Investigation of the Dynamic Characteristics of an Eccentric Annular Seal on the Basis of a Transient CFD Method with Three Whirl Models

Fengqin Li,Baoling Cui,Jia Guo,Guoyou Chen,Lulu Zhai

doi:10.3390/jmse9111290

Abstract

Many annular seals suffer eccentricity because of rotor–stator misalignment or the deflection of a flexible rotor, which has a strong influence on the vibration characteristics and stability of rotating machines. In this article, a transient CFD method based on three whirl models is employed to research the dynamic characteristics of annular seals at various static eccentricities. The influence of the whirl amplitude on the dynamic characteristics of eccentric annular seals are also explored. The results of the transient CFD method are compared with the bulk flow model results and the experimental results. It is shown that the transient CFD method possesses high prediction precision for direct damping, with a maximum error of 25%. Negative kyx increases by 166% when the static eccentricity ratio is increased from 0 to 0.5. The dynamic characteristics of the annular seal operating at high static eccentric ratio are sensitive to whirl amplitude, and the model with an amplitude of 1% Cr has great advantages for the prediction of direct virtual-mass, while the model with an amplitude of 10% Cr has great advantages for the prediction of cross-coupled damping.

Highlights

Centrifugal pumps are commonly employed in the marine field to transport fluids, and annular seals are the key components of centrifugal pumps to reduce the amount of working medium leaking from the high-pressure area to the low-pressure area through the rotor–stator gap [1,2]
The transient CFD method with the whirl models was employed by Voigt [18], Yan et al [19,20] and Jiang [21] to calculate the dynamic characteristics of annular seals
The results showed that equivalent stiffness and equivalent damping decreased with increasing eccentricity, while the aerodynamic work increased with increasing eccentricity, impairing the stable performance of the annular seal

Summary

Introduction

Centrifugal pumps are commonly employed in the marine field to transport fluids, and annular seals are the key components of centrifugal pumps to reduce the amount of working medium leaking from the high-pressure area to the low-pressure area through the rotor–stator gap [1,2]. Li et al [17] used the transient CFD method with a unidirectional harmonic (1D) whirl model, a circular whirl model, and an elliptical whirl model to predict the dynamic characteristics of an annular gas seal.

Results

Conclusion