Design of a cross-over diffuser for a mixed-flow compressor impellor
| dc.contributor.advisor | Van der Spuy, S. J. | en_ZA |
| dc.contributor.advisor | Von Backstrom, T. W. | en_ZA |
| dc.contributor.author | Kock, M. P. | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. | en_ZA |
| dc.date.accessioned | 2017-02-21T11:04:46Z | |
| dc.date.accessioned | 2017-03-29T11:55:56Z | |
| dc.date.available | 2017-02-21T11:04:46Z | |
| dc.date.available | 2017-03-29T11:55:56Z | |
| dc.date.issued | 2017-03 | |
| dc.description | Thesis (MEng)--Stellenbosch University, 2017. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: This research project focused on the design of a cross-over diffuser for a mixed flow compressor employed in a 600 N thrust micro gas turbine (MGT). Due to the exit of a mixed flow impeller having a meridional discharge angle 2a < 90°, the use of a conventional radial diffuser is inappropriate. The cross over diffuser is a single row diffuser that replaces the conventional two row radial to de-swirler diffuser. The cross-over diffuser is suitable for a mixed flow impeller due to its ability to capture the flow from the impeller without inducing flow separation on the meridional passage walls. The initial cross-over diffuser used in this research was designed using a mean line code. A multi-point optimisation of the mean line design was performed using NUMECA Design3DTM, by means of an Artificial Neural Network incorporated into a Genetic Algorithm. The optimised design showed an increase of 8.75% for the compressor stage total-to-total isentropic efficiency, and a 7.7% increase in total-to-total pressure ratio. The optimised diffuser yielded a large increase in static pressure recovery coefficient of 28.33%. The optimised diffuser static-to-static pressure ratio was increased by 21.5%. The overall operating range remained constant, but the choke mass flow rate increased. The stall mass flow rate also increased, thus shifting the operating range up to a higher mass flow rate. An investigation was also done to evaluate the feasibility of vaneless diffusers by using the same passage of the optimised diffuser in a vaneless format. De-swirlers were also added to the vaneless diffuser. The optimised vaned diffuser outperforms the vaneless diffuser but lacks in operating range. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Hierdie navorsingsprojek fokus op die ontwerp van ’n oorgangsdiffusor vir ’n gemengde vloei kompressor wat toegepas gaan word in ’n 600 N stukrag mikro gas turbine (MGT). Die gemengde-vloei kompressor het ’n nie-radiale meridionale uitlaat vloeihoek 2a < 90°, en as gevolg hiervan is die gebruik van konvensionele radiale diffusors nie ’n toepaslike keuse nie. Die oorgangsdiffusor is ’n enkelry diffusor wat die konvensionele twee-ry radiaal-na-aksiale vloeirigter diffusor vervang. Die oorgangsdiffusor is toepaslik vir ’n gemengde vloei kompressor omdat dit die vermoë het om vloei te rig sonder om wegbreking in die meridionale vloei kanaal te veroorsaak. Die aanvanlike oorgangsdiffusor is ontwerp met ’n een-dimensionele kode. ’n Multi-punt optimering is op die een-dimensionele ontwerp toegepas. Die optimerings proses was gedoen met NUMECA Design3DTM sagteware. ’n Kunsmatige neurale netwerk, wat ’n Genetiese algoritme inkorporeer is gebruik om die optimering te voltooi. Die geoptimeerde ontwerp toon ’n toename van 8.75% vir die kompressor totale-tottotale insentropiese benuttingsgraad en ’n 7.7% toename in totale-tot-totale drukverhouding. Die geoptimeerde diffusorontwerp het ’n groot verbetering in statiese drukherwinnings koëffisiënt toename van 28.33% voorspel. Die geoptimeerde ontwerp se staties-tot-statiese drukverhouding het ook met 21.5% toegeneem. Die algehele werks bestek van die kompressor het konstant gebly, maar die smoor en staak massavloeitempo het toegeneem, wat beteken dat die bestek opgeskuif het na ’n hoër massavloei. ’n Studie is gedoen om die lewensvatbaarheid van lemlose diffusors te ondersoek deur gebruik te maak van die geomptimeerde diffusor kanaal in ’n lemlose formaat. Aksiale vloeirigters is ook toegevoeg by die lemlose diffusor en gesimuleer. Die geoptimeerde ontwerp toon beter prestasie as die lemlose diffusor , maar met ’n kleiner bestek. | af_ZA |
| dc.format.extent | 129 pages : illustrations | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/100997 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Diffusers | en_ZA |
| dc.subject | Gas-turbine materials | en_ZA |
| dc.subject | Axial flow compressors | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Design of a cross-over diffuser for a mixed-flow compressor impellor | en_ZA |
| dc.type | Thesis | en_ZA |