刷式封严初期使用特性的实验和数值研究

Experimental and numerical study on the leakage characteristics of brush seals at the early stage of operating

关键词:  刷式封严+  刷丝排列+  使用时间+  泄漏

Key words:  Brush seal +  Bristle arrangement +  Operating time +  Leakage

摘要:

为了获得刷式封严在使用初期的泄漏特性,分别对两组实验件进行了27小时和50小时的泄漏特性实验,并利用多孔介质模型对实验结果进行了数值分析。实验表明:在使用初期,刷式封严的泄漏量与上下游的压差成正比;随着使用时间的增加,其泄漏水平逐渐降低直至最后趋于稳定。数值分析表明:在使用初期,刷丝排列由最初的疏松状态逐渐趋于紧密,并最终稳定在接近于紧密差排的状态,刷丝排列状态的变化改变了刷束的孔隙率,从而改变了刷束对流体泄漏的阻力,导致了刷式封严泄漏水平的变化。

Abstract:

Experiment was carried out to investigate the leakage characteristics for brush seals at the early stage of operating.Two brush seals were tested for 27 and 50 hours,respectively.The experimental results were then analyzed with the porous medium model.The experiment shows that during the early stage the mass flow rate is linear with the pressure drop across the seal.The leakage level of new brush seals gradually decreases and finally keeps on a stable level as the time accumulates.The numerical study indicates that the bristle arrangement is loose at the beginning.Then,it becomes denser and denser and finally reaches a stable level which is close to the staggered arrangement.This process changes the porosity of bristle pack,which leads to the change of the flow resistance.This explains why the leakage level of brush seals changes.