Interactions among soot, thermal radiation, and NOx emissions in oxygen-enriched turbulent nonpremixed flames: A computational fluid dynamics modeling study

L. Wang, Daniel Connell Haworth, S. R. Turns, M. F. Modest

Research output: Contribution to journalArticle

85 Citations (Scopus)

Abstract

Many combustion applications benefit from the use of oxygen-enriched air or pure oxygen as oxidizer. Oxygen enrichment increases the flame temperature, promotes soot formation and oxidation, and can decrease pollutant emissions compared with hydrocarbon-air systems. Adequate and simultaneous accounting for soot, radiation, and pollutant emissions poses challenges in modeling of oxygen-enriched turbulent flames. Here a comprehensive computational fluid dynamics (CFD) model is developed by integrating state-of-the-art models for detailed chemistry, soot formation and oxidation, and thermal radiation into a three-dimensional unstructured CFD code. Detailed hydrocarbon oxidation, soot, and NOx chemistry are represented using a mechanism that contains 122 chemical species and 677 elementary reactions. The soot model includes a detailed description of soot formation and oxidation, and employs the method of moments to describe the evolution of the soot particle size distribution. Two radiation models are implemented, one that accounts for nongray-gas properties and one that does not; both radiation models include self-absorption effects and treat soot radiation as gray. The model is applied to an oxygen-enriched, propane-fueled, turbulent, nonpremixed jet flame. Results show that soot and spectrally radiating gas-phase species are distributed separately in the flame, and this segregation of radiating media strongly affects the radiant heat flux, flame structure, flame temperature, and NOx emissions. Soot radiation decreases flame temperature and NOx emission substantially, especially in the flame-tip region. The effects of nongray-gas-phase radiation are important even in the presence of strong gray soot radiation and must be included to capture the correct distribution of radiative heat flux. Nongray-gas effects are stronger downstream than upstream and, therefore, are particularly important for the burnout of soot. Both soot radiation and nongray-gas radiation are required for accurate predictions of soot and NOx formation within and upstream of the flame zone.

Original languageEnglish (US)
Pages (from-to)170-179
Number of pages10
JournalCombustion and Flame
Volume141
Issue number1-2
DOIs
StatePublished - Apr 1 2005

Fingerprint

Soot
turbulent flames
Heat radiation
thermal radiation
soot
computational fluid dynamics
Computational fluid dynamics
Oxygen
oxygen
nongray gas
Radiation
interactions
radiation
Gases
flame temperature
flames
Oxidation
oxidation
Hydrocarbons
upstream

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Physics and Astronomy(all)

Cite this

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title = "Interactions among soot, thermal radiation, and NOx emissions in oxygen-enriched turbulent nonpremixed flames: A computational fluid dynamics modeling study",
abstract = "Many combustion applications benefit from the use of oxygen-enriched air or pure oxygen as oxidizer. Oxygen enrichment increases the flame temperature, promotes soot formation and oxidation, and can decrease pollutant emissions compared with hydrocarbon-air systems. Adequate and simultaneous accounting for soot, radiation, and pollutant emissions poses challenges in modeling of oxygen-enriched turbulent flames. Here a comprehensive computational fluid dynamics (CFD) model is developed by integrating state-of-the-art models for detailed chemistry, soot formation and oxidation, and thermal radiation into a three-dimensional unstructured CFD code. Detailed hydrocarbon oxidation, soot, and NOx chemistry are represented using a mechanism that contains 122 chemical species and 677 elementary reactions. The soot model includes a detailed description of soot formation and oxidation, and employs the method of moments to describe the evolution of the soot particle size distribution. Two radiation models are implemented, one that accounts for nongray-gas properties and one that does not; both radiation models include self-absorption effects and treat soot radiation as gray. The model is applied to an oxygen-enriched, propane-fueled, turbulent, nonpremixed jet flame. Results show that soot and spectrally radiating gas-phase species are distributed separately in the flame, and this segregation of radiating media strongly affects the radiant heat flux, flame structure, flame temperature, and NOx emissions. Soot radiation decreases flame temperature and NOx emission substantially, especially in the flame-tip region. The effects of nongray-gas-phase radiation are important even in the presence of strong gray soot radiation and must be included to capture the correct distribution of radiative heat flux. Nongray-gas effects are stronger downstream than upstream and, therefore, are particularly important for the burnout of soot. Both soot radiation and nongray-gas radiation are required for accurate predictions of soot and NOx formation within and upstream of the flame zone.",
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Interactions among soot, thermal radiation, and NOx emissions in oxygen-enriched turbulent nonpremixed flames : A computational fluid dynamics modeling study. / Wang, L.; Haworth, Daniel Connell; Turns, S. R.; Modest, M. F.

In: Combustion and Flame, Vol. 141, No. 1-2, 01.04.2005, p. 170-179.

Research output: Contribution to journalArticle

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T1 - Interactions among soot, thermal radiation, and NOx emissions in oxygen-enriched turbulent nonpremixed flames

T2 - A computational fluid dynamics modeling study

AU - Wang, L.

AU - Haworth, Daniel Connell

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AU - Modest, M. F.

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AB - Many combustion applications benefit from the use of oxygen-enriched air or pure oxygen as oxidizer. Oxygen enrichment increases the flame temperature, promotes soot formation and oxidation, and can decrease pollutant emissions compared with hydrocarbon-air systems. Adequate and simultaneous accounting for soot, radiation, and pollutant emissions poses challenges in modeling of oxygen-enriched turbulent flames. Here a comprehensive computational fluid dynamics (CFD) model is developed by integrating state-of-the-art models for detailed chemistry, soot formation and oxidation, and thermal radiation into a three-dimensional unstructured CFD code. Detailed hydrocarbon oxidation, soot, and NOx chemistry are represented using a mechanism that contains 122 chemical species and 677 elementary reactions. The soot model includes a detailed description of soot formation and oxidation, and employs the method of moments to describe the evolution of the soot particle size distribution. Two radiation models are implemented, one that accounts for nongray-gas properties and one that does not; both radiation models include self-absorption effects and treat soot radiation as gray. The model is applied to an oxygen-enriched, propane-fueled, turbulent, nonpremixed jet flame. Results show that soot and spectrally radiating gas-phase species are distributed separately in the flame, and this segregation of radiating media strongly affects the radiant heat flux, flame structure, flame temperature, and NOx emissions. Soot radiation decreases flame temperature and NOx emission substantially, especially in the flame-tip region. The effects of nongray-gas-phase radiation are important even in the presence of strong gray soot radiation and must be included to capture the correct distribution of radiative heat flux. Nongray-gas effects are stronger downstream than upstream and, therefore, are particularly important for the burnout of soot. Both soot radiation and nongray-gas radiation are required for accurate predictions of soot and NOx formation within and upstream of the flame zone.

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