Modeling of the circumferential crack growth under torsional vibrations of steam turbine shafting

Abstract

Long-term operation of steam turbines has one of its consequences the formation of fatigue cracks of various types in their structural elements. Evidence of this are accidents and catastrophic destructions of steam turbines.Maine reason of long-term accumulation of fatigue damage in steam turbines shafting is torsional vibrations caused by the connection of turbogenerator to an electrical network with an inaccurate synchronization. A methodology is proposed to study the process of circumferential crack growth in the turbine shafting because of many such connections. The methodology is based on the use of the 3D finite element model of the steam turbine K-200–130 shafting and a fracture mechanics approach.There was demonstrated that the inaccuracy of turbogenerator connection to an electric network is the most influential factor affecting the crack growth. The conditions for the crack to reach a critical size has been evaluated. In the problem being considered damping capacity of the rotor steel influences the intensity of crack growth insignificantly.