Author(s): A Gajic; P Manzalovic; Z Predic

Linked Author(s):

Keywords: Stay vanes; Trailing edge modification; Dynamic stresses; Vibration; Karman vortex

Abstract: In the purpose of discovering causes of high vibrations and long cracks on stay vanes of the turbines at HPP „Iron Gate I” measuring of stresses in the upper zone and in the lower zone along the stay ring are completed. Investigations performed some 20 years ago, in order to find out the excitation of vibrations, included measurements of the pressure along the trailing edge and stresses on stay vanes. The main frequency was about 36 Hz, which is very close to the natural frequencies of some stay vanes. It was concluded that there were two excitations, one belonging to Karman vortexes and the other to attack flow of the guide vanes, both with very close frequencies, causing beating oscillations. Modification of the stay vanes was made by grinding of the convex part of the trailing edges until half-circular concave of the same radius of 25 mm was reached. On site measurements performed at one unit, with original and modified trailing edge, with the same measuring devices, at the same measuring points and at the nearly same operating regimes. Influence of the modification on the static and dynamic stresses of the stay vanes, as well as their frequencies of the oscillations, is shown in the paper.

DOI: https://doi.org/10.1088/1755-1315/12/1/012055

Year: 2010