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 (y_O2^*) 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 y_O2^* 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 y_O2^* or T_cof^* leads to less production of intermediate species OH and CO. It is worth noting that if y_O2^* is high enough (y_O2^*>80%), increasing y_O2^* does not cause obvious temperature increase.

Key words: jet in hot coflow, moderate and intense low-oxygen dilution combustion, diffusion flame, intermediate specie

摘要： 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 (y_O2^*) 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 y_O2^* 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 y_O2^* or T_cof^* leads to less production of intermediate species OH and CO. It is worth noting that if y_O2^* is high enough (y_O2^*>80%), increasing y_O2^* does not cause obvious temperature increase.

关键词: jet in hot coflow, moderate and intense low-oxygen dilution combustion, diffusion flame, intermediate specie