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