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Numerical investigation of counter-flow diffusion flame of biogas–hydrogen blends: Effects of biogas composition, hydrogen enrichment and scalar dissipation rate on flame structure and emissions.

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Title: Numerical investigation of counter-flow diffusion flame of biogas–hydrogen blends: Effects of biogas composition, hydrogen enrichment and scalar dissipation rate on flame structure and emissions.
Authors: Mameri, Abdelbaki1, Tabet, Fouzi2 fouzi.tabet@dbfz.de
Source: International Journal of Hydrogen Energy. Jan2016, Vol. 41 Issue 3, p2011-2022. 12p.
Subjects: Diffusion, Biogas, Energy dissipation, Flame, Numerical analysis, Atmospheric pressure
Abstract: This study addresses numerically the influence of several operating conditions on the structure and NO emissions of a biogas diffusion flame. The analysis is conducted at atmospheric pressure in counter-flow configuration and mixture fraction space. CO 2 volume in biogas is varied from 25% to 60%, H 2 enrichment from 0% to 20% and the scalar dissipation rate from near equilibrium to near extinction. Particular attention is paid to CO 2 chemical effect. CO 2 contained in biogas can have chemical effects when it participates in chemical reactions and thermal effects when it acts like a pure diluent. Chemical effects of CO 2 are elucidated by using the inert species technique. Flame structure is characterized by solving flamelet equations with the consideration of radiation and detailed chemistry. It is observed that flame properties are very sensitive to biogas composition, hydrogen addition and scalar dissipation rate. CO 2 increment decreases flame temperature, mass fraction of chain carrier radicals and NO emission index. Blending biogas with hydrogen increases the mixture heating value and makes the fuel more reactive. Hence, chain carrier radicals and NO index emission are all increased. The chemical effect of CO 2 is found to be present overall scalar dissipation rate values where it reduces the maxima of temperature and OH mass fraction and increases the maxima of CO and NO mass fractions. H 2 enrichment has a weak influence on CO 2 chemical effect. Hydrogen-rich biogas flames produce less NO at high scalar dissipation rates. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:This study addresses numerically the influence of several operating conditions on the structure and NO emissions of a biogas diffusion flame. The analysis is conducted at atmospheric pressure in counter-flow configuration and mixture fraction space. CO 2 volume in biogas is varied from 25% to 60%, H 2 enrichment from 0% to 20% and the scalar dissipation rate from near equilibrium to near extinction. Particular attention is paid to CO 2 chemical effect. CO 2 contained in biogas can have chemical effects when it participates in chemical reactions and thermal effects when it acts like a pure diluent. Chemical effects of CO 2 are elucidated by using the inert species technique. Flame structure is characterized by solving flamelet equations with the consideration of radiation and detailed chemistry. It is observed that flame properties are very sensitive to biogas composition, hydrogen addition and scalar dissipation rate. CO 2 increment decreases flame temperature, mass fraction of chain carrier radicals and NO emission index. Blending biogas with hydrogen increases the mixture heating value and makes the fuel more reactive. Hence, chain carrier radicals and NO index emission are all increased. The chemical effect of CO 2 is found to be present overall scalar dissipation rate values where it reduces the maxima of temperature and OH mass fraction and increases the maxima of CO and NO mass fractions. H 2 enrichment has a weak influence on CO 2 chemical effect. Hydrogen-rich biogas flames produce less NO at high scalar dissipation rates. [ABSTRACT FROM AUTHOR]
ISSN:03603199
DOI:10.1016/j.ijhydene.2015.11.035