采用计算化学方法解析苯和甲苯红外谱图

本研究应用量子计算化学软件Gaussian 03W HF方法中的3-21G基组优化苯和甲苯分子结构,预测苯和甲苯分子的红外光谱。找到苯环振动吸收峰分别是苯红外图中的1658 cm~(-1)与甲苯红外图中的1667 cm~(-1)。与苯和甲苯文献检索红外谱图相对应(特征吸收峰分别是1478和1485 cm~(-1)),符合较好。还找到苯环C-H拉伸振动吸收峰3080cm~(-1)(苯)和3040 cm~(-1)(甲苯)。能够实用于红外法检测环境中苯和甲苯。     

Viscoelasticity and solution viscosity of perfluoropolyether lubricants

Viscoelastic characteristics including the viscosity, storage modulus, and loss modulus of perfluoropolyether (PFPE) lubricants with reactive endgroups are examined via a rotational rheometer. Both temperature and molecular weight effects on rheological properties are extensively analyzed via the Rouse theory in polymer dynamics. The modified Cole–Cole plots for storage modulus vs. loss modulus exhibits the presence of microstructures due to the interaction among PFPE endgroups. To examine the solvent effect during the dip-coating process, we examined the intrinsic viscosity, or Huggins coefficient for dilute PFPE solutions, which depends on the aspect ratio of PFPE cluster and potential energy among PFPE molecules. We also correlated the viscoelastic data with the tribological data.     

Analysis of viscosity effect on turbine flowmeter performance based on experiments and CFD simulations

Viscosity effect is one important factor that affects the performance of turbine flowmeter. The fluid dynamics mechanism of the viscosity effect on turbine flowmeter performance is still not fully understood. In this study, the curves of meter factor and linearity error of the turbine flowmeter changing with fluid viscosity variations were obtained from multi-viscosity experiments (the viscosity range covered is 1.0×10^–6 m²/s–112×10^–6 m²/s). The results indicate that the average meter factor of turbine flowmeter decreases with viscosity increases, while the linearity error increases. Furthermore, Computational Fluid Dynamics (CFD) simulation was carried out to analyze three-dimensional internal flow fields of turbine flowmeter. It was demonstrated that viscosity changes lead to changes of the wake flow behind the upstream flow conditioner blade and the flow velocity profile before fluid entering turbine rotor blade, which affect the distribution of pressure on the rotor blades, so impact the turbine flowmeter performance.     

The effect of thermal degradation on the non-newtonian viscosity of an aqueous polyacrylamide solution

The objective of the present study was to investigate the effect of thermal degradation on the non-Newtonian viscosity of a dilute polymer solution by measuring the viscosity at a reference temperature before and after heating the solution with different heating temperatures and duration. The test solution was a polyacrylamide (Separan AP-273) 1,000 wppm solution in distilled water. The effect of thermal degradation on the viscosity was greater at relatively low shear rates than at intermediate and high shear rates. The viscosity of the polyacrylamide solution experienced at a relatively high temperature decreased more than that experienced at a relatively low temperature. In addition, the effect of thermal degradation on the viscosity of the polyacrylamide solution showed a strong dependence on the duration of heating.     

Fractionation of liquid lubricants at solid surfaces

The film-forming properties of lubricant base fluid mixtures in elastohydrodynamic contacts have been studied using ultrathin film interferometry. It has been shown that in binary mixtures where one of the components is more polar than the other, the EHD film thickness formed in the very thin film (< 10 nm region) is controlled by the viscosity of the polar component rather than the viscosity of the blend. This means that a mixture of a highly viscous ester in less viscous hydrocarbon gives thicker than predicted lubricant films in the sub 20 nm region and vice versa. This phenomenon can be ascribed to the fractionation of the lubricant mixtures close to the surface caused by lubricant molecule/surface van der Waals forces.     

The temperature, pressure and time dependence of lubricant viscosity

The general form of the pressure (Proc. Am. Acad. Arts Sci. 77 (1949) 117) and temperature (Physical properties of molecular crystals, liquids and glasses (1968) 350) dependence of viscosity has been known for at least 50 years. Viscosity varies with temperature in a greater than exponential manner and temperature–viscosity equations generally allow for an unbounded viscosity at some characteristic temperature. At high-pressures the pressure–viscosity response is likewise greater than exponential, often following a less than exponential response at low-pressures. In spite of this known behavior, tribologists working in EHL have generally assumed less than exponential pressure response as a means of applying the Eyring stress aided thermal activation theory to the viscous regime of EHL traction. As justification, time dependence of the lubricant properties in the response to a pressure transient has been advanced. We present acoustic, capillary and impact measurements for timescales less than EHL. While time dependence of properties may be important in the viscoelastic regime of traction, this paper will show that for the timescale of viscous response, a significant time dependence of viscosity is unlikely.     

Performance of flexible shell journal bearings with variable viscosity lubricants

In heavily loaded rotating machines, both the deformation of the elastic bearing shell and the dependence of lubricant viscosity on pressure become significant and may result in an appreciable change in the performance of the journal bearing system. In this paper, stable solutions for bearing deformation and the lubricant flow field are obtained which combine the effects of the elastic deformation of the bearing shell with the pressure-viscosity dependence of the lubricant. Two elastic models were tried for deformation calculations in the bearing. One which was computationally economical and consistent in accuracy was adopted for the detailed computation. The effects of bearing deformation on the performance characteristics of the journal bearing system are reported for both isoviscous and variable viscosity lubricants.     

The surface chemistry of alkyl and arylphosphate vapor phase lubricants on Fe foil

The surface chemistry of tributylphosphate (TBP) and tricresylphosphate (TCP) on a polycrystalline Fe surface was studied using temperature programmed reaction spectroscopy and Auger electron spectroscopy to illustrate some of the initial steps in the reaction mechanisms of alkyl and arylphosphate vapor phase lubricants. During heating, TBP [(C₄H₉O)₃P=O] adsorbed on the Fe surface decomposes via C–O bond scission to give butyl surface intermediates [C₄H₉–] that react via β-hydride elimination to desorb as 1-butene [CH₃CH₂CH=CH₂] and H₂ without appreciable carbon deposition onto the surface. The thermal decomposition of 1-iodobutane [I-C₄H₉] on Fe was observed to proceed via the same β-hydride elimination mechanism. In contrast to tributylphosphate, meta-tricresylphosphate (m-TCP) [(CH₃–C₆H₄O)₃P=O] decomposes on Fe via P–O bond scission to produce methylphenoxy intermediates [CH₃–C₆H₄O–]. During heating to 800 K, methylphenoxy intermediates either desorb as m-cresol [CH₃–C₆H₄–OH] via hydrogenation or decompose further to generate tolyl intermediates [CH₃–C₆H₄–]. Some of the tolyl intermediates desorb as toluene [CH₃–C₆H₅] via hydrogenation but the majority decompose resulting in H₂ and CO desorption and carbon deposition onto the Fe surface. The P–O bond scission mechanism of m-TCP was verified by showing that the temperature programmed reaction spectra of m-cresol yield products that are almost identical to those of m-TCP. These results provide insight into the origin of the differences in the performance of alkyl and arylphosphates as vapor phase lubricants. The alkylphosphates decompose via alkyl intermediates that readily undergo β-hydride elimination and desorb into the gas phase as olefins, thus removing carbon from the surface. In contrast, the arylphosphates generate aryloxy intermediates by P–O bond scission and aryl intermediates by further C–O bond scission. Neither of these intermediates can undergo β-hydride elimination and thus they decompose to deposit carbon onto the Fe surface. The higher efficiency for carbon deposition may be the primary reason for the superior performance of the arylphosphates over alkylphosphates as vapor phase lubricants.     

A new focus on the Walther equation for lubricant viscosity determination

Lubricants are widely used in industrial machinery in order to separate solid tribological surfaces and support high loads under severe conditions. In tribological contacts, viscosity plays an important role in the film‐forming abilities of the lubricant, but this property is strongly dependent on temperature. Consequently, small variations in temperature cause appreciable variations in the viscosity of lubricating oils. For this reason it is of practical value to be able to predict viscosity changes with temperature. This paper presents a new focus on the Walther equation to determine the viscosity of commercial lubricants at different temperatures. This new approach provides very good correlation with experimental measurements. Copyright © 2006 John Wiley & Sons, Ltd.     

A strategy for the development of optimised lubricants

The design of lubricants has traditionally relied on the use of single dimension constitution / performance or structure / property relationships. In this paper a strategy is described whereby consideration is given to the inherent property / property (physical and chemical) correlations that exist for fluid lubricants. Progress towards the development of optimised lubricants is then achieved by identifying the molecular structural or compositional traits associated with ‘extensions’ to or ‘deviations’ from the mainstream correlations. Some examples of the success of this novel strategy will be provided, and the directions of its further refinement briefly outlined.     

Measurement of the viscosity of biodiesel by using an optical viscometer

In this paper, we report the characterization of the viscosity of biodiesel produced from jatropha curcas. The viscosity measurement has been carried out by using a modified falling ball viscometer as well as optical technology. The viscosity was measured from 28 to 70 °C, which is the interest for determining the quality of biodiesel. We found that the falling ball optical viscometer offers a resolution of a viscosity measurement of ±0.039 mPa s with a relative error of 1.47933%. The measurement process was compared with a commercial viscometer, and it has been demonstrated that the biodiesel produced in Chiapas has good quality.     

Measurements of blood viscosity using a pressure-scanning slit viscometer

A newly designed pressure-scanning slit viscometer is developed to combine an optical device without refraction while measuring blood viscosity over a range of shear rates. The capillary tube in a previously designed capillary viscometer was replaced with a transparent slit, which is affordable to mount optical measurement of flowing blood cells. Using a pressure transducer, we measured the change of pressure in a collecting chamber with respect to the time, p(t), from which the viscosity and shear rate were mathematically calculated. For water, standard oil and whole blood, excellent agreement was found between the results from the pressure-scanning slit viscometer and those from a commercially available rotating viscometer. This new viscometer overcomes the drawbacks of the previously designed capillary viscometer in the measuring whole blood viscosity. First, the pressure-scanning slit viscometer can combine an optical instrument such as a microscope. Second, this design is low cost and simple (i.e., ease of operation, no moving parts, and disposable).     

Synthesis and characterisation of HSIBR used as viscosity index improver for lubricants

Self‐prepared styrene–isoprene–butadiene rubber (SIBR) was anionically synthesised and modified by a hydrogenation reaction. The hydrogenated SIBR (HSIBR) was used as a viscosity index improver in lubricants due to its improved thermal and oxidative resistance. The precursors and corresponding hydrogenated polymers were characterised by size‐exclusion chromatography, Fourier transform infrared, proton nuclear magnetic resonance (¹H‐NMR) spectroscopy, differential scanning calorimetry and thermal gravimetric analysis. Moreover, the efficiencies of HSIBR as viscosity index improvers for SAE 5W‐30 multigrade oils (150N HG base oil) were studied. The results confirm that adding 1 wt.% of HSIBR markedly increases the specific viscosity of base oil, increases the viscosity index (119 for base oil) up to a value between 158 and 164 and maintains the shear stability well. Furthermore, the HSIBR‐containing oil possesses a high high‐temperature and high‐shear viscosity without destroying its low‐temperature fluidity. Copyright © 2012 John Wiley & Sons, Ltd.     

基于回归分析的零件应力预测方法

提出用回归分析法建立零件最大应力与零件关键尺寸函数关系,并对零件应力随该尺寸变化规律进行预测的方法.以某压力机底座内的承压隔板为例,其方孔到隔板承压面的间距X为变量,用有限元方法分析对应不同X值时方孔圆角处的最大应力Y.在此基础上,用回归分析方法建立最大应力Y随间距X变化的预测方程,并对该方程的预测效果进行检验.结果表明预测结果可信.     

Effect of lubricant viscosity grade on mechanical vibration of roller bearings

This work aims to characterize vibration behavior of roller bearings as a function of lubricant viscosity. Experimental tests were performed in NU205 roller bearings, lubricated with mineral oil of three different viscosity grades (ISO 10, 32 and 68). The mechanical vibration was determined through the processing and analysis of bearing radial vibration data, obtained from each of the lubrication conditions, during 2 h of test run for temperature stabilization and under several bearing shaft speeds. The applied radial load was 10% of the bearing nominal load. Through root mean square (RMS) analysis of the vibration signals, it was possible to identify specific frequency bands modulated by the change in lubricant viscosity, which was related to change in oil film thickness.     

Analysis of viscosity interaction on the misaligned conical–cylindrical bearing

Viscosity is an essential property in hydrodynamic lubrication. In general, the lubricant is not considered to have uniform viscosity within a given bearing. The viscosity of the lubricant is affected by both pressure and temperature. The viscosity of the lubricant increases with pressure and for most lubricants, this effect is much larger than that of temperature or shear when the pressure is significantly above than the atmospheric pressure. This study analyzes the thermal effect of conical–cylindrical bearing performance parameters via the viscosity–pressure–temperature relationships of lubricants. The results reveal that pressure increases both the film viscosity and temperature as well.     

Deformability of red blood cells: A determinant of blood viscosity

The suspension of hardened red blood cells (RBCs) differs from the suspension of normal RBCs with respect to their rheological behavior. The present study investigated the effect of deformability of RBCs on blood viscosity. RBC deformability and blood viscosity were measured with a recently developed slit-flow laser-diffractometer and the pressure-scanning capillary viscometer, respectively. At the same level of cell concentration, the viscosity of the hardened RBC suspension is higher than that of the normal RBCs suspension. An increase in cell percentage for hardened RBCs shows the significant increase in the level of blood viscosity compared to the normal RBCs. In addition, it was found that RBC deformability played an important role in reducing viscosity at low shear rates as well as high shear rates. These results present the evidence for the effect of RBC deformability on blood viscosity using newly developed methods, which can be used in early diagnosis of the cardiovascular diseases.     

空心杆泵上循环热水加热降粘的数值研究

稠油开采过程中,准确预测井筒温度及原油的粘度变化对选择合适的采油工艺具有指导意义。运用计算流体力学(Computational fluid dynamics,CFD)数值模拟方法,建立空心杆泵上循环热水加热降粘数值模型,进行数值求解,得出循环热水及原油沿程温度和粘度变化规律,并建立目标函数研究平均降粘及减阻效果。结果表明,根据循环热水进口温度的不同,原油在距离进口30～35 m附近温度达到峰值,随后温度呈降低趋势;循环热水入口温度为分别为80℃、70℃和60℃时,原油全管程的降粘率分别为97.3%、96.7%和94.6%。     

Effect of diesel soot on lubricant oil viscosity

Soot related lubricant oil thickening is a primary concern for heavy-duty diesel engines. Engines which produce a relatively low level of particulate matter in exhaust emissions show a significant level of soot contamination in the lubricant. This contamination results in lubricant breakdown. The soot contaminates the lubricant and changes the chemical properties resulting in the lubricant ceasing to perform its functions. This causes an increase in viscosity of the engine oil causing pumpability problems. Hence, it is necessary to study the effects of soot and lubricant oil additives and their interactions on engine oil viscosity.Statistically designed experiments were developed to study the effect of soot contamination on engine oil viscosity. The oil samples used for the study differed in the base stock, dispersant level, and Zinc Dithiophosphate (ZDP) level. These three variables were formulated at two levels: Low (−1) and High (1), which resulted in a 2³ matrix (8 oil blends). Soot was considered as a variable at three levels: low/0% weight (−1), medium/2% by weight (0), and high/4% by weight (1). This resulted in 24 oil samples, and soot at three levels helped in determining the non-linear effect of soot on oil viscosity.Experiments were conducted at 40 and 90 °C to study the effect of the various factors on viscosity with temperature variation. The results showed that viscosity of the oil samples increased with increase in soot at both 40 and 90 °C. The analysis indicated a nonlinear behavior of viscosity as the amount of soot increased at 40 °C, whereas a linear variation at 90 °C.The results obtained were analyzed using the general linear model (GLM) procedure of the statistical analysis system (SAS) package to determine the significance of variables on viscosity. The statistical analysis system also highlighted the significance of various interactions among the variables on viscosity. The statistical analysis results at 40 and 90 °C showed that the effect of base stock and ZDP levels were negligible at 40 °C, whereas the dispersant level and soot level influenced the viscosity of the oil samples at both temperatures.     

Pressure viscosity coefficients and traction properties of synthetic lubricants for wind turbine gear systems

Synthetic lubricants are increasingly used to provide equipment reliability for wind turbine gear boxes. The majority of synthetic lubricants used today are based on polyalphaolefins. In gear systems where contact pressures are high, the pressure viscosity coefficient and traction values of the lubricant are important fundamental properties. A comparison of these properties for a wind turbine lubricant based on a polyalphaolefin and two lubricants based on polyalkylene glycols has been undertaken. Pressure viscosity coefficients were calculated from viscosity measurements made using an ultra‐high pressure falling needle viscometer at pressures up to 50 000 psi. Significant differences in properties were observed with both polyalkylene glycol lubricants showing lower pressure viscosity coefficients and much lower traction values. A calculation of the film thickness values in the Hertzian contact zone suggests that polyalkylene glycol lubricants may provide elastohydrodynamic films that are approximately 25% thicker than polyalphaolefin lubricants. Copyright © 2012 John Wiley & Sons, Ltd.