Aeroelastic Instabilities in Labyrinth Air Seal Systems

Abstract

An analysis is developed that can be used to calculate the aeroelastic instabilities of labyrinth air seal systems. The formulation considers both the stator and rotor as flexible components and the fluid within the cavity has both axial and swirl components of velocity. The interaction of the leakage flow (through the clearance between lips of the seal and the stator) with the vibratory modes of the rotor and stator provides the mechanism for possible aeroelastic instability. A limited parametric study shows that increasing the stiffness of either the rotor or the stator has the same stabilizing influence as including, in the analysis, swirl flow component of the leakage flow. Further, at frequencies where coincidence between stator and rotor modes occurs, there could be a sharp drop in available aerodynamic damping. These results, which need experimental confirmation, can influence the design of these important components of jet engines.