Potential of CuS and CuO nanoparticles for friction reduction in piston ring–liner contact

ABSTRACT An experimental study on the use of Cu nanofluids as engine oils for reduction of friction in piston ring–liner contact is presented. The Cu nanofluids were prepared using CuS and CuO nanoparticles and blending them in 0.1–6% concentration by weight in the commercial engine oils. The Cu nanoparticles were synthesised and characterised after mixing with the lubricant for their physico-chemical characteristics. The experiments were performed on a reciprocating tribo-tester using actual piston rings and the liners as test specimens. Experiments were performed to investigate the effect of nanoparticle concentration with the change of contact loads and reciprocating frequency on the coefficient of friction. The study reveals that the Cu nanoparticles blended in the engine lubricating oils can significantly reduce friction between piston ring–liner contact, desirable for fuel economy improvement. The Cu nanoparticles are compatible with base lubricants and result in significant friction reduction. The CuS nanoparticles performed significantly better than the CuO nanoparticles. GRAPHICAL ABSTRACT