Model of turbulent diffusion flames and nitric oxide generation

A new view is described of mixing and chemical reactions in turbulent fuel jets discharging into air. Review of available fundamental data from jet flames leads to the idea that mixing begins with a large scale, inviscid, intertwining of entrained air and fuel throughout the jet. Significant molecular mixing is delayed until the end of a cascade to the Kolmogorov scale. A simple mathematical model incorporating these ideas is presented. The model predicts a Reynolds number dependence for the nitric oxide formation rate that is in good agreement with measurements in both methane and hydrogen jets burning in air. These mathematical model concepts have been incorporated into a simplified computer program capable of treating the detailed chemical kinetics of a gas flame. The model has been used to predict NO formation in H2/air and CH4/air flames and results compare favorably with experimental data.