Abstract
Measurements from confined, laminar oxy-methane flames at different O2/CO2dilution ratios in the oxidizer are first reported with measurements from methane-air flames included for comparison. Simulations of these flames employing appropriate chemistry and radiative property modeling options were performed to garner insights into the experimental trends and assess prediction sensitivities to the choice of modeling options. The chemistry was modeled employing a mixture-fraction based approach, Eddy dissipation concept (EDC), and refined global finite rate (FR) models. Radiative properties were estimated employing four weighted-sum-of-gray-gases (WSGG) models formulated from different spectroscopic/model databases. The mixture fraction and EDC models correctly predicted the trends in flame length and OH concentration variations, and the O2, CO2, and temperature measurements outside the flames. The refined FR chemistry model predictions of CO2and O2deviated from their measured values in the flame with 50% O2in the oxidizer. Flame radiant power estimates varied by less than 10% between the mixture fraction and EDC models but more than 60% between the different WSGG models. The largest variations were attributed to the postcombustion gases in the temperature range 500 K–800 K in the upper sections of the furnace which also contributed significantly to the overall radiative transfer.
Highlights
Oxy-fuel combustion, where a fuel is burnt in a mixture of oxygen and recycled flue gas stream, is a promising near-zero emission technology that can be adapted by existing and new electric power generation stations to mitigate the human impact on climate change [1]
Significant variations in the flame radiant fraction predictions between the gray and nongray models and reduced chemistry models were deemed to be accurate for predicting the temperature and major gas species concentrations in industrial applications, detailed chemistry models that account for dissociation were found to be necessary to accurately predict pollutant formation such as CO
The temperature contours and the axial OH concentrations show that the flames resulting from the probability density function (PDF) model are longer than the flames predicted from employing the Eddy dissipation concept (EDC) chemistry model
Summary
Oxy-fuel combustion, where a fuel is burnt in a mixture of oxygen and recycled flue gas stream (containing primarily CO2 and H2O), is a promising near-zero emission technology that can be adapted by existing and new electric power generation stations to mitigate the human impact on climate change [1]. The need to refine models for gas-phase chemistry and radiative properties that have previously been deemed to be accurate in computational fluid dynamic (CFD) simulations of combustion in air has garnered much attention in recent reviews [8, 9]. This has led to the development and validation of gas-phase radiative property models in the form of weighted-sum-of-gray-gases (WSGG) coefficients based on different spectroscopic/model databases [10,11,12,13] and the refinement of kinetic parameters in previously proposed global kinetic mechanisms [14, 15] to improve their prediction accuracy in oxy-combustion scenarios [16,17,18]. The studies indicate that while refined global kinetics, equilibrium based, Reference
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