Combustion characteristics of biodiesel with different dimethyl ether blending strategies

In this study, the effects of adding dimethyl ether (DME) on biodiesel (BD) combustion were studied through counterflow flame modeling. DME was added through two blending strategies, i.e., air-side and fuel-side blending, and methyl decanoate (MD) was used as the surrogate for BD. The profiles of the flame tempera-ture, primarily species, and heat release rates (HRRs) after DME addition into MD were analyzed to explore the kinetic differences between pre-blending and post-blending combustion modes of BD and DME in engines. Re-sults show that the air-side and the fuel-side additions of DME can slightly increase the peak temperature and widen the reaction zones of the flames. MD presents two distinct oxidation zones, while DME is primarily oxidized within an identified flame region with a higher temperature than MD. DME premixing on the fuel side can prompt MD dehydrogenation through enhancing H and OH formation. The flames enriched by air-side DME premixing present significant hybrid heat-release structure that depends on the fuel-side air entrainment as well. The heat-release characteristics of the non-premixed reaction zone (NPZ) of the counterflow flames with air-side DME additions suggest that the increased temperature is the main factor leading to the change of heat-release reaction routes of the flames.