  A series of unsteady simulations, supported by experimental data, are used to characterize the periodic unsteadiness of the tip clearance vortex in an axial compressor rotor. The numerical probes detect significant periodic fluctuations in the blade tip region at near stall conditions. Physical explanations of the periodic fluctuations are made in terms of vortex-core identification, streamlines, etc. With the decrease of mass flow rate, the tip leakage vortex moves upstream to the leading edge of the adjacent blade, resulting in decrease of momentum in the tip clearance and pressure in the leading edge of the adjacent blade. The flow in this blade tip region is similarly affected by another adjacent blade. The intensity of tip leakage vortex is reduced, and the tip leakage vortex core is bent. Without the influence of the leakage vortex, the pressure of leading edge recover which result in enhance of momentum in the tip clearance. And the leakage vortex is strengthened again. The tip leakage vortex will be weakened and strengthened again and again. Such periodic phenomenon doesn’t occur in any geometries and flow conditions. Various combinations of there kinds of tip clearances and two kinds of flow conditions are tested. The criteria for the tip clearance vortex unsteady phenomena is also discussed in this paper. The improved trailing vortex instability theory is used to offer a physical explanation of the source of the periodic unsteadiness.


Periodic Unsteadiness of Tip Clearance Vortex in an Axial Compressor Rotor

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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