Analysis for Incompressible Flow in Annular Pressure Seals

Abstract

An analysis is developed to calculate the static and dynamic characteristics of annular eccentric seals. Effects of inertia forces in the film, tapered geometry and rotor misalignment are taken into account. Derivation of the governing equations for incompressible flow is based on the Navier-Stokes equations, the continuity equation and a turbulence model using the nonlinear analysis developed by Elrod and Ng. The inlet boundary conditions define the initial swirl and the pressure drop due to the fluid acceleration. Perturbation of the flow variables yields a set of zeroth-order and first-order equations. Integration of the zeroth-order equations yields the steady-state solution which defines the seal leakage, the static load and the moment of misalignment. The eccentric and misaligned rotordynamic coefficients are obtained by integration of the first-order pressure equations. Comparisons are made between the stiffness, damping and inertia coefficients derived herein and both theoretical results based on other models and experimental data which were previously published.