基于ALE流固耦合方法的刷式密封泄漏特性理论与实验研究

Theortical and Experimental Study on Leakage Characteristics of Brush Seal Based on ALE Fluid-Structure Compled Methodology

关键词:  刷式密封  ALE流固耦合  泄漏特性  刷丝运动状态  变形接触

Key words:  Brush seal  ALE fluid-structure interaction  Leakage characteristic  Brush wire motion status  Deformation contact

摘要:

现有刷式密封流固耦合求解模型因刷丝变形接触导致网格畸变而难以计算。本文提出了基于ALE（Arbitrary Lagrange-Euler）流固耦合方法考虑刷丝变形接触的三维瞬态双向流固耦合求解模型，设计搭建了刷式密封泄漏特性和可观测刷丝运动轨迹的实验装置。实验研究了刷式密封刷丝运动状态对泄漏特性的影响，不同压比条件下的泄漏特性变化规律，在验证刷式密封流固耦合求解模型准确性基础上，数值分析了不同时刻刷式密封速度分布与刷丝运动状态，并研究了不同结构参数对泄漏特性的影响规律。研究结果表明：基于ALE流固耦合方法解决了传统刷式密封求解模型因刷丝变形接触导致网格畸变而难以计算的问题，可准确计算刷式密封流场特性和力学特性；刷式密封刷丝吹下效应会降低泄漏量，刷丝颤振现象主要发生在气流入口处的前排刷丝域，会引起泄漏量增大，在气流力作用下，刷丝束轴向厚度变小，有利于减小泄漏量；在本文研究条件下，刷丝固定端与自由端的中间部位最先发生变形，随着时间的变化，气流速度逐渐趋于稳定，最大速度出现在末排刷丝与后挡板接触位置，刷丝自由端变形最大；刷式密封泄漏量随径向密封间隙的增大而增大，与径向密封间隙0mm时相比，径向密封间隙0.2mm时泄漏量增加了51.6%~62.8%。随着刷丝排数的增大，泄漏量逐渐减小，当刷丝排数大于25排时，其对泄漏量影响较小。随着刷丝间隙、刷丝与后挡板之间的轴向间隙、后挡板保护高度的增大，泄漏量先逐渐增大后趋于平缓。

Abstract:

The existing brush seal fluid-structure interaction solution model is difficult to calculate because of mesh distortion caused by the deformation contact of brush wire. A three-dimensional transient bidirectional fluid-structure interaction solution model considering the deformation contact of brush wire based on ALE (Arbitrary Lagrange-Euler) fluid-structure interaction method was proposed. An experimental device was designed to study the leakage characteristics of brush seal and the motion trajectory of observable brush wire. The effects of the brush wire motion state on the leakage characteristics and the variation of the leakage characteristics under different pressure ratios were studied experimentally. On the basis of verifying the accuracy of the brush seal fluid-structure interaction solution model, the distribution of brush seal speed and the motion state of brush wire at different time were numerically analyzed, the influence law of different structural parameters on leakage characteristics was studied. The results show that the method based on ALE fluid-structure interaction solves the problem that the traditional brush seal solution model is difficult to calculate because of mesh distortion caused by brush wire contact, and ALE fluid-structure interaction can accurately calculate the leakage characteristics and mechanical characteristics of brush seal. Brush wire blow down will cause leakage reduction, the phenomenon of brush filament flutter mainly occurs in the front brush area at the entrance of the airflow, which will cause the leakage to increase, under the action of airflow force, the axial thickness of the brush beam becomes smaller, which is helpful to reduce the leakage. Under the condition of studying in this paper, the middle part of the brush wire fixed end and the free end deforms firstly, as time changes, the airflow velocity gradually stabilizes, the maximum velocity appears in the contact position between the end-row brush wire and the backing plate fence, the free end of the brush wire deformation is the largest. With the increasing of seal clearance, the leakage increases. Compared to the seal clearance 0mm, the leakage at the seal clearance 0.2mm increases 51.6% ~ 62.8%. With the increase of brush wire row, the leakage gradually decreases. When the number of brush wire rows is more than 25, its influence on the leakage is small. With the increasing of the brush wire clearance, the axial clearance and the protection height of the backing plate fence, the leakage quantity increases gradually and then tends to flatten.