Swirling Flow Computation at the Trailing Edge of Radial-Axial Hydraulic Turbines

28th IAHR symposium on Hydraulic Machinery and Systems

Susan-Resiga, Romeo^1 ; Muntean, Sebastian^2 ; Popescu, Constantin^1

Politehnica University Timioara, Romania^1

Romanian Academy - Timioara Branch, Romania^2

关键词: Flow instabilities;    Francis turbine runner;    Full informations;    New mathematical model;    Numerical algorithms;    Operating points;    Optimization methodology;    Weighted averages;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/49/8/082012/pdf
DOI  :  10.1088/1755-1315/49/8/082012

来源: IOP

【 摘 要 】

Modern hydraulic turbines require optimized runners within a range of operating points with respect to minimum weighted average draft tube losses and/or flow instabilities. Tractable optimization methodologies must include realistic estimations of the swirling flow exiting the runner and further ingested by the draft tube, prior to runner design. The paper presents a new mathematical model and the associated numerical algorithm for computing the swirling flow at the trailing edge of Francis turbine runner, operated at arbitrary discharge. The general turbomachinery throughflow theory is particularized for an arbitrary hub-to-shroud line in the meridian half-plane and the resulting boundary value problem is solved with the finite element method. The results obtained with the present model are validated against full 3D runner flow computations within a range of discharge value. The mathematical model incorporates the full information for the relative flow direction, as well as the curvatures of the hub-to-shroud line and meridian streamlines, respectively. It is shown that the flow direction can be frozen within a range of operating points in the neighborhood of the best efficiency regime.