RELIABILITY ASSESSMENT OF HIGH CYCLE FATIGUE FOR LOW PRESSURE STEAM TURBINE BLADE
RELIABILITY ASSESSMENT OF HIGH CYCLE FATIGUE FOR LOW PRESSURE STEAM TURBINE BLADE
Authors:
Vijaykumar D¹, Jayasheel I Harti², Sahadeva G N³, Anjan Babu V A⁴
Department of Mechanical Engineering, East Point College of Engineering and Technology, Bangalore
LOW PRESSURE STEAM TURBINE BLADE
Vijaykunar D1, Jayasheel I Harti2, Sahadeva G N3, Anjan Babu V A4
1,Department of Mechanical East Point College of Engineering College Bangalore
2, Department of Mechanical East Point College of Engineering College Bangalore
3, Department of Mechanical East Point College of Engineering College Bangalore
4, Department of Mechanical East Point College of Engineering College Bangalore
Abstract - This study investigates the high cycle fatigue behavior of low-pressure steam turbine blades used in thermoelectric power plants, focusing on improving their efficiency, reliability, and lifespan. A computational model was developed, incorporating both a single blade disc and a cyclic symmetric model to assess the turbine's performance. The analysis utilized harmonics of the operational speed and modal analysis of the bladed disk, culminating in a Campbell diagram to evaluate potential resonance frequencies. The results indicated no resonance for Mode 1, but probable resonance for Mode 2, Mode 3, and Mode 5, highlighting critical modes susceptible to high cycle fatigue. Harmonic analysis revealed alternating stresses of 40.33 MPa for Mode 2, 150 MPa for Mode 3, and 3.27 MPa for Mode 5, with a mean stress of 130 MPa calculated from nonlinear static structural analysis. Forced response and mean stress conditions showed vibratory stress below the 107cycle line recommended by Goodman, with a good correlation between analytical calculations and the Goodman diagram. The study underscores the importance of conducting fatigue assessments early in the design process to prevent material degradation, reduce costly redesigns, and ensure the turbine's longevity. The computed fatigue life provides insights into the anticipated number of cycles the component can endure before failure, offering valuable guidance for enhancing the durability and safety of steam turbine blades in power plants.
Keywords: High cycle fatigue; Modal analysis; Vibratory stress; Blade technology; Forced response