The leakage and rotordynamic performance of the novel bulkhead-tooth labyrinth seal

By adding a spoiler bulkhead within the trapezoidal tooth cavity, a labyrinth seal (LS) structure is constructed with a bulkhead-tooth cavity. This design allows the tooth cavities to be subdivided without changing the original seal dimensions, enabling fine-tuned control of the fluid flow field within the cavities to improve the sealing performance. Based on three-dimensional transient computational fluid dynamics (CFD) methods and the self-developed plate test platform of the clearance seal, the leakage control and rotordynamic stability of several typical bulkhead-tooth LSs such as cross tooth (CTLS), side tooth (STLS), bevel tooth (BTLS) bulkhead and standard tooth labyrinth seals (SLS) have been relatively analyzed. The results show that the maximum leakage rate reduction of the CTLS and STLS is approximately 25 % and 22 %, respectively, compared to the standard tooth LS, while the BTLS achieves a reduction of approximately 10 %. The effective damping of CTLS, BTLS, and STLS can be improved by 36.6 %, 21.3 %, and −19.7 %, respectively, while the effective rigidity coefficients increase by 56.1 %, 43.4 %, and 7.5 %, respectively. The more substantial vortex dissipation effect within the cross-tooth and bevel-tooth cavities of LS and its obstruction to the clearance jet can improve the leakage control ability of the BTLS and CTLS. Meanwhile, the stronger vortex and more uniform distribution of circumferential velocity and pressure caused by the increase in fluid viscosity have significantly improved both the direct damping coefficient and the cross-damping coefficient of BTLS and CTLS. The enhanced constriction effect of STLS at the cavity outlet can improve the leakage control ability of STLS, but when superimposed with the negative moments in the tooth cavities, results in significant negative direct stiffness and reduced direct damping coefficient.