The effect of hydrogen addition on flammability limit and NOx emission in ultra-lean counterflow CH4/air premixed flames |
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Authors: | Hongsheng Guo, Gregory J. Smallwood, Fengshan Liu, Yiguang Ju,
mer L. Gü lder |
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Affiliation: | aCombustion Research Group, National Research Council Canada, 1200 Montreal Road, Building M-9, Ottawa, Ont., Canada K1A 0R6;bDepartment of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA;cInstitute for Aerospace Studies, University of Toronto, 4925 Dufferin Street, Toronto, Ont., Canada M3H 5T6 |
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Abstract: | The effect of hydrogen addition to ultra lean counterflow CH4/air premixed flames on the extinction limits and the characteristics of NOx emission was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. The results show that the addition of hydrogen can significantly enlarge the flammable region and extend the flammability limit to lower equivalence ratios. If the equivalence ratio is kept constant, the addition of hydrogen increases the emission of NO in a flame due to the enhancement in the rate of the NNH or N2O intermediate NO formation routes. The addition of hydrogen causes a monotonic decrease in the formation of NO2 and N2O, except flames near the extinction limits, where the emission of NO2 and N2O first increases, and then decreases with the increase in the fraction of hydrogen. Overall, hydrogen enrichment technology allows stable combustion under ultra lean conditions, resulting in significant CO2 and NO emission reduction. |
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Keywords: | Hydrogen enrichment NOx Extinction limit Ultra-lean premixed flame. |
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