Localized Damage Identification in the Last Stage Low-Pressure Steam Turbine Blade Using Dynamic Parameter Measurements

Abstract

Steam turbine blades are the important components in power system shaft lines subjected to severe temperatures, leading to low/high cycle fatigue failures. The transient conditions occurring during startup and shutdown events generate alternative stresses causing the fracture at the blade roots. Present work deals with the effect of localized damage on the vibration characteristics and damage identification study in the last stage LP (low pressure) steam turbine blade. Initially, free vibration studies and transient analysis of the last row LP blade section are conducted using the finite element model. A crack near the root region is modeled by a torsional spring, whose stiffness is expressed in terms of crack depth ratio. Effects of crack depth ratio and location near the roots on the natural frequencies and transient response amplitudes are studied in detail. The relationship between the damage parameters and blade frequencies is established through the back propagation neural network model.

Transient Analysis of Thermal Bending and Vibration of Steam Turbine Rotor

“…Even more intensive heat exchange occurs during the condensation phase in the cold start-up mode, which leads to further thermal stresses and lifetime reduction [1] according to Sátor et al Therefore, the accuracy of lifetime prediction is strongly affected and dependent on the accuracy of the transient thermal state, allowing engineers to design more efficient and reliable systems. Some relevant studies under transient analysis are covered in the references [2][3][4][5][6][7][8][9]. In this study, transient analysis of the thermal bending and vibration of steam turbine rotors was explored using finite element analysis (FEA) simulation with analytical validation.…”