An Investigation of Tip Force Characteristics of Brush Seals

Thanks to their compliant nature and superior leakage performance over conventional labyrinth seals, brush seals found increasing use in turbomachinery. Utilizing high temperature super-alloy fibers and their compliance capability these seals maintain contact with the rotor for a wide range of operating conditions leaving minimal passage for parasitic leakage flow. Consequently, the contact force/pressure generated at seal rotor interface is of importance for sustained seal performance and longevity of its service life. Although some analytical and numerical models have been developed to estimate bristle tip pressures, they simply rely on linear beam equation calculations and other such assumptions for loading cases. In this paper, previously available analytical and/or numerical models for bristle tip force/pressure have been modified and enhanced. The nonlinear cantilever beam equation has been solved and results are compared to a linear cantilever beam equation solution to establish application boundaries for both methods. The results are also compared to experimental data. With the support of testing, an empirical model has been developed for tip forces under operating conditions.