Effect of steam addition on flame structure and NO formation in H2–O2–N2 diffusion flame

Abstract

SUMMARYNumerical analysis is conducted to clarify chemical effects of added steam to either fuel-or oxidizer-side on flame structure and NO emission behaviour with detailed chemistry in hydrogen-oxygen-nitrogen diffusion flames. An artificial species, which has the same thermodynamic, transport, and radiation properties to added H 2 O, is introduced to feasibly isolate chemical effects of added H 2 O. It is found that the reaction step (-R23) is the starting point to induce chemical effects of added steam. Special concern is, thus, focused on the impact of OH radical on flame structure and NO emission behaviour. A strong dependency of the amount of steam addition on OH radical behaviour is clearly displayed, and this modifies flame structure sufficiently to produce higher flame temperature at more than a certain mole fraction of added steam in comparison to that diluted with artificial species. It is also shown that the reaction step (-R23) is closely related to flame temperature and thereby the location of maximum flame temperature. The behaviour of NO emission index is shown to be greatly influenced by the competition between the reaction steps of (R63) and (R65) in addition to Zeldovich NO. It is, consequently, seen that the intermediate active species, HNO, affects NO emission behaviour remarkably. These results may be helpful to understand the role of recirculated steam in the combustion systems with flue gas recirculation to either fuel-or oxidizer-side.

A Numerical Study on the Effects of CO2/N2/Ar Addition to Air on Liftoff of a Laminar CH4/Air Diffusion Flame

“…The effects of adding various components of exhaust gas on the formation of pollutants have also been investigated by some researchers (Bundy et al, 2003;Guo and Smallwood, 2008;Li and Williams, 1999;Liu et al, 2001;Lock et al, 2007;Park et al, 2004;Zhao et al, 2002). Generally an additive to the oxidant or fuel stream of a diffusion flame causes variations in flame liftoff and other properties due to the change in combustion intensity.…”

Impact of Vitiation on a Swirl-Stabilized and Premixed Methane Flame

“…According to the OH concentration profile across the reaction zone, it was observed that the H 2 O and N 2 vitiation gas had almost the same peak concentration, although the adiabatic flame temperature with H 2 O vitiation gas was lower. This can be explained by the results of the previous research work, which indicated that more OH radicals were produced based on the chemical reaction step O + H 2 O → OH + OH [8,9]. At high flame temperature, the steam dissociation could also contribute to OH production [10].…”

A Study on H2−Air Counterflow Flames in Highly Preheated Air Diluted with CO2

“…The previous study compared the experimental data of Rørtveit et al with numerical results simulated with the aforementioned reaction mechanisms for the hydrogen flame diluted with 0.6 mole fraction of added N 2 . It was shown that the predicted temperature profile with the GRI v-3.0 mechanism had the best agreement with the experimental data.…”