The Effect of Tip Clearance on a Swept Transonic Compressor Rotor

Abstract

An experimental and numerical investigation of detailed tip clearance flow structures and their effects on the aerodynamic performance of a modern low-aspect-ratio, high-through-flow, axial transonic fan is presented. Rotor flow fields were investigated at two clearance levels experimentally, at tip clearance to tip blade chord ratios of 0.27 and 1.87 percent, and at four clearance levels numerically, at ratios of zero, 0.27, 1.0, and 1.87 percent. The numerical method seems to calculate the rotor aerodynamics well, with some disagreement in loss calculation which might be improved with improved turbulence modeling and a further refined grid. Both the experimental and the numerical results indicate that the performance of this class of rotors is dominated by the tip clearance flows. Rotor efficiency drops six points when the tip clearance is increased from 0.27 to 1.87 percent, and flow range decreases about 30 percent. No optimum clearance size for the present rotor was indicated. Most of the efficiency change occurs near the tip section, with the interaction between the tip clearance flow and the passage shock becoming much stronger when the tip clearance is increased. In all cases, the shock structure was three-dimensional and swept, with the shock becoming normal to the endwall near the shroud.

Predicted and measured performance and stability of two variants of a military fan

“…This was fed by radial outward flow along the suction surface. Rather similar features were noted by Copenhaver et al [5] on a Wright Research Laboratory aft-swept rotor, and by Hah and Rabe [6] on the first rotor of the two-stage ADLARF fan. These studies employed considerably finer grids with six to ten cells across the tip gap as opposed to only two.…”

Using sweep to extend the stall-free operational range in axial fan rotors

“…Through the aerodynamic bene ts gained, the swept blade came of age in the mid-1980s as a concept to develop a low aspect ratio, ef cient, transonic rotor for aeroengine compression systems. In this ambit, a huge amount of work dealt with rotor aerodynamics [3][4][5][6][7].…”

Performance Impact of Tip Clearance Variation on a Transonic, Low Aspect Ratio, Axial Compressor Stage

“…Copenhaver et al [1] combined experimental and computational approaches to study the effect of tip clearance variation on efficiency for a swept, transonic compressor rotor. Sakulkaew et al [2] performed a computational study on efficiency and found that an optimum tip clearance existed for which the combined, competing effects of tip leakage flow rate and tip leakage mixing loss minimized overall loss.…”