Effect of Lubricant Contaminants on Tribological Characteristics During Boundary Lubrication Reciprocating Sliding

📝 Abstract

This article presents the effect of the presence of solid contaminants, in engine lubricating oil, on the tribological parameters, which impact negatively on the performance of the engine and increase fuel consumption. This study revealed that the lubricant was contaminated by Fe, Cu, Al, Pb and SiO2 particles. The tribological tests were performed using 0.63, 0.85 and 1.1 m s-1 average sliding speeds and 120 N contact load to mimic the boundary lubrication regime of the sliding reciprocating motion of the piston ring/liner interface in an engine. The presence of the solid contaminants in engine oils leads to an increase in friction coefficient, wear and frictional power losses, increasing the surfaces roughness as a consequence. The results showed that grain size and concentrations strongly affected the tribological parameters. In order to minimize the effect of solid contaminants, it is necessary to improve the filtration accuracy for lubricating oils.

💡 Analysis

This article presents the effect of the presence of solid contaminants, in engine lubricating oil, on the tribological parameters, which impact negatively on the performance of the engine and increase fuel consumption. This study revealed that the lubricant was contaminated by Fe, Cu, Al, Pb and SiO2 particles. The tribological tests were performed using 0.63, 0.85 and 1.1 m s-1 average sliding speeds and 120 N contact load to mimic the boundary lubrication regime of the sliding reciprocating motion of the piston ring/liner interface in an engine. The presence of the solid contaminants in engine oils leads to an increase in friction coefficient, wear and frictional power losses, increasing the surfaces roughness as a consequence. The results showed that grain size and concentrations strongly affected the tribological parameters. In order to minimize the effect of solid contaminants, it is necessary to improve the filtration accuracy for lubricating oils.

📄 Content

1

Effect of Lubricant Contaminants on Tribological Characteristics During Boundary Lubrication Reciprocating Sliding Mohamed Kamal Ahmed Ali *, Fawzy M.H. Ezzat, K.A.Abd El-Gawwad, M.M.M.Salem.

Automotive and Tractors Engineering Department, Faculty of Engineering, Minia University, 61111, El-Minia, Egypt.

• Corresponding author: Eng.m.kamal@mu.edu.eg (M. K. A. Ali) Abstract:
  This article presents the effect of the presence of solid contaminants, in engine lubricating oil, on the tribological parameters, which impact negatively on the performance of the engine and increase fuel consumption. This study revealed that the lubricant was contaminated by Fe, Cu, Al, Pb and SiO2 particles. The tribological tests were performed using 0.63, 0.85 and 1.1 m s-1 average sliding speeds and 120 N contact load to mimic the boundary lubrication regime of the sliding reciprocating motion of the piston ring/liner interface in an engine. The presence of the solid contaminants in engine oils leads to an increase in friction coefficient, wear and frictional power losses, increasing the surfaces roughness as a consequence. The results showed that grain size and concentrations strongly affected the tribological parameters. In order to minimize the effect of solid contaminants, it is necessary to improve the filtration accuracy for lubricating oils.
  Keywords: Solid contaminants, Engine oils, Boundary lubrication, Friction, Wear.

1. Introduction The main purpose of lubricating oils is the reduction of friction between surfaces, prevention of wear and rust, cooling by removing the heat resulting from the contact of the surfaces and the cleaning of automotive engines as a protection from damage caused by friction and wear.
   Mechanical frictional losses in automotive engines vary between 17% and 19% of the total energy generated by an engine.1, 2 The piston ring-cylinder liner contributes approximately 40% 2

to 50% of frictional losses in automotive engines. The sliding contact between engine parts comprises a variety of different friction and wear mechanisms during one working cycle of the engine. Due to the variations in speed, load and counter surface effects, the lubrication conditions in an engine are strongly transient, which is reflected by variations in the friction and wear behavior. Maximum values of friction coefficient at top dead center and bottom dead center locations were in the range of 0.10 to 0.15 with mid-stroke values ranging from 0.05 to 0.10 for the study conducted by Ali.3 These values depend on the particular lubricant used, the surface quality and surface material.4
The major sources of these contaminants in lubricating oils are prior blowby, lubricant breakdown, and wear of engine parts. Solid contaminants such as iron (Fe), copper (Cu), aluminum (Al), lead (Pb) and silicon oxide (SiO2) are a result of the wear of the engine parts as a consequence of external contaminants mixing with the lubricating oil, fuel and intake air. Figure 1 displays the types of contamination in pneumatic, fluid, and solid forms as well as its effects. The damage of the parts is dependent on grain size of particles, concentrations, texture of the particles and operating pressure.5 The solid contaminants mainly consist of particles.6 The presence of solid contaminants enhances the oxidation of lubricating oils.7 The lubrication regimes for the piston ring assembly depend on contact load, the kinematic viscosity of lubricating oils, sliding speed and surface roughness.8 A high level contaminant concentration in the form of solid particles leads to high thin-film wear at the start of sliding.9 The presence solid contaminants in lubricating oils responsible for the failure of machine parts.10 The reason for an engine oil change could be due to its deterioration in terms of viscosity and oxidation, as well as solid contaminants that become mixed or dissolved in the lubricating oils. The presence of contaminants in engine oil is generally undesired, as solid contaminant particles are a potentially cause of abrasive wear. On the other hand, liquid contaminants may cause 3

corrosive, viscosity and tribochemical wear changes.11, 12 Contamination of lubricating oils causes wear of piston ring, which generates more contamination. This proceeds via internal wear generating fresh wear debris leading to the opening of the dynamic sealing surfaces. Bore polishing is another undesired impact of small abrasive particles the lubricating oils, while larger particles can cause scratches in the bore.13 The total friction in an engine immediately after a cold-start is four to five times higher than at fully warmed-up conditions.14 The source of the contamination particles may be soot from combustion, silica dust and similar minerals, and wear particles consisting of ferrous, lead, chromium, copper, aluminum, nickel alloys and tin15 The
diesel soot interacts with lubricati

This content is AI-processed based on ArXiv data.