by the South African Air Force (SAAF) in conjunction with Armscor. The methodology encompasses the development of a mean-line code that makes use of 1-dimensional theory in order to create an initial centrifugal compressor geometry which includes a rotor as well as radial vaned diffuser. This is followed by a Computational Fluid Dynamics (CFD) simulation process during which the compressor is optimised in order to maximise its performance. Before manufacturing a Finite Element Analysis (FEA) is done in order to ensure that the rotor does not fail during testing. The testing of the compressor is done to compare the numerical results with the experimental results and in so doing confirms the design process. A previous student had designed a rotor by making use of a mean-line code as well as a CFD optimisation process. The rotor had a measured total-static pressure ratio of roughly 2.8 at 121 kRPM and a total-total isentropic efficiency of 79.1 % at said rotational speed. The inclusion of a vaned diffuser resulted in a higher total-static pressure ratio and accordingly the compressor designed in this report has a CFD determined total-static pressure ratio of 3.0. The efficiency would however drop and as such a total-total isentropic efficiency of 76.5 % was determined theoretically. The theoretical results correlated well with the experimental results and as such it was concluded that the design methodology developed was sound.

AFRIKAANSE OPSOMMING: Hierdie tesis bespreek die metodologie vir die ontwikkeling van ‘n sentrifugale kompressor vir toepassing in ‘n Mikro-Gasturbine (MGT). Die tesis vorm deel van ‘n groter projek, genaamd die Ballast projek, wat deur die Suid-Afrikaanse Lugmag (SALM) daargestel is in samewerking met Krygkor. Die metodologie behels die ontwikkeling van ‘n middel-lyn kode wat gebruik maak van 1-dimensionele teorie om die aanvanklike geometrie van die kompressor te skep. Die geometrie bevat beide die rotor asook die gelemde radiale diffusor. Hierdie proses word gevolg deur ‘n Berekeningsvloeidinamika (BVD) simulasie waartydens die kompressor geoptimeer word om sodoende die verrigting ten volle te verbeter. Voordat vervaardiging plaasvind word ‘n Eindige Element Analise (EEA) toegepas om te verseker dat die rotor nie sal faal tydens toetse nie. Die toetse word gedoen sodat die eksperimentele resultate met die numeriese resultate vergelyk kan word. Sodoende word die proses waardeur die kompressor ontwikkel word bevestig. ‘n Vorige student het ‘n rotor ontwerp deur gebruik te maak van ‘n middel-lyn kode asook ‘n BVD optimerings proses. Die rotor het ‘n gemete totaal-statiese drukverhouding van ongeveer 2.8 teen 121 kRPM gelewer en ‘n totaal-totale isentropiese benutingsgraad van 79.1 % teen dieselfde omwentelingspoed. Met die insluiting van ‘n gelemde radiale diffuser word ‘n hoër totaal-statiese druk verhouding verwag en as sulks lewer die nuut-ontwerpte kompressor soos in die tesis bespreek ‘n teoretiese totaal-statiese drukverhouding van 3.0. Die benutingsgraad sal egter daal en daarvolgens het die nuwe kompressor ‘n totaal-totale isentropiese benutingsgraad van 76.5 % gelewer. Die eksperimentele resultate het goed ooreengestem met die teoretiese resultate en as sulks was dit besluit dat die ontwerps-metodologie goed is.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96052
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