Influence of Compound Lean on an Industrial Steam Turbine Stage

Compound lean implemented on stator of an industrial steam turbine stage in order to reduce secondary losses are discussed. Baseline stator is a prismatic vane with aspect ratio of unity. Compound lean stator blade is designed by shearing the airfoil sections in tangential direction. Modifications are analyzed numerically using commercial code CFX. Three blade rows i.e. one complete stage with a downstream stator are analyzed. Steady state Reynolds averaged Navier Stokes equations are solved. Total pressure loss (TPL) is used as objective function to monitor reduction in secondary losses. Rotor is retained the same for baseline as well as compound leaned stator. Results show reduction in total pressure loss of stator in excess of 5 %. Also, computations of co-efficient of secondary kinetic energy shows significant reduction in secondary losses in excess of 30 % in stator. Efficiency gained by implementation of compound lean are discussed.