The Study of Tip Clearance of a Wide-Chord Fan Blade of a High Bypass Ratio Turbo-Fan Engine

Abstract

The wide-chord swept fan blade (WCSFB) has been extensively used in a advanced high bypass ratio turbofan engines. This paper explores the nature of WCSFB tip clearance. From the static analysis, it is found that the tip radial clearance at leading and trailing edge of WCSFB will be reduced with either bending or torsional deformation of the blade. And the change of the tip radial clearances varies with the twist angle. In this study, dynamic response of the WCSFB with different angular accelerations of the engine has been analyzed. It shows that when the angular acceleration of the fan rotor reaches a certain level, considerable bending and torsional deformation of the blade will occur, accompanied by the reduction of the tip radial clearance, which may lead to abnormal rubbing/impact between the blade tip and the casing. This may cause severe consequence for the blade and casing of the engine. The numerical simulation results show that the rubbing/impact between the WCSFB tip and the casing under angular acceleration loads can lead to local buckling of the tip leading edge of the blade, which will cause severe damage at the blade tip. Moreover, the influence of vibration and mass imbalance of the rotor on the fan blade tip clearance is also analyzed. In this paper, the results of a rig test under irregular acceleration for the WCSFB rotor is also presented, which validates the analytical results. The numerical simulation and test results will assist the blade tip clearance design to reflect the nature of the WCSFB under irregular acceleration to ensure safety.