Experimental investigation of switchable behavior of CuO-MWCNT (85%-15%)/10W-40 hybrid nano-lubricants for applications in internal combustion engines

In this study, we examined the rheological behavior of hybrid nano-lubricant CuO-MWCNT (85%-15%)/10W-40 at the temperature range of 5 to 55 °C and the solid volume fraction of 0.05 to 1% to use in internal combustion engines. According to experimental data, by increasing the solid volume fraction, the amount of nano-lubricant viscosity increases compared with pure lubricant, so that the maximum amount of dynamic viscosity enhancement in solid volume fraction of 1% is about 43.52%. Nano-lubricant behavior is diagnosed by using the Herschel-Bulkley (type Bingham) model, so that in temperatures < 45 °C, nano-lubricant shows non-Newtonian behavior of Bingham pseudoplastic, and it shows Bingham plastic non-Newtonian behavior at temperatures above 45 °C. Finally, to predict the dynamic viscosity of nano-lubricant, a mathematical correlation with second order precision of 0.9846 was presented, which it had acceptable match with experimental data.