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NO formation analysis of turbulent non-premixed coaxial methane/air diffusion flame
Poozesh, S.; Akafuah, N. & Saito, K.
Abstract
Natural gas combustion is one of the primary
sources of harvesting energy for various processes and has
gained a wide attention during the past decade. One of the
most recent applications of natural gas combustion can be
found in non-premixed combustion of methane in a coflow
burner system. One of the main environmental concerns
that arises from the natural gas combustion is the formation
of NO produced by thermal NO and prompt NO mechanisms.
Current paper is devoted on an examination of a 2D
numerical simulation of turbulent non-premixed coaxial
methane combustion in air enclosed by an axisymmetric
cylindrical chamber to study the effects of species concentrations
of reactants on NO formation, their individual
contributions, and the chamber outlet temperature. A finitevolume
staggered grid method is utilized to solve conservation
equations of mass, energy, momentum, and species
concentrations. In order to handle radiation heat transfer,
discrete transfer method is used to solve radiation equation.
Utilizing weighted-sum-of-gray-gases model, based on the
newly obtained high-temperature molecular spectroscopic
data, local variations of species absorption coefficients are
taken into account. To calculate NO concentration, a single-
or joint-variable probability density function in terms
of a normalized temperature, mass fractions of species, or a
combination of both is employed. Plus, published relevant
experimental data are used to validate temperature and
species concentration fields. It is shown that a decrease in
N2 concentration contributes to reducing NO. More
importantly for higher O2 mass fraction, thermal NO
formation becomes the dominant mechanism responsible
for NO emission.
Keywords
Turbulent flame; NO environmental pollution; Natural gas combustion; Finite-volume method; Hightemperature molecular spectroscopic database
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