Diffusion Flame of a CH4/H2 Jet in a Hot Coflow: Effects of Coflow Oxygen and Temperature

Abstract

This paper investigates the effects of coflow O2 level and temperature on diffusion flame of a CH4/H2 jet in hot coflow (JHC) from a burner system similar to that of Dally et al. The coflow O2 mass fraction ( yO2*) is varied from 3% to 80% and the temperature (T*cof) from 1200 K to 1700 K. The Eddy Dissipation Concept (EDC) model with detailed reaction mechanisms GRI-Mech 3.0 is used for all simulations. To validate the modeling, several JHC flames are predicted under the experimental conditions of Dally et al. [Proc. Combust. Inst., 29 (1), 1147–1154 (2002)] and the results obtained match well with the measurements. Results demonstrate that, when yO2* decreased, the diffusion combustion is likely to transform from traditional combustion to MILD (Moderate or Intense Low-oxygen Dilution) combustion mode. When T*cof is higher, the temperature distribution over the whole domain trends to be more uniform. Reducing yO2* or T*cof leads to less production of intermediate species OH and CO. It is worth noting that if yO2* is high enough ( yO2*>80%), increasing y*O2 does not cause obvious temperature increase.