Investigation of the vapour–liquid two-phase flow in the low-pressure cylinder of a 1000 MW nuclear power steam turbine

Abstract

The vapour–liquid two-phase flow in the low-pressure cylinder of a 1000 MW nuclear steam turbine has been investigated. Firstly, a comparative study of the flows with equilibrium and non-equilibrium condensation is described. The vapour extraction and moisture removal processes are included in the calculations to simulate the actual operating conditions in the low-pressure cylinder. Differences in the thermodynamic expansion lines, and in the distributions of wetness and degree of reaction, for equilibrium and non-equilibrium flow calculations are discussed. Secondly, the deposition of the fog and coarse water droplets in the last stage stator is investigated computationally. An empirical approach, together with the predictions of the non-equilibrium flow calculation, is used to redistribute the spanwise profile of the wetness at inlet to the last stage of the turbine. The movement and deposition of the water droplets are tracked in a Lagrangian frame. The variations of the fog and coarse water deposition rates are obtained in both the spanwise and axial-chordwise directions.