A Novel Reverse Swirl Generator Concept for Enhancing the Rotordynamic Stability of Annular Gas Seals Utilizing the Intrinsic Energy of Leakage Flow

Circumferential flow is the major cause of rotordynamic instability in annular gas seals, and anti-swirl techniques are widely adopted to mitigate this issue. However, conventional solutions such as swirl brakes mainly rely on flow-blocking mechanisms, which inherently limit their effectiveness. Inspired by the flow control strategies in aeroengine vector nozzles, this study proposes a novel reverse swirl generator (RSG). The RSG integrates specially designed guiding vanes with a divergent—convergent cavity, allowing the pressure energy of the leakage flow to be effectively transformed into anti-swirl kinetic energy. Numerical simulations are conducted on labyrinth and pocket damper seals equipped with RSG and compared against conventional swirl brake designs. Results demonstrate that the throttling throat of the RSG converts pressure energy into axial kinetic energy, while the tortuous cavity geometry ensures direct impingement on the guiding vanes, completing the conversion into anti-swirl kinetic energy. This mechanism induces a full reversal of circumferential flow in downstream seal regions, changing cross-coupled stiffness coefficients from positive to negative, with magnitudes nearly three times greater than those achieved with swirl brakes. Consequently, the effective damping coefficient of RSG-equipped seals is approximately 2.5 times higher, significantly enhancing system stability. Furthermore, the added resistance from the cavity path contributes to leakage reduction, with the RSG achieving a 12.9% decrease compared to the swirl-brake case. These findings confirm the dual advantages of RSG in both improving sealing performance and reinforcing rotordynamic stability, providing a promising direction for advanced seal design.