An experiemental and computational study of the aerodynamics of turbine blades with damage

Investigations have been made of the aerodynamic effects of in-service damage on the performance of axial turbine blades. Two aspects of blade damage were considered: surface roughening and trailing edge damage. The work is related to gas turbine engine health monitoring.; Correlations for the effects of surface roughness were developed based on a database obtained from Kind et al. (1998). The correlations account for the effects of the roughness height as well as the location and extent of the roughness patch on the blade surface.; The effect of trailing edge damage at transonic flow conditions was investigated both experimentally and computationally. Computational investigation was conducted for only trailing-edge damage using a three-dimensional Navier-Stokes solver developed by Dawes (1988). The computations with trailing edge damage represent a novel application of the code and the wind tunnel measurements were therefore used to validate the computations.; Results showed that surface roughening and trailing edge damage produced significantly different aerodynamic behavior of the flow. Surface roughening largely influences the profile losses and trailing edge damage has a considerable effect on the flow deviation. The effect of trailing edge damage on the loss characteristics of the blades was found to be fairly small over the full range of flow conditions. In fact, the overall measured profile losses were actually lower for 20% damage than for the undamaged blade.; The measured flow deviation increased with the increase in damage size as well as cascade exit Mach number. Computational investigations were made to identify the parameters that influence flow deviation in turbines with both undamaged and damaged blades so that correlations could be developed. It was found that the deviation is primarily determined by the blade loading towards the trailing edge. The blade row parameters which influence this pressure difference were identified. The deviation correlation for undamaged blades is applicable for subsonic flow cases and that for damaged blades is applicable for the full range of Mach numbers studied. The new subsonic deviation correlation for undamaged blades appears to be significantly more successful than existing correlations.; The three dimensional Navier-Stokes solver of Dawes predicted many of the measured results for damaged blades. Particularly, predictions of deviation for different undamaged and damaged blade geometries were found to be quite satisfactory and the code was extensively used to generate deviation data to supplement experimental measurements. (Abstract shortened by UMI.)...