Tribometer Investigation of the Frictional Response of Piston Rings when Lubricated with the Separated Phases of Lubricant Contaminated with the Gasoline Engine Biofuel Ethanol and Water

Abstract

The biofuel ethanol, a viable and cost-effective gasoline substitute, is being blended at increasingly higher concentrations in gasoline, heightening the need to investigate its effects on current automotive engine lubricants in terms of fuel economy and engine durability. The friction at the piston ring/cylinder wall interface with a fully formulated gasoline engine lubricant contaminated with ethanol and water was investigated using a Plint TE77 reciprocating tribometer and reported in a previous paper by the authors. This research takes this one stage further by studying the friction in the same tribometer configuration when lubricated with the separated phases the same contaminated lubricant forms when left undisturbed, as would happen when a vehicle is parked or garaged. The lubricant mixture separated into two distinct phases, an oil phase and a water and ethanol based 'white sludge' phase, both phases characterised by FTIR spectroscopy and viscosity. Significant reductions in friction were obtained when the piston ring-cylinder wall interface was lubricated with the separated phases compared to the formulated reference lubricant. When lubricated with the separated oil phase, temperature was shown to be the dominant contributor to the frictional response. When lubricated with the separated sludge phase, ethanol independently contributed to the frictional response whilst the interactions between ethanol and temperature, water and temperature and water and speed were also important.

Effect of gasoline–bioethanol blends on the properties and lubrication characteristics of commercial engine oil

“…As mentioned earlier, bioethanol is miscible with water but immiscible with oil, so that there would be the formation of emulsions inside bioethanol-water-oil mixture, which leads to serious engine wear and catastrophic engine failure. 15 As a consequence, engine oil needs to be drained on a frequent basis. It has been observed that even a small amount of fuel dilution is possible to degrade the physicochemical properties of lubricant (viscosity, total base number, and total acid number) which play an important role in the lubricating system.…”

Impact of ethanol on the formation of antiwear tribofilms from engine lubricants

“…Despite this challenge, very few studies on the effects of ethanol on friction (De Silva, et al (14,De Silva,et al (15)), lubrication (Chui,et al (12,Boons,et al (17,Chui and Millard (18)) and wear (Ferrarese,et al (13,Volcci (16)) of automotive engine parts can be found in the literature.…”

“…They found that although the presence of ethanol did not affect friction measurements significantly, the combined presence of water and ethanol in the lubricant reduced friction. They also measured friction using the phases separated from a contaminated lubricant when left undisturbed, as would happen when a vehicle is parked or garaged (De Silva, et al (14)), and found friction reduction when the contact was lubricated with the separated oil and the sludge phases of the lubricant/ethanol/water mixtures compared to the formulated reference lubricant.…”

Interactions of Ethanol with Friction Modifiers in Model Engine Lubricants

“…On the other hand, the effects of ethanol contamination on friction are not always detrimental. De Silva and coworkers have shown that in combination with water, ethanol can produce a considerable friction reduction [12,16]. Our previous work has also shown friction reduction for lubricants contaminated with anhydrous ethanol and hydrated ethanol under certain conditions because ethanol fuel can be either anhydrous (when supplied dissolved in gasoline) or hydrated when used on its own.…”