Natural Frequency Evaluation of Low-Pressure Stage Blade of a 210 MW Steam Turbine

Abstract

Steam turbines rely heavily on the performance and reliability of their rotor blades. When a steam turbine blade fails, it can pose a risk to workers' life, need expensive repairs, and cause income losses. The failure mechanism differs from case to case and is typically quite complex. The last stage turbine blades are very long and rotate at high speed. In extreme dynamic loads, these big blades are the most susceptible to failure. So, the dynamic behaviour of the last stage steam turbine blade is of great importance and analysed by numerical simulation in this work. Mode shapes at natural frequencies of the blade at stationary condition and at different speeds of rotation are determined. A Campbell diagram is used to forecast the expected operational conditions that may result in blade resonant vibration.