稀薄气体效应对止推箔片轴承的性能影响
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摘要
为研究稀薄气体效应对微小间隙下气体止推箔片轴承承载力的影响,分别采用连续模型、一阶滑移模型和WU新滑移模型速度边界条件,建立考虑稀薄气体效应的修正雷诺方程,运用有限差分法求解修正雷诺方程,得到3种模型不同箔片变形柔度系数、不同转速、不同轴承间隙下的微型止推箔片轴承的压力分布和轴向承载力。结果表明:止推箔片轴承的箔片变形柔度系数越小,转速越高,轴向承载力越大;在轴承最小间隙低于0.5μm、转速低于20 000 r/min条件下,稀薄气体效应会使止推箔片轴承承载力降低,且一阶滑移及WU新滑移模型的气压和承载力远低于连续模型,模型间的结果偏差随轴承间隙、转速和箔片变形柔度系数的减小而逐渐增大。
In order to study the influence of rarefied gas effect on the bearing capacity of gas thrust foil bearings with small clearance,the modified Reynolds equation considering rarefied gas effect was established by using continuous model,first-order slip model and new WU slip model velocity boundary conditions.The modified Reynolds equation was solved by finite difference method to obtain the pressure distribution,axial bearing capacity of micro foil thrust bearing under different foil deformation flexibility coefficients,rotational speeds and bearing clearance.The results show that the smaller the foil deformation flexibility coefficient of thrust foil bearing is and the higher the rotational speed is,the larger the axial bearing capacity.When the minimum clearance of the bearing is less than 0.5 μm and the rotational speed is less than 20 000 r/min,the rarefied gas effect will reduce the bearing capacity of thrust foil bearing,and the pressure and bearing capacity obtained by the first-order slip and new WU slip models are much lower than that by the continuous model.The results deviation between these models is increased with the decrease of bearing clearance,rotational speed and foil deformation flexibility coefficient.
In order to study the influence of rarefied gas effect on the bearing capacity of gas thrust foil bearings with small clearance,the modified Reynolds equation considering rarefied gas effect was established by using continuous model,first-order slip model and new WU slip model velocity boundary conditions.The modified Reynolds equation was solved by finite difference method to obtain the pressure distribution,axial bearing capacity of micro foil thrust bearing under different foil deformation flexibility coefficients,rotational speeds and bearing clearance.The results show that the smaller the foil deformation flexibility coefficient of thrust foil bearing is and the higher the rotational speed is,the larger the axial bearing capacity.When the minimum clearance of the bearing is less than 0.5 μm and the rotational speed is less than 20 000 r/min,the rarefied gas effect will reduce the bearing capacity of thrust foil bearing,and the pressure and bearing capacity obtained by the first-order slip and new WU slip models are much lower than that by the continuous model.The results deviation between these models is increased with the decrease of bearing clearance,rotational speed and foil deformation flexibility coefficient.
引文
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[7]闫佳佳,刘占生,张广辉,等.考虑稀薄气体效应的止推箔片轴承静特性分析[J].航空动力学报,2016,31(6):1521-1529.YAN J J,LIU Z S,ZHANG G H,et al.Static characteristics analysis of foil thrust bearing considering the rarefield gas effect[J].Journal of Aerospace Power,2016,31(6):1521-1529.
[8]BURGDORFER A.The influence of the molecular mean free path on the performance of hydrodynamic gas-lubricated bearings[J].Trans ASME,Ser D,1959,81:94-100.
[9]张海军,杨琴.微气体轴承润滑模型研究[J].嘉兴学院学报,2009,21(6):75-78.ZHANG H J,YANG Q.Study on lubrication models of micro gas bearings[J].Journal of Jiaxing University,2009,21(6):75-78.
[10]WU L.A slip model for rarefied gas flows at arbitrary Knudsen number[J].Applied Physics Letters,2008,93(25):253103-1-3.
[2]DELLACORTE C,VALCO M J.Load capacity estimation of foil air journal bearings for oil-free turbomachinery applications[J].ASLE Transactions,2000,43(4):795-801.
[3]HESHMAT H,WALOWIT J A,PINKUS O.Analysis of gas lubricated compliant thrust bearings[J].Journal of Tribology,1983,105(4):638-646.
[4]WALOWIT J A,MURRAY S F,MCCABE J T,et al.Gas lubricated foil bearing technology development for propulsion and power systems[R].Air Force Aero Propulsion Lacoratory,AFA-PL-TR-73-92,1973.
[5]IORDANOFF I.Maximum load capacity profiles for gas thrust bearings working under high compressibility number conditions[J].Journal of Tribology,1998,120(3):571-576.
[6]周权,赵祥雄,陈汝刚,等.基于有限差分法的动压气体止推轴承静态特性分析[J].润滑与密封,2009,34(8):6-9.ZHOU Q,ZHAO X X,CHEN R G,et al.Static characteristic analysis of aerodynamic gas thrust bearing based on finite difference method[J].Lubrication Engineering,2009,34(8):6-9.
[7]闫佳佳,刘占生,张广辉,等.考虑稀薄气体效应的止推箔片轴承静特性分析[J].航空动力学报,2016,31(6):1521-1529.YAN J J,LIU Z S,ZHANG G H,et al.Static characteristics analysis of foil thrust bearing considering the rarefield gas effect[J].Journal of Aerospace Power,2016,31(6):1521-1529.
[8]BURGDORFER A.The influence of the molecular mean free path on the performance of hydrodynamic gas-lubricated bearings[J].Trans ASME,Ser D,1959,81:94-100.
[9]张海军,杨琴.微气体轴承润滑模型研究[J].嘉兴学院学报,2009,21(6):75-78.ZHANG H J,YANG Q.Study on lubrication models of micro gas bearings[J].Journal of Jiaxing University,2009,21(6):75-78.
[10]WU L.A slip model for rarefied gas flows at arbitrary Knudsen number[J].Applied Physics Letters,2008,93(25):253103-1-3.