Elastohydrodynamic properties of water-based fire-resistant hydraulic fluids

The elastohydrodynamic (ehd) lubricating properties of commercial fire-resistant hydraulic fluids in rolling point contacts are described. Earlier work is reviewed and new work presented on water-in-oil and oil-in-water emulsions. It is shown that in general, elastohydrodynamic film thicknesses of water-in-oil emulsions are close to those of their base oils. For very fine particle size emulsions, however, thicker films are observed. Commercial oil-in-water emulsions in fully flooded conditions have not been found to give measurable elastohydrodynamic films. However, when the emulsions are destabilized, a localized pool of oil collects in the contact zone which enables ehd films to form, though these films do not survive very high rolling speeds. Polyglycol solutions give low ehd film thicknesses, approximately one third those of mineral oils of corresponding viscosity. This can be attributed to the low pressure—viscosity coefficient of these solutions.     

Some health aspects of infections in oil and emulsions

A variety of potential health hazards associated with microbial infections of cutting oils have been postulated. This paper deals particularly with the inhalation of infected aerosols from such emulsions. An Andersen sampler detected up to 70000 viable bacteria/m³ of air 0.6m from a grinding machine in a machine shop, but this level decreased substantially further from the machine toolsPseudomonas aeruginosa, an accepted opportunistic pathogen, was present in the emulsions in the sumps and was detected in the air. However, when nasal swabs and sputum samples from 38 men were examined there was no indication that the respiratory tract had been colonised by Pseudomonas spp. It is suggested that the spoilage bacteria in the emulsions rapidly lose viability in an aerosol. The droplets however, are of a respirable size and dead bacteria may evoke respiratory response. Animal experiments indicated that infected emulsions exacerbate lung inflammation, serological responses and skin irritation     

Effects of water in oil and oil in water on single-phase flowmeters

The effect of two-phase flow on the performance of a range of single-phase flowmeters has been investigated experimentally using the National Standard Multiphase Flow facilities at NEL. The flowmeters tested were 2-inch and 4-inch positive displacement meters, venturi meters, helicoidal and flat-bladed turbine meters, 2-inch U-tube, 3-inch and 1.5-inch straight tube Coriolis meters and a 4-inch vortex shedding meter. The flowmeters were tested in oil flow with water and water flow with oil. The second component fractions were varied from 3% up to 15% by volume. The aim of the project was to quantify the effect of second-phase fluid components on the basic uncertainty of a range of single-phase. These tests have provided evidence of the suitability of particular flowmeters for two-component flow applications. Comparisons have been made between generic type and size of flowmeter. The oil-in-water and water-in-oil tests indicated that the uncertainty in the outputs of the flowmeters tested were generally within ±1% relative to the reference flowrates, although some errors as high as 5–10% were also observed. Most of the measurements from the turbine flowmeters and the positive displacement flowmeters were within ±0.4% of the reference flowrates.     

Elastohydrodynamic effects in elliptical bearings

In this paper the effect of bearing deformation on the static and dynamic performance characteristics of an elliptical bearing is presented. The finite element method has been used to solve the three-dimensional Navier-Stokes and the continuity equations governing the lubricant flow in the clearance space of the journal bearing and the three-dimensional elasticity equations governing the displacement field in the bearing shell. The static and dynamic performance characteristics are presented at various eccentricities for a wide range of deformation coefficient values which take into account the flexibility of the bearing liner.     

The Mapping of Elastohydrodynamic Contacts

The paper describes an interferometric method of determining the shape and thickness of the clastohydrodynamic oil film formed between a rotating ball loaded against a diamond, sapphire, or glass plate, and a rotating roller loaded against a glass plate. The film shape for both point and line contact is found to depend critically on speed and load. It is found that considerable departure from the static Hertzian shape occurs at quite low speeds. The line contact results show the extent of the end closure and its dependence on the blend radius of the roller.     

Rheology of Perfluoropolyalkylether Fluids in Elastohydrodynamic Lubrication

The rheological characteristics of two branched and two linear, commercial perfluoropolyalkylether (PFPAE) fluids were studied under high pressures and temperatures. The effects of branching and carbon-to-oxygen (C:O) ratio on the pressure-viscosity-temperature behavior and on the non-Newtonian behavior of these fluids were studied experimentally under high pressures and temperatures. The branching and the higher C:O ratio seemed to increase the pressure-viscosity coefficients of these fluids. The effects of the viscosity and the pressure-viscosity coefficient on the capabilities of these fluids to generate elastohydrodynamic lubrication (EHL) film thickness were studied and compared with experimental measurements. All of the fluids studied seemed to follow the Roelands viscosity model and classical EHL theory (1). The C:O ratio also influenced the temperature dependence of the limiting-shear-strength proportionality constant. The results show that for similar-viscosity fluids, the linear PFPAE with higher C:O ratio is most desirable for wide temperature use.     

Experimental Study of Elastohydrodynamic Lubrication

This paper describes experimental measurements of the conditions occurring in the conjunctive region of two lubricated cylindrical disks which roll or roll and slide on their peripheral surfaces under load. The results of these measurements are compared with those of the recent elastohydrodynamic theory, including thermal effects. The measured quantities include lubricant film pressure distribution, surface temperature distribution, and the shape and thickness of the lubricant film, all measured in the direction of rolling. The results suggest several improvements and modifications of the thermal elastohydrodynamic theory including an improved analysis of the inlet region and modification of the lubricant rheological model to include effects of shear or time dependence.     

Elastohydrodynamic lubrication of line contacts

Elastohydrodynamic film thickness measurements for rolling line contact under fully flooded and starved conditions have been made using optical interferometry. From the results it was found that the film shape at the end of the roller becomes more parallel as lubricant starvation increases.

Two main regions of starvation have been studied, namely progressive and catastrophic regions of lubricant starvation. Furthermore, it was found that the severity of conditions within the hertzian contact increases rapidly as m decreases and dry contact conditions are approached. It has been possible to express the dimensionless inlet distance for catastrophic and progressive lubricant starvation conditions respectively as

It has been concluded that the experimental dimensionless central and minimum film thicknesses under starvation conditions can be written respectively as      

Mapping Shear Stress in Elastohydrodynamic Contacts

A new method has been, devised for investigating the theological properties of lubricant films in two-dimensional EHD contacts. A lubricated, sliding contact is produced between a sapphire flat and a steel ball. Thermal infrared emission microscopy is then employed to obtain 2-D maps of the variation of temperature rise due to friction across the contact. These maps are then used in conjunction with moving heal source theory to produce maps of energy dissipation and thus shear strength, of the lubricant film across the contact.

A series of mixtures of two lubricants, one giving high traction and one with low traction, have been studied using this technique to investigate the influence of lubricant, blending on shear stress and traction.     

Formulas Used in Thermal Elastohydrodynamic Lubrication

A numerical solution to the problem of thermal compressible elastohydrodynamic lubrication of rolling/sliding contacts has been tested over a wide range of operating parameters consisting of dimensionless load, speed, slip, and material parameters. A least squares exponential curve fit was used to develop simple formulas for the amplitude and location of the pressure spike, the minimum film thickness, and the maximum lubricant temperature as a function of the operating parameters. These equations can be used to evaluate parameters affecting the performance of rolling/sliding heavily loaded lubricated contacts.     

Elastohydrodynamic lubrication of piston rings

A non-linear finite-element scheme, based on the Newton-Raphson-Murty algorithm, was used to analyze the problems of piston rings according to theories of both elastohydrodynamic and hydrodynamic lubrication. The maximum film pressure and the minimum film thickness were obtained and depicted as functions of the crank angle. For hydrodynamic lubrication the results obtained were compared with those found using the method suggested by Dowson and Ruddy; there was good consistency between them. In this way the accuracy and reliability of the proposed method are demonstrated. Furthermore, the results evaluated using the theory of elastohydrodynamic lubrication give a larger minimum oil film thickness and a flatter pressure distribution than those evaluated using the theory of hydrodynamic lubrication.     

油份在线分析仪在排放水水质监测中的应用

介绍了炼油厂排放水水质监测用油份在线分析仪的选型、验收和运行情况,以及在线分析数据与实验室分析数据的对比结果.实验说明,油份在线分析仪在排放水水质监测中的应用情况良好,可提高对排放水水质的监控力度.     

节电滤波器(TVSS)在油田注水系统中的应用

介绍了SP系列节电滤波器的节电原理、特点及改造后的投资效益，说明了SP系列节电滤波器对抑制瞬流具有的瞬时态、高频次、高电压危害的效果。     

Compression Heating and Cooling in Elastohydrodynamic Contacts

In this study, the infrared temperature mapping technique, originally developed by Sanborn and Winer (Trans ASME J Tribol 93:262–271, 1971) and extended by Spikes et al. (Tribol Lett 17(3):593–605, 2004), has been made more sensitive and used to study the temperature rise of elastohydrodynamic contacts in pure rolling. Under such conditions lubricant shear heating within the contact is considered negligible and this allows temperature changes due to lubricant compression to be investigated. Pure rolling surface temperature distributions have been obtained for contacts lubricated with a range of lubricants, included a group I, and group II mineral oil, a polyalphaolefin (group IV), the traction fluid Santotrac 50 and 5P4E, a five-ring polyphenyl-ether. Resulting maps show the temperature rise in the contact increases in the inlet due to compression heating and then decreases and in most cases becomes negative in the exit region due to the effect of decompression. Temperature changes increase with entrainment speed but in the current tests are always very small, and less than 1 °C. Contact temperature rises from compression were compared to those from sliding contacts (where a slide-roll ratio of 0.5 was applied). Here the contribution to the contact temperature from compression is shown to decrease dramatically with entrainment speed. The lubricant 5P4E is found to behave differently from other lubricants tested in that it showed a peak in temperature at the outlet. This effect becomes more pronounced with increasing speed, and has tentatively been attributed to a phase change in the exit region. Using moving heat source theory, the measured temperature distributions have been converted to maps showing rate of heat input into each surface and the latter compared with theory. Qualitative agreement between theory and experiment is found, and a more accurate theoretical comparison is the subject of ongoing study.     

Elastohydrodynamic Lubrication in a Gyratory Rock Crusher

The highly loaded gyrating contact in the top bearing of a gyratory rock crusher is analyzed and found to operate in the elastohydrodynamic lubrication regime. The analysis is of interest from a number of viewpoints:

(a) The contact rotates around the bush as the crusher gyrates, creating a rolling contact of high speed.

(b) The elliptical contact is aligned with its long axis parallel to the rolling direction, which is unusual.

(c) Due to high loads and large radii, the elastic contact ellipse is very large (39.2 cm × 10.5 cm) by EHL standards.

(d) The calculated film thickness is of the order of 20 μm which is large in EHL terms, but leads to a low λ value of 0.15 when compared with roughness extrapolated to a cut-off length of twice the contact length as recommended in the literature. The bearing has been operating without distress for a year which is at variance with the low λ value.     

凸轮的弹性流体动力润滑的探讨

本文应用弹性流体动力润滑理论,探讨了凸轮机构形成弹性流体动力润滑的条件。     

Thermal Elastohydrodynamic Lubrication of Ceramic Materials

ABSTRACT

The effect of thermal conductivity on point elastohydrodynamic lubrication (EHL) contacts was discussed with representative engineering ceramics and steel by a non-Newtonian thermal EHL analysis. Through this investigation, fundamentals of EHL characteristics of contact surfaces composed of different thermal conductivities were generally revealed and a combination of optimum ceramic materials has been proposed. Furthermore, when the contacting materials are the same, it has been pointed out that the equivalent elastic modulus should be rather small and the thermal conductivity of the contact material should be high to obtain a thick overall film thickness and low film pressure.     

线接触热弹流润滑的数值分析

基于Ree—Eyring流变模型，建立线接触热弹流润滑方程，通过数值计算得出了载荷参数、速度参数、材料参数和滑滚比对于二次压力峰、最小油膜厚度和最大油膜温度的重要影响。     

弹流润滑状态下润滑剂的边界滑移问题

根据大量的实验事实和观察,本文对润滑剂中极性分子与金属界面间相互作用作了初步分析,从而提出了弹流润滑状态下润滑剂在固液界面发生滑移的力学模型,并分析了由于润滑剂在边界滑移对弹流润滑性能的影响。结果表明边界滑移是造成弹流润滑油膜破裂的关键因素。     

Occurrence of Wall Slip in Elastohydrodynamic Lubrication Contacts

Preliminary experimental work has been carried out to identify some of the boundary slip phenomena of highly pressurised polybutenes in an elastohydrodynamic lubrication (EHL) conjunction. The movement of the oil is signified using an entrapment that can be readily formed by the impact of a steel ball against a layer of oil on a glass block in an optical EHL test apparatus. The post-impact lateral movement of the entrapment was investigated under the conditions: (i) pure rolling, (ii) pure glass block sliding (steel ball stationary) and (iii) pure ball sliding (glass block stationary). It was observed that under pure rolling the entrapped oil travels within the contact region at the entrainment speed, which is correlated with EHL theory. Under pure glass block sliding conditions, the speed of the entrapped oil core is less than the entrainment speed, and in the extreme cases, this core can be nearly stationary. Under pure ball sliding conditions, the oil core moves at a speed greater than the entrainment speed. The observation indicates that the oil/steel ball interface can sustain higher shear stress than the oil/glass (chromium coated) interface and there is a boundary slip in terms of relative sliding at the latter interface under the experimental conditions. Furthermore, the amount of slip increases with an increase in the pressure. These experiments provide evidence of the existence of wall slippage, which leads to the abnormal EHL film profile characterised with an inlet dimple as reported earlier.