螺旋槽平面型线对水润滑螺旋槽推力轴承承载能力的影响

不同螺旋槽平面型线对螺旋槽推力轴承的压力场及承载能力会产生不同程度的影响.采用RNG k-ε湍流模型对具有不同螺旋槽平面型线的水润滑螺旋槽推力轴承润滑膜压力场进行了数值模拟,重点探讨了在不同转速条件下,不同螺旋槽平面型线对水膜压力场和承载能力的影响程度.结果表明:抛物线槽产生的压力峰值最大,螺旋线槽则具有最大的承载能力;与其它平面型线相比,螺旋线具有更稳定的压力分布,更适合水润滑螺旋槽推力轴承.     

微气体螺旋槽推力轴承润滑数值模拟

对微气体螺旋槽推力轴承润滑性能进行数值模拟.变换坐标将螺旋线转换为直线使其对网格的适应性更强.在新坐标系下应用有限体积法对考虑微尺度效应的雷诺方程离散,采用分块加权的方法考虑槽台高度不连续性,保证槽台边界上的质量流量守恒,得到适合超高速、微尺度气体螺旋槽推力轴承润滑性能的数值求解方法.利用Newton-Raphson方法求解出各节点压力分布,进而得到微气体螺旋槽推力轴承承载力.通过对比发现,考虑微尺度效应时,微气体螺旋槽推力轴承承载力有所降低;随着轴承间隙的减小,微尺度效应对轴承性能的影响也愈为明显.     

锥面螺旋槽推力轴承的有限元解

本文对用牛顿不可压流体润滑的锥面螺旋槽推力轴承进行了理论分析,螺旋角,槽深,槽台对数等不等时,轴承的承载量亦不同。本文用有限元法计算了轴承的膜压分布及承载量。     

扩压式自泵送机械密封参数化建模研究

目前对机械密封端面型槽多采用多段线拟合或者点拟合的方法来形成近似的螺旋线,模拟效率低且模拟结果准确性不高。提出准确性更高的、参数方程驱动的对数螺旋线型槽绘制方法,基于Visual Basic编程语言对SolidWorks软件进行二次开发,实现对扩压式自泵送机械密封动环端面及其流体计算域的参数化建模。研究表明：参数化所建模型,其密封端面结构及流体域参数可以便捷修改,型槽的绘制更加快速,绘制的槽线更加顺滑,更接近于真实型槽曲线;参数化建模结果能够导入ICEM等软件进行处理,为扩压式自泵送机械密封性能数值模拟效率的提升奠定了技术基础。     

变高度螺旋倾斜槽气体轴承的微尺度数值模拟

基于平面螺旋槽气体止推轴承结构,结合以对数螺旋线为素线的空间螺旋曲面结构,提出一种新型气体止推轴承模型。通过坐标变换推导出适应对数螺旋线轨迹的流量方程,引入一阶滑移和新滑移边界条件修正流量方程,应用数值方法迭代求解了连续型模型和2种滑移模型下新型气体止推轴承的气膜压力分布。结果表明:微尺度下随着气膜厚度减小,边界速度滑移效应会对轴承承载力特性产生很大影响;当Knudsen数增大到过渡区时,一阶滑移和新滑移模型之间的偏差明显增大;在相对较低的转速下,新型轴承的承载力相较于传统轴承明显增大。     

仿生集束螺旋槽干式气体密封特性的数值分析

基于耦合仿生学原理,提出一种仿生集束螺旋槽端面干气密封结构以解决普通单向螺旋槽干气密封在高速条件下存在的泄漏率高、稳定性欠佳等问题。基于气体润滑理论,建立仿生集束螺旋槽的端面几何模型和数学模型,数值模拟分析槽宽比、螺旋角、微槽数及阶梯槽深比对动压开启力增长率、轴向气膜刚度、角向气膜刚度和刚漏比等密封特性参数的影响规律,给出仿生集束螺旋槽主要结构参数的优选值范围。结果表明:在高速低压条件下,相比于普通单向螺旋槽干气密封,仿生集束螺旋槽干气密封的密封性和稳定性等密封性能都有显著改善,其动压开启力增长率、轴向气膜刚度和刚漏比的增幅均超过20%。结果证明基于飞鸟翼翅的端面型槽仿生设计可以显著改善普通单向螺旋槽干气密封在高速条件下的运行稳定性,为相关工程选型与开发设计提供参考。     

变工况运行中结构参数对螺旋槽动压推力气体轴承承载力的影响

基于纳维-斯托克斯(N-S)方程建立了泵入型螺旋槽动压推力气体轴承仿真三维模型,分析了在变工况运行中不同的结构参数对螺旋槽动压气体推力轴承气膜承载力的影响,结果表明:槽深为30~50μm,螺旋角为18°~36°,台区轴承间隙为4~10μm,槽内径比为0.6~0.8,槽宽比为0.7~0.9,槽数为12~25时,该轴承的气膜承载力达到最大;轴承结构不同时,轴承的气膜承载力由大到小排序为凸型槽、平底槽、凹型槽,且泵入型大于泵出型。     

湍流效应对空化流场及密封性能的影响

针对端面螺旋槽液膜密封空化效应及稳态密封性能,基于k-ω湍流模型及Schnerr-Sauer空化模型采用专业流场仿真软件对机械密封端面螺旋槽液膜进行流场模拟研究,对比分析层流和湍流2种流态下不同螺旋槽几何参数和操作参数对密封稳态性能以及空化区域面积的影响。研究结果表明：端面螺旋槽液膜密封在湍流状态下的开启力、泄漏率以及空化面积比均大于层流模型下的值,且随着几何参数和工况参数的变化,层流效应和湍流效应对密封开启力、泄漏率以及空化面积比的影响规律基本相似;在不同条件下,螺旋槽外径侧更容易产生空化效应,且湍流效应下的空化区域明显大于层流效应下的值。研究表明在端面螺旋槽液膜密封中,湍流效应和空化效应对密封稳态性能的影响不可忽略。     

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。     

基于泛函的动压轴承型线集成理论研究

为了得到通用的优化模型,对动压轴承型线数学表达式的本质特点进行了研究.分析了动压轴承产生动压润滑的几何关键因素--楔形间隙的几何条件,结合傅里叶级数的解析特性,提出用傅里叶级数表示动压轴承型线的广义泛函方程,并用此方程详细分析了几种典型动压轴承型线,证明了此广义泛函的正确性.得到的广义泛函集成型线方程突破了动压轴承型线数学模型固有特性的限制,由此可研究表征动压轴承型线本质特征的根本因素.     

Incompressible and Analytical Study on an Out-Pump Type Complex Thrust Gas Bearing

ABSTRACT

The structure of an out-pump type thrust gas bearing was described, and an analytical model was developed under completely incompressible condition. The objectives were to investigate the coupling between aerodynamics and aerostatics in a complex thrust gas bearing and to improve the performance of the bearing. The model showed that the load-carrying capacity had five parts to it and that apparently there were pressure coupling and structure coupling between aerodynamics and aerostatics. The surface feature function was identically positive: it increased the load-carrying capacity greatly. There was also no limit regarding the pressure ratio—when the pressure ratio was 0, the load-carrying capacity increased to about 25%.

     

Numerical simulation and experimental research on passive hydrodynamic bearing in a blood pump

The current research of hydrodynamic bearing in blood pump mainly focuses on the bearing structure design.Compared with the typical plane slider bearing and Rayleigh step bearing,spiral groove bearing has excellent performance in load-carrying capacity.However,the load-carrying capacity would decrease significantly with increasing flow rate in conventional designs.In this paper,the special treatment is made to the upper spiral groove bearing to make sure that both the circulatory flowing and load-carrying capacity are high.Three-dimensional computational fluid dynamics(CFD) models in the space between rotor and shaft are developed by using FLUENT software.Effects of groove number,film height and groove depth on load-carrying capacity of the spiral groove bearings are investigated by orthogonal experiment design.The experimental results show that film height is the most remarkable factor to the load-carrying capacity.The variation tendency of load-carrying capacity reveals that the best combination of geometry is the one with groove number of 8,film height 0.03 mm and groove depth 0.08 mm.The velocity and pressure distributions in spiral groove bearings are also analyzed,and the analysis result shows that the distributions are in conformity with the design of the blood pump based on the principle of hydrodynamic bearing.The displacement of the rotor with the best combination parameters is tested by using laser displacement sensors,the testing result shows that the suspending performance is satisfactory both in axial and radial directions.This research proposes a bearing design method which has sufficient load-carrying capacity to support rotor as an effective passive hydrodynamic bearing.     

螺旋槽狭缝节流动静压气体止推轴承静态特性

为优化动静压气体止推轴承的承载特性,设计一种具有螺旋槽和狭缝节流器结构的动静压气体止推轴承,采用Fluent对轴承静态特性进行仿真分析,通过改变主轴转速、供气压力,研究气膜厚度、螺旋槽宽度、狭缝厚度等参数对轴承静态特性的影响。结果表明:相对狭缝节流止推轴承,增加螺旋槽结构可以提升轴承的动压效应增强,从而提升轴承的承载力和刚度;相同条件下,气膜厚度越大,轴承的承载力和刚度越小;主轴转速和供气压力增加,承载力和刚度均提升明显;螺旋槽宽度增加,轴承的承载力和刚度先增大后减小;狭缝厚度增大,轴承的承载力先增大后不变,刚度先增加后减小;狭缝深度提升,轴承的承载力减小,刚度先增大后减小。     

The influence of the molecular mean free path on spherical thrust gas bearing performance

The performance of a spherical thrust gas bearing under slip flow conditions was investigated and it was shown that as the ratio of the mean free path to the minimum film thickness increased the bearing load-carrying capacity and the lubricant mass flow rate increased while the frictional torque decreased. The effect is more pronounced at lower values of inlet pressure and film thickness.     

Numerical analysis on nanoparticles-laden gas film thrust bearing

Nanoparticles can be taken as additives and added into various fluids to improve their lubricating performances. At present, researches in this area are mainly concentrated on the improvement effects of nanoparticles on the lubricating performances of liquid such as oil and water. Nanoparticles will also affect gas lubrication, but few related studies have been reported. Nanoparticles-laden gas film (NLGF) is formed when adding nanoparticles into gas bearing. Then, the lubricating performances of gas bearing including pressure distribution and load-carrying capacity will change. The variations of pressure distribution and load-carrying capacity in nanoparticles-laden gas film thrust bearing are investigated by numerical method. Taking account of the compressibility of gas and the interactions between gas and nanoparticles, a computational fluid dynamics model based on Navier-Stokes equations is applied to simulate the NLGF flow. The effects of inlet nanoparticles volume fraction and orifice radius on film pressure distribution and load-carrying capacity of the NLGF are calculated. The numerical calculation results show that both of the film land pressure and the maximum film pressure both increase when the nanoparticles are added into gas bearing, and the film pressures increase with the rising of the inlet nanoparticles volume fraction. The nanoparticles have an enhancement effect on load-carrying capacity of the studied bearing, and the enhancement effect becomes greater as the film thickness decrease. Therefore, nanoparticles can effectively improve the lubricating performance of gas bearing. The proposed research provides a theoretical basis for the design of new-type nanoparticles-laden gas film bearings.     

Incompressible and Analytical Study on Load-Carrying Capacity of a Complex Thrust Gas Bearing

ABSTRACT

A type of aerodynamic/aerostatic complex thrust gas bearing was presented in the investigation of the coupling between aerodynamics and aerostatics with the objective of further improving the performance of the thrust gas bearing. Its analytical model was also set up completely under incompressible conditions. Based on this model, the load-carrying capacity function apparently included pressure and structure coupling items. However, this structure cannot be used when the pressure ratio of the complex gas bearing is less than 1.

     

The simultaneous effects of inertia and temperature on the performance of a hydrostatic thrust bearing

An analytical investigation was made of the simultaneous effects of inertia and temperature on the performance of a parallel stepped hydrostatic thrust bearing. Expressions for pressure profile and load-carrying capacity were obtained under conditions of adiabatic flow. Numerical results for pressure distribution and load-carrying capacity were obtained at different step positions and film thickness ratios for several values of thermal conductivity.     

双槽阶梯槽干气密封性能研究

针对干气密封系统在高转速工况下密封性能差、泄漏量大的问题,提出一种双槽阶梯槽端面密封结构.采用CFD对比分析不同压力、转速下单螺旋槽、双槽阶梯槽、阶梯槽3种槽型的密封性能,探讨槽深、螺旋角对密封性能的影响,得出了双槽阶梯槽型优化的结构参数.结果表明:双槽阶梯槽在降低泄漏量和提高综合密封性能上要优于阶梯槽和单螺旋槽;在槽...     

Modeling of Gas Thermal Effect Based on Energy Equipartition Principle

In the present article, a gas thermal effect is modeled based on the energy equipartition principle. Two new independent state equations for an ideal gas are developed that provide a new way to analyze thermal effects in gas lubrication. Furthermore, the energy equation is derived for gas lubrication and the analysis of thermal effects is carried out on a gas spiral thrust bearing and a gas hydrostatic journal bearing. The results show that gas temperature increases significantly in the lubricated region at high speed for both the thrust and hydrostatic journal bearings, and the thermal effect positively influences the load capacity of the thrust bearing. The gas expansion effect makes the gas temperature decrease in the hydrostatic journal bearing, and the gas temperature decreases with an increase in the inlet pressure.     

弹性箔片动压气体推力轴承承载性能研究

气弹耦合解是准确预测弹性箔片动压气体轴承承载性能的有效方法。通过引入箔片的弹性变形以及联立求解动压气体润滑Reynolds方程和弹性箔片的变形方程,给出了弹性箔片动压气体推力轴承的气弹耦合解。应用气弹耦合解理论,将顶层箔片的局部弹性变形纳入考虑范围,对弹性箔片动压气体推力轴承的承载性能进行了计算和分析。有限元数值仿真结果表明:顶层箔片在气膜压力作用下的局部弹性变形直接导致弹性箔片动压气体推力轴承承载能力的降低;根据轴承瓦块上气膜压力分布的特点合理设计支承拱箔的结构形式,可以减小顶层箔片的局部弹性变形,有效提高轴承的承载能力。得到了一种承载能力较高的弹性箔片动压气体推力轴承支承拱箔结构设计方案。