Dynamic tracking characteristic of high-speed dry gas seal considering centrifugal inertia effect and its interaction with complex special flow phenomena

Purpose The purpose of this study is to reveal the influence mechanism of centrifugal inertial effect on the dynamic tracking stability of spiral groove dry gas seal (S-DGS) and to explore the interaction between the special effects of the flow field under high-parameter conditions. Design/methodology/approach The real-gas behavior of carbon dioxide (CO2) is expressed by the Virial equation, and the occurrence of exit choked flow is determined when the exit velocity reaches the sound speed. Perturbation and finite difference methods are used to calculate dynamic gas film characteristic coefficients, and then an axial dynamic model for S-DGS is developed considering centrifugal inertia, choked flow and real-gas effects, which is analytically solved to obtain the axial tracking performance of CO2 S-DGS. Findings The centrifugal inertia effect suppresses the axial tracking capability of the stationary ring in pumping-inward S-DGS, while enhancing it in pumping-outward S-DGS. The real-gas effect primarily influences the inertia effect through gas density, and affects the choked flow effect via dynamic gas film characteristic coefficients. The choked flow effect impacts the real-gas effect through the inlet–outlet pressure differential and affects the inertia effect via dynamic gas film thickness. The inertia effect mainly influences both the real-gas effect and the choked flow effect through gas flow resistance. Originality/value Divergent impacts of centrifugal inertia effect on axial tracking performance of two S-DGSs are revealed, and the complex interaction mechanisms of three special effects on dynamic leakage rate are further investigated, providing a critical theoretical foundation for optimizing the sealing performance of S-DGS.