Development and validation of a reduced polyoxymethylene dimethyl ether 3 – Biodiesel reaction mechanism for engine application

Abstract

Biodiesel and polyoxymethylene dimethyl ether 3 (PODE3) are promising alternative fuel for diesel engines. Moreover, PODE3 can optimize the soot emission and low-temperature flow properties of biodiesel. However, compact chemical reaction mechanism combined biodiesel and PODE3 has rarely been investigated. To deeply study the combustion and emission characteristics of blended PODE3 and biodiesel, this paper focuses on developing a reliable PODE3-biodiesel mechanism by using directed relation graph, directed relation graph with error propagation, computational singular perturbation-based quasi-steady-state approximation, species sensitivity analysis and isomers lumping methods. The final reduced mechanism of PODE3-biodiesel consists of 210 species and 762 reactions. The reduced mechanism was then validated against experimental data and detailed mechanism in terms of ignition delay time, laminar flame speed, species concentrations profile, temperature history and direct injection compression ignition engine. The validation indicates that this reduced mechanism provides reliable reproducibility for PODE3 and biodiesel. The reduced mechanism was further applied in zero-dimension modeling to clarify the interaction between PODE3 and biodiesel oxidation. Moreover, three-dimension computational fluid dynamics engine simulation was conducted to investigate the effect of PODE3 on soot reduction. The results show that the added PODE3 has no significant impacts on the initial oxidation of biodiesel surrogate, while the radicals decomposed from PODE3 combustion, such as OH, CH2O and CH3, greatly facilitate the oxidation of soot related precursor; PODE3 improves the spatial PODE3-biodiesel/air equivalence and increases the late combustion temperature. The improvements in radicals, equivalence ratio and combustion temperature promote the soot oxidation.