New Dependence of NO Emissions on the Equivalence Ratio in Moderate or Intense Low-Oxygen Dilution Combustion

Abstract

The dependence of NO emissions on the equivalence ratio (Φ) is a classic problem in combustion science. In many combustion textbooks, as Φ increases from 0.5 to 1.0, the NO formation generally increases first and then decreases, with the maximum NO emission obtained on the lean side of stoichiometry. However, through experiments and data mining of the literature, we found that there is a new trend of NO emissions in moderate or intense low-oxygen dilution (MILD) combustion. Specifically, with an increase in Φ from 0.5 to 1.0, the NO emission may decrease first and then increase, with the minimum NO emission also occurring on the lean side of stoichiometry. Systematic experiments are conducted to investigate the NO emission under MILD combustion. The experiments are conducted in a 20 kW furnace of firing methane. Detailed in-furnace thermal and species fields and exhaust NO emissions are measured. A series of MILD combustion experiments indeed record a decreasing trend of NO emissions, with an increase in ...