Accelerated wear testing of polyurethane hydraulic seal

The wear characteristics of a polyurethane (PU) hydraulic seal were investigated using a hydraulic seal tester and a pin-on-plate reciprocating tribo-tester, and the results were compared to field data with the aim of developing an accelerated wear test method for hydraulic seals. Tests using a hydraulic seal tester and a pin-on-plate reciprocating tribo-tester were found to reproduce abrasive wear of PU from the field. However, a significant compression set was observed from the test using the hydraulic seal tester. Motivated by the occurrence of abrasive wear from the field, the discolored lubricant and the lubricant with alumina particles were further used for testing using the pin-on-plate reciprocating tribo-tester. The height decrease data of the sealing surface showed that the wear was accelerated by factors of 2.1–3.4 using these degraded lubricants. The outcomes of this work are expected to aid in the design of reliable accelerated life testing for hydraulic seals.     

Observations of acoustically generated cavitation bubbles within typical fluids applied to a scroll expander lubrication system

An experimental study to evaluate the dynamic performance of three different types of cavitation bubbles is conducted. An ultrasonic transducer submerged into the working fluids of a scroll expander is utilised to produce cavitation bubbles and a high speed camera device is used to capture their behaviour. Three critical regions around the ultrasonic source, between the source and the solid boundary, and across the solid boundary were observed. Experimental results revealed that refrigerant bubbles sustain a continuous oscillatory movement, referenced as “wobbling effect”, without regularly collapsing. Analytical results indicate the influence of several factors such as surface tension/viscosity ratio, Reynolds number and Weber number which interpret that particular behaviour of the refrigerant bubbles. Within the refrigerant environment the bubbles obtain large Reynolds numbers and low Weber numbers. In contrast, within the lubricant and the water environment Weber number is significantly higher and Reynolds number substantially lower. The bubble radius and velocity alterations are accurately calculated during the cavitation process. Lubricant bubbles achieve the highest jet velocity while refrigerant bubbles having the lowest jet velocity are not considered as a destructive mean of cavitation for scroll expander systems.     

发动机润滑油品质的可见-近红外光谱快速检测

研究了基于可见-近红外光谱技术的发动机润滑油品质的快速检测方法,包括粘度与含水率的预测。在获取可见-近红外光谱信息的基础上,采用广义回归神经网络分别建立了粘度与含水率的预测模型。预测集样本的确定系数分别达到了0.9818和0.9999。说明可见-近红外光谱技术能够用于发动机润滑油的含水率与粘度的预测。     

Investigation of lubricant induced pre-ignition and knocking combustion in an optical spark ignition engine

An experimental study was performed to investigate lubricant oil induced pre-ignition and knocking combustion process in a single cylinder spark ignition (SI) engine with full bore overhead optical access. Lubricant oil was deliberately injected to the exhaust area through a specially modified direct injector to trigger the stochastic pre-ignition in a premixed air and fuel mixture. Simultaneous heat release analysis and high speed combustion imaging were used to study the pre-ignition and combustion processes. Outlier detection based on robust statistical methods was validated as an effective and efficient approach to identify sporadic pre-ignition. When pre-ignition occurred, the pre-ignited flame-front exhibited much faster propagating speed than that of the normal spark-ignited flame-front in the first stage of flame development. In several cycles, pre-ignition was followed by the pre-ignited propagating flame-front and then a separate spark-ignited flame-front before they subsequently merged together. In a few other cycles, pre-ignition led to heavy knocking combustion caused either by the auto-ignition close to the flame-front or near the cylinder wall, or both. The ultimate knock intensity of such cycles was determined by the timing, size, and location of end-gas auto-ignition of the unburned gas. Furthermore, optical detection of the oil droplet entrained combustion in the cycle subsequent to the knocking combustion cycle implied that high frequency oscillation pressure waves ejected lubricant from the piston-ring crevice.     

纳米润滑材料研究及应用

介绍了纳米无机单质、无机盐、氢氧化物、氧化物、高分子微球和有机无机纳米微球的摩擦学研究及纳米材料的润滑作用机理、应用现状及其发展前景。     

二烷基二硫代磷酸锌的大气压化学电离质谱

采用大气压化学电离质谱技术（APCI－MS）对润滑油抗氧抗腐蚀添加剂丁基、辛基混合烷基硫代磷酸锌进行了分析，并结合APCI－MS技术中特有的源内化学电离检测（CID）功能对二辛基二硫代磷酸锌进行了结构表征；该法简便、快速，与传统方法相比有优越之处。     

STUDY ON HIGH PERFORMANCE ANTI—WEAR ADDITIVES FROM WATER—SOLUBLE POLYMERIC LUBRICANT*

A series of high performance lubricants of water-soluble polymers with telechelic or starstructures has been studied. Their average molecular weights M are 1800--6000. The chemi-cal structures of the lubricants are characterized by their hydrophilic groups (--CH_2CH_2O--),--COOH, --OH, --CONH_2 and antiwear active elements (S, P,Zn and Mo). The results ofassessing for the anti-wear property indicate that this kind of water-soluble polymeric lubri-cants possesses excellent watersolubility, lubricity and anti-wear property. A preliminarystudy on the anti-wear mechanism of the polymers is performed by means of electron probeand scanning electron microscopy (SEM).     

异辛基乙二胺-CF3SO3型质子化离子液体作为液体石蜡添加剂的摩擦学性能

以异辛基乙二胺-CF₃SO₃[HEtHex(TFS)]型质子化离子液体作为钢/钢摩擦副的润滑油添加剂, 考察了不同HEtHex(TFS)含量的液体石蜡(LP)在不同温度和载荷下的摩擦学性能. 通过扫描电子显微镜和X射线能谱仪对钢球表面磨斑的形貌及所含元素进行了分析与表征. 结果表明, 加入HEtHex(TFS)添加剂可明显增大LP的最大无卡咬负荷(P_B)值, 改善LP的减摩抗磨性能. HEtHex(TFS)在LP中添加的最佳质量分数为0.75%, 在25 ℃, 294 N时其减摩效果最好; 在25 ℃, 196 N时其抗磨效果最佳. 元素分析结果表明, 加入HEtHex(TFS)添加剂后在钢球表面形成了一层摩擦保护膜, 从而起到了减摩抗磨的作用.     

The interactions between Z-Tetraol perfluoropolyether lubricant and amorphous nitrogenated- and hydrogenated-carbon surfaces and silicon nitride

The interactions that occur between the hydroxyl-terminated perfluoropolyether Z-Tetraol and the ion beam-deposited amorphous hydrogenated CHx, sputtered amorphous nitrogenated carbon CNx, and sputtered amorphous silicon nitride SiNx surfaces, are investigated via surface energy measurements, kinetic measurements, and ab initio calculations. The film thickness dependence of the Z-Tetraol dispersive surface energy can be fit using a repulsive van der Waals potential, where the repulsion between the Z-Tetraol main chain and the underlying surface increases in the order: CHx (IBC) < CNx < SiNx, due to the increased average separation between the lubricant main chain and the underlying surface. Ab initio calculations on model dimers quantify the separation distances and binding energy of the lubricant/surface interactions. The Z-Tetraol thickness dependence of the polar surface energy indicates that strong polar interactions occur between the applied lubricant and the underlying surface. The decrease in the polar surface energy is correlated to the increased level of bonding between the hydroxyl end groups of Z-Tetraol and the polar sites of the underlying surface. Further analysis of the surface energy data identifies the critical film thickness at which film instability occurs to be near 17.5±1.0 Å for the 2200 molecular weight of Z-Tetraol on the various surfaces. Images of the disk surfaces showing the evolution of lubricant droplets due to dewetting corroborate the surface energy data analysis.     

Tracking lubricants during single screw extrusion of uPVC

Lubrication is one of the most important parameters in unplasticized polyvinyl chloride (uPVC) processing apart from the PVC resin and processing equipment. Lubricants are used in specific ratios to ensure effective fusion of PVC particles. The exact mechanism on how these lubricants interact is not yet fully understood. A widely accepted theory is the interaction mechanism proposed by Rabinovic et al. where lubricants are said to act as surfactants and slip agents. In this study a method for tracking lubricants, by simulating the extrusion process within a single screw extruder, was proposed. A three stage fusion simulation consisted of the feeding zone (stage 1), the compression zone (stage 2) and the metering zone (stage 3). The association interactions between the individual components of a typical uPVC formulation were followed throughout the three stages. External polar and nonpolar lubricants in combination with an internal lubricant was studied. Lubricants were successfully tracked using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). In conclusion it was found that the use of an internal lubricant promotes dispersion of external lubrication towards PVC. It was also found that there is a competition between the internal lubricant and polar external lubricant.