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Axial compressors have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. This relative motion leads to viscous and inviscid (potential) interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of convected wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative axial and circumferential positions of stators or rotors can change these interactions, leading to different unsteady forcing functions on airfoils and different compressor efficiencies. In addition, the axial gaps between adjacent blade rows affect the unsteady forcing functions by modulating the potential interaction between the rows. The current study uses an unsteady, two-dimensional thin-layer Navier-Stokes procedure to investigate the combined effects of stator clocking and varying axial gaps in a low-speed axial compressor design. Relative motion between rotors and stators is made possible by the use of systems of patched and overlaid grids. Results include surface pressures, instantaneous forces and efficiencies for the compressor.

Karen L. Gundy-Burlet
Fri Jul 25 15:51:15 PDT 1997