Acoustic Localization of Vane Faults in Turbomachinery Based on Source Modeling

Abstract

The sound field in the annular duct of a one-stage turbine test-rig is investigated with the aim of detecting the location of stator vane faults. For this purpose, individual stator vanes are artificially damaged by a wedge-shaped cut out at the trailing edge of the vane. Shape and size of the cut out resemble typical vane burn-off faults. The sound field generated by the damaged stator row is measured inside the duct with an array of microphones. Subsequently, the acoustic far-field part of the sound is decomposed into a sum of radial-azimuthal, propagating eigenmodes. Comparison with the undamaged turbine stage reveals that the amplitudes of certain modes increase due to the damage. In order to localize the damaged vanes, the generating mechanism of stator-rotor interaction tones is modeled by lines of dipoles at the leading edge of the rotor blades. Using this model, we demonstrate that the location of the damaged vanes of a stator row can be detected successfully if the fault locations of a reference configuration are known.