Impact of multi-walled carbon nanotubes (MWCNTs) on hybrid biodiesel blends for cleaner combustion in CI engines

Abstract

This study investigates the influence of multi-walled carbon nanotubes (MWCNTs) and hybrid biodiesel blends on the performance, combustion, and emission characteristics of a compression ignition engine. The hybrid biodiesel comprises waste frying oil methyl ester (WFOME), sesame oil methyl ester (SOME), and ultra-low sulfur diesel (ULSD) blended at 20 %:80 % by volume (B20). MWCNTs were added into B20 at 25 ppm and 50 ppm concentrations (B20-25MWCNT and B20-50MWCNT). Experimental analysis was conducted under varying engine loads and injection pressures, complemented by CFD simulations. Results demonstrate that the addition of MWCNTs significantly enhances B20 blend performance, with B20-50MWCNT exhibiting a 25 % increase in brake thermal efficiency and a 17 % reduction in brake specific fuel consumption compared to neat B20. Additionally, the incorporation of MWCNTs resulted in notable reductions in harmful emissions. NOx emissions for the B20 + 50MWCNT blend were reduced by up to 36 % compared to diesel and 43 % compared to B20. Smoke opacity and particulate emissions also showed significant decreases, highlighting the cleaner combustion facilitated by the presence of MWCNTs. The CFD simulations provided detailed insights into the combustion process, validating the experimental findings and elucidating the mechanisms behind the observed improvements. The enhanced fuel atomization, better fuel-air mixing, and catalytic properties of MWCNTs were identified as key factors contributing to the superior performance and reduced emissions.