The Effect of Fuel/Air Mixture Composition on No Formation in Methane, Methanol and Methyl Formate Freely Propagating Flames

Abstract

In this study we have examined the effects of fuel/air mixtures composition on NO formation in methane/air, methanol/air, and methyl formate/air freely propagating flames. The flames have been numerically simulated at pressure of 1 bar and equivalence ratios ( ) from 0.7 to 1.3. Various chemical kinetic mechanisms have been employed and extensively tested so as to ensure validity of the results. A comparison of NO profiles for different equivalence ratios have been done for the three flames. The role of temperature in NO formation is clearly demonstrated in these profiles, with the NO profiles having direct correlation with temperature profiles. It has been established that there is a significant dependency of temperature for NO formation in methane/air as compared to the other flames. This is attributed to dominance of reaction; CH + N2 ! HCN + N, which results in large amount of N atoms taking part in NO formation in temperature dependent Zeldovich thermal NO mechanism. On the other hand, the NO formation in methanol and methyl formate is mostly through reaction: NNH + O ! NH + NO, which is as a result of few CH radical and hence few N atoms responsible for NO formation in temperature dependent Zeldovich mechanism.