Development of Surrogate Model for Oxygenated Wide-Distillation Fuel with Polyoxymethylene Dimethyl Ether

Polyoxymethylene Dimethyl Ether (PODE_n) is a promising green additive to diesel fuel, owing to the unique chemical structure (CH₃O[CH₂O]_nCH₃, n≥2) and high cetane number. Together with the general wide-distillation fuel (WDF), which has an attractive potential to reduce the cost of production of vehicle fuel, the oxygenated WDF with PODEn can help achieve a high efficiency and low emissions of soot, NO_x, HC, and CO simultaneously. In this paper, the first detailed reaction mechanism (225 species, 1082 reactions) which can describe the ignition characteristics of PODE₁ and PODE₃ at low temperature was developed. To validate this mechanism, rapid compression machine (RCM) was used to conduct the quasi-homogeneous experiments to measure the ignition delay time at various effective temperatures (600 K - 1000 K) for four different PODE₁/O₂/N₂/Ar mixture (ϕ=0.25, O₂:Ar=1:5; ϕ=0.5, O₂:Ar:N₂ = 1:2.5:2.5; ϕ=1.0, O₂:Ar:N₂ = 1:2.5:2.5; ϕ=1.0, O₂:Ar:N₂ = 1:5:5) and two different effective pressures (10 bar, 19 bar). Homogeneous Charge Compression Ignition (HCCI) experiments fueled with PODE_n (n=1-4) mixture, in which the mass fraction of PODE₃ is about 88.9% were also conducted in a naturally aspirated single-cylinder HCCI research engine at 1600 r/min, 0.4 charge-mass equivalence ratio, and 42% exhaust gas recirculation (EGR) to take the real engine working condition into consideration. Good agreement was achieved in the comparison of the experimental data and the simulation results utilizing our newly developed mechanism for PODE₁ and PODE₃. Considering the fact that PODE_n is more frequently used as a blending component in diesel engine, a reduced multi-component mechanism (354 species, 943 reactions) for oxygenated WDF with PODE_n (covering surrogates like PODE₃, n-heptane, iso-octane, etc.) was developed and then validated with Direct-Injection Compression Ignition (DICI) engine experiments fueled with oxygenated WDF (gasoline/diesel/PODE_n mixture) at 1600 r/min, 0.8 MPa indicated mean effective pressure (IMEP), and 25% EGR. This surrogate model will contribute to the design of oxygenated WDF by blending PODEn, and to the prediction of the combustion and emission characteristics of engines using oxygenated WDF.