Effects of natural frequencies on the failure of R1 compressor blades

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.

► We analyze failure of rotating blades of heavy duty type gas turbine compressors.
► Fractography studies show that fractures are occurred due to HCF.
► Investigations show that the blades were under resonance of first and second natural frequency mode shapes.
► A precise agreement is observed between static, dynamic and resonance stress analysis results and crack origin zones.