COMPARISON BETWEEN A CFD CODE AND A THREE CONTROL-VOLUME MODEL FOR LABYRINTH SEAL FLUTTER PREDICTIONS

Labyrinth seals are extensively used in turbomachinery to control flow leakage in secondary air systems. While a large number a studies have been performed to investigate the leakage and rotordynamics characteristics of these seals, the studies on their aeroelastic stability remain scarce. Little is known about this phenomenon and the design methods are limited to a stability criterion which does not take into account many of the parameters which are known to influence labyrinth seal aeroelastic stability. As a consequence the criterion can be unreliable or overly pessimistic. The alternative to this criterion is the use of CFD methods which, although reliable, are computationally expensive. This paper presents a three-control-volume (3CV) bulk-flow model specifically developed for flutter calculations in labyrinth seals. The model is applied to a turbine labyrinth seal of a large diameter aero-engine and the results are compared to those of a CFD analysis. Conclusions are drawn on the potential of this 3CV model for design purposes.