NO formation analysis of turbulent non-premixed coaxial methane/air diffusion flame

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 N 2 concentration contributes to reducing NO. More importantly for higher O 2 mass fraction, thermal NO formation becomes the dominant mechanism responsible for NO emission.

Low Temperature deNOx Catalytic Activity with C2H4 as a Reductant Using Mixed Metal Fe-Mn Oxides Supported on Activated Carbon

“…Nitrogen oxides (NO X ) are created during fossil fuel combustion and participate in the formation of acid rain and photochemical smog [1][2][3][4]. Consequently, deNOx technologies have been widely studied and commercially-practiced throughout the world [5]; these include NO X direct decomposition, selective catalytic reduction (SCR), and selective non-catalytic reduction (SNCR) [6].…”

A Computational Fluid Dynamics Study of Turbulence, Radiation, and Combustion Models for Natural Gas Combustion Burner

“…One of those experimental works in a cylindrical combustion chamber with detailed measurement of gas composition and temperature profiles was presented by Garreton and Simonin [3]. A CFD study on the cylindrical burner has been performed by several researchers [4][5][6][7][8][9][10]. They emphasized on the chemistry reaction, turbulence mixing, thermal radiation, pollution formation and buoyancy effect inside the burner.…”

“…It is important to predict the turbulent flow inside the combustion chamber accurately to enable better prediction of the detailed reaction chemistry involved in the combustion process. RANS-based turbulence model, such as: the SKE model is commonly used to resolve the turbulent flow due to its robustness and lesser computational demand [4,[7][8]. Ronchetti et al [9] performed a comparison of different turbulence models on the prediction of temperature and carbon monoxide mass fraction.…”

“…Combustion models, such as: the eddy dissi-pation concept (EDC) [4], eddy break-up (EBU) [10], presumed probability-distributionfunction (PPDF) [10], finite rate/eddy dissipation model (FR/EDM) [8][9], have been widely employed to predict the natural gas combustion. Among all the aforementioned combustion models, EDM is the most commonly used due to its reasonable predictions for methane combustion [11].…”

“…Hence, it is vital to consider the radiation model to the heat transfer model for natural gas combustion. Most of the CFD studies dealing with the natural gas combustion employed discrete transfer radiation model (DTRM) for radiation [4][5][7][8]. It has to be noted that DTRM does not include the effect of radiation scattering and can only be accurate when a large number of rays is modelled (CPUintensive).…”