UNSTEADY AERODYNAMICS AND GUST RESPONSE IN COMPRESSORS AND TURBINES

A comprehensive series of experiments and analyses was performed on co mpressor and turbine blading to evaluate the ability of current, pract ical, engineering/analysis models to predict unsteady aerodynamic load ing of modern gas turbine blading. This is part of an ongoing effort t o 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 c ompressor and turbine blading was generated by upstream wakes and. add itionally for compressors, by a rotating inlet distortion. Fast-respon se hot-wire anemometry and pressure transducers embedded in the airfoi l 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 i n the literature. Several different analyses were used to predict the unsteady component of the blade loading: (1) a classical flat-plate an alysis, (2) a two-dimensional linearized flow analysis with a ''frozen gust'' model, (3)a two-dimensional linearized flow analysis with a '' distorted gust '' model, (4) a two-dimensional linearized Euler analys is, and (5) a two-dimensional nonlinear Euler analysis. Also for the f irst 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 exper iment and their abilities assessed to help guide designers in using th ese prediction schemes.