Bio-lubricant-biodiesel combination of rapeseed oil: An experimental investigation on engine oil tribology, performance, and emissions of variable compression engine

The substitution of petroleum based synthetic lubricant with rapeseed oil based bio-lubricant in a variable compression ratio diesel engine is explored in this study. Rapeseed oil based bio-lubricant was formulated through chemical modifications like epoxidation, hydroxylation and esterification process for improving its thermo-oxidative stability and cold flow properties. The nano CuO (copper oxide) an anti-wear nano additive was added to chemically modified rapeseed oil to improve anti-wear behavior. To study the compatibility of formulated bio-lubricant, two endurance tests of 150 h each were conducted on a four-stroke variable compression ratio engine fueled with B20 rapeseed oil bio diesel at a standard CR (compression ratio) of 17.5:1 using synthetic lubricant (SAE20W40) and formulated bio-lubricant. The various challenges related to performance and emission analysis are discussed and compared with SAE20W40 from no load to full load conditions and at different CR varies from 12:1, 15:1 and 17.5:1 with B20 rapeseed oil based biofuel/bio-lubricant combination. The main findings show that the combined use of biofuel/bio-lubricant of rapeseed oil reduced Fe, Al, Cu wear, soot and ash content, when compared to bio fuel/SAE20W40 combination. The brake thermal, mechanical efficiencies and brake power with rapeseed oil based bio-lubricant is comparable with SAE20W40 and also the similar emission spectra was observed in the bio-lubricant.