Temperature and stress characterization of rotor under zero output condition of low-pressure cylinder

Abstract To obtain the thermal states of the low-pressure rotor in a zero-output low-pressure cylinder turbine under different operating conditions, a mathematical model was established for a 300 MW turbine low-pressure rotor in a power plant. The temperature and equivalent stress distribution characteristics of the low-pressure rotor under various conditions were analyzed. The results indicated that as steam flow decreased, the temperatures of the last-stage and penultimate-stage rotors gradually increased, but remained at 63.98°C and 73.11°C respectively during cylinder-cutoff operation due to spray cooling. With reduced steam mass flow, the stress distribution on the rotor remained similar, with maximum stress located at the root of the last stage, while equivalent stresses in all stages progressively increased, particularly showing a sharp stress surge in the last stage. During zero-output operation of the low-pressure cylinder, spray cooling effectively prevented overheating but caused elevated equivalent stress in the last-stage rotor.