Dynamic loading of an inlet guide vane (IGV) in a transonic compressor is characterized by unsteady IGV surface pressures. These pressure data were acquired for two spanwise locations at a 105 percent speed operating condition, which produces supersonic relative Mach numbers over the majority of the rotor blade span. The back pressure of the compressor was varied to determine the effects from such changes. Strong bow shock interaction was evident in both experimental and computational results. Variations in the back pressure have significant influence on the magnitude and phase of the upstream pressure fluctuations. The largest unsteady surface pressure magnitude, 40 kPa, was obtained for the near-stall mass flow condition at 75 percent span and 95 percent chord. Radial variation effects caused by the spanwise variation in relative Mach number were measured. Comparisons to a two-dimensional nonlinear unsteady blade/vane Navier–Stokes analysis show good agreement for the 50 percent span results in terms of IGV unsteady surface pressure. The results of the study indicate that significant nonlinear bow shock influences exist on the IGV trailing edge due to the downstream rotor shock system. [S0889-504X(00)00303-2]

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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 by experimental analysis methods. The axial spacing between the IGV and rotor was varied between 12%, 26%, and 56% of the rotor chord for a 105% speed near stall operating condition, which is transonic. Unsteady IGV surface pressures were acquired for two spanwise locations on both blade surfaces. Variations in axial spacing have significant influence on the magnitude and phase of the upstream pressure fluctuations. The largest unsteady surface pressure magnitude, 49.6 kPa, was obtained for the 12% axial spacing configuration at 75% span and 95% chord. Spanwise variation effects caused by the increased relative Mach number were measured. The upstream bow shock effect is strongly non-linear in character. The results of the study indicate significant variations in the IGV unsteady loading caused by axial spacing variations. Nomenclature Gas turbines are a vital energy source for both Abstract Subscripts η -normalized s -IGV inlet 1 -IGV upper surface 2 -IGV lower surface