Enhancing the thermophysical properties and tribological behaviour of engine oils using nano-lubricant additives

What is it about?

This paper presents the enhancement of thermophysical properties (thermal conductivity and viscosity) of engine oil using nano-lubricant additives and a characterization of tribological behaviour in terms of sliding contact interfaces (piston ring assembly) in automotive engines. Al2O3, TiO2 and Al2O3/TiO2 hybrid nanoparticles were suspended in commercially available engine oil (5W-30) in a concentration of 0.25 wt.% for formulating the nano-lubricants. The size of Al2O3 nanoparticles were within the range 8-12 nm while the TiO2 nanoparticles used had a size of 10 nm. The tribological experiments were performed using a tribotester to simulate the sliding reciprocating motion of the piston ring/cylinder liner interface in an engine. The performed tribological tests were all carried out under varying speeds, loads and sliding distance. The experimental results showed that nano-lubricant additives enhanced the thermophysical and tribological properties. The thermal conductivity of lube oil was measured by the 3ω-wire method. Nano-lubricants provide low kinematic viscosity and an increase in the viscosity index by 2%. Whilst, thermal conductivity was enhanced by a margin of 12-16% for a temperature range of 10-130 °C facilitating the dissipation of frictional heat and maintain engine oil properties, as compared with commercial lubricant. The tribological tests showed a minimization of the friction coefficient and wear rate of the ring by 40-50% and 20-30%, respectively. According to the results, nano-lubricants can contribute to improving the efficiency of engines and fuel economy in automotive engines.

Featured Image

Why is it important?

Nano-lubricants showed an improvement of 12-16% in thermal conductivity in the temperature range of 10-130 °C due to the Brownian movement of nanoparticles. Al2O3/TiO2 hybrid nano-lubricants presented a maximum enhancement of thermal conductivity because of the reduction in thermal interface resistance between the nanoparticles, as compared with engine oil without nanoparticles.

Perspectives