Analysis of the dynamic response of pump-turbine impellers. Influence of the rotor

• Published in: Mechanical systems and signal processing 2016-02, Vol.68-69, p.330-341
• Main Authors: Egusquiza, Eduard, Valero, Carme, Presas, Alex, Huang, Xingxing, Guardo, Alfredo, Seidel, Ulrich
• Format: Article
• Language: English
• Subjects: Boundary conditions; Computer simulation; Design engineering; Dynamic response; Enginyeria mecànica; Experimental modal analysis; FEM simulation; Hydraulic machinery; Impellers; Mathematical models; Mecànica de fluids; Mode-shapes; Màquines hidràuliques; Pump-turbine impellers; Rotating; Rotors; Runner; Turbines; Àrees temàtiques de la UPC
• ISSN: 0888-3270; 1096-1216
• DOI: 10.1016/j.ymssp.2015.05.034

This paper deals with the dynamic response of pump-turbine impellers. A pump-turbine impeller is a complex structure attached to a rotor and rotating inside a casing full of water with very small clearances between the rotating and the stationary parts. The dynamic response of this type of structures is very complex and it is very much affected by the connection to the rotor as well as by the added mass and boundary conditions. As a consequence its calculation presents several uncertainties. First, the dynamic response of pump-turbine impellers is introduced. Second an experimental investigation in a real impeller attached to the rotor and inside the machine was carried out. For this investigation, the impeller of an existing pump-turbine unit with an installed power of 110MW and a diameter of 2.87m was studied. For a better analysis of the experimental results a numerical model using FEM was also built-up. Frequencies and mode-shapes were identified numerically and experimentally and the characteristics of the structural response analyzed. To determine the influence of the rotor and supporting structures on the impeller response the results were compared with the ones obtained with the same impeller but suspended (non-connected to the rotor). Experimental and numerical simulation were also used for this case. The changes in the dynamic response due to the rotor connection were determined. Finally the results obtained are compared with the results from other pump-turbine impellers of different designs and general conclusions about the dynamics of this type of structures are given. [Display omitted] •The dynamic response of large pump-turbine runners is presented.•The effect of the rotor connection on the natural frequencies of the runner is shown.•Experimental (EMA) and simulation (FEM) results are compared.•General conclusions about the dynamic characteristics of these runners are given.