Effects of Fuel-Side Nitrogen Dilution on Structure and NOx Formation of Turbulent Syngas Non-premixed Jet Flames

Abstract

In the present study, we have numerically investigated the effects of the fuel-side nitrogen dilution on the precise structure and NOx formation characteristics of the turbulent syngas non-premixed flames. The turbulence-chemistry interaction is represented by the Lagrangian flamelet model. In context with the Lagrangian flamelet model, the NO concentration is obtained directly from the flamelet calculation based on the full NOx chemistry, and the radiative heat loss is taken into account through the flamelet energy equation. Computations are made for three fuel-side nitrogen-diluted syngas non-premixed flames. Numerical results indicate that, for the highly nitrogen-diluted case with the higher scalar dissipate rate and the shorter flight time, the flame structure is dominantly influenced by the turbulence-chemistry interaction and marginally modified by the radiation effect. On the other hand, the flame structure for the no-dilution case with the longer flight time and the relatively intermediate scalar dissipate rate is influenced strongly by the radiative cooling, as well as moderately by the turbulence-chemistry interaction. Numerical results suggest that the NOx formation in the syngas turbulent non-premixed flames can be effectively suppressed by increasing the fuel-side nitrogen dilution level.