Modelling of non-laminar phenomena in high reliability hydrostatic seals operating in extreme conditions

A numerical study of hydrostatic seals is presented. The theoretical model takes account of the transition to turbulence and inertia effects in the lubricant fluid film. The thermo-elastic deformations of the seal faces and heat transfer are considered using influence coefficient matrices. To obtain a good correlation between numerical simulations and measurements taken in French nuclear power stations, it is necessary to deal with entrance and exit pressure losses. It is shown that the seal operates in a laminar or near turbulent flow regime, depending on the inlet temperature.     

基于频谱的篦齿轴向窜动与叶尖间隙测量方法

航空发动机低压涡轮带冠叶片篦齿和机匣之间的叶尖间隙参数以及篦齿轴向窜动参数的在线高精度测量是保证涡轮发动机安全运作和气动效率的关键。传统的电容式叶尖间隙测量系统对噪声敏感度大,且不能对篦齿的轴向窜动参数同时进行测量。因此研制了一种“人”字形电容传感器,提出了一种基于频谱的篦齿叶尖间隙参数和轴向窜动参数的提取方法。建立了“人”字形电容传感器测量模型。仿真分析了测量信号的幅度谱特征并提出了一种最优谱线选择方法。提出了基于转速和信号特征频率估计的自适应频域滤波,信号整周期等角度采样,幅度谱估计以及二元多项式曲面拟合相融合的信号处理方法,实现了叶尖间隙参数和轴向窜动参数的动态测量。在实验室环境下搭建了篦齿叶尖间隙参数和轴向窜动参数测试实验平台,完成了标定和测量实验。实验结果显示,篦齿盘工作在1 900 r/min以下时,测量系统在0.5～1.5 mm叶尖间隙及±1 mm轴向窜动范围内,叶尖间隙测量精度达18μm,轴向窜动测量精度达30μm。     

流体密封技术

流体密封作为一门新兴的工程技术学科正越来越受到各行业的关注。本文对流体密封的定义、作用、重要性、分类、涉及的主要学科、主要应用领域以及最新进展作一简单介绍，并阐述了高速透平压缩机轴封经历的四个发展阶段：迷宫密封、浮环密封、机械密封、干气密封。干气密封是最先进的轴端密封形式，已在炼油、化工等行业高速透平压缩机上得到越来越广泛的应用。     

Reciprocating seals

Some of the fundamental work on reciprocating seals is reviewed and ways in which the results can be used in the practical choice of seal types and of seal materials for specific applications are considered. Variation of seal performance from one application to another is discussed     

带阻尼套筒的篦齿封严结构模态计算方法研究

这里采用波传播技术对带阻尼套筒的篦齿封严结构进行了振动特性的计算分析,通过建立接触面刚度矩阵来模拟阻尼套筒对篦齿封严结构固有振动特性的影响,对各参数进行无量纲处理,使所得结论具有通用性效果。     

透平压缩机迷宫密封泄漏量的数值仿真研究

给出了适用于透平压缩机迷宫密封泄漏量的修正模型,并用修正模型对变结构参数下的泄漏量进行规律研究.通过采用工程常用迷宫密封泄漏量理论公式,计算了不同压比下透平压缩机典型平滑型和曲折型迷宫密封流量系数,对比了试验结果,修正了流量系数值;在此基础上,进一步研究了不同间隙和齿数下泄漏量的规律,以研究参数变化对泄漏量的影响.研究结果表明:对于平滑型密封结构,修正模型的修正系数可选择在0.8~1.2;对于曲折型密封结构,修正模型的修正系数可选择在0.7~0.8.本文提供了一种较为准确、工程性的透平压缩机迷宫密封泄漏量模型的修正系数.     

A transient 2D-finite-element approach for the simulation of mixed lubrication effects of reciprocating hydraulic rod seals

This paper presents a method for the computation of soft elasto-hydrodynamic lubrication (EHL) based on the strong coupling of a non-linear finite-element model with the transient Reynolds equation for thin fluid films. This approach allows the usage of arbitrary non-linear elastic or inelastic material models for the finite deformations. The transient Reynolds equation is simultaneously solved within a finite-element computation. In order to account for the effect of surface roughness in the sealing contact, flow factors are incorporated into the transient Reynolds equation. The method is currently restricted to planar or axisymmetric geometries.     

Inter-asperity cavitation and global cavitation in seals: : an average flow analysis

A universal, average Reynolds equation was previously developed to model the combined effects of inter-asperity cavitation and global cavitation in lubricating films between rough surfaces. In this study, the universal, average Reynolds equation is applied to two types of rotating shaft seals: lip seals and mechanical face seals. Inter-asperity cavitation is shown to affect the sealing mechanism of lip seals and to influence the behavior of new, worn, and wavy mechanical face seals.     

电液锤活塞密封窜漏的原因分析及改进

电液锤液气缸活塞密封采用由PTFE制造的格莱圈密封,在使用中液压油会窜入气腔,导致气体压力升高。本文分析了由于缸体膨胀、密封失效而发生窜漏的两种原因,即液膜流过密封环时在气腔积聚和收锤造成的压力冲击。并提出了在格莱圈后安装Yx圈的改进措施。     

Stability of stationary and rotating discs under edge load

The dominant dynamic instability mechanism in circular cutters, grinding wheels and the like is a moving load resonance excited by a constant transverse load at the “critical rotation speed.” The critical speed theory is extended here to include the effects of concentrated in-plane edge loads similar to loading occurring in engineering processes. The theoretical analysis shows the critical speed is only sensitive to edge load when the resonance mode and the mode of static edge load buckling are identical. This always occurs with large edge load, but it is not the case with the smaller edge loads typical of engineering processes. These analyses are confirmed through prediction and measurement of static buckling loads for centrally clamped discs with in-plane, concentrated loads inclined between 0° and 80° to the edge normal.     

Tribological behavior of PEEK-based materials under mixed and boundary lubrication conditions

In modern industries, more and more mechanical components are exposed to mixed and even boundary lubrication conditions, inducing fast wear and even scuffing of the motion systems. In order to enhance the lifetime and reliability of the motion systems, replacing metal–metal friction pairs by metal–polymer ones can be one of the most effective approaches. The present work focuses on tribological behavior of pure polyetheretherketone (PEEK) and a formulated PEEK composite lubricated with diesel and engine oil. It was demonstrated that in mixed and boundary lubrication regimes the structure of PEEK materials affect significantly the tribological performance. Formation of a tribofilm on the surface of metallic counterbody plays an important role on the tribological behavior of the PEEK-based materials.     

The behaviour of friction modifiers under boundary and mixed EHD conditions

The behaviour of a range of model and commercial friction modifiers (FMs) has been evaluated under elastohydrodynamic (EHD) and boundary lubrication conditions. Using a series of long‐chain carboxylic acids, it has been shown that measured boundary friction coefficients (BFCs) decrease with increasing chain length, unsaturation level, temperature, and concentration. Base oil polarity was found to have no effect under these conditions. Commercial oleate esters in synthetic base fluids gave lower BFCs than nitrogen‐containing compounds under the same conditions. This difference was observed over a range of concentrations and temperatures. The friction performance of formulated oils under mixed and full‐film EHD conditions was found to be dependent on FM, base oil, and detergent type. Under boundary conditions, friction was found to vary with FM type, but the effect of changing the base oil and the detergent system was negligible.     

迷宫式最小流量调节阀的设计及应用

论述了迷宫式最小流量调节阀的结构特点、工作原理和主要部件的设计。     

Experimental and numerical evaluation of contact pressure in pneumatic seals

An experimental procedure is presented for measuring contact pressure between a pneumatic seal and its counterface. Measurements were performed using pressure-sensitive films, for which a suited calibration procedure was developed, also taking into account humidity influence. Having validated the experimental procedure on a lip seal rectilinear specimen, tests were carried out on commercial piston seals. Results were compared with those coming from numerical simulations performed using a finite-elements analysis.     

往复式机械密封的防漏设计计算

针对往复式机械密封的泄漏问题，通过对其流体动力学分析和计算，推导了泄漏量的计算公式，研究分析了影响泄漏量的设计因素。     

错齿式迷宫密封流场及泄漏量的数值分析

以某型大功率机车传动齿轮箱轴端迷宫密封为研究对象,采用GAMBIT软件建立错齿式迷宫通道的二维结构化网格模型,应用FLUENT软件模拟迷宫密封腔内流场分布及泄漏特性,分析转速、压比、空腔尺寸对迷宫密封性能的影响.研究结果表明:泄漏量随着进出口压比的增加而增加;转速对泄漏量影响很小;空腔尺寸对密封性能的影响较大.     

迷宫密封流场与泄漏特性研究

应用Fluent软件计算迷宫间隙、齿厚、空腔深度和不同齿型对迷宫密封流场和泄漏量的影响。计算结果表明:迷宫密封泄漏量随间隙宽度呈线性变化;随着密封齿厚度的增加,泄漏量相对减少,泄漏量按线性关系变化;对于空腔深度而言,空腔深度越大,紊流程度下降,泄漏量越大;对不同齿型,半圆形密封齿泄漏量最大,其次是弧形齿,在实际应用中应多使用直齿,梯形齿和三角齿,以减少泄漏量。本研究可为迷宫密封设计与应用提供依据。     

Experiments on magnetic fluid rotary seals operating under vacuum conditions

Magnetic fluid rotary vacuum seals have been shown to be effective in machinery operating in a vacuum chamber. Such seals have the advantages of simple design, zero leakage at almost any rotation speed, and low friction. They have no wear and require no maintenance. This paper presents results obtained from experimental investigations of the operation of magnetic fluid rotary seals under vacuum conditions. The paper discusses the test apparatus and the seals used, the test conditions, and the procedure. The experimental results show characteristic phenomena observed in magnetic fluid rotary vacuum seals, including changes in vacuum pressure, temperature, and frictional moment dependent on the rotation speed of the shaft, number of sealing stages, height of the sealing gap, and mean magnetic flux density in the sealing gap.     

燃机曲折型迷宫密封的泄漏特性研究

以F级燃气轮机中曲折型迷宫密封为研究对象,对其内部流场和泄漏特性进行数值模拟,研究密封间隙、压比对迷宫密封泄漏特性的影响。结果表明：在相同密封间隙下,泄漏量随着压比的提高而增加;相同压比下,泄漏量随着密封间隙的减小而减少。基于数值计算结果,对现有迷宫密封泄漏量计算公式进行修正,建立曲折型迷宫密封的泄漏量计算公式。该公式计算结果与CFD数值模拟结果吻合很好,和同类公式相比,能够更为精确地计算该类型密封结构的泄漏量。     

液压缸活塞杆密封泄漏原因分析与措施

从活塞杆密封结构和受力着手分析液压缸活塞杆密封失效的实例,找出密封型式不当是液压缸活塞杆密封泄漏的主因;液压油夹带气体,则加速了密封的失效。