Effect of the nonaxisymmetric endwall on wet steam condensation flow in a stator cascade

Steam turbines are critical pieces of power equipment in the electric power industry, and the study of wet steam condensation flow is important for improving the efficiency and safety of steam turbines. Wet steam nucleation, which is the main reason for thermodynamic losses, usually occurs downstream of the stator cascade. The mechanism of secondary flow loss control by the nonaxisymmetric endwall is the change of pressure distribution in the cascade channel. This mechanism also affects the wet steam condensation phenomenon. The positive/cosine function was proposed for endwall modification in the nucleation stage of a steam turbine. The design method presented in this paper can be used to produce endwall protrusions with different heights at different axial chords. To analyze the influence of the endwall protrusion design parameters on the condensation flow, nine endwall protrusion models were set up at varied axial positions. In comparison with the original cascade, the total pressure loss coefficient and outlet wetness were found to be ideal when the endwall protrusion maximum height was located at the 50% axial chord length of the stator and the protrusion was 3% of the blade height. The ideal incidence angle of this modified cascade was from -2 degrees to+10 degrees.