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Title: Numerical Assessment Of A New Passive Control Method For Mitigating The Precessing Helical Vortex In A Conical Diffuser
Published In: Conference on Modelling Fluid Flow (CMFF’15) The 16th International Conference on Fluid Flow Technologies Budapest, Hungary
Description: Decelerated swirling flows in conical diffusers (e.g. discharge cone of hydraulic turbines), can develop self-induced instabilities for some configurations of incoming flow. An upstream steady and axis-symmetrical flow becomes unsteady and three-dimensional. As a result, a characteristic precessing helical vortex and associated pressure fluctuations that hinder the operation of hydraulic turbines. This paper introduces a novel approach for mitigating the swirling flow instabilities using a diaphragm into the cone. Consequently, the severe flow deceleration and corresponding central quasi-stagnant region are diminished, with an efficient mitigation of the precessing helical vortex and its associated pressure fluctuations. Five cases (one without and four with diaphragm) are numerically investigated. It is shown that the diaphragm can mitigate the unsteadiness. Moreover, the dynamic-to-static pressure recovery and hydraulic losses in the conical diffuser are computed.
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Publication year: 2015
Keywords:conical diffuser, diaphragm, numerical study, precessing helical vortex
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Authors: TANASA Constantin , SUSAN-RESIGA Romeo , MUNTEAN Sebastian , STUPARU Adrian , BOSIOC Ilie Alin , CIOCAN Tiberiu ,
Type: International Conference Proceedings
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Laboratory: Numerical Simulation and Parallel Computing Laboratory
Institution: UPT