Unsteady Tip Leakage, Bow Shock, IGV Wake Interaction in a Compressor

Unsteady aerodynamic analysis of Inlet Guide Vane (IGV)/rotor interaction is conducted with a commercial CFD solver, STAR-CD. 12% and 26% IGV axial chord IGV/Rotor spacing configurations were examined for 100% corrected speed at choke, peak efficiency and near stall conditions to investigate bow shock/tip leakage interaction within blade rows. Comparison with IGV surface unsteady pressure experimental data indicates good agreement at the IGV trailing edge across the span for both spacing configurations; therefore, validating the modeling of the high speed, highly loaded transonic compressor. The strongest effect on the tip clearance flow physics was caused by decreasing the axial spacing. The 12% axial spacing, baseline configuration had a significant effect on the cross location of the leading edge tip vortex and the rotor bow shock (i.e. the lambda shaped interaction region). In addition, the double leakage moved downstream of the bow shock due to the IGV wake for the close spacing. At 26% axial spacing, the IGV wake influence was not significant. The back pressure influence was important. The high loading at the near stall condition prevented any significant IGV wake interaction effect on the tip clearance flow. For the chocked flow condition, the bow shock structure change (going from a normal shock to an oblique shock) reduces the bow shock strength. The IGV wake caused the tip vortex to intensify, this is mainly caused by a decrease in the bow shock strength. Vortex breakdown occurs due to deceleration after passing a strong shock, which for the choked case does not happen until the vortex reaches the passage shock