Cavitating Turbulent Flow Study for Low Head Francis Turbine by Transient Analysis

This paper introduces the 3D numerical simulation of unsteady turbulent flow in the entire flow passage of a water turbine model with CFD technology. A new and available method for the design of a Francis turbine has been explored. The boundary conditions have been implemented based on the 3D averaged N-S equations. The governing equations are discreted on space by the finite volume method and on time step by the finite difference method. The 3D unsteady turbulent flow in an entire Francis turbine model is calculated successfully using the CFX-TASCflow software and RNG k-εturbulence model. Transient flow fields are simulated in the spiral case, the distributor, the runner and the draft tube. It is presented in this paper that the computer simulation of the flow fields in components of the Francis turbine at the optimum operating condition. Meanwhile, the velocity and pressure at any points in the flow fields can be obtained so as to provide the great value on the performance prediction. According to the simulating results, the flow analysis and the design experience, the design of components in a Francis turbine model can be improved and optimized. In this way, designers may decrease numbers of test and shorten the period for a model. Therefore, the cost of research and produce can be reduced.

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Characteristic analysis of the efficiency hill chart of Francis turbine for different water heads

Advances in Mechanical Engineering ◽

10.1177/1687814017690071 ◽

2017 ◽

Vol 9 (2) ◽

pp. 168781401769007 ◽

Cited By ~ 2

Author(s):

Pengcheng Guo ◽

Zhaoning Wang ◽

Longgang Sun ◽

Xingqi Luo

Keyword(s):

Incidence Angle ◽

Suction Side ◽

Francis Turbine ◽

Small Range ◽

Characteristic Analysis ◽

Wide Range ◽

Low Head ◽

Model Efficiency ◽

Hydraulic Turbines ◽

High Head

According to several model test results of Francis turbines, complete model efficiency hill charts were constructed. The formation and inevitability of diversified hydraulic phenomena on model efficiency hill chart for typical head range were analyzed and the difference is compared, as well as characteristics and commonness toward the curves are discussed and summarized. Furthermore, hydraulic performance and geometric features are presented by particularly analyzing the efficiency hill charts. The inherent characteristics of Francis turbine is expressed by all kinds of curves on the model efficiency hill charts, and these curves can be adjusted and moved in a small range but cannot be removed out. Due to wide range of unit speed in terms of medium-low-head hydraulic turbines, incipient cavitation curve on suction side can be observed and it is positioned close to the operation zone; however, it fails to be visualized for the high-head turbine. The blade channel vortex curves are in the vicinity of optimum region for low-head hydraulic turbines, while high-head shows reverse trend. The interaction between zero incidence angle and zero circulation curve has a significant influence on isoefficiency circles. All comparisons and analyses could provide hydraulic design basis and retrofit references.

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Numerical Simulation of Blade Channel Vortex in a Low Head Francis Turbine

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.291-294.1958 ◽

2013 ◽

Vol 291-294 ◽

pp. 1958-1962 ◽

Cited By ~ 2

Author(s):

Hong Ming Zhang ◽

Li Xiang Zhang

Keyword(s):

Numerical Simulation ◽

Francis Turbine ◽

Transfer Model ◽

Mass Transfer Model ◽

Governing Equations ◽

Cavitation Model ◽

Finite Rate ◽

Low Head ◽

Simulation Results ◽

Volume Method

The paper presents numerical simulation of blade channel vortex in a low head Francis turbine using OpenFoam code. A mixture assumption and a finite rate mass transfer model were introduced to analyze blade channel vortex. The finite volume method is used to solve the governing equations of the mixture model and the pressure-velocity coupling is handled via a Pressure Implicit with Splitting of Operators (PISO) procedure. Simulation results have shown that using cavitation model to analyze blade channel vortex is very effective.

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Finite Element Analysis of Turbulent Flows Using LES and Dynamic Subgrid-Scale Models in Complex Geometries

Mathematical Problems in Engineering ◽

10.1155/2011/712372 ◽

2011 ◽

Vol 2011 ◽

pp. 1-20 ◽

Cited By ~ 1

Author(s):

Wang Wenquan ◽

Zhang Lixiang ◽

Yan Yan ◽

Guo Yakun

Keyword(s):

Finite Element ◽

Turbulent Flow ◽

Turbulent Flows ◽

Stokes Equations ◽

Three Dimensional ◽

Turbulent Channel Flow ◽

Francis Turbine ◽

Complex Geometries ◽

Subgrid Scale ◽

Element Analysis

An innovative computational model is presented for the large eddy simulation (LES) of multidimensional unsteady turbulent flow problems in complex geometries. The main objectives of this research are to know more about the structure of turbulent flows, to identify their three-dimensional characteristic, and to study physical effects due to complex fluid flow. The filtered Navier-Stokes equations are used to simulate large scales; however, they are supplemented by dynamic subgrid-scale (DSGS) models to simulate the energy transfer from large scales toward subgrid-scales, where this energy will be dissipated by molecular viscosity. Based on the Taylor-Galerkin schemes for the convection-diffusion problems, this model is implemented in a three-dimensional finite element code using a three-step finite element method (FEM). Turbulent channel flow and flow over a backward-facing step are considered as a benchmark for validating the methodology by comparing with the direct numerical simulation (DNS) results or experimental data. Also, qualitative and quantitative aspects of three-dimensional complex turbulent flow in a strong 3D blade passage of a Francis turbine are analyzed.

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