基于小孔节流的液体动静压球轴承动态特性分析

以小孔节流方式的液体动静压球轴承为研究对象,建立球轴承的润滑数学模型,推导出层流状态下的Reynolds方程,引入流量守恒原理并结合小孔节流器的流量计算得到油腔和封油边压力分布;采用微扰法推导出扰动压力控制方程,通过有限差分法和松弛迭代法求解扰动压力控制方程得到轴承的刚度和阻尼系数。运用数值分析研究供油压力、转速及油膜间隙等参数对轴承动态特性系数的影响。结果表明,随着油膜间隙减小,供油压力的增大,刚度和阻尼系数会随之增大;随着转速增大,直接刚度变化趋势较小,直接阻尼降低趋势较明显;当油膜间隙为20μm时,轴承刚度和阻尼系数达到最大;转速的提高对于刚度影响较小,而阻尼系数则会明显降低。     

基于小孔节流的静压油膜轴承动态特性分析

静压轴承的动静态特性在很大程度上受到节流装置的影响,以小孔节流的静压轴承为研究对象,开展其动态特性理论的研究。利用两平行平板缝隙液体流量公式推导了轴承油腔流出的流量数学模型,并充分考虑了主轴转子速度对流量的影响因素,使之更符合实际工况;在对小孔节流后流入轴承油腔的流量方程进行线性化处理的基础上,建立了静压轴承系统的流量连续性方程;结合轴承-主轴系统动力学方程,推导出小孔节流的静压轴承系统动态特性的传递函数,分析了小孔节流静压轴承系统的动态特性。结果表明:小孔节流的四油腔静压轴承动态响应速度在0.06~0.12 s范围内变化,增大供油压力、油腔承载面积、主轴转速及减小油膜粘度、油膜间隙等均有助于提高轴承系统的响应速度。研究结果对于指导工程设计具有一定的参考价值。     

不同节流方式的滑动轴承油膜静态性能求解

针对毛细管、小孔、滑阀反馈和薄膜反馈4种节流方式,结合三油腔动静压混合油膜轴承及四油腔静压轴承,建立了轴承油膜静态性能求解的数学模型。从Reynolds方程的离散、间隙函数数学模型的建立、边界条件的确定、连续性方程的建立、不同节流方式的进油流量数学模型的推导、轴承的承载能力及温升等方面分析了轴承油膜静态性能的求解。计算结果表明:采用毛细管和小孔节流轴承的承载能力和油膜刚度较低;而采用滑阀反馈和薄膜反馈节流轴承具有较高的油膜刚度和承载能力。     

基于FLUENT的静压气体轴承节流孔系数研究

在通过求雷诺方程来研究静压气体轴承的特性时,通常假设节流孔系数为常数0.8,这可能会影响雷诺方程求解的精度。结合FLUENT软件和雷诺方程提出一种静压气体轴承节流孔系数的求解方法,该方法通过对比FLUENT和雷诺方程计算得到的质量流量求解节流孔系数;分析气膜厚度、供气压力、节流孔直径等参数对节流孔系数的影响。结果表明：节流孔系数随着膜厚的增加先增大后减少,随着供气压力的增大而减少,随着节流孔直径的增大而增大,但节流孔系数对轴承半径和节流孔长度的变化并不敏感。采用该节流孔系数求解雷诺方程得到的轴承承载力,与FLUENT计算得到的承载力结果基本一致,验证了该方法的正确性与可行性。     

三瓦翻转压力坝轴承设计参数对承载能力的影响

建立三瓦压力坝轴承的几何模型并求解得到油膜厚度分布。基于雷诺方程建立滑动轴承理论模型,采用单元流量平衡法来离散复杂轴瓦结构的Reynolds方程并用MATLAB求解,得到轴承承载力。采用载荷约束条件和模式搜索相结合的方式求解定载荷方向下的轴承静态特性,并得到载荷收敛的油膜厚度分布与压力分布。分别改变压力坝轴承结构参数,分析各参数对轴承承载能力的影响。结果表明:椭圆率和轴承长径比对轴承承载力影响较大,其他参数的影响都相对较小;随着椭圆率和轴承长径比的增加轴承承载力提高。     

不同参数对三瓦翻转压力坝轴承承载能力的影响

建立三瓦压力坝轴承的几何模型并求解得到油膜厚度分布。基于雷诺方程建立滑动轴承理论模型,采用单元流量平衡法来离散复杂轴瓦结构的Reynolds方程并用MATLAB求解,得到轴承承载力。采用载荷约束条件和模式搜索相结合的方式求解定载荷方向下的轴承静态特性,并得到载荷收敛的油膜厚度分布与压力分布。分别改变压力坝轴承结构参数,分析各参数对轴承承载能力的影响。结果表明：椭圆率和轴承长径比对轴承承载力影响较大,其他参数的影响都相对较小;随着椭圆率和轴承长径比的增加轴承承载力提高。     

考虑边界滑移状态的液体动静压球轴承稳定性分析

液体动静压球轴承稳定性分析包括探究其动态特性及临界转速,其刚度和阻尼系数对轴承转子系统稳定性具有重要影响,而研究临界转速可有效避免轴承转子系统发生涡动失稳。考虑边界滑移条件,将小孔节流器进入油腔流量与封油边流出流量相等作为边界条件,求解出边界滑移状态下的Reynolds方程得到油腔压力和封油边压力;对边界滑移状态下瞬态Reynolds方程采用小扰动法推导出扰动压力偏微分方程,结合有限差分法和松弛迭代法求解方程得到边界滑移状态下液体动静压球轴承的刚度和阻尼系数,进而通过线性稳定性方法求解临界失稳转速,探讨滑移系数、供油压力、转子转速之于轴承动态特性的影响及临界转速之于滑移系数的变化规律。结果表明,滑移系数增大会导致4个刚度系数和交叉阻尼系数减小、直接阻尼增大;供油压力增大将导致8个动态特性系数均增大,转速增大将导致刚度增大及阻尼减小,且滑移效应的发生不影响上述规律;临界转速随滑移系数的增大而减小,系统稳定性降低。     

PM流量控制器节流液体静压轴承静动态特性分析

将PM流量控制器用于无周向回油槽四腔向心静压轴承,建立了PM流量控制器静压轴承数学模型,重点研究分析了轴承结构参数及PM流量控制器参数对静压轴承特性的影响。研究结果表明:轴承轴流封油边系数越小、周流封油边系数越大,轴承油膜刚度和承载力越大,初始油膜间隙增大,油膜刚度减小;润滑油动力粘度较大且初始油膜间隙较小时,油膜刚度和承载力较大;液阻比越小,比流量越大,油膜刚度越大;供油压力越大,油膜刚度、承载力和流量越大。同时基于线性化下液体静压轴承系统的传递函数,利用Matlab Simulink软件在时域和频域内分别研究了静压轴承系统的动态特性。研究结果表明:在阶跃载荷作用下,随着供油压力和比流量的提高,过渡过程时间越短,静压轴承系统的动态特性越好;在正弦载荷作用下,提高供油压力、比流量都会使轴心偏移量的稳态幅值减小,油膜动刚度增大,且供油压力较比流量对系统频率特性的影响显著。     

计入气穴影响的径推联合动静压浮环轴承稳定性研究

研究了计入气穴影响的径推联合动静压浮环轴承的动态性能和稳定性.给出了控制径推联合浮环动静压轴承内、外膜的气油两相流变密度、变黏度无量纲动态Reynolds方程及压力边界条件和深腔流量平衡方程;用有限元法对不同转速、不同偏心率下含气率为0和0.1的内外油膜进行了有限元计算,得到各部分的刚度系数和阻尼系数;计算了该径推浮环轴承的稳定性参数.结果表明:气穴使得径向、推力内外层油膜的刚度系数和阻尼系数均有所下降,随着偏心率的增大及转速的提高,气穴的影响程度减小;气穴使得轴承的无量纲临界转子质量降低,因此在供油压力急剧变化时必须考虑气穴的影响.     

基于弹流耦合算法的船舶艉轴承润滑特性分析

采用耦合算法研究不同因素对船舶艉轴承弹流润滑性能的影响。以重载工况的船舶艉轴承为研究对象,建立轴瓦三维有限单元模型;通过有限单元法结合耦合算法求解油膜压力、油膜厚度、弹性变形,探讨了弹性模量、轴承间隙、长径比3种影响因素对艉轴承弹流润滑特性的动态影响。结果表明：弹性变形和油膜压力沿周向和轴向都近似抛物线分布,呈现先增后减的趋势,在周向180°附近取得最大值,因此在轴承周向和轴向的中点附近受轴承参数的影响较大,润滑状况需要特别关注;随弹性模量增加,油膜峰值压力增加,最大弹性变形量和最小厚度均减小,摩擦力和端泄流量同时增加,因此在一定区间内增大弹性模量能有效减小轴瓦产生的弹性变形;随轴承间隙增大,油膜峰值压力增加,最大弹性变形量和最小油膜厚度均减小,摩擦力和端泄流量变化不明显,因此在轴承安装时需控制合理的轴承间隙,确保轴承处于良好的润滑环境;随长径比增大,最大弹性变形量近似线性增加,油膜峰值压力、摩擦力、端泄流量均减小,最小油膜厚度几乎不变,因此在设计艉轴承长径比时,应综合考虑艉轴承在重载工况下可能产生的弹性变形以及弹性变形对润滑特性的影响。     

Stability of multilobe hybrid bearing with short sills—part II

A small amplitude perturbation analysis has been carried out to determine the rotordynamic characteristics of multilobe hybrid bearings with short axial and circumferential sills. Unsteady state recess flow continuity equation has been written for orifice compensated bearing in terms of dynamic recess pressures by perturbing steady state flow equation. Dynamic recess pressures are evaluated by solving unsteady recess flow continuity equations to determine the dynamic load capacity of the bearing. Stiffness and damping coefficients of the bearing are determined from the dynamic load capacity of the bearing. Results of dynamic characteristics of three lobe and four lobe hybrid bearings are presented for various offset factors, speed, concentric pressure and eccentricity ratios. Multilobe hybrid bearings with offset factors more than one are found to exhibit better dynamic behaviour than circular hybrid bearings.     

Determination of the dynamic coefficients of the coupled journal and thrust bearings by the perturbation method

This paper proposes a method to calculate the stiffness and the damping coefficients of the coupled journal and thrust bearings. Reynolds equations and their perturbation equations of journal and thrust bearings are transformed to the finite element equations by considering the continuity of pressure and flow at the interface between the journal and the thrust bearings. It also includes the Reynolds boundary condition in the numerical analysis to simulate the cavitation phenomenon. The stiffness and damping coefficients of the proposed mathematical method are compared with those of the numerical differentiation of the bearing force with respect to finite displacements and finite velocities of bearing center. It shows that the proposed method can calculate the dynamic coefficients of a coupled journal and thrust bearing more numerically stable and computationally efficient than the differentiation method. It also investigates the coupling effect of the coupled journal and thrust bearing and it shows that the proposed method makes it possible to calculate the cross-coupled dynamic coefficients in the radial–axial direction of the coupled journal and thrust bearing.     

螺旋槽气体轴承动态特性及失稳分析

针对高速动静压气体轴承气膜的复杂非线性动力学行为,以球面螺旋槽动静压气体轴承为研究对象,建立润滑分析数学模型;采用有限差分法与导数积分法进行求解,得到动态扰动压力分布及动态特性系数,并研究切向供气条件下螺旋槽参数、径向偏心率、供气压力、转速对气膜刚度阻尼系数的影响规律;建立线性稳定性计算模型,预测气膜涡动失稳转速,分析运行参数对失稳转速的影响。结果表明:气膜阻尼是一种抑制涡动的因素,气膜的稳定性取决于气膜刚度与阻尼的协同作用;气膜刚度阻尼随着槽宽比、槽深比、螺旋角的增大,整体上呈先增大后减小的趋势;刚度随转速的升高而增大,阻尼则随转速的升高而减小;径向偏心率和供气压力越大,气膜刚度和阻尼越大;在一定范围内,提高供气压力、增大径向偏心率能够提高系统失稳转速;合理地选取轴承结构参数和运行参数,能够优化轴承动态特性,保证气体轴承较高的运行稳定性。     

水润滑动静压轴承三维压力及温度场分布理论研究

以4腔、毛细节流形式下的深腔动静压轴承为研究对象,采用有限差分数值方法求解了广义雷诺方程,该过程考虑了紊流、粘度和密度随压力及温度变化的影响。研究得到了在水介质润滑下的动静压轴承三维压力分布、温度场分布及动特性系数。结果表明在高速高压水润滑条件下的动静压轴承表现出了与粘度较大的油润滑条件下不同的液腔压力分布、温度分布等特性。水润滑轴承第3和第4个液腔压力较大,第1个液腔主要用来增加其稳定性,而同等条件下的油润滑轴承第2和第3个油腔压力较大,第4个液腔增加其稳定性。相比油润滑轴承,水润滑轴承温升较高,因此对于低粘度介质润滑下的轴承性能研究需要考虑温升影响。     

Steady state and dynamic characteristics of axial grooved journal bearings

The steady state and dynamic characteristics including whirl instability of oil journal bearings with single axial groove located at the top of the bearing and then at some angular interval from the top from which oil is supplied at constant pressure are obtained theoretically. The Reynolds equation is solved numerically by finite difference method satisfying the appropriate boundary conditions. The dynamic behaviour in terms of stiffness and damping coefficients of fluid film and stability are found using a first-order perturbation method for each location of the groove. It has been shown that both load capacity, end flow is maximum when the feeding groove is at 12° location and thereafter the load capacity falls, stability improves for smaller groove angle and groove length at higher value of eccentricity ratio and speed. The stiffness and damping coefficient magnitude is found to be higher for the bearing with smaller groove angle and groove length, the difference between the hydrodynamic and hydrostatic load increases at 12° groove location.     

Performance Analysis of Capillary-Compensated Hydrostatic Lead Screws with Discontinuous Helical Recesses Including Influence of Pitch Errors in Nut

This article investigates the axial static and dynamic characteristics of capillary-compensated hydrostatic lead screws with discontinuous helical recesses considering the influence of the pitch errors of the nut. The mathematical model is based on the Reynolds equation, including rotational lubricant inertia and the flow continuity equation. The finite difference method and the perturbation technique are applied. The results show that the pitch errors cause the inequality of recess pressures on the same flank surface of the nut thread; the influence of pitch errors on the axial load capacity is not significant within the dimensionless axial displacement of the nut of 0.6, but the effect on the axial stiffness and damping coefficients is significant under larger axial displacement.     

Dynamic stiffness and damping coefficients of aerodynamic tilting-pad journal bearings

The dynamic gas–film forces of aerodynamic bearing often can be characterized by eight linear stiffness and damping coefficients. How to theoretically predict these coefficients is a very difficult issue for tilting-pad gas bearing design because of its structural complexity. The current study presents a novel and universal theoretical analysis method for calculating the dynamic stiffness and damping coefficients of aerodynamic tilting-pad bearing. The gas–film pressure within the bearing is expressed in the form of dimensionless compressible gas-lubricated Reynolds equation, which is solved by means of the finite element method. With the assumption that the journal and the pads are disturbed with the same frequency, the dynamic coefficients of tilting-pad gas bearing are computed by using the partial derivative method and the equivalent coefficient method. Finally, the investigations are conducted about the effects of bearing number, perturbation frequency of the journal and the pads, eccentricity ratios, preload and length-to-diameter ratio of the bearing on the dynamic coefficients of aerodynamic tilting-pad journal bearing. The numerical results indicate that the dynamic stiffness and damping coefficients of tilting-pad gas bearing are closely related with these factors. The proposed analytical method provides a valuable means of predicting dynamic performances of tilting-pad gas bearing. The solution can be used for the purpose of prediction of dynamic behavior of the rotor systems supported by aerodynamic tilting-pad bearings.     

间隙环流中同心涡动转子动特性的研究

考虑轴向流动因素的影响，采用紊流整体流动模型和Moody壁面摩擦系数方程，建立间隙环流3D非线性微分方程，运用摄动法和线性振动理论分析求解间隙环流中同心涡动转子动特性系数。实例计算结果表明，间隙环流中同心涡动转子动特性系数与间隙的大于有关，同时分析轴向压差、壁面粗糙度、长径比及入口预旋等参数对大、小间隙环流中同心涡动转子的动特性系数的影响。     

不同雷诺数下螺旋槽径向气体轴承承载特性分析

为研究螺旋槽径向气体轴承在不同雷诺数下承载力的变化规律,建立基于Ng-Pan理论修正的气体轴承润滑模型,利用有限差分法求解该模型,得到不同雷诺数下轴承的承载特性,分析轴承几何参数和槽型参数的变化对承载力的影响。结果表明：螺旋槽径向气体轴承在非层流润滑状态下承载力大于层流润滑状态下的承载力;轴承几何参数对承载特性影响显著,其中随偏心率增大承载力呈发散式增大,且非层流状态下承载力与层流状态下承载力差距加大,随长径比增大承载力呈收敛式增加;轴承槽型参数中槽宽比、槽深比对承载特性有明显影响,随槽宽比、槽深比增加轴承承载力增加,而槽数对轴承承载力的影响并不显著,螺旋角对非层流状态下轴承承载力影响较大;轴承进口压力对承载性能有明显影响,随进口压力增大,承载力在层流状态下增加,在非层流状态下波动较大。     

径向动压气体轴承承载能力的CFD分析

为改进计算精度和提高计算效率,采用CFD软件Fluent对径向动压气体轴承承载能力进行分析.使用软件Solidworks建立径向动压气体轴承三维物理建模;从可压缩流体润滑方程及连续性方程出发,得到等温条件下动压润滑雷诺方程的基本形式,运用有限差分法计算径向动压轴承的压力分布及承载力等特性;采用Fluent进行有限元仿真...