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Engineering Failure Analysis, Volume 25, October 2012, Pages 304-315
E. Poursaeidi (1), A. Babaei (2), M.R. Mohammadi Arhani (3), M. Arablu (1)
(1)Department of Mechanical Engineering, University of Zanjan, Zanjan, Iran
(2) South Pars Gas Co., Asalooyeh, Booshehr, Iran
(3) Mobin Arya Power Engineering & Research Co., Karaj, Alborz, Iran
Abstract
There has been a statistically increased rate of a common failure in the first stage compressor blades of frame-type gas turbines installed in a seaside power plant. A root cause analysis was performed for these failures. This paper presents the results of an experimental and numerical analysis of the effects of natural frequencies on these failures. Fractography analysis showed striations on the fractured surfaces of the blades, which are a common result of high cycle fatigue (HCF). Therefore, the focus of this study is determining the modes of vibration and the corresponding resonant frequencies. To this end, a 3-D model of the blade and its disk under static and dynamic forces was analyzed with ANSYS software. The simulation results showed that high stresses occurred in the areas where the cracks initiated under both dynamic and static forces. Furthermore, from a Campbell diagram it was concluded that the resonance of the blades under the first and second natural frequency modes is the primary reason for the fatigue fractures of these blades.
