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摘要: 阻旋栅可改变密封进口流体周向流动与进口预旋，是提高系统稳定性的主要方法之一. 本文作者应用计算流体力学方法研究了阻旋栅几何参数对梳齿密封动静特性的影响，计算分析了阻旋栅在不同长度、间隙、周向个数及不同进口预旋比下密封流场分布与动力特性系数，并与无阻旋栅梳齿密封进行对比. 研究表明：阻旋栅能够有效抑制密封进口周向流动、降低密封腔室周向压力；随着阻旋栅周向个数与阻旋栅间隙的减小，其抑制效果增强，阻旋栅长度的增加对周向速度影响则越来越小；提高预旋比将使密封内流体周向速度增加. 与传统梳齿密封相比，具有阻旋栅的梳齿密封直接阻尼增加，交叉刚度降低，进而有效阻尼提高. 阻旋栅间隙s=0.20 mm、长度l=3.25 mm、数量n=90时密封有效阻尼较大，系统稳定性最好.Abstract: Swirl brakes can dramatically change the circumferential swirl flow and the preswirl at the seal inlet. The swirl brake is generally used to improve the stability of seal system. In this paper, the geometric parameters of a swirl brake were studied to evaluate its effect on the static and rotor dynamic performance for the labyrinth seal by employing computational fluid dynamics (CFD) method. Influences of length, clearance and number of the swirl brake, and inlet preswirl ratio were analyzed and compared with the conventional labyrinth seal without swirl brakes. The result showed that the swirl brake significantly reduced the circumferential velocity and pressure at the seal inlet. With the increasing number and decreasing clearance, the efficiency of swirl brakes was improved. While the effect on the circumferential velocity degraded as the swirl brake length increased. Preswirl ratio enhanced the circumferential velocity. In addition, compared with the conventional labyrinth seal, the labyrinth seal with swirl brakes showed greater direct damping, lower cross-coupled stiffness, and resultant larger effective damping. Regarding to the optimization of swirl brake geometry, the effective damping and stability of the seal system showed best performances with the clearance of 0.20 mm, length of 3.25 mm and circumferential number of 90.
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图 3 具有阻旋栅的梳齿密封几何尺寸
Figure 3. Geometric dimensions of the labyrinth seal with swirl brakes
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图 4 具有阻旋栅的梳齿密封网格分布
Figure 4. Grid distribution of the labyrinth seal with swirl brakes
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图 6 不同阻旋栅间隙下密封腔周向速度分布
Figure 6. Circumferential velocity distribution for various swirl brake clearances
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图 7 不同阻旋栅长度下密封腔周向速度分布
Figure 7. Circumferential velocity distribution for various swirl brake lengths
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图 8 不同阻旋栅个数下密封腔周向速度分布
Figure 8. Circumferential velocity distribution for various swirl brake numbers
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图 9 不同阻旋栅间隙下密封周向速度云图及阻旋栅间速度分布
Figure 9. Circumferential velocity cloud and velocity distribution for various swirl brake clearances
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图 10 不同阻旋栅长度下密封周向速度云图及阻旋栅间速度分布
Figure 10. Circumferential velocity cloud and velocity distribution for various swirl brake lengths
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图 11 不同阻旋栅数量下密封周向速度云图及阻旋栅间速度分布
Figure 11. Circumferential velocity cloud and velocity distribution for various swirl brake numbers
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图 12 不同预旋比下密封腔周向速度分布
Figure 12. Circumferential velocity distribution for different preswirl ratios
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图 13 不同阻旋栅结构下密封周向压力分布
Figure 13. Pressure distribution with different structures of swirl brakes
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图 14 不同阻旋栅间隙下直接阻尼C随涡动频率变化
Figure 14. Direct damping vs whirling frequency for various swirl brake clearances
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图 15 不同阻旋栅间隙下交叉刚度k随涡动频率变化
Figure 15. Cross-coupled stiffness vs whirling frequency for various swirl brake clearances
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图 16 不同阻旋栅间隙下有效阻尼Ceff随涡动频率变化
Figure 16. Effective damping vs whirling frequency for various swirl brake clearances
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图 17 不同阻旋栅长度下直接阻尼C随涡动频率变化
Figure 17. Direct damping vs whirling frequency for various swirl brake lengths
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图 18 不同阻旋栅长度下交叉刚度k随涡动频率变化
Figure 18. Cross-coupled stiffness vs whirling frequency for various swirl brake lengths
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图 19 不同阻旋栅长度下有效阻尼Ceff随涡动频率变化
Figure 19. Effective damping vs whirling frequency for various swirl brake lengths
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图 20 不同阻旋栅数量下直接阻尼C随涡动频率变化
Figure 20. Direct damping vs whirling frequency for various swirl brake numbers
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图 21 不同阻旋栅数量下交叉刚度k随涡动频率变化
Figure 21. Cross-coupled stiffness vs whirling frequency for various swirl brake numbers
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图 22 不同阻旋栅数量下有效阻尼Ceff随涡动频率变化
Figure 22. Effective damping vs whirling frequency for various swirl brake numbers
表 1 几何参数
Table 1 Geometric parameters
Parameter Description Specification L/mm Seal length 35.7 d/mm Rotor diameter 60 h/mm Cavity depth 3.3 w1/mm Cavity bottom width 2.3 w2/mm Tooth bottom width 1.5 t/mm Tooth tip width 0.25 Cr/mm Seal radial clearance 0.2 n Swirl brake number 30, 60, 90 l/mm Swirl brake length 2.25, 3.25, 4.25 s/mm Swirl brake clearance 0.15, 0.20, 0.25 r/mm Swirl brake radius 0.508 
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表 2 计算工况参数
Table 2 Calculation condition parameters
Parameter Specification Working fluid air(ideal gas) Wall adiabatic smooth wall Turbulence model k-ε Preswirl ratio, λ 0.36, 0.51, 0.81 Whirling speed, Ωi/Hz 20, 40, 60, …, 260, 280 Pressure inlet, Pin/MPa 1 Pressure outlet, Pout/MPa 0.3 Inlet temperature, T/K 293 Rotational speed, ω/(r/min) 5 000 Time step, t/s 0.000 069
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