Based on a single-head bluff-body and swirl model combustor,the flame structure,flame stability,and emission characteristics of premixed methane flames(CH4/air)were studied,which were regulated by additives of H2,O2,and CO2.Fraction control of the additives was conducted and flame conditions were designed for various premixed mixtures.The flame structure was measured by using the digital camera and the technology of Planar Laser-Induced Fluorescence of OH radical.The flue gas temperature and emissions of pollutants CO and NOx were measured using the Testo340 gas analyzer.The results show that the addition of H2 and O2 leads to a more compact flame and enhances the combustion intensity,while the addition of CO2 is potential to mitigate such effects,causing a more distributed flame shape and a lower combustion intensity.When the oxygen-rich combustion occurs with O2 addition,both CO and NOx increase significantly,which is not favorable to reduce the emission.In contrast,the H2 addition can reduce the CO emission,while almost not affecting the NOx emission.Simultaneously,although replacing N2 with CO2 can increase the CO emission,it significantly reduces the NOx.The additives of H2 and CO2 exhibit complementary regulating effects,and their combination is an effective method to achieve stable and low emission combustion of methane.
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