CFD study on prediction of vortex shedding in draft tube of Francis turbine and vortex control techniques

Anup Kc, Young Ho Lee and Bhola Thapa

Renewable Energy, 2016, vol. 86, issue C, 1406-1421

Abstract: Francis Turbine when operated at part load suffers flow instability due to swirl component of the velocity attached with exiting flow downstream the runner. The swirling flow at runner outlet generates corkscrew-shaped draft tube vortex invites undesirable flow features like pressure pulsation, fluctuation in torque, axial and radial forces and structure vibration causing the turbine. This paper presents the results obtained from the numerical analysis regarding prediction of unsteady vortex behavior at the draft tube and flow instabilities specific to Francis hydro turbines occurring at the part load operating regime, using ANSYS CFX. The RNG k-ε turbulence model is adopted for turbulence treatment and better prediction of the non-cavitating vortex core and its effects. A single part-load operating condition is chosen to analyze the vortex breakdown. To minimize vortex shedding and flow instability, two vortex control techniques viz. Misaligned Guide Vanes (MGVs) and J-grooves in draft tube are evaluated numerically. Two different MGV angles were selected and four different depths of J-grooves were analyzed separately to see their effect on flow features. The use of MGV did not help much in minimizing swirl intensity whereas the use of J-groove showed better swirl control and flow enhancement in the draft tube.

Keywords: Francis turbine; Part-load operation; Vortex rope; Vortex control; Misaligned guide vanes; J-groove (search for similar items in EconPapers)
Date: 2016
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (20)

Downloads: (external link)
http://www.sciencedirect.com/science/article/pii/S0960148115303207
Full text for ScienceDirect subscribers only

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:86:y:2016:i:c:p:1406-1421

DOI: 10.1016/j.renene.2015.09.041

Access Statistics for this article

Renewable Energy is currently edited by Soteris A. Kalogirou and Paul Christodoulides

More articles in Renewable Energy from Elsevier
Bibliographic data for series maintained by Catherine Liu ().