Monograde Oils Research Articles

Fullerene Oil Tribology in Compression Piston Rings under Thermal Considerations

To enhance the efficiency of automotive engines, a comprehensive understanding of friction generation within their components is paramount. Moreover, extensive global research efforts have been dedicated to nanoparticles, leading to the emergence of nanolubricants. In this study, an investigation was conducted focused on the piston ring–cylinder tribological interaction using fullerenes as additives. This is a very important issue since the friction forces can be significantly reduced. In order to solve this problem, a 2D CFD approach was implemented, taking into account a roughness model and temperature variations. The obtained results clearly show a friction reduction using fullerenes as additives compared to both synthetic and monograde oils. Furthermore, using fullerene oils, the performance of the compression piston ring system is improved due to friction reduction and the change of the temperature distribution. This study is beyond SOTA, since there is a limited contribution in the field of such nanolubricants in compression piston ring system. It is evident that the friction force is reduced by 42% compared to synthetic oils, showing a perspective on more tribologically efficient internal combustion engines.

Modeling and simulation of frictional energy loss in mixed lubrication of a textured piston compression ring during warm-up of spark ignition engine

Road vehicles account for a substantial portion of energy consumed by transportation. A large amount of this energy is lost to overcome friction within vehicle engines, in which the piston compression rings are a major source of such parasitic losses. The internal losses of engines increase several times in the case of unfavorable warm-up conditions. Recent developments in surface modification showed promising results in improving the frictional behavior of piston rings. Analyses are often idealized, such as isothermal conditions and unrealistic engine operating conditions. This study presents a numerical investigation of the frictional behavior of mixed-hydrodynamic interaction in a textured piston compression ring–cylinder liner during the warm-up process. The transient Reynolds equation is solved with a mass-conserving cavitation algorithm, realistic oil rheology, and practical engine operating conditions. Several multigrade and monograde oils are considered to draw comprehensive conclusions. The results show that ring surface texturing substantially reduces energy loss during the entire warm-up phase.

English

In this study, physicochemical characteristics of Pakistani fresh and used monograde (SAE-40, SAE-50) and multigrade (SAE-20W/50) engine oils have been studied. The samples were analyzed for specific gravity at 60/60°F, kinematic viscosity at 100 and 40°C, kinematic viscosity index, pour point, flash point, total base number, copper strip corrosion and sulphur contents following the ASTM (American Society of Testing and Material) standard methods. Five samples of automotive lubricating oils of different API (American Petroleum Institute) grades as mentioned above were included in this investigation. Samples were taken from the sumps of five different engines, that is, three spark engines, and two compression ratio diesel engines(one ordinary duty and other heavy duty engine oil) after covering several mileage of service (ranging from 800 to 2800 km). Results show the deterioration of the samples with increased reduction as the vehicle covers more distance with the same oil which needs to be replaced. Specific gravity increases with usage due to engine wear and induction of oxidation products. Viscosity of all samples decreases as the oil ages, which is due to lighter end contaminants. Pour point of monograde oil slightly decreases with usage but no change in pour point was found in more stable multigrade oil. Flash point and Total Base number decreases depending upon the usage of oil. Sulfur contents of used oil were recorded higher because of the presence of wear caused between the moving parts as the oil strength decreases with increased usage which then cannot prevent the friction among the moving parts of the engine. Key words: Physico-chemical, characteristics, used engine oil, Pakistan.

The effect of load and viscosity on the minimum operating oil film thickness of piston-rings in internal combustion engines

Computer simulations are now routinely used in the design and analysis of ring packs for internal combustion engines. Commonly they predict that an increase in engine load decreases minimum operating film thickness because oil availability and oil transport through the ring pack are reduced under these conditions. To assess the reliability of new simulations, investigators compare the output of computer models with experimental measurements of parameters on operating engines. Contributing to this process this paper presents an experimental study of an investigation into the effect of load on the minimum oil film thickness between piston rings and cylinder liner in a fired compression ignition engine. Oil film thickness data were collected using capacitance-based transducers located near top dead centre and mid-stroke. Experiments were performed at 2000 r/min using two mono-grade oils (SAE 50 and SAE 20) and one multi-grade oil (SAE 5W50) under a range of fixed engine loads. The experimental data obtained are discussed in the context of experimental and theoretical work published by other investigators.

Heat transfer characteristics of some oils used for engine cooling

This paper reports the results of an experimental investigation of heat transfer from a cast iron test specimen to engine oils under boiling conditions. The work is aimed at evaluating the thermal characteristics of some engine oils in contact with high temperature parts in internal combustion engines. Three mono-grade oils and two multi-grade oils are examined at heat fluxes from about 30 to more than 400 kW/m2 for bulk temperatures of 40, 60, 80, 100, 125, 150 and 175 °C. The considered oils are analyzed and tested according to some ASTM standards to determine their additives concentration and to obtain some of their thermophysical properties. The results indicated that oil additives, oil properties and bulk temperatures have substantial effects on the oil characteristics. The boiling heat flux, for the best oil, rises by a factor of 1.65 as the bulk temperature decreases from 175 to 40 °C. The mono-grade oils produce superior heat transfer characteristics compared to those produced by multi-grade oils. The oil with the best additive concentrations produces boiling heat fluxes up to 4.44 times higher than those produced by some other oils. Comparing the results of the tested oils revealed that the oil that has the largest concentrations of boron, magnesium, phosphorus and zinc with low concentration of calcium yields the best heat transport characteristics among the other tested oils. These additives provide superior detergent and dispersant characteristics, reflected in the large alkalinity and low corrosivity of the oil. On the other side, calcium has a negative interaction with other additives and yields an adverse effect on heat transfer characteristics even when it exists in oil with large concentrations of boron, magnesium, phosphorus and zinc.

Assessment of Oxidation in Automotive Crankcase Lube Oil: Effects of Metal and Water Activity

The changes in oxidation stability of two grades of crankcase lube oil, monograde (SAE 40) and multigrade (SAE 20W50), and their base oils were monitored by measuring their carbonyl peak index with respect to time in order to corroborate the results of sludge deposit and soluble acidity characteristics. The carbonyl peak index was calculated as the difference in the ratios of the absorbance of the carbonyl band at 1700 cm-1 and of the basic peak methyl stretching vibration at around 3000 cm-1 at oxidation time t and the start of the experiment. The results showed that the base oils were oxidized to a greater extent than the formulated oils. The monograde oil and its base oil had higher carbonyl peak indexes than their respective multigrade counterparts, showing that the monograde oils were less resistant to oxidation than the multigrade oils. However, results of sludge deposits and soluble acidity showed that the multigrade oils formed more oxidation products than the monograde oils, which also incidental...

The role of metals in the oxidative degradation of automotive crankcase oils

The influence of oil/metal interactions on the oxidation of automotive crankcase oils (monograde and multigrade) is investigated in a modified turbine oil oxidation stability test apparatus, using oil soluble organometallic salts and fresh elemental metals of zinc, nickel and aluminium to simulate the homogeneous and heterogeneous oil/metal interactions respectively. The presence of the metals in the oils exhibits a catalyst-inhibitor conversion phenomenon by acting as auto-oxidants. Although the action of the metals in the two forms appeared non-specific, zinc and nickel were found to be more active oxidation catalysts in the heterogeneous form. Furthermore, the metals were found to cause significant reductions in sludge deposit formation in the oils by interfering with the polymerization of the oxidation products, through reactions that may involve metal-directed decarboxylation of carboxylic acids. In general, the metals showed more catalytic effects in the monograde oil relative to the multigrade oil and this is related to the differences in the types of hydrocarbons in the base oils.

Carbonyl peak index technique in the study of lubricant oxidation

A technique known as the Carbonyl Peak Index (CPI) is used to assess the relative oxidation stabilities of two competing grades of commercial automotive crankcase oils, their base oils, and the oxidation characteristics resulting from oil/metal interactions. The CPI provided empirical data from the infrared spectra which enabled a more lucid explanation of the oil soluble acidity and sludge deposition characteristics of the oils. A combination of these parameters has confirmed that the hydrocarbon type composition of the oils gave some stability to the fully formulated monograde oil. Consequently, the monograde base oil was found to possess a greater stability towards oxidation than the multigrade base oil under the conditions of test. However, the fully formulated oils were found to be more stable than the base oils, mainly due to the added antioxidants. Metals in the oils acted as antioxidants initially, but later turned to pro-oxidants. The reversal of metal action from inhibition to autooxidative catalysis was also found to be base-oil hydrocarbon-type dependent and this has been related to the natural antioxidant capacity of the oils.

Studies on the ageing characteristics of automotive crankcase oils

The ageing characteristics of two competing lubricants, monograde and multigrade crankaase oils, have been studied. A combination of oil acidity, deposit formation and infra-red spectroscopy were used to follow the ageing of the lubricating oils. Both oils showed a similar pattern of ageing. However, the monograde oil, showed a higher tendency to form carbonyl compounds, but the multigrade oils formed more active carbonyl compounds, which polymerized rapidly to form deposits. Consequently, the multigrade oil aged faster than the monograde oil.