柴油中不同组分的摩擦特性及表征

采用蒸馏法对国产柴油进行分离并对不同馏分段柴油的摩擦性能进行了考察,同时采用色谱柱分离法将分离出不同的柴油极性组分并对其润滑性进行了考察;通过SEM扫描电镜对不同含量的极性组分润滑下的磨斑形貌进行了表征,应用高频往复试验机分析了摩擦力及电阻曲线。试验结果表明,随着柴油馏出温度的逐渐升高,其抗磨性能逐渐增加;随着柴油极性的增大,柴油组分的润滑性能越好。柴油的摩擦特性与氮含量和多环芳烃之间有较好相关性,柴油的润滑性关键取决于其中的极性有机物及其数量。     

生物柴油调合燃料润滑性能的研究

对不同来源的生物柴油、车用柴油及其生物柴油调合燃料的润滑性能及影响因素采用高频往复试验机法(HFRR)进行研究,认为不同原料的生物柴油其调合柴油燃料的润滑性能存在差异;生物柴油的精制深度会减弱调合柴油燃料的润滑性能;生物柴油体积分数大于20%的调合燃料其润滑性基本与纯生物柴油达到一致;生物柴油体积分数为5%的调合燃料中超标的水含量会降低其润滑性能,但幅度不大,其润滑性主要由5%的生物柴油决定,抗氧、防锈剂、流动改进剂不影响润滑性能;与车用柴油不同,生物柴油调合燃料的运动黏度与磨斑直径没有很好的对应关系。     

基于SRV磨损试验机评定柴油润滑性能评定

采用SRV线摩擦磨损试验机考察柴油的润滑性与柱塞偶件磨损的相关性。结果表明,低硫（S含量wS≤500 μg/g）低润滑柴油润滑时柱塞偶件磨损比较严重,其润滑性与柱塞偶件磨损没有相关性;高硫低润滑柴油的承载能力较高,其润滑时柱塞偶件磨损相对较轻,且润滑性与柱塞偶件磨损相关性较好;适量的酸性组分有助于提高柴油的润滑性和承载能力。部分直馏工艺生产的高硫含量柴油虽经HFRR测试润滑性较差,但在适量酸性组分、较高运动黏度共同作用下,实际SRV测试时并未出现严重的磨损。     

基于SRV磨损试验机的柴油润滑性能评定

采用SRV线摩擦磨损试验机考察柴油的润滑性与柱塞偶件磨损的相关性。结果表明,低硫(S含量wS≤500μg/g)低润滑柴油润滑时柱塞偶件磨损比较严重,其润滑性与柱塞偶件磨损没有相关性;高硫低润滑柴油的承载能力较高,其润滑时柱塞偶件磨损相对较轻,且润滑性与柱塞偶件磨损相关性较好;适量的酸性组分有助于提高柴油的润滑性和承载能力。部分直馏工艺生产的高硫含量柴油虽经HFRR测试润滑性较差,但在适量酸性组分、较高运动黏度共同作用下,实际SRV测试时并未出现严重的磨损。     

水溶性稠化剂的流变性及成膜性能试验研究

水溶性稠化剂的成膜能力是衡量其润滑性能的一个重要指标,为研究水溶性稠化剂的成膜性能,选用水溶性稠化剂聚氧乙烯(PEO)作为试验材料,利用流变仪在不同温度对不同质量分数的PEO水溶液进行流变性试验,再利用自制的点接触弹流润滑实验台对不同质量分数的PEO水溶液成膜性能进行研究。结果表明:PEO水溶液呈现剪切变稀的非牛顿流体特性,随着PEO质量分数的增加,PEO水溶液的非牛顿性增强;PEO水溶液在卷吸速度较高时的润滑行为符合弹流润滑规律,而在较低卷吸速度时的润滑行为符合薄膜润滑规律;不同质量分数的PEO水溶液其薄膜润滑转变为弹流润滑的临界速度不同,PEO质量分数越高,其临界速度越高;对于相同质量分数的PEO水溶液,载荷越大,其膜厚越小;在同一载荷下,水溶液中PEO质量分数越大,润滑膜中心膜厚越大。     

柴油润滑性与其组成关系的研究

研究直馏柴油、催化柴油及加氢精制柴油的组成变化和其润滑性的关系,考察柴油的馏程、90％馏出温度与其润滑性的对应关系。结果表明,催化柴油的润滑性能最好,直馏柴油的润滑性能次之;对于加氢柴油,随着加氢深度增大,柴油抗磨性能变差;柴油中某些能改善其润滑性的组分,多集中在高馏程中;柴油90%馏出温度与柴油润滑性线性相关性较好,柴油中的有效抗磨组分多集中在重组分中,重组分含量增加,柴油的抗磨性能变好。     

发动机燃料润滑性的研究进展

为适应汽车排放对燃料品质提出的严格要求,研究提高燃料润滑性是当务之急,中报道了测试柴油,汽油润滑性的HFRR和SBOCLE方法,以及组成对燃料润滑性质的影响和规律。     

直馏柴油的润滑性和抗磨损性能

柴油是柴油发动机燃料供给系统的润滑剂,其润滑性影响发动机动力性和经济性.采用高频往复试验,研究了国产直馏柴油的润滑性,采用SRV模拟试验和柴油发动机喷射系统台架试验, 研究了国产直馏柴油的抗磨性能.结果表明,低硫低润滑性的柴油会导致发动机柱塞偶件严重磨损,而高硫低润滑性也可能导致柴油发动机高压喷射系统出现严重的磨损,应根据柴油发动机抗磨损需求, 研究提出柴油润滑性指标.     

我国柴油润滑性检测方法标准的发展与变化

2005年之前,我国一直参照国际标准ISO 12156-1-1997《柴油高频往复设备(HFRR)用润滑剂性能评定.第1部分：试验方法》进行柴油润滑性试验,直至2005年9月发布实施了我国的第一个柴油润滑性试验方法：SH/T 0765-2005《柴油润滑性评定法(高频往复试验机法)》,经过多年的积累和我国的实际情况,对第一版试验方法加以调整修改,于2022年5月实施了第二版试验方法NB/SH/T 0765-2021《柴油润滑性的评定高频往复式试验机法》。结合工作实际,对我国两次发布的试验方法加以归纳总结和分析。     

烷烃乳液润滑Si3N4陶瓷摩擦副的摩擦学特性研究

采用多种烷烃乳液以及添加剂对氮化硅陶瓷摩擦副进行润滑试验。试验结果表明:对于氮化硅陶瓷摩擦副来说,所有的烷烃都可以得到较好的润滑效果,摩擦因数最高的基础油也仅有0.13;相对于包含直链烷烃、支链烷烃和环状饱和烃的基础油和柴油,正构烷烃的摩擦因数更低,抗磨性能更好;润滑性能最佳的液体石蜡中添加极性添加剂氯化石蜡和油酸后,乳液的润滑性能变差,但加入有机硅乳液后则润滑性能大大提高,摩擦因数进一步降低为0.017。基于试验试剂的结构特征,得出对于水乳润滑剂来说,化学性质和分子结构与氮化硅陶瓷相似的有机物可以更好地在陶瓷摩擦副表面聚集从而起到更好的润滑效果的结论。     

The Lubricity of Gasoline

A study has been made of the lubricating properties of gasoline fuel. A conventional HFRR diesel fuel lubricity tester has been modified to measure gasoline wear. Using this test equipment, a number of features of gasoline lubricity have been investigated, including the comparative lubricating behavior of gasoline, the influence of detergent additives and oxygenates on wear and the wear behavior of a series of refinery streams employed in gasoline blending.

The lubricity of a range of pure organic chemicals known to be present in gasoline has also been studied. From these measurements it has been shown that, except for components such as dienes and diaromatics, the HFRR lubricating properties of most gasoline hydrocarbon constituents are broadly independent of chemical structure bur depend significantly on viscosity. Using these measurements, predictive wear equations based on gasoline group analysis have been developed.

Because it has been found that viscosity plays a role in determining the wear properties of gasoline, the elastohydrodynamic (EHD) film-forming and friction properties of gasoline have been measured and compared to those of diesel fuels. This shows that the combination of gasoline's very low viscosity and low pressure-viscosity coefficient results in very thin EHD film thickness generation and also very low friction in full-film EHD conditions.     

Boundary lubrication of low‐sulphur diesel fuel in the presence of fatty acids

This paper presents an overview of the effect of aliphatic acids on the tribological properties of selected hydrocarbons and petroleum fractions. The major experimental part of the work focuses on improvements to the lubricity of low‐sulphur diesel fuel. Experiments were carried out using a pin‐on‐disc friction machine and HFRR test rig. The wear results obtained clearly show a specific effect of the test acids dissolved in hydrocarbons in the concentration range 0.005–0.1% (50–1000 ppm). Although the overall picture presented by these results is very complex, it can be concluded that a very small amount of the selected acids dramatically improves low‐sulphur diesel fuel lubricity.     

低沸点燃料二甲醚润滑性评估实验台的研制

二甲醚在常温常压下为气态,不能用传统方法评估其润滑性能。根据低沸点燃油的物理特性和高频往复机(HFRR)的基本原理,设计可加压的高频往复机,初步搭建用于低沸点燃油的摩擦磨损试验台架,并采用常规燃油进行油品的可分辨性试验。结果表明,该台架可以用于评价不同油品的润滑性,为二甲醚等低沸点燃油润滑性能评估方法的建立奠定了基础。     

Wear and Electrical Resistance on Diesel Lubricated Surfaces Undergoing Reciprocating Sliding

Tribological tests, using the high-frequency reciprocating rig (HFRR), were carried out on commercial diesel fuels with a range of lubricities as well as on solutions of methyl stearate and stearic acid in ultra-low-sulphur, additive-free diesel. The surfaces of discs used in the HFRR tests were measured with micro-Raman and time-of-flight secondary ion mass spectrometry (ToF-SIMS). These measurements showed that amorphous carbon was formed during reciprocating sliding, the structure of which was related to the lubricity as measured by the average wear scar on the ball. Magnetite (Fe₃O₄) and hematite (-Fe₂O₃) were also detected on the surfaces. In most cases, the detection of hematite in the wear track was also associated with low wear. However, hematite was found in the wear particles of all samples. The build up of a film, measured by electrical resistance, was attributed to the presence of hematite, which has a much lower electrical conductivity than magnetite.     

Evaluation of ball and disc wear scar data in the HFRR lubricity test

The high‐frequency reciprocating rig (HFRR) lubricity tester has become a widespread method for determining the lubricity of diesel fuels. The test is a ball‐on‐disc method, in which a steel ball scrapes over a steel disc immersed in the liquid to be tested. According to standards, the wear scar generated on the ball, in the form of the average of the x‐ and y‐axes, is used for evaluating the lubricity of the sample. Generally, the smaller the wear scar, the greater the lubricity of the sample. However, a wear scar is also generated on the disc. The size of the wear scar on the disc also depends on the lubricity of the sample. In this work, the wear scar data of the balls and discs of 230 samples related to the testing of biodiesel and related compounds with petrodiesel were evaluated. Data comparisons for all wear scar combinations correlated well by linear regression. Although correlations are slightly better when using only ball wear scar data (r² > 0.99), other wear scar data, including those generated on the disc, appear just as useable (r² ≈ 0.97–0.99) for evaluating lubricity by the HFRR test. The wear scars on the disc have the advantage of being more easily measurable and recognisable under the microscope, especially if the wear scars are small. Limits for all wear scar values corresponding to current limits for average ball wear scar data in standards are presented. Published in 2007 by John Wiley & Sons, Ltd.     

Effect of Carbon Coating on Scuffing Performance in Diesel Fuels

Low-sulfur and low-aromatic diesel fuels are being introduced in order to reduce various types of emissions in diesel engines to levels in compliance with current and impending U.S. federal regulations. The low lubricity of these fuels, however, poses major reliability and durability problem for fuel injection components that depend on diesel fuel for their lubrication. In the present study, the authors evaluated the scuff resistance of surfaces in regular diesel fuel containing 500 ppm sulfur and in Fischer-Tropsch synthetic diesel fuel containing no sulfur or aromatics. Tests were conducted with the high frequency reciprocating test rig (HFRR) using 52100 steel balls and H-13 tool-steel flats with and without Argonne's special carbon coatings. Test results showed that the sulfur-containing fuels have about 20% higher scuffing resistance than does fuel without sulfur. The presence of the carbon coating on the flat increased scuffing resistance in both regular and synthetic fuels by about ten times, as measured by the contact severity index at scuffing. Coating removal was observed to be a necessary, but not sufficient condition for scuffing failure in tests conducted with coated surfaces. The loss of coating from the surface occurred by the two distinct mechanisms of spalling and wear.     

Development of laboratory tests to predict the lubricity properties of diesel fuels and their application to the development of highly refined diesel fuels

In the last few years there has been an increasing requirement for the provision of environmentally benign diesel fuels. However, the introduction of such fuels into service has been associated with high levels of field failure of rotary distribution fuel pumps due to wear. This is because the refining processes necessary to produce ecologically acceptable fuels result in greatly reduced levels of sulphur compounds, aromatics, and polar material, many of which are potential lubricity agents. This paper describes the development of bench test methods to evaluate diesel fuel lubricity and thus enable the identification of appropriate ‘solutions’. It has been found that the key to obtaining good correlation between field experience and bench tests is (1) to reproduce the thermal conditions present in operating pump contacts and (2) to ensure that the same mechanisms of wear operate in the bench test as in the pump environment. The physical and chemical processes involved in the lubrication of fuel pumps and the influence of temperature on these processes are outlined. As a result of the work described in this paper, effective additive solutions have been discovered for controlling the failure of diesel fuel pumps in the field and a provisional ISO (ISO/TC 22 / SC 7 M595: ‘Diesel engines - diesel fuel - performance requirement and test method for assessing fuel lubricity’) and CEC test method for assessing diesel fuel lubricity has also been developed.     

Comparison of the Effects of Biodiesel and Mineral Diesel Fuel Dilution on Aged Engine Oil Properties

Dilution of engine oil occurs when fuel is injected late in the combustion cycle to regenerate the diesel particulate filter used for trapping particulate emissions. Fuel dilution reduces oil viscosity and the concentration of engine oil additives, potentially compromising lubricant performance. Biodiesel usage may compound these issues due to its oxidative instability, and its higher boiling point compared to mineral diesel potentially causes it to concentrate more in the oil sump.

In this work, different amounts of mineral diesel and biodiesel (soy methyl ester, SME) were combined with 15W-40 CJ-4 diesel engine oil in laboratory oil aging experiments. Fuel was added and oil samples were withdrawn at periodic intervals. The oils were analyzed using typical oil analysis procedures to determine their condition, and wear evaluations under boundary lubricating conditions were determined using a high-frequency reciprocating rig (HFRR). Results showed that fuel dilution accelerated engine oil degradation, with biodiesel having a larger effect. However, friction remained unchanged with dilution, and wear actually decreased for fuel-diluted oils after 48 h of aging compared to aging without fuel dilution. Examination of the tribofilms by ultraviolet (UV) and visible Raman spectroscopy as well as Auger electron spectroscopy showed that additional carbon-containing components were present on tribofilms formed from fuel-diluted oils. These fuel-derived components may be responsible for the decreased wear observed.     

柴油润滑性添加剂研究

针对柴油的低硫化引起的喷油泵磨损问题,研制了一种酯类柴油润滑性添加剂。经实验室分析研究,表明研制产品具有优异的润滑性能外,同时还具有一定的抗氧、防腐作用,且具有良好的贮存稳定性以及与柴油其它添加剂的配伍性;苛刻条件下BOSCH高压油泵台架试验后,其润滑性能无明显变化,油泵无明显磨损现象,泵的输出性能没有损失,没有任何有关燃油或者润滑剂的兼容性问题。加入量仅为150~250mg/kg。