In this study, the difference of temperature and the component of chemical species on soot formation in CH4/air fuel-rich diffusion flames were investigated. Furthermore, for decreasing soot formation in fuel-rich diffusion flames, we added H2 in CH4, investigated the property of combustion, and compared with methane/air fuel-rich flames. We have paid much attention to the influence of the equivalence ratio of methane (+H2)/air, the swirl strength of combustion air and the concentration of C2H2 on the soot formation. The experimental combustor for CH4(+H2)/air combustion was designed, and the soot resulting from the exhaust gas collected with a silica filter and its weight was measured. The microstructure of the soot particles were analyzed with a Scanning Electron Microscopy (SEM). The temperature profiles in the combustor were measured by thermocouples, and the concentrations of the species O2, CO2, H2, CH4 and C2H2 were determined by a TCD (thermal conductivity detector) gas chromatograph (GC) and FID (flame ionization detector) GC. The soot yields diminished with increasing swirl strength and the C2H2 concentration. When H2 was added to the fuel, combustion was promoted and C2H2 concentration in the exhaust gas was diminished. But using strong swirl, fuel and air were mixed quickly, the effect of H2 addition was decreased.

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