Calculation of leakage and dynamic coefficients of stepped labyrinth gas seals

Abstract

Rotor-fluid interactions can cause self-excited vibrations in high-density turbomachines. One of the most important sources for excitation is the flow through labyrinth seals. The gas flow through the seals creates net pressure and shear forces acting on the rotor. It is necessary to predict these forces exactly for reliably operating turbomachines. The labyrinth seal forces are characterized by rotordynamic coefficients. This paper presents a theoretical work on the calculation of leakage and dynamic coefficients for stepped labyrinth gas seals. The continuity and circumferential momentum equations are given for compressible flow in a stepped labyrinth seal. Periodic and analytic solutions of these equations are obtained for the case of time dependent flow generated by a non-axisymmetric rotation of the rotor using an axisymmetric solution based on different assumption about the flow coefficient. The rotordynamic coefficients are then calculated and the results of this analysis are compared with relatively recent experimental data. © 2003 Elsevier Inc. All rights reserved.