Influence of Geometrical Parameters on the Performance of Brush Seals for Aero-Engines Bearing Chambers

Abstract

Recent developments in the aeronautic domain focus on the optimization of the lubrication oil system for civil aircraft gas turbine engines, in order to reduce air and oil consumptions. Specifically, over the last few decades, as brush seals have shown tremendous leakage performance in sealing secondary flows compared to classic labyrinth seal, an increasingly popular idea is to extend their utilization to bearing chambers applications. In the frame of the European FP7 E-Break project, the Aero-Thermo-Mechanics department of ULB collaborates with French aircraft engine manufacturer SNECMA in order to investigate experimentally the brush seal behaviour in an environment simulating the bearing chamber working conditions. The aim is first to deepen the brush seal behaviour knowledge by identifying the most influential geometric parameters acting on the leakage performance on both sides of the seal (oil and air), and on its wear, and by evaluating the friction torque and the dissipated heat. The paper will first highlight the effect of the brush seals geometric parameters on the air consumption and the torque friction. Results highlight a trade-off to be made between these two performance levels. Also, relations have been developed to predict the performance of a carbon brush seal with non-canted bristles. The bristle free length and the axial density must carefully be chosen first to dictate the brush seal porosity. The distance between the backing plate and the front plate acts as a secondary parameter to adjust the bristle pack stiffness, and it is proposed to mount such a carbon brush seal with a reduced interference to limit the effect of the brush seal wear on the air consumption. Finally, the carbon brush seals performance was compared with the latest ones, with promising results being shown to expect carbon brush seals to be employed at a higher scale in bearing chambers in the future.