Impact of Variable-Geometry Stator Hub Leakage in a Low Speed Axial Compressor

The impact of hub leakage flow associated with the clearance gaps of hub-shrouded variable-geometry stator rows in axial compressors is investigated experimentally. The objectives of this work are to investigate the sensitivity of performance to chordwise leakage location and to provide guidance for the mechanical design of variable stator hub trunions. Although blade loading near the hub is increased when leakage occurs at the leading edge, losses also increase for both design and off-design operating conditions. Leading edge leakage also causes a greater spanwise variation in absolute turning angle over the first 20% of span from the hub. Results show that for a moderately separated stator, the optimum leakage configuration features trailing edge leakage with the leading edge sealed. This confirms the current practice of most engine companies in placing the hub trunion at the blade leading edge.