Blade Stress Analysis of Control Stage in Different Governing Mode

Using different governing modes in the process of large steam turbine load variations will make the thermal characteristic and force of unit get complicated, especially affect the thermal characteristic and force change of the control stage notability the most. This article researched the governing mode problems of the domestic-type 600 MW steam turbine, analyzed different characteristics in different governing modes of control valve, calculated the control stage blade force in different loads and governing modes, and the blade force variations on the main steam pressure change in the same load, based on large amount of field test data. By calculating and analyzing, we found that, the blade force of sequential valve governing mode is significantly higher than the single valve governing mode in domestic-type 600 MW steam turbine. For the same load, the higher the main steam pressure, the smaller the main steam flow, the greater control stage blade force is. Therefore, in the process of unit actual operation, it should try to avoid the risk of working conditions of control stage blade stress in order to ensure the safety of unit operation when the governing modes are switching or the control valve opening is changing to regulate the load.