A self-twisting flow seal for leakage reduction via global leakage path reconfiguration

In turbomachinery, annular gas seals play an essential role in controlling leakage and maintaining operational efficiency. Nonetheless, the effectiveness of these seals in preventing leakage is notably influenced by the kinetic energy carry-over (KEC) effect. Conventional KEC suppression methods primarily focus on localized flow control, which limits their effectiveness. Inspired by the aerodynamics of vectoring nozzles, this study introduces a self-twisting flow seal (STFS) that suppresses KEC by reconfiguring the global leakage path using the intrinsic energy of leakage flow. The STFS combines tandem divergent-convergent cavities with upstream bypass injection passages. Driven by the inter-cavity pressure differential, the self-induced bypass jet interacts with the main leakage flow, triggering a stage-coupled flow deflection that develops into a global self-twisting flow pattern. This reconfigured flow pattern weakens the direct carry-over pathway of the leakage jet and simultaneously enhances the vena contracta effect at tooth tips. Through this synergy, STFS's leakage performance is enhanced. To validate the improvement, CFD simulations and equivalent flat-plate experiments are conducted in comparison with the cutting-edge air curtain technology (ACT). Results indicate that the STFS outperforms ACT across all the studied operating conditions. With the conventional labyrinth seal as a baseline, the STFS attains a maximum reduction in discharge coefficient of approximately 65%, which is four times that of the ACT. More importantly, the STFS maintains lower leakage than the ACT even at larger clearances, improving clearance tolerance and reducing potential rubbing/wear risk. Overall, this design shifts KEC control from localized impedance to global leakage path reconfiguration, offering a feasible route for high-performance turbomachinery seals.