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  • 1
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    Multi-objective shape optimization of runner blade for Kaplan turbine (2014)
    Institute of Physics (IOP)
    Details
    Publication Date: 2014-12-11
    Description: Automatic runner shape optimization based on extensive CFD analysis proved to be a useful design tool in hydraulic turbomachinery. Previously the authors developed an efficient method for Francis runner optimization. It was successfully applied to the design of several runners with different specific speeds. In present work this method is extended to the task of a Kaplan runner optimization. Despite of relatively simpler blade shape, Kaplan turbines have several features, complicating the optimization problem. First, Kaplan turbines normally operate in a wide range of discharges, thus CFD analysis of each variant of the runner should be carried out for several operation points. Next, due to a high specific speed, draft tube losses have a great impact on the overall turbine efficiency, and thus should be accurately evaluated. Then, the flow in blade tip and hub clearances significantly affects the velocity profile behind the runner and draft tube behavior. All these features are ...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 2
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    Numerical simulation of full load surge in Francis turbines based on three-dimensional cavitating flow model (2014)
    Institute of Physics (IOP)
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    Publication Date: 2014-12-11
    Description: The two-phase 1D-3D model of full load surge, presented previously by the authors, is applied to simulation of self-excited oscillations in prototype power station. The model consists in 1D hydro-acoustic equations for the penstock domain, and 3D two-phase unsteady RANS equations for turbine domain, including the cavitating flow in the draft tube. Both systems of equations are linked together by pressure and discharge at the penstock-turbine interface and solved simultaneously. To demonstrate the work of the model over-load pressure pulsations are simulated for high head prototype power plant. The influence of numerical parameters is investigated. It was shown that the choice of cavitation model has a strong effect on the amplitude of pulsations. The structure of the vapor cavity is investigated. The computed frequency is compared to the results of 1D model and with experimental data. Amplitudes and frequencies of the pulsations agree well with experiment, showing the potential ...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 3
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    Numerical analysis of the cylindrical rigidity of the vertical steel tank shell (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-11-04
    Description: The paper deals with the study of rigidity of a vertical steel cylindrical tank and its structural elements with the development of inhomogeneous subsidence in ANSYS software complex. The limiting case is considered in this paper: a complete absence of a base sector that varies along an arc of a circle. The subsidence zone is modeled by the parameter n. A finite-element model of vertical 20000 m 3 steel tank has been created, taking into account all structural elements of tank metal structures, including the support ring, beam frame and roof sheets. Various combinations of vertical steel tank loading are analyzed. For operational loads, the most unfavorable combination is considered. Calculations were performed for the filled and emptied tank. Values of the maximum possible deformations of the outer contour of the bottom are obtained with the development of inhomogeneous base subsidence for the given tank size. The obtained parameters of intrinsic rigidity (deformabili...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 4
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    Modelling of a Francis Turbine Runner Fatigue Failure Process Caused by Fluid-Structure Interaction (2016)
    Institute of Physics (IOP)
    Details
    Publication Date: 2016-12-14
    Description: In the present paper considered is the problem of the numerical simulation of Francis turbine runner fatigue failure caused by fluid-structure interaction. The unsteady 3D flow is modeled simultaneously in the spiral chamber, each wicket gate and runner channels and in the draft tube using the Euler equations. Based on the unsteady runner loadings at each time step stresses in the whole runner are calculated using the elastic equilibrium equations solved with boundary element method. Set of static stress-strain states provides quasi-dynamics of runner cyclic loading. It is assumed that equivalent stresses in the runner are below the critical value after which irreversible plastic processes happen in the runner material. Therefore runner is subjected to the fatigue damage caused by high-cycle fatigue, in which the loads are generally low compared with the limit stress of the material. As a consequence, the stress state around the crack front can be fully characterized by linear e...
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    Topics: Geography , Geosciences , Physics
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  • 5
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    Mitigation of self-excited oscillations at full load: CFD analysis of air admission and effects of runner design (2016)
    Institute of Physics (IOP)
    Details
    Publication Date: 2016-12-14
    Description: In full and over load operating points some Francis turbines experience strong selfexcited pressure and power oscillations, which restrict the range of operation and maximum output of the turbine. Previously the authors proposed a 1D-3D two-phase model and numerical method for investigation of this phenomenon. In the present paper this model is further extended and applied to investigation of countermeasures, used for prevention of high load oscillations. First, the third phase - non-condensable air - is introduced into the model in order to investigate the effect of air admission. Then, several modifications of runner cone are examined, showing negligible effect on the amplitude and frequency of full load oscillations. Next, different modifications of runner blade shape are considered, giving different axial and circumferential velocity profiles downstream the runner. It is shown that variation of blade shape significantly affects the onset and intensity of self-excited oscilla...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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