A Study on Fundamental Combustion Properties of Oxymethylene Ether-2

Abstract

Oxymethylene ethers (OMEn, n=1-5) are a promising class of synthetic fuels that have the potential to be used as diesel additives or substitutes. A comprehensive understanding of their combustion properties is required for their safe and efficient utilization. In this study, a combined experimental and modeling work on oxidation of OME2 is reported: (i) Ignition delay time measurements of stoichiometric OME2 / synthetic air mixtures diluted 1:5 with nitrogen using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) laminar flame speeds of OME2 / air mixtures using the cone angle method at pressures of 1, 3 and 6 bar. The experimental data obtained have been used for validation of three detailed reaction mechanisms of OME2. The results of ignition delay times showed that OME2 exhibits a two-stage ignition in the lower temperature region. The mechanism from Cai et al. (2020) best predicted the temperature and pressure dependence of ignition delay times. For laminar flame speeds, the experimental data were well matched by the mechanism from Ren et al. (2019) for all the conditions of pressures and equivalence ratios considered. From sensitivity analyses, it was observed that chain reactions involving small radicals, i.e., H, O, OH, HO2, and CH3 control the oxidation of OME2. The results obtained in this work will contribute to a better understanding of the combustion of oxymethylene ethers, and thus, to the design and optimization of burners and engines as well.

Influence of Oxymethylene Ethers (OMEn) in Mixtures with a Diesel Surrogate

“…Sun et al [7] have measured the LBV of OME 3 at 408 K and 1 atm with the peak value found at ϕ = 1.2 as well. The same findings were observed within the different studies of OME 2 from Eckart et al [8] and Ngugi et al [9], who have presented LBV values at various temperatures and pressures ranging, in total, from 383 K to 473 K and from 1 bar to 6 bar.…”

“…To the best of our knowledge, experimental LBV data of OME 4 are presented for the first time; thus, allowing only for a comparison to literature data with other OME n . In general, measurements of higher OME n (n ≥ 2) have been published by Sun et al [7], Eckart et al [8], and Ngugi et al [9]. Sun et al [7] have measured the LBV of OME 3 at 408 K and 1 atm with the peak value found at ϕ = 1.2 as well.…”

“…Regarding experimental studies focusing on the combustion properties of higher OME n (n ≥ 2), only a limited database is available in literature. Particularly, data for their laminar burning velocities are rare-in 2017 Sun et al [7] published measurements of OME 3 at 1 atm and 408 K; recently, those of OME 2 were studied by Eckart et al [8] and Ngugi et al [9] at various temperatures and pressures. Though engine tests are often performed, e.g., such as those reported in Omari et al [5] and Pélerin et al [6], basic studies focusing on the sooting behavior are rare.…”

Investigation of the combustion chemistry in laminar, low-pressure oxymethylene ether flames (OME0–4)

“…As a consequence, the position of the reaction zone is moving to larger distances with decreasing chain length [51]. Indeed, the laminar flame speed is found to increase with the OME chain length [15,16,52,53]. This is even more obvious when the CH2O peak maxima, one of the first species formed (see Fig.…”

“…Following up to Sun et al, He and coworkers provided another model for OME3 [14].. Focusing on OME2, Ngugi et al have studied laminar flame speed as well as ignition delay times and autoignition of OME2 [15]. They have shown similar oxidation pathways for OME2 and OME1.…”