A model for precessing helical vortex in the turbine discharge cone

27th IAHR Symposium on Hydraulic Machinery and Systems

Kuibin, P.A.^1 ; Susan-Resiga, R.F.^2 ; Muntean, S.^3

Kutateladze Institute of Thermophysics SB RAS, 1 Lavrentyev ave., Novosibirsk

630090, Russia^1

Department of Hydraulic Machinery, University Politehnica Timioara, Bv. Mihai Viteazu 1, Timioara

RO-300222, Romania^2

Centre of Advanced Research in Engineering Sciences, Romanian Academy, Timioara Branch, Bv. Mihai Viteazu 24, Timisoara

RO-300223, Romania^3

关键词: 3D unsteady flow;    Axi-symmetrical;    Design and optimization;    Full three-dimensional;    Helical vortices;    Operating points;    Operating ranges;    Precessing vortex core;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/2/022024/pdf
DOI  :  10.1088/1755-1315/22/2/022024

来源: IOP

【 摘 要 】

The decelerated swirling flow in the discharge cone of hydraulic turbine develops various self-induced instabilities and associated low frequency phenomena when the turbine is operated far from the best efficiency regime. In particular, the precessing helical vortex («vortex rope») developed at part-load regimes is notoriously difficult and expensive to be computed using full three-dimensional turbulent unsteady flow models. On the other hand, modern design and optimization techniques require robust, tractable and accurate a-priori assessment of the turbine flow unsteadiness level within a wide operating range before actually knowing the runner geometry details. This paper presents the development and validation of a quasi-analytical model of the vortex rope in the discharge cone. The first stage is the computing of the axisymmetrical swirling flow at runner outlet with input information related only to the operating point and to the blade outlet angle. Then, the swirling flow profile further downstream is computed in successive cross-sections through the discharge cone. The second stage is the reconstruction of the precessing vortex core parameters in successive cross-sections of the discharge cone. The final stage lies in assembling 3D unsteady flow field in the discharge cone. The end result is validated against both experimental and numerical data.