Enriching various biodiesel feedstocks with Al2O3 nanoparticles in diesel engines: Performance, emissions, and exergy analysis

Abstract

The inherent drawbacks of biodiesel, particularly its poor performance in cold climates, necessitate the use of nano-additives to improve its cold flow properties such as the cloud point (CP), pour point (PP), and cold filter plugging point (CFPP). In this study, transesterification was employed to produce methyl esters from waste cooking oil, corn oil, and jatropha oil. These biodiesels were blended with diesel fuel at a 20% biodiesel and 80% diesel volume ratio and enriched with nano-Al₂O₃ at concentrations of 25, 50, and 100 mg/L. The aim of this study is to evaluate the impact of nano-Al₂O₃ on engine combustion, performance, exergy, and emissions of diesel engines using different biodiesel feedstocks. The addition of nano-Al₂O₃ to methyl ester mixtures (JB20A100, CB20A100, and WB20A100) resulted in enhancements in thermal efficiency by 8%, 11%, and 13%, respectively. CO emissions were reduced by 12%, 17%, and 22% for jatropha, corn, and waste cooking oil blends, respectively, with 100 ppm alumina. This reduction in CO emissions can be linked to the enhanced oxidation process facilitated by the high surface area of the nanoparticles, which act as catalysts, promoting more complete combustion. Similarly, UHC emissions decreased by 14%, 18%, and 23%, and smoke concentrations were significantly reduced by 14%, 17%, and 24% across the biodiesel blends. However, the introduction of alumina led to the rise in NO_x emissions by 9%, 15%, and 19% for JB20A100, CB20A100, and WB20A100, respectively. The study also revealed increases in cylinder pressure by 2%, 4%, and 8%, and maximum heat release rates by 3%, 6%, and 10% for JB20, CB20, and WB20, respectively, upon the incorporation of 100 ppm Al₂O₃. Exergetic efficiencies improved by 6%, 17%, and 23% for JB20A100, CB20A100, and WB20A100, respectively, and the sustainability index showed enhancements of 2%, 4%, and 7%. Among the tested blends, WB20 with 100 ppm of nano-Al₂O₃ demonstrated the most promising results, significantly improving engine exergy, combustion, and performance while mitigating emissions to acceptable levels. This study underscores the potential of nano-additives to advance the sustainability and efficiency of diesel engine operations, particularly in cold climate.