Evaporation, Combustion, and Emission Characteristics of OME and Biodiesel Blends with Fossil Diesel in a Comrpession Ignition Engine

The transition toward low-carbon energy systems has intensified interest in oxygenated fuels and electrofuels (e-fuels) as alternatives to conventional Diesel, particularly for hard-to-electrify sectors such as heavy-duty transport and marine applications. Among these, oxymethylene ethers (OMEn) and biodiesel are promising due to their inherent oxygen content and favorable combustion characteristics. This study investigates the evaporation, combustion, and emission behavior of oxygenated fuel blends in a compression ignition (CI) engine, focusing on OME₃ (oxymethylene dimethyl ether) and palm oil-based biodiesel blended with Diesel at oxygen mass fractions of 2% and 5%. Droplet evaporation experiments were conducted using a shadowgraph high-speed imaging system under elevated temperatures. The results show that OME₃ exhibits the fastest evaporation rate, followed by Diesel, while biodiesel evaporates the slowest. These differences are attributable to variations in volatility, viscosity, boiling range, and molecular structure. The high oxygen content and absence of C-C bonds in OME₃ could promote rapid phase change and improved mixture formation. Engine tests on a V8 Diesel engine at 1600 rpm under varying loads show that oxygenated blends reduce ignition delay compared to Diesel, with OME₃ blends exhibiting the shortest ignition delay. Increasing oxygen content further enhances auto-ignition, leading to a reduced premixed combustion fraction and lower peak cylinder pressure. Emission results indicate significant reductions in soot and unburned hydrocarbon (HC) emissions with increasing oxygen content. OME₃ blends consistently produce the lowest emissions, followed by biodiesel blends. The superior performance of OME₃ is linked to its rapid evaporation, improved air-fuel mixing, and chemical structure, which suppresses soot formation and enhances oxidation. Fuel-bound oxygen significantly enhances evaporation, combustion, and emissions performance, with OME₃ showing strong potential as a clean Diesel blending component.