Abstract

Within a European project which aimed at the investigation of stator wake - rotor blade interactions, measurements were carried out to determine the unsteady pressure distribution downstream of a transonic high pressure turbine stage. 

The experiments were conducted in the wind-tunnel for rotating cascades at the DLR Góttirrgen (RGG). The RGG is a closed loop facility, that enabled real engine Mach and Reynolds numbers in ihe turbine stage. The stator vanes had coolant ejection slots close to the trailing edge at the pressure side. A Pitot Probe, equipped łrrith a fast response pressure transducer and a cornmon pneumatic pressure tube was installed downstream of the rotor. The measurement position was 0.5 axial rotor chords downstream of the rotor trailing edge at midspan. The stator vane passing frequency as seen by the rotor was 5,6 kHz and the rotor blade passing frequency as seen by the probe was 8.4 kHz. The pneumatic Pressure was used as a reference for the rather inaccurate dc-readings of the fast response transducer. 

Measurements were carried out for two different coolant ejection rates. Firstly with no coolant ejected and secondly with 3% of the main mass flow ejected. 

In the mean values of the total pressure downstream of the stage, the stator wake is clearly visible. The Periodic fluctuations of the total pressure downstream of the rotor are about 50% smaller in the region of the stator wake than in the region of undisturbed inlet flow. Thus, the statorwake damps the total pressure fluctuations generated by the rotor.