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Investigation of secondary flow in low aspect ratio turbines using CFD
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this thesis, secondary flow in a two stage, low aspect ratio turbine is investigated using CFD. A parameter study is carried out to investigate how the turbine performance is affected by the choice of aspect ratio. This is done in two steps, first by changing the blade height and then the blade size. The study shows that increasing the aspect ratio will lead to a significant increase of efficiency, but the effect diminishes for large aspect ratios, at which the efficiency moves towards an asymptotic value. Furthermore it is shown that increasing the aspect ratio to a certain value by changing the blade height results in a higher efficiency compared to changing the blade size, which is due to the difference in hub-to-tip ratio. An attempt to quantify the secondary losses is also made by looking at the radial kinetic energy at the outlet of a blade row. It turns out though, that the radial kinetic energy does not follow the same trend as the total pressure loss coefficient, which implies that it can not be used to quantify the secondary losses. Lastly, an effort to improve the method used for generating blade profiles is made, and the updated method is used to redesign rotor 2 to reduce losses.

Place, publisher, year, edition, pages
Keyword [en]
CFD, Turbines, Secondary flow
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-143528OAI: diva2:706909
Educational program
Master of Science in Engineering - Vehicle Engineering
Available from: 2014-06-11 Created: 2014-03-23 Last updated: 2014-06-11Bibliographically approved

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