Development of a diesel-biodiesel-ethanol combined chemical scheme and analysis of reactions pathways

Diesel-biodiesel-ethanol blends have been the focus of intense research quite recently. Diesel is a complex fuel composed of hundreds of compounds indicating the difficulty of using diesel for experimental studies associated with numerical simulations. Biodiesel is also a complex mixture of methyl esters. When injected in a diesel engine in the pure form, it induces changes in combustion behavior which can impact pollutants emission. Consequently simplified synthetic fuels, called “surrogate fuels”, with shorter chain lengths and known physical chemical properties are chosen to carry combustion studies. Finally, ethanol is one of the liquid alternative fuels most widely studied. The present paper focuses on numerical studies of the combustion of diesel-biodiesel-ethanol blends using 0D auto-ignition delay and 1-D freely-propagating gaseous premixed flame configurations. The objective is to develop and validate a new chemical scheme by carefully combining two existing chemical schemes from the literature. The first one is the scheme due to Andrae (2011) for the combustion of diesel-ethanol blends and the second one is due to Luo et al. (2012) for a biodiesel surrogate. The approach consists of merging non common elementary reactions from both chemical schemes and analyzing the common reactions (having different reaction constants) in both chemical schemes in order to chose most relevant chemical pathways from each scheme so that the resulting merged scheme gives a good prediction of the auto-ignition delay and laminar flame speed.