Study on oil flow and leakage characteristics of bearing chamber graphite sealing structure considering cavitation effect
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摘要:
为探究石墨封严结构对滑油流动与泄漏特性的作用机理，对常规石墨封严结构提出4种开槽方案，深入探究考虑气穴效应情况下，不同结构参数和工况参数对轴承腔石墨封严间隙中滑油流动特性的影响规律。研究结果表明：未考虑气穴效应时，在低于饱和蒸汽压力情况下，液态滑油气化的影响被忽略，导致封严间隙内出现压力为负值的现象，此时有悖于客观实际。而考虑气穴效应后，封严间隙压力为负值现象消失，因此在研究石墨封严间隙滑油流动特性时应该将气穴效应考虑在内。当流动工质为滑油时，在进出口压差和转速相同条件下，石墨负开槽和转子正开槽方案的阻力和剪切力的合力在轴向的分量方向由封严腔指向轴承腔，利于将滑油泵送至轴承腔，有效抑制滑油泄漏，起到封油效果；当开槽方向相反时，泵送效应沿轴向的方向为由轴承腔指向封严腔，加剧滑油从轴承腔的泄漏，设计过程中应当避免该种情况。
Abstract:The objective of this study is to investigate the impact of graphite sealing structures on the flow and leakage characteristics of lubricating oil. To this end, four slotting schemes are proposed for conventional graphite sealing structures. The study employs a comprehensive approach, examining the influence of different structural parameters and working condition parameters on the flow characteristics of lubricating oil in the graphite sealing gap of bearing chambers, taking into account the cavitation effect. The results indicate that the omission of the cavitation effect leads to a phenomenon where pressure is negative in the sealing gap when oil vaporisation occurs under conditions lower than the saturated vapor pressure. This is contrary to objective reality. However, the consideration of the cavitation effect eliminates this negative pressure phenomenon. Therefore, it is essential to consider cavitation when studying lubricating oil flow characteristics in a graphite sealing gap. When lubricating oil is employed as the flow medium, it is observed that the resultant force
F J , derived from case resistancef and shear forceFτ , which arises from negative slotting of graphite and positive slotting of the square rotor, is directed from the sealing cavity to the bearing cavity in an axial component direction. This facilitates pumping lubricating oil into the bearing cavity, effectively inhibiting leakage and achieving a seal. Conversely, if the groove direction is opposite, then the axial pumping effect will direct lubricating oil from the bearing cavity to the sealing cavity, which will exacerbate leakage from the bearing cavity. This situation should be avoided during the design process. -
图 1 航空发动机轴承腔封严系统示意图
Figure 1. Aero-engine bearing cavity sealing system schematic diagram
图 3 轴承腔封严间隙计算域网格划分
Figure 3. Meshing of bearing cavity seal clearance calculation domain
图 7 数值模拟和试验结果液相体积分数对比
Figure 7. Comparison of liquid volume fraction between numerical simulation and test results
图 11 不同开槽结构石墨密封速度分布云图（ω=
12000 r/min）Figure 11. Velocity distribution cloud diagram of graphite seal with different slotted structures （ω=
12000 r/min）
图 12 不同开槽结构石墨密封压力分布云图（ω=
12000 r/min）Figure 12. Graphite seal pressure distribution cloud diagram of different slotted structure （ω=
12000 r/min）
图 13 不同开槽方案滑油泄漏量对比（Δp=100 kPa, ω=
12000 r/min）Figure 13. Comparison of oil leakage of different slotting schemes （Δp=100 kPa, ω=
12000 r/min）
图 14 10%轴向截面压力分布（ω=
12000 r/min）Figure 14. Distribution of 10% axial section pressure （ω=
12000 r/min）
图 15 不同开槽结构石墨密封压力分布云图（Δp=100 kPa，ω=
12000 r/min）Figure 15. Graphite seal pressure distribution cloud diagram of different slotted structure （Δp=100 kPa，ω=
12000 r/min）
图 16 不同开槽结构石墨密封滑油泄漏量 （ω=
12000 r/min）Figure 16. Leakage of graphite seal oil with different slotted structures （ω=
12000 r/min）
图 17 不同开槽结构石墨密封截面压力云图 （ω=
12000 r/min）Figure 17. Pressure cloud diagram of graphite seal section with different slotted structures （ω=
12000 r/min）
图 18 不同开槽结构石墨密封压力分布图 （ω=
12000 r/min）Figure 18. Pressure distribution diagram of graphite sealing with different slotted structures （ω=
12000 r/min）
图 19 密封间隙中润滑油蒸汽的体积分数分布图（ω=
12000 r/min）Figure 19. Volume fraction distribution diagram of lubricating oil vapor in the sealing gap （ω=
12000 r/min）表 1 石墨密封结构几何参数
Table 1. Geometric parameters of graphite sealing structure
参数 Base GRP0 GRP1 ROT0 ROT1 旋转半径 r/mm 128 128 128 128 128 宽度 b/mm 6 6 6 6 6 槽数 N 0 45 45 45 45 槽宽 d/mm 0 1.6 1.6 1.6 1.6 槽轴向长度 l/mm 0 4.8 4.8 4.8 4.8 角度 β/（°） 0 −45 45 −45 45 槽深 h/μm 0 50 50 50 50 密封间隙 τ/μm 50 50 50 50 50 
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