Transonic Compressor Influences on Upstream Surface Pressures With Axial Spacing

A set of inlet guide vane (IGV) unsteady surface pressure measurements is presented. The unsteady aerodynamic effects of a highly loaded, high speed downstream compression stage on the upstream inlet guide vane stator surface pressures are characterized through experimental and computational analysis. The axial spacing between the IGV and rotor was varied between 12%, 26%, and 56% of the IGV chord for a 105% speed, peak efficiency operating condition, which is transonic. Unsteady IGV surface pressures were acquired for two spanwise locations on both blade surfaces. The largest unsteady surface pressure magnitudes were obtained at the 12% axial spacing configuration and 95% chord location. In general, spanwise variations were found to be important. The upstream bow shock effect is non-linear in character. Comparisons to a two-dimensional, non-linear unsteady multi-blade row Navier-Stokes analysis at 50% span show a good agreement with the IGV unsteady surface pressure results and higher harmonic content. The results of the study indicate significant variations in the IGV unsteady loading caused by changes in axial spacing.