Efficiency Improvements in an Industrial Steam Turbine Stage: Part 1

The present work approaches the idea of increasing the efficiency of an industrial steam turbine stage. For this endeavor, an industrial steam turbine stage comprising of prismatic stator and rotor is considered. With the velocity triangles as input, airfoil design is carried out. Firstly, the rotor is redesigned to take care of any incidence issues in the baseline case. In rotor blades, the peak Mach number is reduced in blade to blade flow passage and hence, efficiency of stage is increased. Rotor is made front loaded. After finalizing the rotor, the stator is redesigned. Stator is made more aft-loaded when compared to the baseline case. By making the stator aft-loaded, the efficiency increased by reducing profile losses. This design modification also showed advantage in secondary losses. The total pressure loss in the stator was reduced by a delta of 0.15. When creating an airfoil for stator or rotor, MISES was used in order to evaluate profile losses. The design verification for the stage was numerically done using commercial CFD software ANSYS CFX. Steady state RANS simulations were carried out. The stator and the rotor still being prismatic, only by virtue of airfoil design, the total to total stage efficiency improvement of 0.33% was predicted.