Numerical study of the dehumidification structure optimization based on the modified model

Abstract

Nowadays, the vast majority of electricity is extracted from the steam turbine, while the non-equilibrium condensation will take place because of the high steam velocity and low superheat temperature in steam low-pressure stage, which will not only reduce the efficiency but endanger the safety of the steam turbine by corroding the blade. The aim of this work is to optimize the novel dehumidification structure to reduce the wetness loss and increase the efficiency of steam turbine. Firstly, the modified model is developed to predict the non-equilibrium condensation flow. The modified model is validated in stator cascade, which shows a greater agreement with the experimental data compared with original model, especially the Wilson point and pressure rise caused by the non-equilibrium condensation. Secondly, two novel dehumidification structures are presented on the basis of my previous study, and the dehumidification effect is checked using the modified model. With the passage outlet diameter increasing in the PICS, the reduction of the outlet average liquid mass fraction and wetness loss in cascade has the same tendency, and the more the passage outlet diameter, the lower the outlet average liquid mass fraction, the less the wetness loss caused by the non-equilibrium condensation in cascade. Thirdly, compared with the original cascade, the PICS with the φ=5° having the divergence nozzle characteristic and larger outlet diameter presents the best dehumidification effect and succeeds in reducing the average liquid mass fraction and wetness loss to 3% and 3.06 kJ/kg, respectively.