Unsteady Transition in an Axial Flow Turbine: Part 1 — Measurements on the Turbine Rotor

Previously published measurements in a low speed, single stage, axial flow turbine have been reanalysed in the light of more recent understanding. The measurements include time-resolved hot wire traverses and surface hot film gauge measurements at the midspan of the rotor suction surface with three different rotor-stator spacings. Part 1 investigates the suction surface boundary layer transition process using surface-distance time plots, and boundary layer cross sections to demonstrate the unsteady and two-dimensional nature of the process. Part 2 of the paper will describe the results of supporting experiments carried out in a linear cascade together with a simple transition model which explains the features seen in the turbine.