Numerical Analysis of a Steam Turbine Rotor subjected to Thermo-Mechanical Cyclic Loads

Abstract

The contribution at hand discusses the thermo-mechanical analysis of a steam turbine rotor, made of a heat-resistant steel. Thereby, the analysis accounts for the complicated geometry of a real steam turbine rotor, subjected to practical and complex thermo-mechanical boundary conditions. Various thermo-mechanical loading cycles are taken into account, including different starting procedures (cold and warm starts). Within the thermal analysis using the FE code ABAQUS, instationary steam temperatures as well as heat transfer coefficients are prescribed, and the resulting temperature field serves as input for the subsequent structural analysis. In order to describe the mechanical behavior of the heat-resistant steel, which exhibits significant rate-dependent inelasticity combined with hardening and softening phenomena, a robust nonlinear constitutive approach, the binary mixture model, is employed and implemented in ABAQUS in two different ways, i.e. using explicit as well as implicit  methods for the time integration of the governing evolution equations. The numerical performance, the required computational effort, and the obtained accuracy of both integration methods are examined with reference to the thermo-mechanical analysis of a steam turbine rotor, as a typical practical example for the numerical analysis of a complex component. In addition, the obtained temperature, stress, and strain fields in the steam turbine rotor are discussed in detail, and the influence of the different starting procedures is examined closely.