Effect of Axial Throughflow Swirl on Flow and Heat Transfer in a Compressor Disc Cavity

Abstract Flow and heat transfer in turbomachinery high-pressure compressor disc cavities can be inherently highly three-dimensional, unsteady, and unstable, thus challenging both experimentally and numerically. Previous studies have clarified some of the flow and heat transfer mechanisms under nonswirled axial throughflow conditions. The present study focuses on the effect of swirl in the axial throughflow, usually found in turbomachinery operating conditions. Wall-modeled large-eddy simulations are conducted for relatively high rotational Reynolds numbers up to Reϕ=1.0×107. The inlet swirl ratios range from −1.0 to 2.0. A positive inlet swirl increases shroud heat transfer but decreases disc heat transfer, giving lower core temperature and related fluctuations. A negative inlet swirl shows the opposite effect. This is attributed to changes in the unsteady flow structure modifying the heat and mass exchange between throughflow and cavity flow affected by the inlet swirl. Theoretical modeling is investigated for heat transfer on the shroud, discs, and disc bores, emphasizing the effect of the inlet swirl. Under high Reynolds numbers, the positive inlet swirl restrains the transition from laminar to turbulent in the disc Ekman layer and related disc heat transfer at lower radii and, however, promotes transition and disc heat transfer at high radii. The present study gives insights into lower-order thermal modeling and aero-engine internal air systems design.