Seal-Inlet Disturbance Boundary Condition Correlations for Rotordynamics Models, Part 1: Correlation Development

Abstract

Systematic parametric studies were performed to better understand seal-inlet rotordynamics. A CFD-perturbation model was employed to compute the seal-inlet flow disturbance quantities. Seal inlet disturbance boundary condition correlations were proposed from the computed seal-inlet quantities using the important parameters. It was found that the cosine component of the seal-inlet swirl velocity disturbance W _1C has a substantial impact on cross-coupled stiffness, and that the correlations for W _1C and W _1S should be used to replace the historical guess that seal inlet W _1C = 0 and W _1S = 0. Also, an extremely precise relationship was found between the cross-coupled stiffness and the seal-inlet swirl velocity (ω R _sh −[Wbar] ₀ ). Thus, the number of experiments or computer runs needed to determine the effect of spin speed, shaft radius, and/or inlet swirl velocity on cross-coupled stiffness could be greatly reduced by plotting the simplified relationship of the cross-coupled stiffness against the swirl slip velocity. In addition, the upstream chamber size and shape were found to have a substantial influence on the seal-inlet swirl disturbance velocity W _1S which plays a significant role in determining the direct stiffness.

Final manuscript approved June 2, 2006

Review led by Tom Lai

KEY WORDS:

• Dynamic Modeling
• Seals
• Labyrinth

ACKNOWLEDGEMENT

The authors are grateful to the Texas ATP, the Turbomachinery Symposium of Texas A&M University and to the Supercomputer Center of Texas A&M University for financial support.

Notes

Final manuscript approved June 2, 2006

Review led by Tom Lai

*All the labyrinth teeth have a uniform width of 0.254 mm.