Nitric oxide emissions from laminar diffusion flames: Effects of air-side versus fuel-side diluent addition
- Pennsylvania State Univ., University Park, PA (United States)
Flue gas recirculation (FGR) is a well-known method used to control oxides of nitrogen (NO{sub x}) in industrial burner applications. The objective of the present investigation is to ascertain to what degree chemical kinetics and/or molecular transport effects can explain the differences in NO{sub x} reduction observed between fuel-side and air-side introduction of flue gases by studying laminar diffusion flames. Numerical simulations of counterflow diffusion flames using full kinetics were performed and NO{sub x} emission indices calculated for various conditions. Studies were conducted in which N{sub 2} diluent was added either on the fuel- or air-side of the flame for conditions of either fixed initial velocities or fixed fuel mass flux. Results from these simulation studies indicate that a major factor in diluent effectiveness is the differential effect on flame zone residence times associated with fuel-side versus air-side dilution. Experiments using laminar jet flames were conducted in which either the air or fuel stream was diluted with N{sub 2}. The experiments showed that fuel-side dilution results in somewhat greater NO{sub x} emission indices than air-side dilution. The higher flame temperatures measured with fuel dilution appear to be the principal cause of the higher emissions. The results of both the numerical simulations and the experiments suggest that, although molecular transport and chemical kinetic phenomena are affected by the location of diluent addition depending on flow conditions, the dramatically greater effectiveness of fuel-side over air-side introduction of recirculated flue gases in practical applications likely results also from differences in turbulent mixing and heat transfer.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG04-95AL87310
- OSTI ID:
- 619594
- Journal Information:
- Combustion and Flame, Journal Name: Combustion and Flame Journal Issue: 1-2 Vol. 113; ISSN CBFMAO; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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