Pre-vaporized ignition behavior of ethyl- and propyl-terminated oxymethylene ethers

Journal Article · Sat Oct 29 00:00:00 EDT 2022 · Proceedings of the Combustion Institute

DOI:https://doi.org/10.1016/j.proci.2022.08.065· OSTI ID:2338101

Lucas, Stephen P. ^[1]; Labbe, Nicole J. ^[2]; Marchese, Anthony J. ^[3]; Windom, Bret ^[2]

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1. Colorado State Univ., Fort Collins, CO (United States); Colorado State University
2. Colorado State Univ., Fort Collins, CO (United States)
3. Univ. of Rhode Island, Kingston, RI (United States)

Oxymethylene ethers (OMEs) have been studied in recent years for use as compression ignition fuel blendstocks, but the methyl-terminated OMEs commonly studied exhibit properties that are poorly optimized for engine use and distribution. Recent work has shown that OMEs with larger (ethyl, propyl, or butyl) end groups may have superior properties for fuel usage/storage. In this work, we consider ignition of four OMEs - diethoxymethane (E-1-E), dipropoxymethane (P-1-P), ethoxy-(methoxy)₂-ethane (E-2-E), and diisopropoxymethane (iP-1-iP) - as representatives of the possible effects of changes to OME structures. To our knowledge, ignition behaviors of the latter three fuels have not been studied prior to this work. Further, we find that all of the tested linear OMEs (E-1-E, P-1-P, and E-2-E) show two-stage ignition at low temperatures and nonlinear ignition behavior, consistent with literature on methyl-terminated OMEs and E-1-E. The nonlinear, branched OME (iP-1-iP) required higher pressure and temperature to ignite than the linear OMEs; further, this fuel experienced only single stage ignition and a linear ignition delay curve. By analogy to existing kinetic mechanisms for ethers and higher alcohols, the chemical basis for the observed trends are hypothesized. Faster ignition of E-2-E results from the additional oxymethylene group providing additional sites for ROO formation and more possible QOOH structures. Slower low temperature ignition of P-1-P is driven by lower H abstraction rates in comparison to E-1-E, however at high temperatures P-1-P ignites faster, driven by increasing abstraction from the additional H site on the propyl group that opens up additional QOOH formation pathways. iP-1-iP ignition is slowed significantly by preferential H abstraction from the central carbon of the isopropyl group, which is crowded and unlikely to bond with O₂, however at high temperatures, abstraction from H sites on the methyl groups allows for the ROO cascade initiation and subsequent rapid ignition.

• Research Organization: Colorado State Univ., Fort Collins, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Bioenergy Technologies Office (BETO)
• Grant/Contract Number: EE0008726
• OSTI ID: 2338101
• Journal Information: Proceedings of the Combustion Institute, Journal Name: Proceedings of the Combustion Institute Journal Issue: 1 Vol. 39; ISSN 1540-7489
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
fuel reactivity
low emission fuels
oxygenated fuels
oxymethylene ether
rapid compression machine