Stability of operation of Francis turbines. Model test procedure

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A characterization procedure for the dynamic behavior of Francis turbines : Practical comparison of elbow and Moody type draft tubes

Characterization from model tests of the dynamic behavior of hydraulic turbines operating off design conditions is an important step in the knowledge of instability phenomena. IMHEF at EPF-Lausanne, Switzerland meets this purpose with a standard test procedure . Simple , fast and efficient, it yields complete and easily interpreted results. This test procedure is used here to compare the dynamic characteristics of elbow and Moody type draft tubes . Relevant frequencies and cavitation compliance are expressed as functions of the machine flow rate. The runner design has a dominant influence on the occurrence of part - load resonance on the tested model. Modifications of dynamic phenomena by an internal structure of the draft tube are shown. The need for generalization of such tests appears clearly from these results.

International Association For Hydraulic Research1988

Surging of 140 MW Francis turbines at high load, analysis and solution

High load surging is a specially delicate side of Francis turbines' dynamic behavior. There is yet no sure method to predict the occurrence of pulsations on a full-size machine, either from model test results or theoretical analysis. Upon commissioning of the Saucelle-Huebra power plant, high load surging made it impossible to operate in the maximum power output range. The turbine designer brought the oscillations to an acceptable level by a modification of the runner cone, without air admission. Thorough lab testing on a scale model allowed a better understanding of the problem. Influences of the runner cone, test head and tailrace tunnels are highlighted. A modal analysis using the cavitation compliance evaluated from model tests provides an explanation for the surge in the plant.

International Association For Hydraulic Research1992

Evaluation from Model Tests for a Prediction of the Stability of Operation of Francis Turbines

This paper presents similitude laws for steady-oscillatory phenomena associated with the off-design operation of Francis turbines. An appropriate procedure is proposed for stability of operation tests to be performed along with standard model tests. The elaboration and presentation of oscillatory data is discussed.

International Association For Hydraulic Research1994