Low-Temperature Combustion of n -Heptane Blended with Biobased Oxygenated Fuel

Abstract

The coupling of biobased oxygenated fuels with low-temperature combustion (LTC) technologies offers a promising pathway to reduce dependence on fossil fuels and optimize compression-ignition combustion processes. However, a systematic understanding of how the fuel molecular structure regulates the reactivity of blended fuels remains limited. In this study, using n-heptane as a diesel surrogate fuel, the low-temperature combustion characteristics of methyl caprate (MC), dipropylene glycol dimethyl ether (DPDME), and five other ether-ester oxygenated fuels were investigated at various blending ratios using a cooperative fuel research (CFR) engine system. The results indicated that blending 40% and 60% MC yielded a superior fuel modification effect; a minor ratio of DPDME blending was advantageous for enhancing the oxygen content of the fuel. A 20% blend of MEA or 3-MTBA exhibits favorable heat release intensity and ignition phasing, whereas PGMEA and EGMEA are more suitable as low-ratio oxygenated additives. All ratios of BGA blending combusted effectively, with 20% BGA blending exhibiting optimal performance, characterized by an elevated exothermic intensity and favorable ignition timing. With the proper combination of fuel additives, favorable heat-release behavior and ignition phasing can be obtained under the present CFR/LTC conditions, indicating the potential of selected biobased oxygenated fuels as blending components for diesel surrogate fuels. Furthermore, this study indicated that a minor proportion of oxygenated fuel blending can alter the fuel oxidation conditions and in-cylinder temperature, hence enhancing the combustion performance and benefiting the whole combustion process.