000171243 001__ 171243
000171243 005__ 20181203022529.0
000171243 0247_ $$2doi$$a10.1016/j.apm.2011.03.052
000171243 022__ $$a0307-904X
000171243 02470 $$2ISI$$a000292176200007
000171243 037__ $$aARTICLE
000171243 245__ $$aMathematical modelling of swirling flow in hydraulic turbines for the full operating range
000171243 260__ $$bElsevier$$c2011
000171243 269__ $$a2011
000171243 336__ $$aJournal Articles
000171243 520__ $$aWe introduce and validate a novel mathematical model for computing the radial profiles of both axial and circumferential velocity components, respectively, of the swirling flow exiting the runner of hydraulic turbines within the full operating range. We assume an incompressible, inviscid, axisymmetrical, and steady swirling flow, with vanishing radial velocity at runner outlet. First we find the correlation between the flux of moment of momentum downstream the turbine runner and the operating regime given by turbine's discharge and head. Second, we express the relationship between the axial and circumferential velocity components, corresponding to the fixed pitch runner blades, using the swirl-free velocity instead of the traditional relative flow angle at runner outlet. It is shown that the swirl-free velocity profile practically does not change with the operating regime. Third, we introduce a constrained variational problem corresponding to the minimization of the flow force while maintaining the prescribed discharge and flux of moment of momentum. This formulation also accounts for a possible central stagnant region to develop when operating the turbine far from the best efficiency point. Fourth, we show that by representing the unknown axial velocity profile with a suitable Fourier-Bessel series, the discharge constraint can be automatically satisfied. The resulting numerical algorithm is robust and produces results in good agreement with available data for both axial and circumferential velocity profiles measured on a model Francis turbine at several operating regimes. Our mathematical model is suitable for the early optimization stages of the runner design, as it provides the swirling flow configuration at runner outlet without actually computing the runner. By optimizing the parameterized swirl-free velocity profile one can achieve through the inverse design approaches the most suitable runner blades configuration at the trailing edge. (C) 2011 Elsevier Inc. All rights reserved.
000171243 6531_ $$aSwirling flow
000171243 6531_ $$aHydraulic turbine
000171243 6531_ $$aConstrained variational problem
000171243 6531_ $$aFourier-Bessel series
000171243 6531_ $$aVortex Breakdown
000171243 6531_ $$aDraft Tube
000171243 6531_ $$aVortices
000171243 6531_ $$aPipe
000171243 700__ $$aSusan-Resiga, R. F.
000171243 700__ $$aMuntean, S.
000171243 700__ $$0241012$$g104417$$aAvellan, F.
000171243 700__ $$aAnton, I.
000171243 773__ $$j35$$tApplied Mathematical Modelling$$q4759-4773
000171243 909C0 $$xU10309$$0252135$$pLMH
000171243 909CO $$pSTI$$particle$$ooai:infoscience.tind.io:171243
000171243 917Z8 $$x102085
000171243 937__ $$aEPFL-ARTICLE-171243
000171243 973__ $$rREVIEWED$$sPUBLISHED$$aEPFL
000171243 980__ $$aARTICLE