MILD combustions at different fuel-air patterns

Abstract

This paper experimentally investigates the global performances of the non-premixed (NP), partially-premixed (PP) and fully-premixed (FP) MILD (moderate or intense low-oxygen dilution) combustions at a laboratory-scale furnace. Experiments are carried out at the firing rate varying from 7.5 kW to 15 kW and the equivalence ratio changing from φ = 0.5 to φ = 1. The furnace temperatures and NOx emissions of the three premixing patterns are compared and discussed. The PP MILD combustion produces the highest NOx emissions. The exhaust temperatures of all the cases are found to decrease as φ increases. For the present furnace and burner configuration at φ < 0.97, the variation of the premixing modes or firing rates does not influence the CO emissions, and the establishment of the MILD combustion can guarantee the fully oxidation of the fuel. The Damköhler number (Da) of the MILD combustion is found to be ∼O(1). Moreover, the reaction regime of the FP MILD combustion is found to be located on the flamelets-in-eddies regime of turbulent combustion.