Performance improvements in an industrial compressor through airfoil clocking

Axial compressors have inherently unsteady flow fields because of relative motion between rotating and stationary airfoil rows. This relative motion leads to viscous and inviscid interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of convected wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative circumferential positions of airfoils in adjacent rotating or non-rotating blade rows can change these interactions, leading to different time-averaged losses and stage efficiencies. As the Mach number increases the interaction between blade rows can be intensified due to potential effects. It has been shown, both experimentally and computationally, that airfoil clocking can be used to improve the efficiency and reduce the unsteadiness in multiple-stage axial turbomachines with equal blade counts. While previous investigations have focused on idealized geometries, the goal of the current research is to improve the performance of a compressor used in a production industrial gas turbine. Quasi three-dimensional simulations have been performed using both simplified and actual blade counts. Time-averaged and unsteady data (including performance quantities) are presented. In addition, a technique is introduced for determining the optimum clocking position during the early stages of the design process.