The influence of carbon chain length and branch chain effect on the low-temperature combustion characteristics of bio-based ether-ester double functional group fuel.

• Analyze the impact of the carbon chain length and branch chain effect on the combustion characteristics. • Explore the types and concentration trends of low-temperature oxidation intermediates of different fuels. • Speculate the formation path of intermediate products and affect activity mechanistic. • Study the relationship between NTC stage, fuel activity and ignition timing. Bio-based oxygenated fuels offer potential as alternative fuels or additives for enhancing engine efficiency and curbing pollutant emissions. This study aims to investigate the impact of carbon chain length and branched chain structure on low-temperature combustion characteristics. Five oxygenated fuels with distinct structures, namely 2-methoxyethyl acetate (MEA), 2-ethoxyethyl acetate (EGMEA), 2-butoxyethyl acetate (BGA), Propylene glycol methyl ether acetate (PGMEA), and 3-methoxybutyl acetate (3-MTBA), were selected to examine low-temperature exothermic traits and oxidation intermediate products under varying compression ratios. The findings indicate that increasing carbon chain length enhances the low-temperature oxidation activity of fuels, while the branched chain effect inhibits this activity, impacting the occurrence and persistence of the negative temperature coefficient (NTC) stage as commonly observed with their hydrocarbon analogs. Acids and cyclic ethers, along with unique ester products in the intermediate stage, play pivotal roles in regulating the low-temperature oxidation process. Besides the ketohydroperoxide (KHP) mechanism, distinct products emerge by preserving ester groups and undergoing bond-breaking reactions at other active sites. Additionally, it is observed in the experiment that some products have selectivity towards oxidation/decomposition under the conditions in the cylinder, and the intermediate products are completely reacted before compression ignition. Mechanistically, the manipulation of carbon chain length and the branch chain effect influences the overall low-temperature oxidation activity by affecting the formation path of QOOH. [ABSTRACT FROM AUTHOR]