Experimental and Numerical Investigations of Steam Expansion Rate in Low Pressure Steam Turbine

Abstract This study focused on the expansion rate of steam; the effect on efficiency was investigated experimentally and numerically by varying the expansion rate of steam in the stage where condensation occurs by varying the flow rate and inlet temperature using a five-stage model steam turbine. The steam expansion rate of the stator blades in each stage was evaluated from the measured wall pressure and total pressure. In addition, the turbine efficiency was evaluated from the measured torque and mass flow rate, and the effect of flow rate and condensing stage can be taken into account for losses caused by condensation. In addition, numerical calculations to account for the effects of non-equilibrium condensation were performed using ANSYS CFX. The numerical calculations were able to show the details of the nucleation situation and the resulting changes in flow patterns. Numerical evaluation of the subcooling loss showed that there was no difference in subcooling loss between different mass flow rates. The steam expansion rate was evaluated from the measurement results, and it was found that there was no difference in the steam expansion rate due to differences in mass flow rate. This corresponds to the numerical result that the subcooling loss does not vary with flow rate.