Experimental and kinetic modeling study of diethyl ether flames

Diethyl ether (DEE, C4H10O) is being considered as a promising biofuel. However, its combustion chemistry has not been well studied. Particularly lacking are quantitative intermediate species profiles in flames that provide a stringent test for kinetic models, and flame speed data at elevated pressures. In the present paper, we obtain species distributions in low-pressure flames and measure flame speeds at elevated pressure to gain insights into high-temperature combustion chemistry of DEE. Specifically, a fuel-rich DEE flame (phi similar to 1.8) with 25% argon dilution at 4 kPa was investigated by using a dedicated combination of electron ionization (EI) molecular-beam mass spectrometry (MBMS) with gas chromatography (GC) and tunable synchrotron vacuum ultraviolet (VUV) photoionization (PI) MBMS. High-pressure flame speeds of DEE were measured in a constant-volume cylindrical chamber at an initial temperature of 298 K at an equivalence ratio of phi = 1.4 and pressure up to 507 kPa. Moreover, a new detailed kinetic model for DEE combustion was developed, with the most noticeable advances over the solely existing model by Yasunaga et al., 2010 being a more complete description of the reactions of DEE radicals and the use of accurate theoretical methods, i.e. CBS-QB3, to determine the rate constants for important primary reactions. In contrast to the previously published one, the present model includes reactions of DEE radicals that directly involve the formation of ethyl vinyl ether (EVE), an addition supported by identification and quantification of EVE by PI-MBMS in the flame experiment. Finally, the results showed that DEE flames yield low concentrations of aromatic species. However, high acetaldehyde emission was observed, originating from the dominant pathways of DEE consumption via H-abstractions from C-alpha positions followed by beta-scissions. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.