A study of porous media resistance coefficients for brush seals

Official URL: http://risc01.sabanciuniv.edu/record=b1589552 (Table of Contents)

Developments in turbine technologies lead to higher operating temperature and pressure conditions. Parasitic leakage flows around the turbine account for considerable efficiency losses that increase fuel cost dramatically. Brush seal has recently emerged as an improved sealing technology to provide better leakage performance and to replace classical labyrinth seals. In order to optimize efficiency, comprehensive study of the factors causing the leakage is required. The leakage performance of the brush seal is directly related with geometry, operating inlet and outlet boundary conditions, bristle pack configuration. Brush seal flow and pressure profiles with turbine operating conditions become complicated, and analytical formulations remain inadequate to correlate design parameters and leakage performance in operating conditions. Recently brush seals have found ever increasing applications in steam turbines. Literature review indicates that there is very limited studies of brush seal for steam environment. There is also no correlation available for brush seal porosity coefficients in the literature. In an attempt to meet this need, six brush seals have been tested in a rotary test rig up to 100 psi upstream pressure. Analytical correlations and CFD (Computational Fluid Dynamics) simulations have been performed for test seals and results have been correlated with the test data. Axisymmetric CFD models have been designed to reach anisotropic resistance coefficients for the brush seals based on experiments. Porous Medium Approach has been applied for representing bristle pack. Leakage rate of brush seals (steam environment) has been optimized through CFD models. Moreover, velocity and pressure characteristics in the bristle pack have been illustrated for an optimum solutions. Consequently, empirical correlations for brush seal porosity coefficients have been correlated through a systematic methodology.