Investigation of unsteady effects in transonic turbomachinery flows using particle image velocimetry

Within two projects funded by the European Union and the Austrian Science Foundation unsteady effects in transonic turbomachinery flows were investigated to optimise these turbine stages used for power generation. A continuously operated cold-flow test rig with up to 2.8 MW shaft power and 11000 rpm was used. This work focuses on the application of stereoscopic Particle Image Velocimetry (PIV) for velocity and vorticity studies in combination with Laser Vibrometry (LV) and Laser-Doppler-Anemometry (LDA). With these techniques the wake flow between stator and rotor blades was investigated at subsonic and transonic Mach numbers. Special emphasis was put on phase-locking effects between stator vortex shedding and rotor blade passing frequency at transonic flow conditions.