Development of a Highly Loaded Rotor Blade for Steam Turbines : 2nd Report, Three-Dimensional Stage Performance Verifications

In order to improve steam turbine internal efficiency, a new highly loaded rotor blade for the high and intermediate pressure (HIP) stages, has been developed. The blade configuration is expressed by a 5th-order Bezier curve and an interactive technique is adopted in combination with a 2-D turbulent blade-to-blade flow analysis. The inverse method is adopted to modify the blade shape by optimizing the blade aerodynamic loading distribution near the root section which should decrease not only profile loss, but also endwall loss. Three-dimensional stage flow analysis and air turbine tests are carried out to verify the stage performance of the new blade. It is found that the new blade has improved blade performance near the root and the midspan; in particular, higher blade performance near the midspan contributes to an improvement in stage efficiency by about 0.3% at the design point. Consequently, it is verified that the new rotor blade is effective to improve steam turbine internal efficiency and to lower manufacturing cost by reducing the blade number by 15%.