Abstract
This article presents the study of Tip Chordline Sweeping (TCS) and Axial Sweeping (AXS) of low-speed axial compressor rotor blades against the performance of baseline unswept rotor (UNS) for different tip clearance levels. The first part of the paper discusses the changes in design parameters when the blades are swept, while the second part throws light on the effect of sweep on tip leakage flow-related phenomena. 15 domains are studied with 5 sweep configurations (, TCS, TCS, AXS, and AXS) and for 3 tip clearances (0.0%, 0.7%, and 2.7% of the blade chord). A commercial CFD package is employed for the flow simulations and analysis. Results are well validated with experimental data. Forward sweep reduced the flow incidences. This is true all over the span with axial sweeping while little higher incidences below the mid span are observed with tip chordline sweeping. Sweeping is observed to lessen the flow turning. AXS rotors demonstrated more efficient energy transfer among the rotors. Tip chordline sweep deflected the flow towards the hub while effective positive dihedral induced with axial sweeping resulted in outward deflection of flow streamlines. These deflections are more at lower mass flow rates.
Highlights
Sweep is incorporated to a baseline turbomachinery blade by tilting its stacking axis in relationship to the flow field
When the blades are given forward sweep they are found to receive the flow at lower incidences
This is true all over the span for the axial sweeping while tip chordline sweeping is observed to result in little higher incidences below the mid span
Summary
Sweep is incorporated to a baseline turbomachinery blade by tilting its stacking axis in relationship to the flow field. This is achieved by linearly translating the aerofoil blade sections from hub to tip for a given sweep angle in such a way that the amount of movement is zero at the hub and highest at the tip. Three dimensional forward sweep designs have shown increased compressor efficiency and operating range [1,2,3,4,5], higher pressure rise with moderate sweep angles [4], suppression of secondary losses [1, 5, 6], reduced blade loading near the tip leading edge portions [4, 6], and low tip clearance flow blockage [7]. Major sweep effects in compressor rotors are found above the mid span, near the tip, where the flow leaking from the finite tip gap already has its own influence
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