Numerical investigation of the condensation flow characteristics and modification optimization of a condensing steam turbine cascade

Abstract

Purpose The purpose of this study is to improved the efficiency of condensing steam turbines by legitimately reforming the flow structure. It is of great significance to study the condensation flow characteristics of wet steam for optimizing the operation of condensing steam turbines. Design/methodology/approach A two-fluid model was used to study the wet steam flow in a stator cascade. The effects of the inlet temperature and pressure drop on the cascade performance were analyzed. On this basis, endwall protrusion models were set up at varied axial position on the pressure surface to evaluate the wetness control and loss under different design conditions for cascade optimization. Findings The analysis indicates that increasing the inlet temperature or decreasing the pressure drop can effectively control the steam wetness but increase the droplet radius. The increasing inlet temperature can delay the condensation and alleviate the deterioration of the aerodynamic performance of cascades. The non-axisymmetric endwall can significantly affect the distribution of steam parameters below its height and slightly reduce the droplet radius. Compared with the original stator cascade, the optimum design conditions reduce the steam wetness by 8.07 per cent and the total pressure loss by 6.91 per cent below a 20 per cent blade height. Originality/value These research results can serve as a reference for condensing steam turbine wetness losses evaluation and flow passage optimization design.