Effect of Tip Clearance on the Aeroelastic Stability of a Wide-Chord Fan Rotor

Abstract

This research presents a series of simulations that investigate the effects of tip clearance on the aeroelastic stability of a wide-chord high-speed transonic fan rotor. The results show that the stall margin and the total pressure ratio decreases as the tip clearance increases. The effect of tip clearance on the blade loading can extend to 30% span. The phase of the influence coefficient without tip clearance is different from that with clearance, which causes the most unstable aerodynamic damping to shift in the nodal diameter. As the clearance increases from 0.25 mm to 2 mm, the damping decreases. The nonmonotonic behavior found by other researchers was not observed in this study. We conclude that the tip clearance affects the aeroelastic stability in two ways. The first is to change the blade loading so that the amplitude of the unsteady pressure increases or decreases, while the phase hardly changes, resulting in changes in aerodynamic damping. The second is to change the local flow so that the unsteady pressure amplitude and the phase change locally.