Preparation and evaluation of vegetable oil derived biodiesel esters as lubricity additives

Various vegetable‐oil derived esters using methyl, ethyl, butyl, and 2‐propyl alcohols were prepared and tested as diesel fuel lubricity additives in a roller‐on‐cylinder lubricity evaluator. At1% additive treat rate, the canola methyl and 2‐propyl esters, the best‐performing esters, increased the lubricity number of a reference fuel by 60%. Statistical analyses indicated strong effects of fatty acids and alcohols on the wear, friction, and lubricity number of the fuel. While no single fatty acid was identifiably responsible for the wear reduction, certain non‐linoleic compounds correlated with the wear data in a semi‐log relationship. The low‐temperature behaviour of the biodiesel was studied using differential scanning calorimetry. The major transitional peak temperature of the biodiesel esters changed with the melting points of their primary fatty acids, and decreased with the lengthening and branching of the tail alkyl groups.     

影响柴油润滑性检测结果的因素

利用作者多年来从事柴油润滑性检测工作的经验积累,对影响柴油润滑性检测结果的诸多因素进行探讨,介绍柴油抗磨剂以及生物柴油的检测情况,这对即将在全国范围开展的柴油润滑性检测工作具有一定的指导意义.     

Wear with low-lubricity fuels II. Correlation between wear maps and pump components

Increasingly severe refinery processes remove many of the compounds necessary for effective lubrication with diesel fuels. No widely recognized lubricity test or standard currently exists relating to the needs of the fuel injection system on compression ignition equipment. The Ball-on-Cylinder Lubricity Evaluator (BOCLE) is commonly used by the US Air Force to measure aviation turbine fuel lubricity. However, the tribological requirements of fuel-lubricated components in aviation may not coincide with the needs of ground vehicles. This study uses the wear-mapping technique developed in the preceding paper (“Development of a wear mapping technique”) to indicate the significance of the BOCLE test methodology in this context. In particular, the work highlights the effects of various contact parameters on fuel-lubricated wear that are not revealed by the BOCLE results.

Where possible, both the BOCLE and wear map data are compared with the results of full-scale pump stand tests detailed in the previous paper. Additional nonstandard bench wear tests were performed to further evaluate the contact conditions present within the operating pump. The wear mechanisms of each fluid were determined to be strong functions of both metallurgy and contact stress. Moreover, the onset and severity of each wear mechanism appear to be controlled by different fuel properties. As a result, the relative lubricity observed between fuels depends on the test conditions chosen so it is unlikely that fuel lubricity may be uniquely defined by a single bench wear test procedure.     

一种二甲醚专用润滑性改进剂的性能研究

采用四球机和高频往复试验机研究了一种二甲醚(DME)专用润滑性改进剂在不同基础试验液体中的润滑特性,考察了其与醚的互溶性能及对金属的腐蚀性能,并与其它润滑性改进剂进行了对比,从而为DME发动机选择合适的燃料润滑改进剂提供了依据。结果表明:该DME专用润滑性改进剂添加量少,润滑效果显著,与DME相容性好,没有腐蚀性。     

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.     

A method for the evaluation of the boundary lubricating properties of aviation turbine fuels

Using the principle of the Amsler machine, a method has been developed for evaluating the boundary lubricating properties (lubricity) of aviation turbine fuels over a temperature range from ambient to 150°C in a controlled atmosphere. The method of fuel supply was found to be a critical factor, a single-pass flooded system being superior to both trickle feed and static flooded arrangements. Equally important were the hardness and surface finish of the test specimens. Fuel lubricity properties were quantified using a derived failure load based on coefficient of friction, a parameter which, for aviation turbine fuels, accurately reflected the lubrication conditions at the rubbing contact. Failure loads based on wear and gross seizure were less satisfactory. The correlation of friction failure loads with practical experience in the field was excellent for a wide selection of Jet A-1 type fuels including low lubricity fuel with added lubricity-improving boundary lubricating additive. The method is recommended for measuring the lubricity performance of candidate lubricity-improving additives, for monitoring low lubricity fluids used in hardware development and for investigating lubricity problems as they occur in practice.     

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。     

柴油润滑性的机制研究

利用作者从事柴油润滑性研究与检测工作十年来积累的大量数据,将柴油的常规理化分析指标以及质谱分析结果与柴油润滑性的相关性进行归纳总结,探讨柴油润滑性的机制。结果表明:脱硫工艺过程与柴油的润滑性有很好的相关性;磨损对某些含硫物质的多少并不敏感;柴油中氮含量越高,润滑性越好;柴油的黏度和密度越大,润滑性越好;馏出点温度越高,馏分的润滑性越好;饱和烃中的链烷烃和环烷烃对润滑性起负作用,而非饱和烃对润滑性有贡献,在芳烃组分中,多环芳烃比单环芳烃对提高润滑性的贡献大。     

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。     

Boundary Tribological Behaviors of Untreated and Surface-Modified M50 Steel Lubricated by Fuel JP-10

To explore the possibility of using advanced surface engineering techniques (ASETs) to solve the wear problems caused by the poor lubricity of pure, low-viscosity aviation fuel JP-10, polished M50 bearing steel sample surfaces were treated with nitrogen ion implantation, TiAlN coating deposition, and Ta coating deposition followed by high current pulsed electron beam (HCPEB) irradiation, respectively. Boundary tribological behaviors of these ASET-treated and untreated steel samples sliding in pure JP-10 against a Si₃N₄ ball (ball-on-disc model) were investigated under 2.0 GPa in the atmosphere and the friction tests indicated that significant, reductions, although to different extents, in friction and wear were achieved by these modified surfaces. Simultaneously considering the tribological performance and potential pollution caused by wear debris to JP-10, HCPEB-treated Ta coating with a lowest average friction coefficient of 0.11 and a specific wear rate of around zero was the fittest to offset the inadequate lubricity of JP-10 itself under the laboratory condition.     

Development of novel lubricity additives: hydroxyalkyl ester of ortho-phenylene phosphate

Hydroxyalkyl esters of ortho-phenylene phosphate have been designed as novel lubricity additives for carboxylate-type synthetic oils. Excellent wear prevention and load carrying properties have been observed with hydroxyalkenyl esters. It is suggested that the presence of carbon-carbon double bonds is a key functional group to improve the lubricity of phosphate additives.     

水-乙二醇液压液极压抗磨添加剂二聚酸钾的研究

本对合成的一种应用于水-乙二醇液压液的极压抗磨添加剂二聚酸钾进行了润滑性能测试和抗磨作用机理研究．四球实验表明,二聚酸钾的水溶性能和抗磨性能优于水溶性改性ZDDP和Lubrizol5642,以二聚酸钾作为极压抗磨添加剂的水-乙二醇液压液KGY的润滑性能与N46抗磨液压油相当。钢球磨斑表面元素EDS分析表明,在极压条件下,二聚酸钾与摩擦表面发生某种摩擦化学反应,形成了一层有机类抗磨膜。     

柴油成膜润滑机制探讨

柴油是发动机燃料供给系统的润滑剂,其润滑性非常重要。在高频往复试验机上对不同柴油样品进行了润滑性评价,对试验后的金属件进行磨斑表面分析,通过对比研究,探讨了柴油成膜润滑机制。结果表明,柴油成膜组分少,不能形成良好润滑保护膜,或者因腐蚀反应不能形成有效润滑保护膜,是柴油润滑性差并导致偶件磨损的原因。     

A tribological study of refrigeration oils under HFC-134a environment

HFC-134a is a potential alternative material for CFC-12, which depletes the ozone layer. However, problems arise when used together with conventional refrigeration oils due to the extreme polarities of HFC-134a. PAG (polyalkylene glycol) and esters are tested with HFC-134a. This investigation enhances the testing method by taking the compressor's environment into account. Miscibility and material compatibility are proved with sealed glass tests. A testing environment charged with refrigerant gas more closely simulates the conditions of a compressor. The conventional refrigeration oils (mineral oils, alkylbenzene, PAO (polyalpha olefin)) tested here are immiscible with HFC-134a. However the PAG and ester oils are miscible with HFC-134a. The friction coefficient of the PAG/HFC-134a system is similar to that of the mineral oil/CFC-12 system at operating conditions. Ester oils are preferable at the start and stop condition in the lubricity aspect. PAG shows good lubricity in conditions of extreme contact pressure. Consequently, this test provides reliable results on compressor lubricity and material compatibility of refrigeration oils with HFC-134a. It suggests a methodological way for the proper selection of refrigeration oils that may improve the durability and performance of a compressor.     

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.     

Alternative and low sulfur fuel options: boundary lubrication performance and potential problems

Studies of alternative fuels at Penn State include biodiesel, dimethyl ether (DME) and low sulfur diesel fuels. The fuel studies include bench tests, laboratory engine tests and vehicle tests. DME was evaluated in a campus shuttle bus operating on its regular campus route. A 25:75 vol% mixture of DME and diesel fuel was used. Laboratory engine tests of oxygenated fuels, including biodiesel, resulted in significant particulate reductions. However, some alternative fuels exhibit low lubricity. Bench tests comparing friction and wear characteristics of the fuels are described.     

Study of the effect of dilution on the lubricity of hydrotreated jet engine fuels

Hydrotreated fuels lack lubricity. Dilution with chemically treated conventional fuels is reported to restore lubricity. Studies revealed that some conventional fuels have lubricity inferior to the hydrotreated fuels. Thus dilution with conventional fuel is not a sure cure.     

Esters of dicarboxylic acids as additives for lubricating oils

Five samples of dibasic acid esters with varied chemical structures were synthesized. These included didecyl carbonate, didecyl adipate and didecyl sebacate as well as modern oligomeric esters of adipic acid and sebacic acid. These esters were tested in terms of their suitability as additives of fully synthetic engine oils. It was noted that an addition of 10% of the respective esters to oils based on polyalphaolefins led to an improvement of their properties. The pour point of the oils as well as their low temperature viscosity were reduced. The viscosity index rose and oil lubricity improved. Esters of oligomeric structures synthesized by the transesterification of dimethyl adipate or dimethyl sebacate with a mixture of neopentyl glycol and decanol showed particularly suitable properties. The tested esters were compatible with the other oil components, forming a stable solution in a wide temperature range.     

Analysis of Tribological Properties of Palm Biodiesel and Oxidized Biodiesel Blends

Biodiesel has become an increasingly significant alternative fuel to replace conventional diesel completely or partially. Although biodiesel has several advantages, such as environmental friendliness, renewability, and reduced emissions, it also has major drawbacks. Tribology is one of the major concerns for biodiesel usage, in which biodiesel lubricity deteriorates by usage and/or by storage because of its oxidative nature. The present study aims to investigate the lubrication behavior of oxidized and pure palm biodiesel blends by using a four-ball tribotester machine. Tests were carried out in diesel, pure biodiesel (B100), their blends (B10 [10% biodiesel in diesel], B20, B30, and B50), and oxidized biodiesel (Oxd B100) and its blends (Oxd B10, Oxd B20, Oxd B30, and Oxd B50). Tests were conducted at room temperature under a normal load of 40 kg for 1 h at 1,200 rpm. Surface analyses were carried out by scanning electron microscopy, energy-dispersive spectrometry, and optical microscopy, and fuel analysis was performed by gas chromatography–mass spectroscopy. Diesel fuel showed the highest wear and friction. Surface deformation, wear, and friction decreased as the biodiesel concentration increased in the blend. Oxidized biodiesel blends showed improved lubricity compared to pure biodiesel and blends. However, Oxd B100 showed higher wear than Oxd B50.