SPANWISE TRANSPORT IN AXIAL-FLOW TURBINES .1. THE MULTISTAGE ENVIRONMENT

Selected experimental results, obtained from a detailed investigation into the flow fields within two low-speed multistage turbines, are pre sented. A repeating stage condition occurred typically after two stage s, with the secondary flows an important factor in the low aspect rati o geometry. A tracer gas technique was employed to identify the domina nt mechanisms of spanwise transport and their relative significance. I n the first stages of both machines, tracer transport was more intense near the endwalls than at midspan, while in the multistage environmen t the transport was approximately constant across the whole span. The convective influence of classical secondary flow, shroud leakage, and wake passage through a downstream blade was identified and shown to be as significant as turbulent diffusion in effecting cross-passage and spanwise transport. The data show that spanwise transport should be in cluded within any throughflow model and are used to calibrate two scal ing models. These models are presented in Part 2, where the influence of incorporating spanwise transport into a throughflow model is invest igated.