Measurements of Wake-Generated Unsteadiness in the Rotor Passages of Axial Flow Turbines

This paper describes an investigation into the free-stream unsteadiness which is found in the rotor passages of axial flow turbines and which is caused by the interaction of the stator wakes with the rotor blades. The major part of this investigation was conducted at the midspan of the rotor of a large-scale, single-stage air turbine. Measurements are presented of the unsteady free-stream velocities and blade surface pressures. These are supplemented by further results which were obtained during a flow visualization experiment in a small-scale water turbine. It is shown that the unsteadiness is dominated by the convected phenomena associated with the passage of the wakes through the rotor.