The lubricity of diesel fuels

The main chemical factors influencing the lubricity of diesel fuels have been investigated by carrying out wear tests on diesel fuels, diesel fuel fractions and model fuels.It has been found that, under the test conditions used, sulphur-containing components were pro-wear. Nitrogen-containing components tended to reduce wear but only at concentrations in excess of those normally found in diesel fuels. Polyaromatic species and, in particular, oxygen-containing components, were found to reduce wear significantly at concentrations normally found in fuels.     

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.     

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。     

Wear with low-lubricity fuels I. Development of a wear mapping technique

Use of low-lubricity fuels such as Jet A-1 is now relatively common in military ground equipment, while severe refinery processes such as hydrotreating are removing reactive components from commercially available diesel fuels. Under critical conditions, durability problems with fuel-sensitive equipment emerge with the use of Jet A-1. Consequently, a bench wear test that accurately reflects the environment within the fuel injection system is needed. However, a better understanding of the primary wear mechanisms present in the fuel injection system and their relationship with potential bench wear tests is first required.

Wear maps have previously been used to study ceramic materials and to define the wear mechanisms in metallic contacts. This technique systematically produces a data base according to a self-consistent methodology and allows the effects of each contact parameter to be precisely described. This paper, the first of two, details the initial test development required to ensure that the data base is completed according to a single well-defined procedure. The second paper, “Correlation between wear maps and pump components”, uses the test methodologies and results developed to elucidate the wear mechanisms present in fuel-lubricated contacts and to assist in bridging the gap between laboratory tests and practical applications.     

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.     

Laboratory screening tests for low sulphur diesel fuel lubricity

Since the beginning of October 1993, environmental legislation in the USA has required the sulphur content of diesel fuel to be reduced to less than 0.05 wt.% for road vehicles. Pressure for such reductions to be adopted in other markets is growing: notably, sulphur levels as low as 10 ppm are being encouraged in Sweden by the use of tax incentives. However, it is suspected that fuel pumps suffer from lubrication problems with the use of low sulphur diesel (LSD). Additive treatment of fuels and fuel blending is thought to mitigate such problems but there is a need for an industrial method of screening candidate fuel treatments prior to expensive service or rig trials. This paper outlines a test procedure based on the Plint TE-77 reciprocating test rig. Initial investigations have enabled fuels of known pump performance to be ranked correctly through an assessment of scuffing wear. In this test, scuffing is evaluated by surface profilometry of the flat specimen and the mechanism is verified by the detection of ‘white’ etching layers on surfaces. The test also allows the separate evaluation of mild wear by measurement of the width of the scar generated on the roller by the line contact configuration.     

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.     

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。     

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.     

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.     

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.     

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.     

The effect of biodiesel and ultra low sulfur diesel fuels on emissions in 11,000 CC heavy-duty diesel engine

It seems very difficult to comply with upcoming stringent emission standards in vehicles To develop low emission engines, better quality of automotive fuels must be achieved Since sulfur contents in diesel fuels are transformed to sulfate—laden particulate matters as a catalyst is applied, it is necessary to provide low sulfur fuels before any Pt-based oxidation catalysts are applied In general, flash point, distillation 90% and cetane index are improved but viscosity can be worse in the process of desulfunzation of diesel fuel Excessive reduction of sulfur may cause to degrade viscosity of fuels and engine performance in fuel injection systems This research focused on the performance of an 11,000 cc diesel engine and emission characteristics by the introduction of ULSD, bio-diesel and a diesel oxidation catalyst, where the bio—diesel was used to improve viscosity of fuels in fuel injection systems as fuel additives or alternative fuels     

Effect of anti‐oxidants on the lubricity of B30 biodiesel–diesel blend

Biodiesel is used in many countries as blends with diesel fuel. However, the main obstacle in biodiesel/diesel blends acceptance, commercialization worldwide and using higher blends seems to be its ability to oxidise and increase wear and friction of automotive parts. An experimental investigation has been carried out to analyse the effect of three different anti‐oxidants on the lubricity of palm biodiesel–diesel blend (B30) and to optimise anti‐oxidant concentration based on the performance. The three phenolic anti‐oxidants, butylated hydroxytoluene, propylgallate and pyrogallol, were tested using four‐ball tribotester for 1 h with 1500 rpm and 40 kg load, at ambient temperature. These three anti‐oxidants were used in varying concentrations of 200, 400 and 600 ppm. Propylgallate anti‐oxidant showed most effective results by enhancing the lubricity of the blend in terms of reduced wear and friction. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of coconut oil‐blended fuels on diesel engine wear and lubrication

This paper presents the results of an experimental investigation into the wear and lubrication characteristics of a diesel engine using ordinary coconut oil (COIL)‐blended fuels. The blended fuels consisted of 10, 20, 30, 40, and 50% COIL with diesel fuel (DF2). Pure DF2 was used for comparison purposes. The engine was operated with 50% throttle setting at a constant speed of 2000 rpm for a period of 100 h with each fuel. The same lubricating oil, equivalent to SAE 40, was used for all fuel systems. A multi‐element oil analyser was used to measure wear metals (Fe, Cr, Cu, Al, and Pb), contaminant elements (Si, B, and V), and additive elements (Zn, Ca, P, and Mg) in the used lubricating oil. Fourier transform infrared analysis was performed to measure the degradation products (soot, oxidation, nitration, and sulphation products) in the used lubricant. Karl Fischer (ASTM D 1744) and potentiometric titrations (ASTM D 2896) were used to measure water concentration and total base number (TBN), respectively. An automatic viscometer (ASTM D 445) was used to measure lubricant viscosity. The results show that wear metals and contaminant elements increase with an increasing amount of COIL in DF2. An increasing amount of COIL in the blends reduces additive elements, with the reduction for blends of up to 30% COIL being quite similar to that for DF2. Soot and sulphation decrease with increasing COIL in the blended fuels due to reduced aromatics and sulphur in comparison to DF2. The water concentration increases for blended fuels with more than 30% COIL. The TBN and viscosity changes are found to be almost normal. The engine did not appear to have any starting and combustion problems when operating with the COIL‐blended fuels. The lubricating oil analysis data from this study will help in the selection of tribological components and compatible lubricating oils for coconut oil‐ or biofuel‐operated diesel engines.     

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.     

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。     

Effect of antioxidants on the oxidative stability and combustion characteristics of biodiesel fuels in an indirect-injection (IDI) diesel engine

Biodiesel fuels that consist of saturated and unsaturated long-chain fatty acid alkyl esters are an alternative diesel fuel produced from vegetable oils or animal fats. However, autoxidation of biodiesel fuels during storage is easily caused by air, reducing fuel quality by adversely affecting its properties such as kinematic viscosity and acid value. One approach to improve the resistance of biodiesel fuels to autoxidation is to mix them with antioxidants. This study investigated the effectiveness of five such antioxidants in mixtures with biodiesel fuels produced by three biodiesel manufacturers: butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), propyl gallate (PrG) and α-tocopherol. An engine test was also performed to investigate the combustion characteristics of biodiesel fuel with antioxidants in an indirect-injection (IDI) diesel engine. Oxidation stability was determined using Rancimat equipment. The results showed that TBHQ, BHA, and BHT were the most effective and α-tocopherol was the least effective in increasing the oxidation stability of biodiesel. The combustion characteristics and exhaust emissions in diesel engine were not influenced by the addition of antioxidants in biodiesel fuel. This study recommends TBHQ and PrG to be used for safeguarding biodiesel fuel from the effects of autoxidation during storage.     

Wear behaviour of hydrogenated DLC in a pin-on-disc model test under lubrication with different diesel fuel types

The wear behaviour of hydrogenated diamond like-carbon (DLC) coating in DLC/steel tribological contact in a pin-on-disc model test under lubrication with two diesel fuels is presented in this work. The first diesel fuel was standard EN590 that contained ester-based antiwear additives. In contrast to EN590, the second diesel fuel, called GDK650, did not contain antiwear additives. It was experimentally observed that the antiwear additives are detrimental to the DLC. The effects of load, speed and temperature on the DLC and steel counterbody wear were investigated. Steel counterbody wear volume was found to be not affected by pressure, temperature, speed and lubricant, whereas the DLC-coating revealed correlation between the parameters and wear rate. Regarding the results of the tribological tests under both diesel lubrications, new mathematical wear laws were developed.     

低硫柴油润滑性的研究

探讨了低硫柴油燃料的润滑性和活性抗磨添加剂。低硫柴油抗磨性能既取决于含氧、含氮极性物质，又随粘度增加线性提高。醇、醚、酯、羧酸以及酰胺等化合物均具有一定的抗磨性能，脂肪酸和酯性能比较突出，且与结构类型有关，其中长链脂肪酸单脂抗磨性能最为优越。