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.
