Computed NOx emission characteristics of opposed-jet syngas diffusion flames |
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| Authors: | Hsin-Yi Shih Jou-Rong Hsu |
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| Affiliation: | 1. Department of Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA 92093-0411, USA;2. Institute for Powertrains and Automotive Technology, Vienna University of Technology, Gusshausstrasse 27-29/315, A-1040 Vienna, Austria;3. Combustion Engineering Department, Solar Turbines Inc., Caterpillar, San Diego, CA 92186, USA;1. Key Laboratory of Advanced Energy and Power, Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China;2. Research Center for Clean Energy and Power, Chinese Academy of Sciences, Lianyungang, Jiangsu 222069, China;3. University of Chinese Academy of Sciences, Beijing 100049, China;1. School of Mechanical and Aerospace Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea;2. Department of Safety Engineering, Incheon National University, Songdo-dong 119 Academy-ro, Yeonsu-gu, Incheon, Republic of Korea;1. Key Laboratory of the Three Gorges Reservoir Region''s Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, China;2. School of Urban Construction and Environmental Engineering, Chongqing University, Chongqing 400045, China;3. Sichuan Electric Power Design & Consulting Cor. LTD, Chengdu 610041, China;4. Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education of China, Chongqing 400044, China;5. College of Mechanical and Power Engineering, Chongqing University of Science & Technology, Chongqing 401331, China |
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| Abstract: | This paper reported a numerical study on the NOx emission characteristics of opposed-jet syngas diffusion flames. A narrowband radiation model was coupled to the OPPDIF program, which used detailed chemical kinetics and thermal and transport properties to enable the study of 1-D counterflow syngas diffusion flames with flame radiation. The effects of syngas composition, pressure and dilution gases on the NOx emission of H2/CO synthetic mixture flames were examined. The analyses of detailed flame structures, chemical kinetics, and nitrogen reaction pathways indicate NOx are formed through Zeldovich (or thermal), NNH and N2O routes both in the hydrogen-lean and hydrogen-rich syngas flames at normal pressure. Zeldovich route is the main NO formation route. Therefore, the hydrogen-rich syngas flames produce more NO due to higher flame temperatures compared to that for hydrogen-lean syngas flames. Although NNH and N2O routes also are the primary NO formation paths, a large amount of N2 will be reformed from NNH and N2O species. For hydrogen-rich syngas flames, the NO formation from NNH and N2O routes are lesser, where NO can be dissipated through the reactions of NH + NO → N2 + OH and NH + NO → N2O + H more actively. At a rather low pressure (0.01 atm), NNH-intermediate route is the only formation path of NO. Increasing pressure then enhances NO formation reactions, especially through Zeldovich mechanisms. However, at higher pressures (5–10 atm), NO is then converted back to N2 through reversed N2O route for hydrogen-lean syngas flames, and through NNH as well for hydrogen-rich syngas flames. In addition, the dilution effects from CO2, H2O, and N2 on NO emissions for H2/CO syngas flames were studied. The hydrogen-lean syngas flames with H2O dilution have the lowest NO production rate among them, due to a reduced reaction rate of NNH + O → NH + NO. But for hydrogen-rich syngas flames with CO2 dilution, the flame temperatures decrease significantly, which leads to a reduction of NO formation from Zeldovich route. |
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