Fluid-structure interaction investigation on the flow field and mechanical characteristic in brush seals with bristle deflections

Bristle deflections have important influence on the flow field characteristic and mechanical characteristic. The problems of the leakage, hysteresis and bristle fracture produced by the deflections of bristle are very prominent. The flow field characteristic and dynamic characteristic in brush seal were predicted using a three-dimensional computational model with consideration of bristle deflections depending on two-way fluid-structure interaction and moving grids techniques. Firstly, based on the cantilever beam theory, the mechanics model of bristle was analyzed. Secondly, based on the fluid solid coupling method verified with the theoretical model and experimental results, the flow field characteristic, the law of bristle deflections, the mechanical characteristic and hysteresis characteristic were predicted. The research results show that the bristle deflections caused by forward flow impact is oscillating gradually, and the maximum stress of the bristle root is also oscillating gradually depending on the bristle deflections. Bristle deflections increase the clearance between the bristle and the rotor surface, which leads to the increases of leakage; as the bristle row number increases, the leakage decreases rapidly, then decreases slowly, and finally tends to be a stable value. The increase of the axial clearance between the last row bristle and the back plate makes the relative pressure coefficient decrease, and the axial clearance can effectively reduce the hysteresis characteristic.