Observation of flow structure past a full-stage axial air turbine at the nominal and off-design states

The air flow inside single-stage test turbine is studied experimentally by Particle Image Velocimetry (PIV). Here we report the measurements results at axial-tangential plane just behind the rotor wheel at middle blade radius. We studied one nominal state and two off-design states. We discuss the applicability of resolution of our PIV system to this flow – we can distinguish the largest vortical structures in the shear layers between blade wake and jet, but the bottom part of the cascade is invisible for us at this moment. Spatial distributions of statistical moments of vorticity show a non-classical behavior at the cross-points of stator and rotor jets. We use our previously published algorithm for calculating spatial energy spectrum and display the turbulent kinetic energy colored by different length-scales of the fluctuations.