Seal-Inlet Disturbance Boundary Condition Correlations for Rotordynamics Models, Part 2: Assessment

Nearly all seal rotordynamics models were forced to assume that the seal-inlet swirl velocity disturbance boundary condition components (W 1C and W 1S ) are zero. The companion (Part 1) paper employs an extensive parametric study to develop a complete set of widely applicable seal-inlet disturbance boundary condition correlations that will alleviate this shortcoming. The benefits of using the new seal-inlet boundary condition correlations were assessed by implementing them into a CFD-perturbation model. Two widely different test cases were employed. Case 1 is a test of the correlations for large upstream chambers using a simple liquid smooth-plain seal, and Case 2 is a test for small, as well as radial injection, upstream chambers using a complicated gas labyrinth seal. For both cases, consistently improved agreement with measurements was obtained for the options with non-zero W 1C and W 1S compared to the option with W 1C = W 1S = 0. Specifically, the correlation set using the W 1C -profile option gave a clearly better prediction of the effective damping and the cross-coupled stiffness than did the set using the W 1C -bulk option for the higher spin speed case of the challenging gas labyrinth. For the smooth-plain liquid seal case, the correlations with the W 1C -profile and W 1C -bulk options gave nearly the same level of agreement with measurements. Final manuscript approved June 2, 2006 Review led by Tom Lai