Chemical effects of CO₂ addition to oxidizer and fuel streams on flame structure in H₂–O₂ counterflow diffusion flames

Numerical simulation of CO₂ addition effects to fuel and oxidizer streams on flame structure has been conducted with detailed chemistry in H₂–O₂ diffusion flames of a counterflow configuration. An artificial species, which displaces added CO₂ in the fuel- and oxidizer-sides and has the same thermochemical, transport, and radiation properties to that of added CO₂, is introduced to extract pure chemical effects in flame structure. Chemical effects due to thermal dissociation of added CO₂ causes the reduction flame temperature in addition to some thermal effects. The reason why flame temperature due to chemical effects is larger in cases of CO₂ addition to oxidizer stream is well explained though a defined characteristic strain rate. The produced CO is responsible for the reaction, CO₂+H=CO+OH and takes its origin from chemical effects due to thermal dissociation. It is also found that the behavior of produced CO mole fraction is closely related to added CO₂ mole fraction, maximum H mole fraction and its position, and maximum flame temperature and its position. Copyright © 2003 John Wiley & Sons, Ltd.