Role of CH2O moiety on laminar burning velocities of oxymethylene ethers (OMEn): A case study of dimethyl ether, OME1 and OME2

Oxymethylene ethers (OMEn) are an important family of e-fuels that can be produced sustain -ably from carbon dioxide and hydrogen via renewable electricity. In this work, laminar flame prop-agation of dimethyl ether (DME, which can be deemed as OME0), dimethoxymethane (OME1) and methoxy(methoxymethoxy)methane (OME2) was investigated in a constant-volume cylindrical combustion vessel. Laminar burning velocities (LBVs) of the three fuels were derived at 423 K, 1-10 atm and equiva-lence ratios of 0.7-1.5. A kinetic model for the high-temperature oxidation of the three fuels was developed with the isomerization and decomposition reactions of OME2 radicals theoretically calculated. Reasonable predictions can be achieved by the present model during the validation against the new data in this work and previous data in literature. Based on the modeling analysis, fuel-specific flame chemistry of the three fuels was analyzed, especially for the key formation pathways of major intermediates including formaldehyde, methyl formate and CH3. Special attentions were paid on the role of CH2O moiety, which is demonstrated by the variation of LBV and flame chemistry with the ratio (& alpha;) of CH2O moiety to the rest moiety in the fuel molecule (& alpha; = 1, 2 and 3 for DME, OME1 and OME2). It is observed from the experimental and sim-ulated results that as & alpha; increases, the LBV profile has close peak values and peaks towards rich conditions, which results in the crossings of profiles and ascending LBV values under the richest conditions. Reactions involving fuel-specific radicals HCO and CH3 result in the peak shift of H profile and different LBV values, especially under the richest conditions. Furthermore, extended & alpha; values at 0 and & INFIN; by using methane and formaldehyde respectively were also explored with kinetic modeling to provide more insight into the effects of fuel molecular structures.& COPY; 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.