Study of the influence of water vapour and carbon dioxide dilution on pollutants emitted by swirled methane/oxygen-enriched air flames

Abstract

The effects of Exhaust Gas Recirculation (EGR) through the dilution by carbon dioxide and water vapour on methane flames/oxygen-enriched air in the case of the pressurized premixed combustion encountered in gas turbines are studied. The chosen configuration is a confined swirled premixed flame with a constant swirl number (Sn = 0.90). The input parameters are the initial temperature, adiabatic flame temperature, pressure (0.1 MPa), and the flow rates and concentrations of CH4, O2, CO2, H2O and N2. The pollutant emissions of NO and CO were measured at the exit of the combustion chamber and expressed as a volume fraction on dry gas. The gaseous emissions of NOx, CO, CO2 and O2 were measured by a HORIBA PG250 analyser, and in the case of high CO2 dilutions, the CO2 concentration measurements were made using a HORIBA VA-3000 analyser. The pollutant emissions were measured for the two initial temperatures T0 = 373 and 473 K and for the four adiabatic temperatures (1773, 1873, 1973 and 2073 K). Finally, the role of parameters (enrichment, diluent, equivalence ratio) likely to play a part in the production of CO and NO pollutant emissions was analyzed. The influence of the diluent on the emissions is highlighted. Dilution with CO2 decreases NO emissions but leads to an increase in CO. Dilution with water vapour is more attractive since at a constant adiabatic temperature, it leads to lower emissions of CO2, CO and NO.