Effect of Micro Texture on Tribological Performance of Piston Ring-Cylinder Liner System under Different Lubrication Regimes

The main drawbacks of the IC engine are low thermal and mechanical efficiencies with a significant proportion of fuel energy is dissipated as heat, and about 12% fuel energy is lost due to friction. Many research works are going on to reduce these losses in IC engine, as, even if, reduction of 10% in total friction loss can be achieved it will result in 1.5% drop in fuel consumption, which will ultimately give huge economic benefit. It has been recently identified, that optimally texturing of a tribological surface reduces friction and wear at sliding contact interfaces, as it acts as a micro-reservoir for lubricant and entraps wear particles. In the present study, this theory is utilized to reduce friction in piston ring-cylinder liner (PRCL) contact by using micro textured piston ring. Tribological performance of micro textured PRCL system is investigated under medium passenger vehicle engine operating conditions using reciprocating tribometer test rig. Texturing is done using laser surface texturing method. Segments of steel piston ring and grey cast iron cylinder liner were used as test samples. Experiments are performed in Bruker’s UMT Tribolab with a stroke length of 15 mm and temperature is maintained at 80 °C. To simulate the different lubricating regimes the sliding frequency is varied from 0.1 Hz to 5 Hz and 8 Hz, while the contact pressure has been kept constant at 3 MPa. PAO is used as a lubricant. It has been found that the coefficient of friction is decreasing in boundary and mixed lubrication regimes for a textured surface, while in hydrodynamic regime value of CoF remains unchanged. The reason for this reduction is the additional hydrodynamic force provided by lubricant entrap inside the dimples.