The lifespan penalties of a steam Turbine’s governing stage rotor blade during the rapid peak shaving of new power system

The integration of renewable energy as main power sources in new power system necessitates increased peak shaving and frequency regulation tasks for thermal power units. The damage to high-temperature rotor blades due to integrated effects of frequent and rapid load changes and temperature variations is critical for power system reliability but remains unclear. This paper presents a thorough study on this issue, revealing the damage mechanism through analysis of the coupled creep and fatigue effect inside the rotor blades under steady-states and transient regulation scenarios. It is found that, during the transient processes, the low cycle fatigue damage of the blades at a load-variation rate of 5 % load per minute is about four times higher than at 2 % load per minute. According to the nonlinear fatigue-creep model, the low cycle fatigue damage caused by rapid load changes unexpectedly amplifies the cumulative damage from the coupling of fatigue and creep. This mechanism results in the following findings: in a one-day cycle regulation from half load to full load (including steady states and transient processes), a load variation rate of 5 % load per minute leads to around two times of mixed creep and fatigue damage on the rotor blades compared to 2 % load per minute, with corresponding lifespan penalties reduction of 75 % and 43 %, respectively.