Investigating the dehumidification characteristics of the low-pressure stage with blade surface heating

Abstract

At present, the vast majority of electricity is generated by steam turbines. Nonequilibrium condensation will occur in the low-pressure stage, which will not only reduce efficiency but also corrode blades and endanger the safety of the steam turbine. The aim of this work is to optimize the blade surface volume heating scheme to reduce the wetness loss. Based on thermodynamic theory, the nucleation model and droplet growth model were studied. A two-fluid model of homogeneous condensation was established from the point of view of the volume average, and the accuracy of the model was verified. The effects of stator blade surface volume heating, rotor blade surface volume heating and coupling heating on the wet steam condensation characteristics in the nucleation stage were analyzed. The research shows that stator blade surface volume heating can satisfactorily prevent steam condensation. When the stator blade surface volume heating rate is 0.375 J /(mm2·s), the average outlet wetness of the stage is 0.0158, which decreases 69.34% compared with the non-heating condition, and the entropy increase is only 0.26% higher than that of the non-heating condition. Blade surface heating can inhibit steam condensation very well and improve the turbine efficiency to a certain extent.