Numerical study on leakage flow characteristics of carbon fiber brush seal between counter-rotating shafts
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摘要:
航空发动机对转轴间部位对密封结构的封严性能有着更高要求。提出了对转轴间碳纤维旋转刷式密封结构，基于刷丝离心效应力学理论和多孔介质理论，采用刷丝形变量修正孔隙率和阻力系数方法，建立了对转轴间碳纤维旋转刷式密封泄漏流动特性求解模型。分析了刷丝安装角、刷丝直径、转速对碳纤维刷丝力学变形特性的影响，研究了对转轴间刷式密封的泄漏流动特性。研究结果表明：提高内转子转速、减小刷丝直径、增大刷丝安装角，刷丝的形变量和转角将增大。考虑刷丝受离心效应作用，内转子转速为
3230 r/min时，在转子径向方向的T650碳纤维刷丝形变量为Haynes25刷丝形变量的16.43%；内转子转速为10000 r/min时，将刷丝安装角从30°增至45°，刷丝在转子径向形变量增加104.02%；相同工况下，细直径刷丝密封效果更好，当刷丝与外转子接触间隙为0 mm时，刷丝直径从0.07 mm减小到0.05 mm，泄漏量减少12.42%。Abstract:There are higher requirements for the seal performance and service life of the sealing structure between counter-rotating shafts of the aero-engine. The structure of carbon fiber rotating brush seal between rotating shafts was proposed. Based on the theory of bristles centrifugal effect mechanics and porous media theory, the method of bristles shape variable correction porosity and resistance coefficient was used to establish a solution model for the leakage flow characteristics of carbon fiber rotating brush seal between rotating shafts. The influence of bristle lay angle, bristle diameter and rotating speed on the mechanical deformation characteristics of carbon fiber bristles was analyzed, and the leakage flow characteristics of brush seal between rotating shafts were studied. The results showed that the deformation and rotation angle of the bristle could increase by increasing the speed of the inner rotor, reducing the diameter of the bristle and increasing the bristle lay angle. Considering the centrifugal effect of the bristles, when the inner rotor speed was
3230 r/min, the deformation of the T650 carbon fiber bristles in the radial direction of the shaft was 16.43% of the deformation of the Haynes25 bristles. When the inner rotor speed was10000 r/min, the bristle lay angle increased from 30° to 45°, and the radial deformation of the bristles on the shaft was increased by 104.02%. Under the same working conditions, the fine-diameter bristles sealing effect was better. When the contact gap between the bristles and the outer rotor was 0 mm, the bristle diameter was reduced from 0.07 mm to 0.05 mm, and the leakage was reduced by 12.42%. -
图 6 旋转刷式密封泄漏流动特性求解流程
Figure 6. Solution process for leakage flow characteristics of rotating brush seal
图 9 刷丝在转子周向产生的形变
Figure 9. Deformation of the bristles in the circumferential of shaft
图 12 0.07 mm直径刷丝在转子径向的形变量
Figure 12. Deformation of the bristles with a diameter of 0.07 mm in the radial of shaft
图 14 不同直径刷丝在转子径向的形变量（T650）
Figure 14. Deformation of different diameter bristles in the radial of shaft （T650）
图 15 相同长度刷丝形变随安装角的变化
Figure 15. Deformation of the same length bristles changes with the bristle lay angle
图 16 不同长度刷丝形变随安装角的变化
Figure 16. Deformation of the different length bristle changes with the bristle lay angle
图 17 不同内转子转速的刷丝尖端压力分布
Figure 17. Bristle tip pressure distribution of different inner rotor speed
图 18 外转子表面压力分布（Rp=3.0）
Figure 18. Pressure distribution on outer rotor surface （Rp=3.0）
图 19 不同内转子转速A-A剖面总速度分布
Figure 19. Total velocity distribution of A-A section with different inner rotor speed
图 23 不同内转子转速对刷丝尖端间隙泄漏量的影响
Figure 23. Influence of different rotor speed on the bristles tip clearance leakage
图 24 密封泄漏量随外转子转速变化（d=0.07 mm）
Figure 24. Leakage of the seal with the outer rotor speed change （d=0.07 mm）
图 25 不同直径刷丝的密封泄漏量（T650）
Figure 25. Leakage of seal with different diameter bristles （T650）
图 26 刷丝直径对刷丝尖端间隙泄漏量的影响
Figure 26. Influence of bristles diameter on the bristles tip clearance leakage
对比项 迷宫密封 石墨密封 刷式密封 封严性能 泄漏量大 泄漏量低 泄漏量低 使用寿命 寿命长 寿命短 寿命较长 润滑需求 多 少 少 冷却需求 无需冷却 需冷却 少量冷却 
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表 2 材料性能参数
Table 2. Material performance parameters
参数 Haynes25 T650 密度/（g/cm3） 9.1 1.7 杨氏模量/1011 Pa 2.2 2.6 泊松比 0.29 0.3 抗拉强度/109 Pa 1.1 4.3
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表 3 旋转刷式密封结构参数
Table 3. Rotating brush seal structure parameter
参数 数值 刷丝长度l/mm 11.0 刷丝束厚度 b/mm 1.5 刷丝安装角 β/（°） 30.0，38.5，45.0 刷丝直径 d/mm 0.05，0.07，0.09 外转子内半径 rout/mm 60.0 内转子外半径 rin/mm 50.0 刷丝间距0.1d/mm 0.005，0.007，0.009 挡板厚度B/mm 1.5 前挡板保护高度h1/mm 2.0 后挡板保护高度h2/mm 1.4
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表 4 多孔介质模型系数计算结果
Table 4. Coefficient of porous media model calculation results
参数 轴向（z） 径向（r） 周向（θ） $\varepsilon _i $ 0.237 0.175 0.286 ci 1.029 4.299 1.133 （1/αi）/1011 7.55 0.258 3.26 Ci/105 1.86 0.636 8.02
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表 5 网格无关性验证
Table 5. Grid independence verification
网格数量/万 泄漏量相对误差/% 1801 42.59 2029 10.88 2640 4.76 3432 3.65
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