A Comprehensive Experimental and Kinetic Modeling Study of the Combustion Chemistry of Diethoxymethane

The potential biohybrid
fuel diethoxymethane (DEM) shows similar
efficiency in reducing the peak mole fraction of soot precursors as
oxymethylene ethers with having a higher energy density. In the present
work, the fundamental combustion chemistry of DEM is studied experimentally
and theoretically to obtain a comprehensive description of its combustion
characteristics. A detailed kinetic model is developed to describe
the pyrolysis and oxidation processes at low and high temperatures.
To achieve this, rate coefficients for the unimolecular fuel decomposition
and the thermal dissociation of a relevant Q̇OOH radical are
predicted from high-level ab initio calculations.
In addition, ignition delay times of DEM have been measured in a shock
tube and in a laminar flow reactor over a wide range of conditions
(p = 1–50 bar, T = 480–1170
K, and equivalence ratios of 0.5, 1.0, and 2.0). Laminar burning velocity
experiments of DEM/air mixtures have been performed in a spherical
combustion vessel at an initial temperature of 398 K, at pressures
from atmospheric pressure to 2.5 bar, and at equivalence ratios from
0.8 to 1.7. In addition, the experimental measurement campaign in
this study was complemented with the determination of extinction strain
rates for non-premixed DEM flames in a laminar counterflow burner.
All of these experiments substantially extend the current database
describing DEM oxidation. The validation of the newly developed model
is performed with the data sets from this work and available literature.
Rate of production and sensitivity analyses were performed to identify
critical pathways and to understand the mechanism in more detail.
In contrast to other highly reactive fuels, the characteristic of
autoignition behavior of DEM is different and does not show negative
temperature coefficient (NTC) behavior under the conditions investigated.
The chemical reactivity at intermediate temperature of DEM is controlled
by two fast β-scission reactions and HȮ2 elimination
reactions.