Numerical Study on Prediction and Mitigation of Aeroelastic Instabilities in Labyrinth Seals

Labyrinth seals are non-contact fluid sealing elements widely employed at rotor–stator interfaces in turbomachinery to minimize leakage and maintain pressure differentials across various stages, thereby enhancing overall efficiency. However, their lightweight and compact configuration often leads to reduced structural stiffness, making them susceptible to aeroelastic instabilities. In this study, a fluid–structure interaction (FSI) analysis is conducted to evaluate the aeroelastic behavior of a labyrinth seal. The methodology involves importing mode shape data from structural modal analysis into an unsteady CFD simulation with mesh deformation to compute aerodynamic modal damping. Simulations are performed over a range of pressure ratios, revealing increased aeroelastic instability with higher pressure ratios. Additionally, the influence of seal-clearance variation is analyzed, showing a decrease in aerodynamic damping as clearance increases. The computed damping ratios are validated against established analytical aeroelastic stability criteria. Based on a qualitative analysis of aerodynamic work distribution on the fluid–structure interface, geometric modifications were introduced in the labyrinth seal by progressively increasing the fin tip clearance in the direction of flow. The modified configuration resulted in a 454% increase in the aerodynamic modal damping ratio (ξaero) compared to the baseline design, indicating a significant improvement in aeroelastic stability. Additionally, the modified seal demonstrated approximately a 4% reduction in leakage flow, reflecting enhanced sealing efficiency alongside flutter suppression.