Chemical Kinetics Investigations of Dibutyl Ether Isomers Oxidation in a Laminar Flow Reactor

The combustion kinetics of three symmetric diesel-boiling-range
ether isomers were investigated experimentally using a plug flow reactor.
The isomers were di-n-butyl ether (DNBE), diisobutyl
ether (DIBE), and di-sec-butyl ether (DSBE). The
flow reactor experiments employed oxygen as the oxidizer and helium
as the diluent, with oxidation carried out at atmospheric and elevated
pressure conditions and temperatures from 400 to 1000 at 20 K intervals.
The fuel, oxidizer, and diluent flow rates were varied at different
temperatures to maintain a constant initial fuel mole fraction of
1000 ppm under stoichiometric conditions and a residence time of 2
s. Reaction products were analyzed by gas chromatography (GC). Depending
on the structure, ethers showed different degrees of negative temperature
coefficient (NTC) behavior. Speciation results from the GC analysis
were then compared to simulations using existing and newly developed
chemical kinetic models. Most of the simulated product concentrations
showed reasonable agreement with the experimental data. The chemical
kinetic models were utilized to elucidate key features of the reactivity
and NTC behavior of the different isomers. The chemical kinetic analysis
indicates that the combustion behaviors of the three isomers are influenced
by the key species formed at the low-temperature reaction regime.
The key species identified for DNBE, DIBE, and DSBE at atmospheric
pressure are n-butanal, isobutanal, and sec-butanol, respectively.