LES STUDY ON SPRAY COMBUSTION WITH RENEWABLE FUELS UNDER ECN SPRAY-A CONDITIONS

Poly-Oxymethylene Dimethyl Ethers (OMEx) are being intensively investigated because of their potentially renewable synthesis path, which make them suitable as liquid fuels for low-carbon transport applications. In the present contribution, a computational study on the difference in combustion characteristics between dodecane and OMEx-type fuels under Engine Combustion Network (ECN) Spray A conditions is reported. In particular, a blend of different OMEx fuels have been investigated and compared to dodecane, which is a more conventional diesel-like fuel. The modelling framework consists of a high-fidelity LES approach together with a Eulerian-Lagrangian spray model and flamelet-based turbulent combustion model. Results indicate ignition delay time and lift-off length according to the fuel reactivity properties, with the OMEx fuel performing similarly to dodecane. Flamelet calculations show that ignition of the oxygenated fuels is in general similar to that of dodecane, but it occurs at higher mixture fraction values due to the differences in stoichiometry. One of the most relevant outcomes of the study is the important effect that the oxygenated characteristics of OMEx has on the flame structure. Results show that for OMEx the reaction front is stabilized at distances closer to the nozzle than for dodecane, and that the flame shape as well as its internal structure is clearly affected.