Numerical investigation on bristles buoyancy effect of brush seals with fluid-structure interaction
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摘要:
基于简化悬臂梁模型分析了刷式密封刷丝浮升效应理论,采用ALE(arbitrary Lagrange-Euler)流固耦合方法建立了刷式密封刷丝浮升效应三维瞬态数值求解模型,在验证了数值模型准确性基础上,研究了刷丝总体变形特性,量化分析了刷丝自由端轴向、径向和总体变形量,研究了结构参数与工况参数对刷式密封刷丝浮升效应的影响规律,揭示了刷式密封刷丝浮升效应诱发机理。研究结果表明:刷式密封刷丝浮升效应是前排刷丝受非定常径向气流作用产生的刷丝扰动现象,刷丝浮升效应会使前排刷丝向来流方向发生较大变形,并使前排刷丝与转子面产生径向间隙,泄漏量增加。当进出口压比从2提高至4,刷丝自由端平均变形量增加了47%,将前挡板保护高度从1.5 mm提高至2.5 mm,刷丝自由端平均变形量增加了36%,均使刷丝浮升效应增强。刷式密封前挡板与刷丝束间隙提供的径向气流通道,进出口压差在前挡板与刷丝束间隙内产生的径向压力梯度是刷丝浮升效应的诱发条件,提高刷丝直径和降低前挡板与刷丝束间隙均可降低刷丝浮升效应。
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关键词:
- 刷式密封 /
- 刷丝浮升效应 /
- ALE(arbitrary Lagrange-Euler)方法 /
- 流固耦合 /
- 变形特性
Abstract:The bristles buoyancy effect of brush seal directly affect its sealing performance and service life. The theory of brush seal bristles buoyancy effect was analyzed, and the three-dimensional transient numerical model of brush seal bristles buoyancy effect was established using arbitrary Lagrange Euler (ALE) fluid-structure coupling method. Based on the accuracy of numerical model, the overall deformation characteristics of bristles were studied, and the axial, radial and total deformations of bristle tips were quantitatively analyzed. The effects of structural parameters and working parameters on bristles buoyancy effect of brush seal were studied, and the inducing mechanism of bristles buoyancy effect of brush seal was revealed. The research results showed that the bristles buoyancy effect of brush seal contributed to the disturbance of the front bristles caused by the unsteady radial airflow. The bristles buoyancy effect of brush seal can cause large deformation of the front bristles in the direction of the flow, generate radial clearance between the front plate and the rotor surface, and increase the leakage. When the inlet and outlet pressure ratio increased from 2 to 4, the average deformation of bristle tips increased by 47%, and the protection height of the front plate increased from 1.5 mm to 2.5 mm, and the average deformation of bristle tips increased by 36%, both of which enhanced the bristles buoyancy effect. The radial airflow channel was provided by the clearance between the front plate and the bristle pack, and the radial pressure gradient was generated by the inlet and outlet pressure difference in the clearance between the front plate and the bristle pack as the inducing condition of the bristles buoyancy effect. The bristles buoyancy effect can be reduced by increasing the diameter of the bristles and reducing the clearance between the front plate and the bristle pack.
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表 1 刷式密封结构参数
Table 1. Strctural parameters of brush seals
结构参数 数值 前挡板宽度wf/mm 1.0 后挡板宽度wb/mm 2.0 刷丝束轴向厚度ws/mm 1.5 前挡板保护高度hf/mm 1.5、2.0、2.5 后挡板保护高度hb/mm 1.0 刷丝束与转子面间隙hg/mm 0 刷丝束与前挡板间隙wg/mm 0.6、0.7、0.8 刷丝直径D/mm 0.06、0.07、0.08 刷丝间距d/mm 0.006、0.007、0.008 刷丝径向长度L/mm 10.4 表 2 网格无关性验证
Table 2. Grid independence verification
网格数量/104 泄漏量相对误差/% 75 14.25 126 8.63 188 2.14 226 0.88 264 0.6 表 3 模型工况参数
Table 3. Operating parameters of model
工况参数 数值 进口压力/MPa 0.2、0.3、0.4 出口压力/MPa 0.1 刷丝与刷丝间摩擦因数 0.3 刷丝与挡板间摩擦因数 0.3 -
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