Secondary Flow in an Annular Cascade of High Turning Angle Turbine Blades

Abstract

<p>Approximately half of the aerodynamic losses in a turbomachine blade row are attributed to cascade secondary losses. Looking at the existing literature on secondary flows, there is a lack of detailed experiments carried out on annular cascade of high turning angle turbine blades.</p> <p>The purpose of this investigation was to construct and carry out detailed experiments on a unique large scale annular cascade of high turning angle turbine blades. Cascade tests, at a Reynolds number based on the blade chord of 3 x 10⁵ to 6 x 10⁵, consisted of inlet and exit flow parameters traverses, blade passage pressure distributions and flow visualization. The results, presented in the form of contours and radial distributions, were analysed and compared with the results of previous investigations.</p> <p>The tests showed that the flexibility designed into the cascade rig has achieved the purpose of tailoring the inlet flow conditions according to the test requirements. The total pressure loss contours revealed a large single loss region at the middle of the blade passage. The yaw angle contours showed regions of significant flow underturning and overturning in the main stream. Good agreement was found between the measured cascade secondary loss coefficient and those calculated from the available correlations.</p>