Analysis of High Pressure Liquid Seal Ring Distortion and Stability Using Finite Element Methods

Abstract

The evaluation of floating bushing ring oil seals is of great importance for designs of high pressure centrifugal compressors. This is a result of their enhanced damping capacity at low speeds and their strong destabilizing action at speeds in excess of twice the compressor first critical speed. Accurate prediction of oil seal leakage and exit temperature is very important from the standpoint of the pump and cooler selection for the seal oil console. The previous research has performed thermohydrodynamic (THD) analysis of bushing seal rings with various geometries. The current work is to evaluate the influence of the mechanical deformation on the thermohydrodynamic analysis of the bushing seal ring. The finite element method is used to predict the mechanical deformation of the bushing seal ring due to oil pressure and to solve the nonlinear and coupled Reynolds and energy equations for the pressure and temperature distributions, respectively. The perturbation technique is used to evaluate the stiffness and damping coefficients of the oil seals. Eigenvalue analysis is performed to study the dynamic stability of the compressor rotor. Results comparing the seal leakage, seal oil outlet temperatures, stiffness and damping coefficients, growth factors and damped natural frequencies from the THD analyses with and without the influence of the mechanical deformation of the bushing seal ring are presented. The results indicate that under high pressure conditions the influence of the mechanical deformation of the bushing seal ring on the seal performance is very significant.