Modeling of Frictional Interbristle Contact in Brush Seals With Shaft Radial Movements

Abstract

Brush seals are utilized in turbines to minimize leakage flows and enhance thermal efficiency. Their widespread use faces challenges like pressure-stiffening and hysteresis, leading to unpredictable performance. This work introduces an advanced numerical model to simulate interbristle frictional contact, shaft and backing ring interaction, and three-dimensional (3D) bristle bending. The model is adopted to investigate multibristle brush seal's behavior under shaft radial movements and pressure loading. Backing ring friction emerges as a vital factor in hysteresis modeling, lessening the impact of shaft friction. When the shaft retracts, modeling the bristle tip clearance becomes important. The clearance greatly increases leakage flowrate and changes bristles' aerodynamic loading distribution. With clearance, the normal force on upstream bristles rises markedly, opposing bristle hang-up, while the axial force decreases in downstream bristles, alleviating the bristle pack compression. Considering these factors, an improved model for pressurized seals in the shaft retraction phase is developed and compared to experimental data in the literature. Frictional interbristle contact significantly modifies the distribution of local tip force through the pack. These effects would influence localized wear and heat generation across the brush seal pack, shedding light on the uneven wear patterns often observed in experiments. The present high-fidelity model can capture these complex interactions, offering a means to deepen our understanding of the physical mechanisms underpinning novel brush seal designs.