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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 cof T* is higher,the temperature distribution over the whole domain trends to be more uniform.Reducing y*O2 or cof T* 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.
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 demonstrated 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. Chen cof T * is higher, the temperature distribution over the whole domain trends to be more uniform. Reducing y * O2 or cof T * 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.