Experimental and theoretical rotordynamic stiffness coefficients for a three-stage brush seal

Experimental and theoretical results are presented for a multistage brush seal. Experimental stiffness is obtained from integrating circumferential pressure distribution measured in seal cavities. A CFD analysis is used to predict seal performance. Bristle packs are modeled by the porous medium approach. Leakage is predicted well by the CFD method. Theoretical stiffness coefficients are in reasonable agreement with the measurements. Experimental results are also compared with a three-teeth-on-stator labyrinth seal. The multistage brush seal gives about 60% leakage reduction over the labyrinth seal. Rotordynamic stiffness coefficients are also improved: the brush seal has positive direct stiffness and smaller cross-coupled stiffness.

► New experimental data on local direct and cross-coupled stiffness coefficients.
► Multistage brush seal has positive local direct stiffness.
► Functions of free radial clearance and bristle pack thickness under pressurization.
► CFD model with porous medium approach provides adequate predictions.