Computational Study of Clocking an Embedded Stage in a 4-Stage Industrial Turbine (original) (raw)

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001

Abstract

ABSTRACT Multi-stage turbines 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 alter these interactions, leading to different time-averaged losses and stage efficiencies. In addition, interaction between blade rows can intensify with increasing Mach number due to potential effects.It has been shown in previous studies, both experimental and computational, 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 for the most part focused on two-stage turbines, the goal of the current research is to evaluate the effects of clocking an embedded stage within a larger turbine system. Quasi-three-dimensional simulations of airfoil clocking have been performed for a four-stage industrial turbine. Time-averaged and unsteady data (including performance quantities) are presented. The results show a 0.5% efficiency variation in the stage where the vanes were clocked, and smaller efficiency variations in the upstream and downstream stages. The overall efficiency of the turbine system varies with the efficiency of the clocked stage, although by a smaller amount.

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