Formation of nitric oxide in a multi-air staged gas flame

In this study, a numerical simulation was developed which was capable of pr edicting the characteristics of NO formation in pilot scale combustor adopt ing the air-staged burner flame. The numerical calculation was constructed by means of establishing the mathematical models for turbulence, turbulent combustion, radiation and turbulent nitric oxide chemistry. Turbulence was solved with standard k-epsilon model and the turbulent combustion model was incorporated using a two step reaction scheme together with an eddy dissip ation model. The radiative transfer equation was calculated by means of the discrete ordinates method with the weighted sum of gray gases model for CO 2 and H2O. In the NO chemistry model, the chemical reaction rates for therm al and prompt NO were statistically averaged using the beta probability den sity function. The results were validated by comparison with measurements. For the experiment, a 0.2 MW pilot multi-air staged burner has been designe d and fabricated. Only when the radiation was taken into account, the predi cted gas temperature was in good agreement with the experimental one, which meant that the inclusion of radiation was indispensable for modeling multi -air staged gas flame. This was also true of the prediction of the NO forma tion, since it heavily depended on temperature. Subsequently, it was found that the multi-air staged combustion technique might be used as a practical tool in reducing the NO formation by controlling the peak flame temperatur e.