Understanding casing flow in Pelton turbines by numerical simulation

28th IAHR symposium on Hydraulic Machinery and Systems

Rentschler, M.^1 ; Neuhauser, M.^1 ; Marongiu, J.C.^1 ; Parkinson, E.^1

ANDRITZ Hydro, Rue des Deux-Gares 6, Vevey

1800, Switzerland^1

关键词: CFD simulations;    Mesh-less methods;    Numerical tools;    Numerical viscosity;    Orders of magnitude;    Pelton turbines;    Rehabilitation projects;    Turbine housings;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/49/2/022004/pdf
DOI  :  10.1088/1755-1315/49/2/022004

来源: IOP

【 摘 要 】

For rehabilitation projects of Pelton turbines, the flow in the casing may have an important influence on the overall performance of the machine. Water sheets returning on the jets or on the runner significantly reduce efficiency, and run-away speed depends on the flow in the casing. CFD simulations can provide a detailed insight into this type of flow, but these simulations are computationally intensive. As in general the volume of water in a Pelton turbine is small compared to the complete volume of the turbine housing, a single phase simulation greatly reduces the complexity of the simulation. In the present work a numerical tool based on the SPH-ALE meshless method is used to simulate the casing flow in a Pelton turbine. Using improved order schemes reduces the numerical viscosity. This is necessary to resolve the flow in the jet and on the casing wall, where the velocity differs by two orders of magnitude. The results are compared to flow visualizations and measurement in a hydraulic laboratory. Several rehabilitation projects proved the added value of understanding the flow in the Pelton casing. The flow simulation helps designing casing insert, not only to see their influence on the flow, but also to calculate the stress in the inserts. In some projects, the casing simulation leads to the understanding of unexpected behavior of the flow. One such example is presented where the backsplash of a deflector hit the runner, creating a reversed rotation of the runner.