Tribological Effects of Diesel Engine Oil Contamination on Steel and Hybrid Sliding Contacts
01 Jan 2020-pp 279-296
TL;DR: In this paper, the influence of contaminants and their interactions on diesel engine oil using Electro Sensing (ES) monitoring was investigated using a pin-on-disc (PoD) tribometer, all tests were carried out under ambient conditions at 5 m/s sliding speed and contact stress of 1.5-2.05 GPa.
Abstract: In advanced automotive engines, especially in diesel engines, consumer demand for ever increasing service intervals for vehicles has led to longer oil drain periods. Consequently this has increased contamination levels in lubricating oils that will in turn reduce engine efficiency and increase the possibility of system failure due to increases in viscosity and the potential of oil starvation leading to scuffing and catastrophic failure of the engine. Therefore it is necessary to understand the effects of contaminants in diesel engine oil on the tribological performance of tribo-contacts and also the possible interaction between the contaminants. The paper aims to investigate the influence of contaminants and their interactions on diesel engine oil using Electro sensing (ES) monitoring. Using pin-on-disc (PoD) tribometer, all tests were carried out under ambient conditions at 5 m/s sliding speed and contact stress of 1.5–2.05 GPa to simulate a valve-train in a diesel engine with fully formulated heavy-duty diesel engine oil used as lubricant. In the first phase, using a parametric study examining the effect of four contaminants (soot, oxidation, moisture, and sulphuric acid) at varying levels (four for each) on steel-on-steel sliding contact. It was observed that all contaminants and contaminant levels reduce the conductivity of the oil. Oxidation and soot contaminants produced large increases in viscosity. The wear rate was mainly influenced by acid and soot additions, while the coefficient of friction was increased by all contaminants and contaminant levels. The steady-state charge levels changed for some contaminants. The best correlation of steady-state charge with the other measured tribological parameters of wear rate, friction, and temperature is seen for the series of oxidized oils. The multi-contaminated oil (L4× 4) shows remarkably little degradation in tribological performance. Analysis of the wear mechanisms shows that soot and oxidation produced abrasion and polishing wear, respectively, while sulphuric acid and moisture produced corrosive wear. In the second phase, investigates the effects of diesel contaminants and their interaction on tribological properties for bearing steel (En31) and ceramic (Si3N4) sliding contacts using a factorial study. The contaminants are soot, sulphuric acid, moisture and oxidation, and each contaminant has three different level of concentration (low, medium and high) in the test matrix. The factorial test matrix consisted of 20 tests, constructed from a quarter fractional factorial test matrix with four points at the medium values for the contaminants. Results from this matrix required six further tests to elucidate aliased pairs of interactions using Bayesian model selection. A pin-on-disc tribometer was used to carry out all the experiments. The factorial study showed that charge was influenced by tribo-couple material; the silicon nitride discs produced higher charge than steel discs. However, it was opposite for friction; the silicon nitride disc gave lower friction and the pins showed higher friction than their steel counterparts. For wear scar and temperature, soot contaminant was found to be important. The two important interactions were found for the charge response, with the interaction between sulphuric acid and pin material being more important than sulphuric acid–oxidation interaction. Similarly to charge, an interaction between sulphuric acid and pin material interaction was found for friction. To conclude, the ES monitoring was sensitive to the presence and levels of contaminants in diesel lubricating oil, particularly diesel soot. The change in charge levels indicated the concentration of soot level present in the contact, which was directly related to wear. ES monitoring also detected interactions between the contaminants through statistical analysis. ES monitoring has shown that monitoring lubricant performance and the effects of contamination are feasible under laboratory conditions.
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TL;DR: In this article, the performance of both new and worn motor oils with different American Petroleum Institute (API) performance classifications, which were taken from various motor trains during maintenance or oil change, was assessed.
Abstract: Internal combustion engine lubrication is essential for unwanted energy and material losses. As part of the experimental work, the lubricity of both new and worn motor oils of Society of Automotive Engineers (SAE) 15W-40 and SAE 10W-40 with different American Petroleum Institute (API) performance classifications, which were taken from various motor trains during maintenance or oil change, was assessed. A total of sixteen lubricant samples were evaluated. Lubricity, i.e., the load capacity of the lubricating film, was evaluated on the basis of the Reichert test. Viscosity, as one of the most important parameters of lubricants, was evaluated by the Stabinger Viscometer. Chemical degradation of motor oils (oxidation, nitration, sulfation), contamination of oils with fuel, soot, water, and loss of antioxidant zinc dialkyldithiophosphate (ZDDP) were monitored by Fourier-transform infrared (FTIR) spectroscopy. Of the fresh motor oils, OMV 10W-40 API SL/CF motor oil had the best lubricity. URANIA LD 15W-40 API CI-4 and M7ADS V 15W-40 API CI-4 CH-4/SL oils showed similar lubricity. M7ADS III 15W-40 API CF-4/SG motor oil showed the highest wear of wear surface, i.e., the lowest lubricity, of the tested new motor oils. Correlation analysis of the experimental data confirmed that the fuel content penetrated the motor oils significantly negatively correlates with the viscosity (R = −0.87). The low water contamination in motor oil does not cause a significant negative effect on lubricity. A significant correlation between the oxidation, nitration, and sulfation products of chemical degradation of the tested oils was confirmed (R ≥ 0.90). These degradation products improve lubricity due to their polarity, i.e., they have caused better lubricity of worn oils compared to new motor oils. Even the depletion of the antioxidant ZDDP did not affect the reduction in lubricity and anti-abrasion properties of chemically degraded motor oils. The experimental results of testing of worn motor oils taken from motor trains showed that current motor oils have excellent lubricity, which they maintain throughout their life.
18 citations
01 Jan 1987
TL;DR: In this article, a CD 10W-30 engine oil additive was developed by selection of additives from the viewpoint of capability to neutralize sulfuric acid and the developed product demonstrated very good wear protection performance in the bench tests using EGR equipped engines.
Abstract: Piston ring moving zone in the cylinder is one of the most critical lubrication regimes in diesel engines. This area is susceptible to combustion substances. In particular, abnormal wear is occasionally detected due to Exhaust Gas Recirculation (EGR) system equipment. In Japan, NO/sub x/ emission requirements for passenger car diesels have become more stringent effective October 1, 1986. OEMs tend to apply EGR systems to reduce NO/sub x/ in exhaust gas. In order to identify the phenomenon of abnormal cylinder wear of EGR equipped engine, engine bench tests were conducted under varied conditions in EGR equipment, cooling water temperature and fuel sulfur content. The test results suggest that wear caused at low temperature is mainly corrosive wear attributable to sulfuric acid formed by reaction with fuel sulfur and condensed water. Engine oil additives behavior against sulfuric acid was studied for control of corrosive wear and excellent CD 10W-30 engine oil was developed by selection of additives from the viewpoint of capability to neutralize sulfuric acid. The developed product demonstrated very good wear protection performance in the bench tests using EGR equipped engines.
2 citations
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TL;DR: In this paper, the authors provide a comprehensive overview of various lubrication aspects of a typical powertrain system including the engine, transmission, driveline, and other components, as well as the integration of these lubrication and surface engineering concepts into a unified automotive power-train system.
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TL;DR: In this article, the effects of soot contaminated engine oil on wear of engine components was examined using a statistically designed experiment using three oil properties studied were phosphorous level, dispersant level and sulfonate substrate level.
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TL;DR: In this article, a pin-on-plate tribometer with the reciprocating motion of SiC against yttria-doped tetragonal zirconia polycrystal (Y-TZP) plates was used to investigate the wear resistance of TZP ceramics.
Abstract: Using a pin-on-plate tribometer with the reciprocating motion of SiC against yttria-doped tetragonal zirconia polycrystal (Y-TZP) plates, the friction and wear of Y-TZP ceramics were investigated as a function of grain size in dry N2 at room temperature. The results showed that the overall wear resistance increased as the grain size of Y-TZP ceramics decreased. For grain sizes ≤0.7 μm, the wear results revealed a Hall-Petch type of relationship (d−1/2) between wear resistance and grain size. In this case, the main wear mechanisms were plastic deformation and microcracking. For grain sizes ≥0.9 μm, the wear resistance was proportional to the reciprocal of the grain diameter. In this regime, delamination and accompanying grain pullout were the main mechanisms. In this case, the phase transformation to monoclinic zirconia had a negative effect on the wear resistance of TZP ceramics. The coefficient of friction tended to be higher for fine-grained TZP-SiC couples than for coarse-grained TZP-SiC couples, whereas, for a specific regime of grain size, the coefficient of friction was almost independent of the grain size.
92 citations