支点位置分布对径向可倾瓦滑动轴承热动力润滑性能的影响

径向可倾瓦滑动轴承瓦块支点的分布情况对轴承性能影响很大.本文详细分析了瓦块支点位置分布对滑动轴承热动力润滑性能的影响.结果表明采用非均布支点布置有利于提高在大型低速重载条件下径向可倾瓦滑动轴承的热动力润滑性能.     

支点位置分布对径向可倾瓦滑同承热动力润滑性能的影响

本文详细了瓦块支点位置分布对滑动轴承热动力润滑性能的影响。结果表明采用非均布支点布置有利于提高在大型低速重载条件下径向可倾瓦滑轴承的热动力润滑性能。     

贯流式水轮发电机组径向可倾瓦滑动轴承的性能研究

详细分析了径向可倾瓦轴承瓦块支点分布情况对轴承性能的影响。结果表明瓦块支点分布位置对低速重载滑动轴承性能影响很大。采用非均布支点布置有利于提高在低速重载条件下径向可倾瓦滑动轴承的润滑性能。     

瓦面凹槽结构参数对可倾瓦推力轴承润滑性能的影响

为了研究瓦面凹槽对可倾瓦推力轴承润滑性能改善的优势,在瓦块进油边设计一种圆弧槽结构,建立考虑槽结构的可倾瓦推力轴承热动力润滑模型,分析不同槽深和槽半径对轴承性能的影响规律。结果表明:在瓦块进油边开槽可以改善轴承润滑性能,与不开槽相比,油膜厚度和瓦块的进油流量增加,油膜温度降低;当槽深达到一定值后,油膜温升增大;推力轴承润滑性能随着槽半径增加而变差,轴承各性能参数随槽深的增加表现出极值特性;最优开槽参数为(1.2～1.5,1),该参数下轴承最小油膜厚度比无槽轴承的增加约10%,最大油膜温度降低约3℃。     

多瓦可倾瓦径向滑动轴承热弹流润滑分析

考虑轴瓦弹性变形,建立多瓦可倾瓦径向滑动轴承热弹流润滑(TEHD)分析的数学模型,对比分析多瓦可倾瓦径向滑动轴承热流体动力润滑(THD)与TEHD模型的润滑性能差异,分析轴瓦弹性变形对轴承润滑性能的影响.结果表明,轴瓦弹性变形导致最小油膜厚度减小、流体动压力的梯度下降,但对瓦面温度的影响较小;THD模型高估了轴承的承载能力,在高速重载的场合,这种误差可能导致轴承润滑失效.因此,在滑动轴承设计中有必要考虑轴瓦弹性变形对轴承润滑性能的影响.     

刚性和弹性支撑可倾瓦推力轴承稳态特性分析

建立刚性球头支撑和弹性橡胶垫支撑可倾瓦推力轴承热弹流耦合模型；在弹性橡胶垫支撑可倾瓦推力轴承橡胶垫的弹性变形分析中采用了变形协调矩阵方法，以协调匹配橡胶垫变形和水膜厚度分布，同时在搜索稳态解的过程中引入模拟退火算法；基于变分原理求解Reynolds方程，得到了轴承水膜压力分布，并比较2种推力轴承在转子存在角不对中时的静特性。结果表明：理想工况下，刚、弹支可倾瓦推力轴承稳态特性没有明显区别；当转子存在不对中时，刚性球头支撑可倾瓦轴承在不同瓦块之间受力偏载严重，进而导致瓦面最小水膜厚度过小，瓦块容易出现磨损，而弹性支撑瓦不同瓦块之间水膜力分布更均匀，利于轴承的长期可靠运行。     

可倾瓦推力轴承中进口压力对热动力润滑性能的影响

从理论上研究了进口压力对推力轴承热动力润滑性能的影响。进口压力的存在,使油膜厚度增大,油膜内粘性能耗散减少,进油流量增大,温升减低,有利于提高润滑性能,轴承转速愈高,进口压力也就愈大。因此,进口压力是分析研究高速轻载可倾瓦推力轴承热动力轴承热动力润滑性能中的一个不可忽略的重要因素。     

轴线偏斜对多瓦径向滑动轴承热润滑性能的影响

分析轴线偏斜对多瓦可倾瓦径向滑动轴承热流体动力润滑性能的影响。计及轴线偏斜与瓦块自由度,推导可倾瓦径向滑动轴承的油膜厚度方程,建立数学模型,计算单自由度、双自由度2种瓦块支承的径向滑动轴承在不同偏斜程度时的最小油膜厚度、压力和三维温度分布,并分析偏斜对这2种轴承热流体动力润滑性能的影响。结果表明,轴线偏斜对单自由度瓦径向滑动轴承有较大影响,会使单自由度瓦块的可倾瓦径向滑动轴承的油膜压力在轴向分布不对称,导致瓦块支承处产生不平衡的力矩,而对双自由度瓦径向滑动轴承的润滑性能几乎没有影响。     

运转参数对可倾瓦轴承油膜特性的影响

为了确定汽轮机运行时运转参数对汽轮机可倾瓦轴承油膜特性的影响,以四瓦可倾瓦轴承为例,采用Pro/E建模,选用湍流SST三维模型,考虑到瓦块间隙及瓦块相互之间的影响,采用ANSYS模拟出进口油压、进口油温、偏心距、轴颈转速对四瓦可倾瓦轴承油膜特性的影响。结果表明:进口油压对油膜特性影响较小,进油温度、轴颈偏心距、轴颈转速对汽轮机可倾瓦油膜特性影响较大,故在运行中应严格监控这3个参数。     

多瓦可倾瓦径向滑动轴承热润滑性能分析

考虑变黏度、密度的情况,建立多瓦可倾瓦径向滑动轴承的数学模型,用有限差分法求解其热流体动力润滑(THD)模型,分别计算12块瓦可倾瓦径向滑动轴承的最小油膜、压力分布和三维温度场分布,分析不同载荷、不同转速、不同润滑油黏度等对轴承各瓦的热润滑性能影响。结果显示,建立的模型及其计算程序能计算分析多瓦可倾瓦径向滑动轴承的热润滑问题。润滑油黏度和转子转速对多瓦可倾瓦径向滑动轴承的热润滑性能有较大的影响;瓦块绕支点的倾斜以及瓦块所处的角度位置会影响部分瓦块的热润滑性能,出现与普通圆形径向滑动轴承不一致的润滑性能变化。     

Measured Performance of Tilting-Pad Journal Bearings over a Range of Preloads—Part I: Static Operating Conditions

This article presents the measured static characteristics for five tilting-pad journal bearings with a range of preload factors. The bearings had five shoes with static forces applied both on the pad and between pads. The journal diameter was 70 mm, with a length-to-diameter ratio of 0.75, a pivot offset ratio of 0.50, and a nominal assembled radial clearance of 81.3 μm. The rocker-backed pads have nominal radial machined clearances of 176.8, 114.3, 91.4, 73.7, and 61.0 μm. These clearances constitute a range of preloads from ?0.333 to 0.540. Most tilting pad bearings are intentionally designed with positive preloads, although with pivot wear and/or pad and pivot distortion or machining tolerances, bearings can operate with zero or negative preloads. Measured results for bearings with negative preload factors have not previously been available. Measurements reported here were made for a variety of speed-load conditions encompassing a Sommerfeld number of 0.1 to 4.5. The measured parameters are eccentricity magnitude, attitude angle, film thickness, and temperatures sufficient to define thermal boundary conditions. Also measured are oil supply pressure, flow rate, and on-shaft pressure profiles. The focus of the work presented herein is to quantify the influence of preload on film thickness, maximum pad temperature, and eccentricity magnitude and attitude angle. Measurements showed preload had a moderate influence on operating eccentricity but not on attitude angle. Negative preloads resulted in the greatest temperature rise, although all temperature rises were relatively small.     

支点弹性、阻尼可倾瓦轴承动力特性数值仿真及试验研究

依据考虑瓦块摆动和沿几何预载荷方向微幅振动的可倾瓦轴承完全动力特性的解析模型及其对应的八参数简化动力模型,设计制备了支点弹性、阻尼特性可倾瓦轴承。该轴承通过在瓦块支点与轴承体之间设置弹性垫片,使瓦块支点支撑在弹性垫片上,弹性垫片与轴承体之间存在微小间隙并与轴颈润滑系统共享油路以实现局部挤压油膜效应。根据不同加工工艺,制备了两种形式的新型支点弹性、阻尼轴承,并通过理论计算模拟与试验分析对两种新型轴承的动力特性进行研究。结果表明,支点弹性、阻尼可倾瓦轴承能够增大转子的一临界阻尼,有效提高转子系统稳定性。     

可倾瓦轴承的完整动力分析模型及计算方法

提出求解可倾瓦径向滑动轴承完整动力特性的解析模型和计算方法,给出可倾瓦轴承完整动力特性系数矩阵的简明表达形式.基于瓦块和轴颈间的运动耦合关系,建立瓦块局部坐标系统.与瓦块和轴颈运动相关的全局广义位移矢量可以通过简练的步骤转换为局部动坐标系下轴颈的位移矢量;利用求解固定瓦轴承动力特性的方法求得的局部动坐标系下的油膜力及其Jocabian矩阵,该油膜力矢量可以精确地转换为全局广义坐标系下的表达形式.在轴承的平衡位置处,全局坐标系下的油膜力矢量关于广义位移和广义速度的Jocabian矩阵为轴承完整动力特性系数矩阵的负值.给瓦块一个设定的扰动频率,就可以得到简化的当量动力特性系数矩阵.此解析方法求解简单方便,可用于分析可倾瓦轴承-转子系统.     

可倾瓦气体动压轴承承载能力的数值分析

应用MATLAB的偏微分方程工具箱,采用有限元法求解气体润滑Reynolds方程,通过完全装配分析法计算了可倾瓦动压气体轴承的承载能力,研究了轴承偏心和瓦块预负荷对可倾瓦轴承的承载能力、最小气膜厚度和最大气膜压力以及瓦块摆角的影响。计算结果表明,随轴承偏心或瓦块预负荷增大,各瓦块的承载能力和摆角发生明显变化,轴承的最小气膜厚度减小,最大气膜压力增大,承载能力增大。从理论上解释了可倾瓦轴承的承载能力与轴承偏心和瓦块预负荷的密切相关性。     

PTFE-faced centre pivot thrust pad bearings: Factors affecting TEHD performance

The paper presents a thermoelastohydrodynamic (TEHD) analysis of thrust bearings with polytetrafluoroethylene (PTFE) faced pads. The influence of pad active surface geometry on main characteristics such as temperature profile, film thickness and pressure field are investigated. Due to the high compliance of the PTFE layer, deformations of the active surface due to pressure are quite large and have to be taken into account. The initial geometry of the pad is also of great importance; a parametric study on the pad geometry permits clarification of both geometry and deformation effects. The geometry of the pad, particularly for centrally pivoted pads, has to be considered in order to accurately predict performance of PTFE-faced tilting-pad thrust bearings.     

径向可倾瓦轴承的热弹流润滑分析

用Newton-Raphson法一次性求出了所有瓦块的压力分布和轴心的位置,用步进扫描法对轴承进行了三维温度场分析,用20节点有限元法构造了瓦块的压力变形矩阵和热变形矩阵。     

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.     

螺旋面扇形瓦推力轴承热动力润滑性能分析

提出了一种适用于推力轴承的新型瓦——螺旋面扇形瓦,并对其热动力润滑性能进行了分析。螺旋面瓦与平面瓦比较,因其本身具有一定的斜度而具有许多特点,如油膜厚度大,承载能力大,剪切速率低,粘性耗散小,温升较小,功耗少而且制造加工容易等,因此可以很好地取代平面扇形瓦。