• Title/Summary/Keyword: Laminar Flamelet Model

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Laminar Flamelet Modeling of Combustion Processes and NO Formation in Nonpremixed Turbulent Jet Flames (Laminar Flamelet Model을 이용한 비예혼합 난류제트화염의 연소과정 및 NO 생성 해석)

  • Kim, Seong-Ku;Kim, Hoo-Joong;Kim, Yong-Mo
    • Journal of the Korean Society of Combustion
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    • v.4 no.2
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    • pp.51-62
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    • 1999
  • NOx formation in turbulent flames is strongly coupled with temperature, superequilibrium concentration of O radical, and residence time. This implies that in order to accurately predict NO level, it is necessary to develop sophisticated models able to account for the complex turbulent combustion processes including turbulence/chemistry interaction and radiative heat transfer. The present study numerically investigates the turbulent nonpremixed hydrogen jet flames using the laminar flamelet model. Flamelet library is constructed by solving the modified Peters equations and the turbulent combustion model is extended to nonadiabatic flame by introducing the enthalpy defect. The effects of turbulent fluctuation are taken into account by the presumed joint PDFs for mixture fraction, scalar dissipation rate, and enthalpy defect. The predictive capability of the present model has been validated against the detailed experimental data. Effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

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Laminar Flamelet Modeling of Combustion Processes and NO Formation in Nonpremixed Turbulent Jet Flames (Laminar Flamelet Model을 이용한 비예혼합 난류제트화염의 연소과정 및 NO 생성 해석)

  • Kim, Seong-Ku;Kim, Hoo-Joong;Kim, Yong-Mo
    • 한국연소학회:학술대회논문집
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    • 1999.10a
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    • pp.93-104
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    • 1999
  • NOx formation in turbulent flames is strongly coupled with temperature, superequilibrium concentration of O radical, and residence time. This implies that in order to accurately predict NO level, it is necessary to develop sophisticated models able to account for the complex turbulent combustion processes including turbulence/chemistry interaction and radiative heat transfer. The present study numerically investigates the turbulent nonpremixed hydrogen jet flames using the laminar flamelet model. Flamelet library is constructed by solving the modified Peters equations and the turbulent combustion model is extended to nonadiabatic flame by introducing the enthalpy defect. The effects of turbulent fluctuation are taken into account by the presumed joint PDFs for mixture fraction, scalar dissipation rate, and enthalpy defect. The predictive capability of the present model has been validated against the detailed experimental data. Effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

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Modeling for Soot Formation Coupled with Detailed Chemistry in Laminar Pressurized Non-premixed Flames (층류 고압 비예혼합 화염에서 상세화학반응과 결합된 매연입자 생성 모델링)

  • Kim, Taehoon;Jeon, Sangtae;Kim, Yongmo
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.139-140
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    • 2012
  • In laminar non-premixed flame situation, the flamelet model is not suitable for simulating slow processor like soot and radiation. Thus in this study, we overcome this limitation by using the transient flamelet model. Also, for soot formation on laminar non-premixed flame, transient flamelet coupled with two-equation soot model has been adopted due to its inherent advantages in terms of accuracy and availability. Based on numerical results, the detailed discussion has been made for the precise structure and soot formation processes in the pressurized methane air flames.

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Unsteady Flamelet Modeling for Flame Structure and Soot Formation of Lanimar Non-premixed CH4/Air Flame (비정상 화염편 모델을 이용한 대기압 층류 비예혼합 CH4/Air 화염장의 매연입자 생성 특성 및 화염구조 해석)

  • Kim, Taehoon;Jeon, Sangtae;Kim, Yongmo
    • 한국연소학회:학술대회논문집
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    • 2012.11a
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    • pp.137-138
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    • 2012
  • The two-equation soot model based on the transient laminar flamelet model is implemented for soot formation of laminar non-premixed $CH_4/Air$ flame with detailed chemical reaction mechanism and complex thermodynamic properties. The soot model represents nucleation, growth and oxidation with gas-phase chemistry. This represented unsteady flamelet soot model has been tested and compared using well verified reference calculation result obtained solving the Full Transport Equations method.

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Numerical Study of PAH Formation Characteristics in Laminar Non-Premixed C2H4 Jet Flames (층류 비예혼합 C2H4 제트 화염장에서의 PAH 생성특성 해석)

  • Kim, Taehoon;Kim, Yongmo
    • 한국연소학회:학술대회논문집
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    • 2014.11a
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    • pp.133-134
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    • 2014
  • The full transport equation approach for laminar non-premixed flame with detailed chemistry, soot and radiation has an advantage in accuracy and describing for emission pathway, but this approach requires the excessive computational cost especially for a higher-order hydrocarbon fuel flames. On the other hand, the standard flamelet model has an efficiency and accuracy for non-premixed flame, though this model is not suitable for simulating slow processor like soot and radiation in laminar non-premixed flame situation. To overcome this limitation, modified transient flamelet model is developed which coupled with two-equation soot model involved in soot formation and evolution mechanism such as nucleation, surface growth, oxidation and agglomeration.

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Flamelet Modelling of Soot Formation and Oxidation in a Laminar $CH_4$-Air Diffusion Flame (화염편모델을 이용한 층류확산화염장의 매연 생성 및 산화과정 해석)

  • Kim, Gun-Hong;Kim, Hu-Jung;Kim, Yong-Mo;Kim, Seung-Ku
    • 한국연소학회:학술대회논문집
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    • 2003.12a
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    • pp.3-9
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    • 2003
  • By utilizing a semi-empirical soot model, the applicability of the laminar flamelet concept for simulating the formation and oxidation of soot in the laminar diffusion flame has been studied. The source terms for two transport equations of the soot formation and oxidation are calculated in the mixture fraction/scalar dissipation rate space for laminar flamelets and stored in a library. In this study, emphasis is given to the interaction associated with radiation and soot formation. The radiative heat loss is obtained by solving the radiative transfer equation using the unstructured grid finite volume method with the WSGGM. The calculated temperatures and soot volume fractions agree relatively well with the experimental data and the previous numerical results of Kaplan et al. using the detailed chemistry.

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Flamelet Modeling of Structures and $NO_{x}$ Formation Charateristics in Bluff-Body stabilized Methanol Flames (메탄올 Bluff-Body 난류 화염내의 화염구조 및 $NO_{x}$ 생성 특성에 대한 수치적 연구)

  • Lee, Joon-Kyu;Kim, Seoung-Ku;Kim, Yong-Mo;Kim, Sae-Won
    • Proceedings of the KSME Conference
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    • 2001.06d
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    • pp.37-42
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    • 2001
  • This paper computes the bluff-body stabilized jet and flame. This study numerically investigates the nonpremixed $C_{2}H_{4}-air$ jet for the nonreacting case and the nonpremixed $CH_{3}OH-air$ turbulent flames for the reacting case using the laminar flamelet model on modified KIVA2 code. And this study predicts $NO_{x}$ formation characteristics using Eulerian Particle Flamelet Model. In the present study, the turbulent combustion model is applied to analyze both nonreacting and reacting case. And both standard $k-{\varepsilon}$ model and modified $k-{\varepsilon}$ model are used in nonreacting case. Calculations are compared with experimental data in terms of velocity, mixture fraction, mixture fraction Root Mean Square and Temperature. The present model correctly predicts the essential features of flame structures and $NO_{x}$ formation characteristics in the bluff-body stabilized flames.

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Flamelet Modelling of Soot Formation and Oxidation in a Laminar $CH_4-Air$ Diffusion Flame (화염편 모델을 이용한 층류확산화염장의 매연 생성 및 산화과정 해석)

  • Kim Gunhong;Kim Hoojoong;Kim Yongmo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.1
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    • pp.68-75
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    • 2005
  • By utilizing a semi-empirical soot model, the applicability of the laminar flamelet concept fur simulating the formation and oxidation of soot in the laminar diffusion flame has been studied. The source terms for two transport equations of the soot formation and oxidation are calculated in the mixture fraction/scalar dissipation rate space for laminar flamelets and stored in a library. In this study, emphasis is given to the interaction associated with radiation and soot formation. The radiative heat loss is obtained by solving the radiative transfer equation using the unstructured grid finite volume method with the WSGGM. The calculated temperatures and soot volume fractions agree relatively well with the experimental data and the previous numerical results of Kaplan et al. using the detailed chemistry.

A Study on Structures and NOx Formation Characteristics in Coflow and Counterflow Diffusion Flamelet (분류 및 대향류 확산 소화염의 구조 및 NOx 생성특성 비교 검토)

  • Oh, C.B.;Kim, J.S.;Lee, C.E.;Lee, K.M.
    • Journal of the Korean Society of Combustion
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    • v.3 no.2
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    • pp.29-40
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    • 1998
  • Flame structures and NOx formation characteristics in the flame lets of coflow and counterflow diffusion flame are numerically studied. Calculations were carried out twice with the $C_2-Full$ and $C_2-Thermal$ Mechanism for each flame. Mixture fractions and scalar dissipation rates are used as the parameters to compare the flame let structures and NOx formation characteristics quantitatively. It was found that there is a similarity in flame temperature and stable species profiles except radical profiles between two flamelets. And there are some differences in NOx concentration and production rates. These results imply that the flow effects must be considered in calculations for NOx formation of turbulent flames using Laminar Flamelet Model.

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Comparison of the combustion characteristics between air combustion and oxy-combustion with $CO_2$ recirculation ($CO_2$ 재순환에 의한 순산소 연소와 공기 연소의 화염 특성 비교)

  • Lee, Seung-Hwan;Huh, Kang-Y.
    • Journal of the Korean Society of Combustion
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    • v.13 no.3
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    • pp.24-32
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    • 2008
  • Steady Laminar Flamelet Model (SLFM) calculation is performed to compare the turbulent combustion characteristics of air combustion and oxy-combustion with $CO_2$ recirculation. Radiative heat loss is considered by the optically thin limit assumption. For more realistic simulation the first-order conditional moment closure(CMC) model is applied to SANDIA PILOTED FLAME D again for the oxidants of air and mixture of $O_2$ and $CO_2$. The chemical kinetic machanism for methane is GRI Mech 3.0. Results show that oxy flames are much more stable than air flames, while comparable stability is maintained with 65% $CO_2$ recirculation. The comparable peak temperature is maintained with 80% $CO_2$ recirculation. Higher the temperature, higher the fractions of intermediate species, CO and OH, due to dissociation.

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