Development of a reduced primary reference fuel – oxymethylene dimethyl ether (PRF-OME x ) mechanism for diesel engine applications

Abstract

Oxymethylene dimethyl ethers (OME_x), having a chemical formula of CH₃O-(CH₂O)_x-CH₃ where x varies from 1 to 5, have been widely considered as a promising fuel to partially replace diesel in CI engines in terms of reducing soot emissions. This work is focused on developing a reduced primary reference fuel (PRF)-OME_x chemical mechanism to better describe the combustion and emission characteristics of gasoline/diesel blends with OME_x. The novelty of this work lies in the fact that the OME_x part of the mechanism is represented not only by OME₃ as done in most studies found in literature, but also with other OME chain lengths that is, OME_2-4 which are considered to be optimum and better represent the commercial OME_x blends. For this purpose, a detailed OME_x mechanism is reduced by applying different reduction techniques considering a wide range of operating conditions including pressure, temperatures, equivalence ratios and fuel compositions. The result is merged with an already validated PRF mechanism to form a reduced PRF-OME_x mechanism consisting of 213 species and 840 reactions. The newly formed mechanism is validated against a wide set of experimental data including ignition delay times, laminar flame speeds and species concentration profiles. Furthermore, a rigorous set of numerical simulations for various diesel-OME_x blends in a compression ignition engine are carried out at two different operating points to validate the developed mechanism. Simulation results highlight that the developed mechanism not only replicates the experimental behavior in terms of in-cylinder pressure and heat release rate but exhibits a better combustion phasing closer to experimental data when compared with other mechanisms where only OME₃ is utilized to represent OME_x. Overall, the developed PRF-OME_x mechanism proves to be realistic and suitable for application in engine combustion simulations involving gasoline/diesel and OME_x blends.