Laser-Induced Fluorescence Measurements of Nitric Oxide Formation in High-Pressure Premixed Methane Flames

Abstract

ABSTRACf-We have obtained quantitative LIF measurements of NO concentration in the postllame zone of a series of lIat, laminar, premixed CH./O,(N, lIames (0.5:s ",:S 1.6) at pressures ranging from 1-14.6 atm. The temperatures of the lIames were 1660-1960 K, indicating that prompt NO was the primary pathway for NO formation in the majority of these flames. In addition, we have modeled many of the experimentaillames using the chemical reaction mechanism ofGlarborg-MiJler-Kee as modified by Drake and Blint (GMK-DB). This model accurately predicts the behavior of NO with increasing pressure and shows reasonable quantitative agreement for many of the lIames at pressures :s 6.1 atm. At pressures greater than 6.1 atm, inaccuracies in the predicted temperature field preclude good quantitative agreement between the modeled and measured NO concentrations. Detailed NO measurements in ultra-lean ('" = 0.55-0.8) flames showed higher NO emissions with increasing pressure, a result consistent with kinetic modeling of these lean lIames via the GMK-DB mechanism.

Pressure dependence of NO formation in laminar fuel-rich premixed CH4/air flames

“…Knowledge of the fuel-rich conditions, which occur in a wide variety of combustion systems. For example, comparison of the measured and calculated NO concentrations in atmospheric-pressure CH 4 /air flames at an equivalence ratio of 1.3 [1,3] plotted as a function of the measured flame temperature shows that the predictions are a factor of 2 too high for most of the flames studied. Experiments and calculations performed at atmospheric pressure and higher [4] in fuel-rich CH 4 /O 2 /N 2 flames (with O 2 /N 2 ratio close to that of air) also show that the calculations significantly overpredict the measurements for atmospheric-pressure flames, while at higher pressures the agreement is better.…”

“…Less information is available regarding the pressure dependence of NO formation in fuel-rich laminar flames, although an empirical relation for Fenimore NO formation has been derived for diffusion flames [10]. While a few experimental and numerical investigations of NO formation in fuelrich premixed flames have been performed at different pressures (see, for example, [4,11]), to our knowledge no attempts have been made so far to derive a functional pressure dependence under these conditions, which is dominated by the Fenimore mechanism.…”

NO formation in high pressure premixed flames: Experimental results and validation of a new revised reaction mechanism

“…Interestingly, they highlighted the importance of the branching ratios for the reaction NCN+H→ products, especially at high pressure, but this mechanism was validated only on results from Klassen et al. [20] in laminar premixed CH4/O2/N2 flat flames at pressures ranging from 1 to 14.6 atm.…”

“…The complete understanding of the chemical kinetics involved in the production of NO at high pressure requires accurate in situ measurements of NO concentration. Most of the studies dedicated to NO measurements in laminar high pressure flames were performed using Laser Induced Fluorescence by the groups of N.M. Laurendeau [20][21][22][23][24][25][26][27][28][29][30] and R.K. Hanson [31][32][33][34][35].…”

Effects of pressure and carbon dioxide, hydrogen and nitrogen concentration on laminar burning velocities and NO formation of methane-air mixtures

“…Finally, we study numerically the effect of increasing pressure from 1 to 5 atmospheres on NO formation of Methane-air fuel mixture diluted with carbon dioxide, hydrogen and nitrogen in stoichiometry condition. Few experimental and numerical studies have been done about the NO formation in premixed flames in different pressure [39,40]. In Fig.…”