Online determination of transient thermal stresses in critical steam turbine components using a two-step algorithm

The article presents a novel algorithm for robust calculation of thermal stresses in steam turbine components during transient operating conditions. Stress calculations are performed in 2 steps: in the first step an unsteady radial temperature distribution in the component model is computed, and based on this thermal stresses at critical locations are determined in the second step. The radial temperature distribution is obtained by solving the Fourier-Kirchhoff equation for a cylinder or sphere by means of a finite difference method. The thermal stresses are computed using the Duhamel integral and Green functions evaluated with a constant heat transfer coecient and used with an equivalent steam temperature obtained from the surface heat flux.