High Resolution Measurement of Turbulence in Axial Compressors

Summary

In a low speed axial compressor the instationary flow field behind a rotor at 50% blade height has been measured with hot-film probes in split-film technique. Continuous measurement over many rotor revolutions and evaluation with the ‘Ensemble Averaging Method’ and high temporal and spatial resolution renders average values and momentary fluctuations for the flow velocity in each point. Description of velocities and fluctuations in a mainflow / crossflow system seems more appropriate for a correct physical understanding than the axial / circumferential coordinate system familiar in turbomachines.

Since the measuring technique applied cannot render a continuous velocity signal for a certain point, but is rather a sampling at a relatively low time rate, the fluctuations measured are not necessarily resulting from turbulence, but could have also other causes. Statistical evaluations are used to investigate their character in more detail.