Brush Seal Structural Analysis and Correlation With Tests for Turbine Conditions

Abstract

Bristle tip contact forces and resulting stress levels under engine conditions are critical to optimizing brush seal performance as well as to achieving operational safety. Literature survey reveals the lack of test data and analysis methods for evaluating seal stiffness and stress levels under operating conditions. In an attempt to meet this need, a custom test rig design and methodology has been developed to perform stiffness tests under pressure and rotor speed of 3000 rpm. Finite element simulations have been performed for brush seals and results have been correlated with the test data of this study. Considering the critical importance of contact loads on brush seal overall performance and system health, and due to the complicated structure of brush seals, where bristles are contacting with each other as well as with the backing plate and the rotor, CAE analyses with high fidelity is required to simulate the test and turbine operating conditions. For this purpose, FE methodology has been developed for structural analyses of brush seals. 3D finite element models of brush seals have been constructed and simulations have been performed for pressurized rotor-rub conditions. CAE model of brush seals includes rotor-bristle, bristle pack-backing plate and inter-bristle contacts with friction. Simulations with non-rotating rotor and transient analyses with rotating rotor have been conducted, and the extracted bristle tip force levels are correlated with the test results. Inertial effects during dynamic tests have also been simulated through transient analyses and results show good agreement with the dynamic test data. Displacement and stress profiles obtained from correlated FE models give better understanding of brush seal behavior under turbine operating conditions.