Dynamic Characteristics of the Diverging Taper Honeycomb-Stator Seal

Abstract

This paper introduces a variant on the honeycomb-stator seal, which can extend the already strong stabilizing influence of this seal geometry for centrifugal compressors. The paper presents predicted and measured dynamic characteristics, demonstrating how a clearance, which diverges axially from inlet to outlet, increases the maximum effective damping of a honeycomb-stator seal, even though the average clearance is increased. The results also show a strong negative direct stiffness at zero and low frequency for this seal geometry (termed the “diverging taper honeycomb seal (DTHCS)”). The predictions are made with ISOTSEAL, software developed at The Texas A&M Turbomachinery Laboratory. (This code was developed within the Turbomachinery Laboratory and is not a commercial product (not for sale).) The test data, also obtained at the Turbomachinery Laboratory, confirm the nature and magnitude of both these dynamic characteristics with close fidelity. However, measured leakage falls significantly below predicted leakage. The frequency dependence of the seal dynamic characteristics and the strong negative static stiffness require careful attention in rotor dynamics analysis.