Numerical study on NO formation in CH4-O2-N2 diffusion flame diluted with CO2

Abstract

SUMMARYNumerical study with momentum-balanced boundary conditions has been conducted to grasp chemical effects of added CO 2 , to either fuel-or oxidizer-side on flame structure and NO emission behaviour in CH 4 -O 2 -N 2 diffusion flames. Cautious investigation is made for the comparison among the behaviours of principal chain branching and important H-removal key reactions. This describes successfully the reason why flame temperatures for fuel-side dilution are higher than those for oxidizer-side dilution. The role of the principal chain branching reaction is also recognized to be important even in the change of major flame structure caused by chemical effects.The importantly contributing reaction steps to NO production are examined. The reduced production rates of thermal NO and prompt NO due to chemical effects are much more remarkable for fuel-side dilution. It is also found that the reaction step, H+NO+M=HNO þ M plays a decisive role of the formation and destruction of prompt NO.

Physical and Chemical Effects of CO2 and H2O Additives on Counterflow Diffusion Flame Burning Methane

“…The mole fractions of CO 2 and N 2 vary correspondingly in the allowable range with a fixed value of O 2 . The global strain rate a is obtained considering the balance of momentum flux , a = prefix− 2 V normalO L [ 1 + V F − V O ρ F ρ O ] where L is the separation distance of two opposed jets; in the present study, L = 2 cm. V represents the velocity, and subscripts F and O mean the fuel and oxidizer, respectively.…”

Flameless combustion role in the mitigation of NOXemission: a review

“…The formation mechanism depends on the mixing rate of fuel and air. The formation of prompt NO follows the following reaction paths : The reactions of N 2 with hydrocarbon fragments produce cyanide (HCN). Ammonia radicals (NH, NH 2 ) are generated by HCN hydrogen abstraction reactions with oxy‐cyanogens. Ammonia radicals form NO.…”

“…The formation mechanism depends on the mixing rate of fuel and air. The formation of prompt NO follows the following reaction paths [10,24,40,43,44]:…”

Numerical study on flame structure and NO formation in CH4-O2-N2 counterflow diffusion flame diluted with H2O

“…Tomeczek and Gradon (2003) proposed a new way of forming HCN via N 2 O and NNH reacting CH i radicals, and recognized that the new mechanism was more probable than Fenimore's direct reaction of N 2 with CH i radicals. Hwang et al (2003) have stressed the importance of N 2 O mechanism, especially at low flame temperature in CO 2 À added methane flames.…”