Numerical analysis of condensation effects on final-stage rotor-blade rows in low-pressure steam turbine

摘要

The causal relationship between unsteady forces of wet-steam flows on rotor-blade rows and the steam condensation in low pressure steam turbines is still one of unresolved issues. In this study, we investigate the effect of condensation on the time-dependent torque of final-stage long-rotor blade rows in a low pressure steam turbine. Then we simulate unsteady wet-steam flows through the three-stage stator-rotor blade rows in the steam turbine while changing the inlet temperature condition. The variation of the inlet temperature results in creating a flow field with a different amount of wetness due to condensation. The temperature and pressure in the flow field obtained from a different inlet temperature are compared with each other, and the torques calculated from the time-dependent pressure on a final-stage long-rotor blade are also relatively compared. The calculated results in this study indicate that the time-dependent torques on the final-stage long-rotor blade significantly depend on the latent heat added by condensation and that the amount of condensation is highly sensitive to variations in the inlet temperature. This study also suggests that an optimal inlet temperature may be exist for optimizing the torque of low pressure steam turbines.