Investigation of the scuffing characteristics of candidate materials for heavy duty diesel fuel injectors

The objective of this study is to characterize and understand the evolutionary processes that produce changes in the friction and surface damage in materials for possible use as heavy duty diesel fuel injector plungers. This work has involved the development of test methods to impart reciprocating motion to various metals, ceramics, and coated specimens in the presence of diesel fuel-like fluids. Commercial and candidate plunger materials, including 52100 steel, zirconia, cermets (TiC in Ni₃Al matrix), and TiN coatings, were evaluated on a crossed-cylinders-like scuffing test we call the ‘pin-on-twin’ geometry. Contacts were lubricated by on-highway #2 diesel and Jet A aviation fuels. Using friction-based criteria, the material ranking was in good agreement with field experience with actual injectors from the diesel engine industry. Zirconia and cermets exhibited promising scuffing resistance in both fuels. Scuffing generally became more severe in the Jet A fuel. Experimental results indicated that smoother surfaces that are required to sustain higher injection pressures could be more vulnerable to scuffing due to their thinner lubricant films. Material transfer was the major scuffing mechanism of zirconia, cermets, and TiN coatings against steel. Micro-scratches were also observed on the matrix material of cermets.     

Scuffing Performance of Amorphous Carbon During Dry-Sliding Contact

Scuffing is a major problem that limits the life and reliability of sliding tribo-components. When scuffing occurs, friction force rises sharply and is accompanied by an increase in noise and vibration; severe wear and plastic deformation also occur on the damaged surface. Attempts have been made over the years to combat scuffing by enhancing the surface properties of the machine elements, and by methods involving lubricant formulation and coating application.

In this study, the authors evaluated the scuffing performance of an amorphous, near-frictionless carbon (NFC) coating that provides super-low friction under dry sliding conditions. The test configuration used a ball-on-flat contact in reciprocating sliding. The coating was deposited on HI3 steel. An uncoated 52100 steel ball was tested against various coated flats in room air. Compared to uncoated surfaces, the carbon coating increased the scuffing resistance of the sliding surfaces by two orders of magnitude. Microscopic analysis shows that scuffing occurred on coaled surfaces only if the coating had been completely removed. It appears that depending on coating type, the authors observed that coating failure occurs before scuffing failure by one of two distinct mechanisms: the coating failed in a brittle manner and by spoiling, or by gradual 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.     

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     

Compatibility of DLC coatings with formulated oils

In the present study, the tribological performance and compatibility of hydrogenated amorphous carbon coating (a-C:H) and metal-doped diamond-like carbon (DLC) coating (Me-C:H) with formulated oils under the boundary lubrication regime was investigated. The investigation employed ball-on-flat contact geometry in reciprocating sliding motion and six formulated oils (manual gearbox oil, automatic gearbox oil, hydraulic oil, compressor oil, and normal and high performance motor oil), with pure poly-alpha-olefin (PAO) oil used as a reference. In addition, DLC coatings behavior in diesel and gasoline fuel was evaluated.Compared with the uncoated steel surfaces a-C:H coatings give improved wear resistance in base PAO as well as in fully formulated oils and fuels. On the other hand, W-doped DLC coatings show the lowest steady-state friction under boundary lubrication, especially when using oils with high additive contents.     

A study on the usability of biodiesel fuel derived from rice bran oil as an alternative fuel for IDI diesel engine

The world is faced with a problem of air pollution due to the exhaust emissions from automobile. Recently, lots of researchers have been attracted to develope various alternative fuels and to use renewable fuels as a solution of these problems. There are many alternative fuels studied in place of diesel fuel made from petroleum. Biodiesel fuel (BDF) is a domestically produced, renewable fuel that can be manufactured from vegetable oils, used vegetable oils, or animal fats. In this study, the usability of BDF, one of the oxygenated fuels as an alternative fuel for diesel engines was investigated in an IDI diesel engine. Emissions were characterized with a neat BDF and with a blend of BDF and conventional diesel fuel. Since the BDF includes oxygen of about 11%, it could influence the combustion process strongly. Therefore, the use of BDF resulted in lower emissions of carbon monoxide and smoke emissions with some increase in emissions of oxides of nitrogen. It is concluded that BDF can be utilized effectively as a renewable fuel for IDI diesel engines.     

Performance and combustion characteristics of a diesel engine with titanium oxide coated piston using Pongamia methyl ester

Owing to the increasing cost of petroleum products, fast depletion of fossil fuel, environmental consideration and stringent emission norms, it is necessary to search for alternative fuels for diesel engines. The alternative fuel can be produced from materials available within the country. Though the vegetable oils can be fuelled for diesel engines, their high viscosities and low volatilities have led to the investigation of its various derivatives such as monoesters, known as bio diesel. It is derived from triglycerides (vegetable oil and animal fates) by transesterification process. It is biodegradable and renewable in nature. Biodiesel can be used more efficiently in semi adiabatic engines (Semi LHR), in which the temperature of the combustion chamber is increased by thermal barrier coating on the piston crown. In this study, the piston crown was coated with ceramic material (TiO₂) of about 0.5 mm, by plasma spray method. In this present work, the experiments were carried out with of Pongamia oil methyl (PME) ester and diesel blends (B20 & B100) in a four stroke direct injection diesel engine with and without coated piston at different load conditions. The results revealed 100% bio diesel, an improvement in brake thermal efficiency (BTE) and the brake specific fuel consumption decreased by about 10 % at full load. The exhaust emissions like carbon monoxide (CO) and hydrocarbon (HC) were decreased and the nitrogen oxide (NO) emission increased by 15% with coated engine compared with the uncoated engine with diesel fuel. The peak pressure and heat release rate were increased for the coated engine compared with the standard engine.     

Combustion characteristics of an agricultural diesel engine using biodiesel fuel

Biodiesel has great potential as an alternative fuel for diesel engines that would reduce air pollution. It is a domestically produced, renewable fuel that can be manufactured from fresh or used vegetable oils, or from animal fats. In this study, a biodiesel fuel derived from rice bran oil was tested as an alternative fuel for agricultural diesel engines. The emissions were characterized for both neat and blended biodiesel fuels, and for conventional diesel fuel. Since this biodiesel fuel contained 11% oxygen, it strongly influenced the combustion process. The use of biodiesel fuel resulted in lower carbon monoxide, carbon dioxide, and smoke emissions, without any increase in nitrous oxide emissions. The study demonstrated that biodiesel fuel could be effectively used as a renewable and environmentally innocuous fuel for agricultural diesel engines.     

Relation between scuffing resistance and the increase in surface hardness during tests under conditions of rolling/sliding

The effect on scuffing resistance of a change in the condition of the rubbing surfaces, especially surface hardness, was investigated using a two-disc machine. Scuffing resistance increased with increasing surface hardness during testing. The increase of surface hardness by work hardening is more beneficial in preventing scuffing than is a change in carbon content or heat treatment. Work-hardened disc surfaces allow surface film formation as a result of plastic deformation. Materials with large Meyer indices and high surface hardness are less prone to scuffing.     

Model of scuffing based on the vulnerability of an elastohydrodynamic oil film to chemical degradation catalyzed by the contacting surfaces

A model of scuffing is developed based on the premise that metallic surfaces can catalyze degradation of the lubricant film in situ. A failure mechanism for elastohydrodynamic films based on rapid decomposition of mineral and synthetic oils involving chemical reaction between entrapped oil and the containing surfaces is proposed. It is suggested that this destruction of the elastohydrodynamic oil film allows adhesion between nascent metal of opposing surfaces in the contact which in turn causes scuffing. Suppression of scuffing by the application of coatings that do not catalyze the oil decomposition and by the action of some lubricant additives which may block the catalytic effect of metallic surfaces is discussed. Effect of solid lubricant films and contaminant layers on scuffing is also described.     

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。     

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。     

Size distributions and number concentrations of particles from the DOC and CDPF

Particulate matters (PM) from diesel combustion comprise the major portion of harmful components of air in urban areas. In this study, the effects of DOC and/or CDPF on the size distributions and catalytic reactions of these nano-sized particles were investigated to clarify the exhaust mechanism and to minimize the emission of the nano-sized PM. Parameters of interest in the investigation included sulfur content of the fuels used, air-fuel equivalence ratio, fuel injection pressure, and the engine speed. The number concentration of the particles in diluted exhaust gas was measured by a SMPS in the diametric range of 10–385 nm. The number of nanometer-sized particles increased when the engine was operated at high equivalence ratio with diesel fuel that contained 500 ppm of sulfur. As the sulfur concentration in the fuel increased, the number of the particles smaller than 30 nm increased upon passing DOC and CDPF in the exhaust system of the common-rail diesel engine.     

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.     

Study of performance and emission characteristics of IC engines by using diesel–water emulsion

Due to the shortage of petroleum products and its increasing cost, efforts are on to develop alternate fuels, especially diesel oil, for partial or full replacement. Also, internal combustion engines generate undesirable emissions during combustion process. The emissions exhausted in to the surroundings pollute the atmosphere and causes several problems. The emissions of concern are: unburnt hydrocarbons, oxides of carbon, and oxides of nitrogen (NO_X). Advanced diesel fuel formulations offer significant emission reductions to new and older in-use engines every time the fuel tank is filled. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation. The incorporation of water also reduces NO_X emissions by lowering the peak combustion temperatures through high heat of vaporization. When using water blend diesel, the engine fuel system recognizes the liquid as diesel fuel because the water droplet is encapsulated within a diesel fuel. In this experiment, we have used single cylinder four-stroke engine and the water-blend diesel emulsion is used and the diesel emission test, emulsion emission test, and various gases has been analyzed; smoke meter test is also conducted for various rate of loads. The test results from the engine fuelled with water-blend diesel showed reduction in emissions as compared to that of engine fuelled with conventional diesel. The better emissions in the CI engine using water-blend diesel is due to the incorporation of water which reduces NO_X emissions by lowering the peak combustion temperatures. Water-blend fuel enhances fuel atomization by micro-explosion. The addition of water to diesel fuel lowers particulate emissions by serving as diluents to the key combustion intermediates that lead to particulate formation     

Scuffing Behavior of Al-Si Alloy Modified by Fine Particle Bombarding and Powder Impact Plating Hybrid Surface Treatment

The occurrence of scuffing is widely observed on tribological components made of Al-Si alloys. The object of this study is to investigate the scuffing behavior of Al-Si alloy modified by fine particle bombarding (FPB) and powder impact plating (PIP) hybrid surface treatment. FPB treatment, PIP treatment, and hybrid treatment consisting of FPB and PIP were conducted on Al-Si alloy samples. The surface morphology, microstructure, and hardness of the samples were examined. Block-on-ring tests were performed to investigate the scuffing resistance of the samples. The test results show that the scuffing resistance of Al-Si alloy depends on the surface hardness and friction coefficient. Scuffing resistance is improved by FPB treatment, which increases the surface hardness by nanocrystallization and reduces the friction coefficient by decreasing the surface roughness and producing a microdimpled surface. PIP treatment reduces the friction coefficient by generating an Sn coating on the surface of the sample, thereby improving the scuffing resistance. After FPB and PIP hybrid surface treatment, the surface hardness is increased and the friction coefficient is further reduced. Therefore, the sample modified by hybrid surface treatment exhibits the highest scuffing resistance.     

Wear and scuffing characteristics of composite polymer and nickel/ceramic composite coated piston skirts against aluminum and cast iron cylinder bores

The purpose of this research was to evaluate the tribological behavior and compatibility between coated piston skirts and aluminum or cast iron bore counterfaces. Aluminum piston skirts with either composite polymer coatings (CPCs) or nickel/ceramic composite coatings (NCCs) were evaluated. Among the NCC coated piston skirts, Ni–P–BN showed consistent low wear on either cast iron or the aluminum bores. The tin plated piston skirt generated low wear depths on cast iron or 390 Al bore surfaces, but higher wear depths on 413 Al or 356 Al bore. All the CPCs generated much less wear on cast iron or aluminum cylinder bores compared with the Ni–P–SiC or Ni–P–Si₃N₄ skirt coatings. Even the wear tests using 413 Al and 356 Al bores showed very low wear depths. Among the CPCs, two coatings with different percentages of molybdenum disulfide and graphite particles dispersed in the resin generated the lowest wear on 390 Al bore. Using a CPC over a hard-anodized surface, the bore wear depth was further reduced and became much more consistent compared with using a CPC alone. The response of the coatings to a simulation of the oil starvation associated with scuffing conditions revealed that the CPCs had intrinsic resistance to scuffing. However, the durability was not very good. The Ni–P–BN coating had intrinsic resistance to scuffing and good durability when sliding against 390 Al bore in the unlubricated conditions. The hard anodized surfaces with the CPCs showed much improved coating durability with good scuffing resistance.     

Performance and emission characteristics of conventional engine running on jatropha oil

A number of studies have recently been conducted to determine a suitable alternative fuel for conventional engine. The use of renewable fuels such as bio-ethanol, biogas, and biodiesel is thus investigated for this purpose. Performance tests were conducted on an indirect injection compression ignition engine by using diesel, unheated jatropha oil (JO), and preheated JO as fuels. The effects of fuel injection pressure and fuel inlet temperature on engine performance and emission for the different fuels were analyzed. Test results showed that the brake thermal efficiency of the engine with heated JO oil is superior to that with unheated JO, increasing from 28.4% with neat unheated JO to a maximum of 30.8%. The brake specific fuel consumption was reduced from 0.301 kg/kWh to 0.266 kg/kWh. Smoke opacity was also reduced relative to the neat unheated JO operation.     

The effect of phosphating on the friction and wear properties of grey cast iron

The friction and wear resistance of two commercial manganese phosphate coatings have been evaluated. Grey cast iron wear pins were treated by the two processes and were tested by sliding against a steel disc, under both lubricated and dry sliding wear conditions.Phosphating increases the sliding distance to scuffing as well as the scuffing load, whilst marginally reducing the coefficient of friction. No advantage was found in phosphating dry sliding surfaces.Phosphating reduces the likelihood of adhesive wear in marginal or poorly lubricated sliding couples. The choice of phosphate coating is primarily dependent on the surface finish of the sliding counterface; thin coatings are suitable if the counterface is smooth but thicker coatings are superior against rougher surfaces.     

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.