Optimal Equivalence Ratio to Minimize NO Emission during Moderate or Intense Low-Oxygen Dilution Combustion

Abstract

The influence of injection conditions on NO emission during moderate or intense low-oxygen dilution (MILD) combustion was investigated through experiments and numerical simulations. The detailed GRI-Mech 2.11 mechanism and finite-rate chemistry effects were considered in simulations. The model was systematically validated using detailed in-furnace and exhaust emission measurements. The initial conditions investigated included the equivalence ratio (Φ), oxidant preheating temperature (TO), and thermal input (P). Notable modeling results were found: under MILD combustion, with Φ increasing from 0.5 to 1.2, NO production first decreases and then increases, with the minimum NO emission obtained at Φ ≈ 0.8. Moreover, this trend is obtained at various P and TO, although NO emission increases monotonically with increasing P or TO. Furthermore, we found that CO emission is generally extremely low and can be ignored when Φ ≤ 0.85 but is much higher when Φ > 0.9. Consequently, for the furnace considered here, an op...