Descripción



A simple nondimensional model to describe the flutter onset of labyrinth seals is presented. The linearized equations for a control volume which represents the interfin seal cavity, retaining the circumferential unsteady flow perturbations created by the seal vibration, are used. Firstly, the downstream fin is assumed to be choked, whereas in a second step the model is generalized for unchocked exit conditions. An analytical expression for the nondimensional workpercycle is derived. It is concluded that the stability of a twofin seal, depends on three nondimensional parameters, which allow explaining seal flutter behaviour in a comprehensive fashion. These parameters account for the effect of the pressure ratio, the cavity geometry, the fin clearance, the nodal diameter, the fluid swirl velocity, the vibration frequency and the torsion center location in a compact and interrelated form. A number of conclusions have been drawn by means of a thorough examination of the workpercycle expression, also known as the stability parameter by other authors. It was found that the physics of the problem strongly depends on the nondimensional acoustic frequency. When the discharge time of the seal cavity is much greater than the acoustic propagation time, the damping of the system is very small and the amplitude of the response at the resonance conditions is very high. The model not only provides a unified framework for the stability criteria derived by Ehrich [1] and Abbot [2], but delivers an explicit expression for the workpercycle of a twofin rotating seal. All the existing and well established engineering trends are contained in the model, despite its simplicity. Finally, the effect of swirl in the fluid is included. It is found that the swirl of the fluid in the interfin cavity gives rise to a correction of the resonance frequency and shifts the stability region. The nondimensionalization of the governing equations is an essential part of the method and it groups physical effects in a very compact form. Part I of the paper details the derivation of the theoretical model and draws some preliminary conclusions. Part II of the corresponding paper analyzes in depth the implications of the model and outlines the extension to multiple cavity seals.  
Internacional

Si 
Nombre congreso

ASME Turbo Expo 2018: Turbine Technical Conference and Exposition 
Tipo de participación

960 
Lugar del congreso

Oslo, Noruega 
Revisores

Si 
ISBN o ISSN

9780791851159 
DOI

10.1115/GT201875958 
Fecha inicio congreso

11/06/2018 
Fecha fin congreso

15/06/2018 
Desde la página

176 
Hasta la página

190 
Título de las actas

ASME Proceedings  Structural Mechanics and Vibration 