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EFFECTS OF STRAIN RATE AND CO2 ON NO FORMATION IN CH4/N2/O2 COUNTER-FLOW DIFFUSION FLAMES

ABSTRACT
The reduction of nitrogen oxides in the high temperature flame is the key factor affecting the oxygen-enriched combustion performance. A numerical study using an OPPDIF code with detailed chemistry mechanism GRI 3.0 was carried out to focus on the effect of strain rate(25-130 s-1) and CO2 addition(0-0.59) on the oxidizer side on NO emission in CH4/N2/O2 counterflow diffusion flame. The mole fraction profiles of flame structures, NO, NO2 and some selected radicals (H, O, OH) and the sensitivity of the dominant reactions contributing to NO formation in the counterflow diffusion flames of CH4/N2/O2 and CH4/N2/O2/CO2 were obtained. The results indicated that the flame temperature and the amount of NO were reduced while the sensitivity of reactions to the prompt NO formation was gradually increased with the increasing strain rate. Furthermore, it is shown that with the increasing CO2 concentration in oxidizer, CO2 was directly involved in the reaction of NO consumption. The flame temperature and NO production were decreased dramatically and the mechanism of NO production was transformed from the thermal to prompt route.
KEYWORDS
PAPER SUBMITTED: 2017-09-22
PAPER REVISED: 2017-12-28
PAPER ACCEPTED: 2017-12-20
PUBLISHED ONLINE: 2018-02-18
DOI REFERENCE: https://doi.org/10.2298/TSCI170922062R
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2018, VOLUME 22, ISSUE Supplement 2, PAGES [S769 - S776]
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© 2018 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence