A comparative study on natural and synthetic additive with juliflora methyl ester operated CI engine in a LHR mode

Biodiesel is a promising alternative fuel derived from renewable feedstocks like vegetable oils and animal fats. However, biodiesel usage in compression ignition (CI) engines reduces performance and increases NOx emissions compared to petroleum diesel. This study aims to improve the efficiency of juliflora methyl ester (JFME) biodiesel and simultaneously reduce NOx emissions by converting a CI engine into low heat rejection (LHR) mode and adding natural and synthetic antioxidants. The transesterification process produced JFME biodiesel from Juliflora seeds. A 20% blend of JFME biodiesel with diesel (JFME20) was optimal based on fuel property analysis. The CI engine was coated with lanthanum oxide to create a LHR engine. Natural (Albizia lebbeck leaf extract) and synthetic antioxidants were added to JFME20 at 0.01% concentration. Engine tests showed that JFME20 with natural antioxidants in LHR mode decreased NOx by 15.4% and smoking by 5.48% compared to baseline diesel in a normal CI engine at full load. The brake thermal efficiency of the LHR engine with natural antioxidants increased by 1.8%. CO and HC emissions reduced by 30.76 and 36.95%, respectively. The synthetic antioxidant was less effective than the natural one. In summary, the antioxidant-enriched JFME20 biodiesel blend in the LHR engine demonstrated superior performance over baseline diesel while substantially reducing NOx and other emissions.