Transient two-phase CFD simulation of overload pressure pulsation in a prototype sized Francis turbine considering the waterway dynamics

27th IAHR Symposium on Hydraulic Machinery and Systems

Mössinger, P.^1 ; Conrad, P.^1 ; Jung, A.^1

Voith Hydro Holding GmbH and Co KG, St Pöltener Straße 43, Heidenheim

89522, Germany^1

关键词: Computational resources;    Full three-dimensional;    Hydroacoustic tests;    Implicit finite-difference schemes;    Numerical investigations;    One-dimensional approach;    One-dimensional model;    Pressure oscillation;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/3/032033/pdf
DOI  :  10.1088/1755-1315/22/3/032033

来源: IOP

【 摘 要 】

At high load operation points, Francis turbines generally produce large cavitation volumes of central vortex character in the draft tube. In order to gain a deeper understanding of the flow behaviour at high load conditions a combined 1D-3D transient two-phase numerical investigation at prototype size was carried out and these results were compared with measured site data. A one-dimensional model to capture hydroacoustic effects along a pipeline will be presented. The corresponding PDEs were solved using an implicit finite difference scheme on a staggered grid. In contrast to previous studies this model is coupled to the commercial software ANSYS CFX through an interface which exchanges pressure and discharge data within every time step until convergence. Results of the one-dimensional approach as well as the coupled solution were validated with commercial one-dimensional software (SIMSEN) and a full threedimensional calculation for hydroacoustic test cases. Unlike former investigations the described 1D-3D approach is used to compare site data with a numerical analysis at prototype size focused on the amplitude and frequency of the pressure pulsation at overload condition. The combined model is able to capture the occurring phase change in the draft tube as well as the propagating pressure oscillation through the hydraulic system without solving for the whole penstock in a 3D manner, thus saving time and computational resources.