考虑刷丝变形的刷式密封流场特性与力学特性流固耦合研究

应用双向流固耦合与动网格技术，建立了考虑刷丝变形的刷式密封流场与力学特性双向流固耦合瞬态三维求解模型.首先应用悬臂梁理论建立了刷丝的力学理论模型，将该流固耦合方法计算结果分别与理论模型和实验结果相互验证，在此基础上，分析了刷式密封的流场特性、刷丝的变形规律与应力特性以及刷式密封的滞后特性.研究结果表明:刷丝在气流力作用下会产生摆振运动，刷丝根部所受的应力也随着刷丝摆振运动而呈振荡变化；刷丝变形增大了刷丝与转子面间隙导致密封泄漏量增大，随着刷丝排数的增加，泄漏量先迅速下降，然后下降速度趋缓，最后趋于稳定；刷式密封随着末排刷丝与后挡板轴向间隙的增大，后挡板处相对压力系数逐渐降低，增加末排刷丝与后挡板的轴向间隙可有效降低滞后效应. 

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.