Moderate or intense
low-oxygen dilution (MILD) combustion of liquid
fuels has attracted attention because of its advantages in industrial
burners and gas turbine applications. Here, numerical investigation
has been conducted on an experimental MILD turbulent spray burner.
The H∥ flame of Delft spray in a hot co-flow burner
is selected, and the Reynolds averaged Navier–Stokes/eddy dissipation
concept framework with 40 species/180 reversible reactions through
a skeletal chemical mechanism is used in addition to unsteady Lagrangian
tracking of spray droplets to investigate the flame structure and
chemical kinetic of reacting flow field. At first, current
numerical results were compared with experimental measurement data
and also quantitatively compared with previous numerical works. Overall,
the trends of the experimental result are well predicted, although
there are some deviations in maximum temperature and prediction of
fine droplets. Subsequently, after inspection of thermal and velocity
fields, as well as heat release, five distinct zones have been distinguished.
Each zone is analyzed by an equivalent perfectly stirred reactor,
and ethanol consumption pathways are studied. They unravel specific
characteristics of ethanol consumption under MILD combustion. It was
revealed that high co-flow temperature and distributed heat release
can strengthen the endothermic direct decomposition route of ethanol
to ethylene and weaken the exothermic production of C2H5O isomer radicals which are dominant in ordinary combustion.
Furthermore, stable intermediates such as ethylene,
acetaldehyde, and methane accumulate under fuel-rich and moderately
high-temperature conditions of the internally reacting region because
of the absence of loss routes in the chemical pathways.