Measurement and prediction of the flow through an annular turbine cascade

Abstract

An annular turbine cascade was designed and manufactured for laser Doppler velocimetry and probe measurements in a small-scale rig. The purpose of the experiment was to determine the limitations of these measurements in a confined annulus, and to compare the experimental results with numerical predictions. Downstream probe surveys were conducted at a Reynolds number of 500000. Total pressure and temperature measurements were taken upstream of the test section, and hub static pressure was measured downstream of the cascade. A two-dimensional laser anemometer was used to obtain preliminary velocity field measurements for code validation. The two main problem areas identified were the type of seeding material used and the configuration of the optical access window. Flowfield characteristics were predicted using a three-dimensional viscous code, which were then compared to experimental measurements. The comparison showed that the numerical simulator predicted well the general features of the flow field that were measured in the experiment. Recommendations are made which would improve the mapping of the velocity field for a more complete code validation