Abstract

Geometric discontinuities cause a large variation of stress and produce a significant increase in stress. The high stress due to the variation of geometry is called as ‘stress concentration’. This will increase when the loads are further applied. There are many investigators who studied the stress distribution around the notches, grooves, and other irregularities of various machine components. This paper analyses the effect of stress concentration under thermal and dynamic loads in a steam turbine rotor grooves under the operating conditions. Stresses due to thermal and dynamic loads in high pressure steam turbine rotor of 210 MW power station were found in two stages. A source code is developed for calculating the nominal stress at each groove section of HPT rotor. Maximum stress is obtained using FEA at the corresponding section. Stress concentration factors due to thermal and dynamic loads at each section was calculated. It is observed that the stress concentration due to the combined effect of thermal and dynamic loads is exceeding the safe limits at temperatures beyond 540°C.

Key words: Stress concentration factors, HPT rotor, thermal loads, dynamic loads.