Study on the Combustion Process of Premixed Methane Flames with CO 2 Dilution at Elevated Pressures

The article presents the results of experimental and numerical investigation of turbulent premixed methane flames diluted by carbon dioxide (up to 30%) at atmospheric and elevated pressures (up to 0.5 MPa). The study included the influence of fuel properties and operation parameters on the emission of NO_x and CO as well as flame properties. The investigation has been prepared for two combustion system configurations (axisymmetric flames and flames supported by a pilot flame) in a wide range of air/fuel equivalence ratios (ϕ = 0.42 ÷ 0.85). It has been reported that reduction of NO_x emission by CO₂ fuel dilution reached a level of up to 45% in atmospheric conditions and 30% at elevated pressure, decreasing with a drop in the equivalence ratio. The results have shown influence of pressure on NO_x composition, where for pressurized tests, NO₂ was doubled compared to atmospheric tests. Carbon monoxide emission rises with CO₂ content in the fuel as a result of thermal dissociation, but this phenomenon is mitigated by a pressure increase. Planar laser induced fluorescence (PLIF) study has shown that flame length decreases with an increase in pressure and CO₂ content in the fuel. Fuel staging increased NO_x emission, especially for richer flames (ϕ > 0.6) at low pressure, while CO increased in the whole range of equivalence ratios.

Abstract licence: CC BY

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