Analysis of floating foil gas seal performance based on bump foil deformation

doi:10.11949/0438-1157.20220119

Abstract

Abstract:

In order to ensure the stable operation of the dynamic sealing of aero-engines, for the floating foil gas film seal, the bump foil stiffness model considering the Coulomb friction is adopted, and the central difference method and the over-relaxation iterative method are used to couple the foil deformation equation, pressure control equation and gas film thickness control equation. And the small disturbance method, combined with the balance between pressure and foil deformation, obtain the flow field distribution of the wedge-shaped lubricating gas film, and the influence of working condition parameters, foil structure parameters and linear dynamic pressure groove distribution position on the static and dynamic characteristics of the seal is analyzed. The research results show that: Benefiting from the deformation of the sealing surface, the floating foil gas film seal can independently adjust the gas film gap according to operating conditions; The gas film floating force and leakage of the inlet straight groove are bigger than those of the middle straight groove; The sealing characteristics are closely related to the gas film pressure and the sealing gap, but they are little affected by the Coulomb friction effect; Both the Coulomb friction effect and the thickened foil increase the rigidity of the foil to a certain extent, making the sealing surface “rigid"; The comprehensive performance of the floating foil air-film seal in the high-speed service environment is good. The research results laid a theoretical foundation for the structural design and experimental testing of the floating foil gas film seal in the future.

Key words: gas film lubrication, elastic foil, dynamic pressure groove, small disturbance method, finite difference method, sealing characteristics

摘要：

为保证应用于航空发动机动密封的稳定运行，针对浮动式箔片气膜密封，采用考虑库仑摩擦作用的波箔片刚度模型，利用中心差分法和超松弛迭代法耦合求解箔片变形方程、压力控制方程和气膜厚度控制方程，并运用小扰动法，结合压力与箔片变形的平衡关系，获得锲形润滑气膜的流场分布，分析了工况参数、箔片结构参数以及直线动压槽分布位置对密封静、动态特性的影响规律。研究结果表明：受益于密封面的变形作用，浮动式箔片气膜密封可根据运行工况自主调节气膜间隙；进口直线槽的气膜浮升力和泄漏量均大于中间直线槽；密封特性与气膜压力和密封间隙密切相关，但受到库仑摩擦效应的影响很小；库仑摩擦效应和加厚箔片都可在一定程度上增大箔片刚度，使得密封表面变“刚”；浮动式箔片气膜密封在高转速服役环境下的综合表现良好。研究成果为今后浮动式箔片气膜密封的结构设计和试验测试奠定了理论基础。

关键词: 气膜润滑, 弹性箔片, 动压槽, 小扰动法, 有限差分法, 密封特性

CLC Number:

TH 117.2

Jie XU, Shurong YU, Xuexing DING, Haitao JIANG, Junhua DING. Analysis of floating foil gas seal performance based on bump foil deformation[J]. CIESC Journal, 2022, 73(5): 2083-2093.

徐洁, 俞树荣, 丁雪兴, 蒋海涛, 丁俊华. 基于波箔片变形的浮动式箔片气膜密封性能分析[J]. 化工学报, 2022, 73(5): 2083-2093.

Figures/Tables 15

Fig.1 Floating foil gas film seal

Fig.2 Schematic diagram of elastic foil deformation

Fig.3 Computational domain meshing

Fig.4 Calculation flow chart

Table 1 Structural parameters and mechanical properties

参数名称	数值	参数名称	数值
半径/mm	28.66	波箔片厚度/mm	0.60
密封宽度/mm	52	波箔片节距/mm	4.60
平均气膜间隙/μm	10	波箔片弦长/mm	3.60
偏心率	0.6	波箔片半径/mm	3.40
周期数	15	波箔片角度/(°)	63.93
动压槽宽/mm	6	泊松比	0.30
动压槽长/mm	22	弹性模量/Pa	2.10×10¹¹
槽深/μm	2

Table 2 Working condition parameters

参数名称	数值	参数名称	数值
环境压力/MPa	0.101325	介质密度/(kg/m³)	1.1425
介质压力/MPa	0.2	介质黏度/(Pa·s)	1.8×10^-5
转速/(r/min)	18000	摩擦因数	0.1

Fig.5 Verification of flow field calculation program

Table 3 Verification of the correctness of the stiffness calculation program

波箔片刚度/(N/m³)		相对误差/%
文献[30]	本文	相对误差/%
10.4000×10⁹	10.3761×10⁹	0.23

Fig.6 Distribution of bump foil deformation

Fig.7 Distribution of gas film pressure

Fig.8 Distribution of gas film pressure

Fig.9 Influence of inlet pressure

Fig.10 Influence of speed

Fig.11 Influence of friction factor

Fig.12 Influence of bump foil thickness

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