A steady-state simulation methodology for predicting runaway speed in Francis turbines

27th IAHR Symposium on Hydraulic Machinery and Systems

Hosseinimanesh, H.^1,3 ; Vu, T.C.^2 ; Devals, C.^3 ; Nennemann, B.^2 ; Guibault, F.^3

Department of Mechanical Engineering, Ecole Polytechnique de Montréal, Montréal

QC, Canada^1

Andritz-Hydro Ltd., Pointe-Claire

QC, Canada^2

Department of Computer and Software Engineering, École Polytechnique de Montréal, Montréal

QC, Canada^3

关键词: Computational effort;    Iterative algorithm;    Operating condition;    Performance factors;    Steady-state simulations;    Unsteady cfd simulations;    Unsteady simulations;    Unsteady turbulent flows;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/3/032027/pdf
DOI  :  10.1088/1755-1315/22/3/032027

来源: IOP

【 摘 要 】

Runaway speed is an important performance factor for the safe operation of hydropower systems. In turbine design, the manufacturers must conduct several model tests to calculate the accurate value of runaway speed for the complete range of operating conditions, which are expensive and time-consuming. To study runaway conditions, the application of numerical tools such as unsteady CFD simulations can help to better understand the complex flow physics during transient processes. However, unsteady simulations require significant computational effort to compute accurate values of runaway speed due to difficulties related to unsteady turbulent flow modelling and instabilities. The present study presents a robust methodology based on steady-state RANS flow simulations capable of predicting the runaway speed of a Francis turbine with an adequate level of accuracy and in a reasonable simulation time. The simulations are implemented using a commercial flow solver and an iterative algorithm that relies on a smooth relation between turbine torque and speed coefficient. The impact of friction has been considered when estimating turbine torque, in order to improve the accuracy. The results of this study show good agreement with experiments.