Unsteady Aerodynamics and Gust Response in Compressors and Turbines

Abstract

A comprehensive series of experiments and analyses were performed on compressor and turbine blading to evaluate the ability of current, practical, engineering/analysis models to predict unsteady aerodynamic loading of modern gas turbine blading. This is part of an on-going effort to improve methods for preventing blading failure. The experiments were conducted in low-speed research facilities capable of simulating the relevant aerodynamic features of turbomachinery. Unsteady loading on compressor and turbine blading was generated by upstream wakes and, additionally for compressors, by a rotating inlet distortion. Fast-response hot-wire anemometry and pressure transducers embedded in the airfoil surfaces were used to determine the aerodynamic gusts and resulting unsteady pressure responses acting on the airfoils. This is the first time that gust response measurements for turbines have been reported in the literature. Several different analyses were used to predict the gust response of the blading: (1) a classical flat-plate analysis, (2) a 2-D linearized flow analysis with a “frozen gust” model, (3) a 2-D linearized flow analysis with a “distorted gust” model, (4) a 2-D linearized Euler analysis, and (5) a 2-D non-linear Euler analysis. Also for the first time, a detailed comparison of these analyses methods is made and the importance of properly accounting for both vortical and potential disturbances is demonstrated. The predictions are compared with experiment and their abilities assessed to help guide designers in using these prediction schemes.