Research Center for Engineering of
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Title: Analysis of the swirling flow downstream a Francis runner
Published In: Journal of Fluids Engineering, vol. 128, pp. 177-189
Description: An experimental and theoretical investigation of the flow at the outlet of a Francis turbine runner is carried out in order to elucidate the causes of a sudden drop in the draft tube pressure recovery coefficient at a discharge near the best efficiency operating point. Laser Doppler anemometry velocity measurements were performed for both axial and circumferential velocity components at the runner outlet. A suitable analytical representation of the swirling flow has been developed taking the discharge coefficient as independent variable. It is found that the investigated mean swirling flow can be accurately represented as a superposition of three distinct vortices. An eigenvalue analysis of the linearized equation for steady, axisymmetric, and inviscid swirling flow reveals that the swirl reaches a critical state precisely (within 1.3%) at the discharge where the sudden variation in draft tube pressure recovery is observed. This is very useful for turbine design and optimization, where a suitable runner geometry should avoid such critical swirl configuration within the normal operating range.
Publication year: 2006
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Authors: SUSAN-RESIGA Romeo , CIOCAN Gabriel Dan , ANTON Ioan , AVELLAN Francois ,
Type: International Journal Article
Laboratory: Numerical Simulation and Parallel Computing Laboratory
Institution: UPT