Viscoplastic model-based analysis of in-service oscillation temperature and thermal stress in a rotating component

Abstract

The thermal gradient in the rotor is a key influential factor in thermal stress. Steam temperature fluctuations cause temperature oscillations in the rotor, leading to variation in the thermal gradient and finally changing the rotor's thermal stress behavior. This study aimed to identify the influence of steam temperature fluctuations on the rotor's oscillation temperature and thermal stress behavior. Thus, the extent to which the rotor temperature is influenced by steam temperature fluctuations and the associated temperature change behavior in the rotor could be predicted in detail. The convective heat transfer between the steam and the rotor is characterized by the third boundary condition, and the thermal stress is described with a viscoplastic constitutive model with damage. Realistic in-service operating data during startup and steady-state operation phases were chosen to investigate the oscillation temperature and thermal stress induced by steam temperature fluctuation in a steam turbine rotor. With the benefits to the rotor design and power plant operation, the temperature fluctuating amplitude range was categorized into four groups by transient thermomechanical finite-element analysis, and the temperature differences in the rotor between sets of two adjacent locations are listed to demonstrate the heat congestion.