Theoretical Analysis of Textured “Damper” Annular Seals

Abstract

The present work presents a theoretical approach for the analysis of textured annular “damper” seals. The data for the seal were extracted from the work of Childs and Fayolle (ASME J. Tribol. 121(1), pp. 42–49). The texture of the stator consists of equally spaced cylindrical holes of an order of magnitude larger than the seal clearance. The main idea of the present work is that the static and dynamic characteristics of the textured annular seal can be predicted by using a slightly modified bulk-flow model. The modifications are introduced by considering the textured seal as being geometrically similar to a straight seal with the same clearance. The presence of the texture is taken into account by considering modified friction laws for the rotor and for the stator, separately. An additional inertia effect due to the texture is also added as a source term to the momentum equations. The modified friction laws and the inertia effect are deduced from a three-dimensional Navier-Stokes analysis of the flow in the textured seal. This computational analysis is carried on for a single texture element extracted from the round-hole pattern of stator by using periodicity boundary conditions. The stiffness and the damping of the annular seal were calculated by using the modified bulk-flow model and results were compared with the experimental data from Childs and Fayolle. The use of the present model shows a net improvement of the predictions for the direct and cross-coupling stiffness and for the cross-coupling damping. The results obtained for the direct damping are still under discussion.