Study of dynamic characteristics of stepped labyrinth seals

Abstract

In recent years, there is concern about decreased stability of the eye seal used for impellers due to the increase in pressure of the turbo compressors. On the other hand, the eye seal is required to have low leakage, and convergent stepped labyrinth seal are used in general because of good assembling in impellers and high sealing performance. However, there are few experimental studies on the destabilizing force of the convergence stepped labyrinth seal in the past studies, and its rotor dynamic characteristics have not been fully clarified. In this study, the dynamic characteristics of the convergent stepped labyrinth seal were evaluated by experiments and CFD analysis. The rotor dynamic coefficients that influence instability were in good agreement between experiments and analysis. It is known that the dynamic characteristics of the seal are affected by the pre-swirl, so we evaluated the dynamic characteristics due to the difference in the inlet swirling flow velocity and compared the characteristics with the straight labyrinth seal. The response of effective damping to pre-swirl was shown to be smaller with the step seal compared with the straight seal. It was suggested that the step seal is less unstable than the straight seal, even if the pre-swirl is large.

Keywords

• flow induced force
• labyrinth seal
• step seal
• rotor dynamic characteristics
• cfd analysis
• experimental study