Attachment mechanisms of diffusion flames

Takahashi, Fumiaki; Schmoll, W. J.; Katta, Viswanath R.

doi:10.1016/s0082-0784(98)80460-8

Cited by 79 publications

(43 citation statements)

References 10 publications

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“…While premixed flames propagate (and stabilize) due to heat transport from the burned to the unburned mixture, nonpremixed flames do not possess such a simple stabilization mechanism in the vicinity of a cold surface. A common view of nonpremixed flame stabilization proposed by Takahashi and Katta [5] focuses on the upstream mass transport of radicals from a reaction kernel that represents a region of high reactivity. This radical flux is believed to increase the chemical reaction rates for important reaction steps near a stabilization point that is located in a small premixing zone.…”

Section: Introductionmentioning

confidence: 99%

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

Puri

Aggarwal

Ratti

et al. 2001

Combustion and Flame

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Section: Introductionmentioning

confidence: 99%

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

Puri

Aggarwal

Ratti

et al. 2001

Combustion and Flame

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“…The flame base diffuses the heat in all downward directions; the temperature at the end of the diffusion flame is therefore reduced. This phenomenon is also seen in the flame bases of lifted nonpremixed flames without triple flame (30) . The heat release rates along the premixed flames (Fig.…”

Section: Resultsmentioning

confidence: 63%

Identification of Triple Flame Based on Numerical Data for Laminar Lifted Flames

Noda

Yamamoto

2006

JSME international journal. Ser. B, Fluids and thermal engineer

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The flame base structures of laminar lifted flames are numerically investigated in order to develop a model of triple flame applicable to the flamelet model. The lifted flames formed in the downstream expanded duct developed by Kioni et al.(1) are calculated systematically in terms of the fuel concentration gradient at the inlet using a variant of the HSMAC method, modified so as to deal with variations of density. The triple flame is formed at the flame base of lifted nonpremixed flame for every case, even the case which does not initially have partial mixing. The diffusion flame appears to be supported by the enhancement of the surrounding premixed flames, resulting in a temperature rise. All scalar quantities along the premixed flames of the triple flame decline along a similar profile in mixture fraction space, and scalar quantities in the region surrounded by the premixed flames are almost completely conserved. On the basis of the results, we developed a model of triple flame that is applicable to the flamelet model. In the model, the region without reaction upstream of the flame base is referred to as the unburned region (frozen flow structure region), followed by the transition region outside the premixed flames, in which the flame changes from the frozen structure to the fully burning diffusion structure. The region surrounded by the premixed flames is referred to as the triple flame structure region. The region following the triple flame structure region is the fully burning diffusion flame structure region.

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“…The underestimation of the quenching scalar dissipation rate must be caused by intermediate reactions, as reported by Takahashi et al (20) and Takahashi and Katta (21) . Accordingly, we used the rate formula given by Eq.…”

Section: Geometry and Boundary Conditionsmentioning

confidence: 62%

“…2 (III) and 4 (III) have hook-shaped distributions, with the tip directed towards the fuel-lean side (air side). Takahashi et al (20) reported similar distributions in the heat-release rate at the flame base of jet diffusion flames, the peak spot termed the reaction kernel, by implementing calculations of co-flow methane-air jet diffusion flames with a detailed chemistry model. In their study, it was concluded that radicals diffusing radially near the reaction kernel cause the expansion of the flame base towards the fuel-lean side.…”

Section: Geometry and Boundary Conditionsmentioning

confidence: 93%

Numerical Investigation of Edge Flame Structure of Counterflow Nonpremixed Flames with Local Extinction Due to Flame Stretch

Noda

Tsubokura

2005

JSME international journal. Ser. B, Fluids and thermal engineer

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Laminar counterflow nonpremixed flames with local extinction caused by nonuniform inflows are numerically investigated in two-dimensions in a system governed by Lewis numbers of unity and assuming a single-step, irreversible, finite-rate reaction. A numerical method based on the SIMPLE algorithm is used. Edge flame structures are investigated through the introduction of a new progress variable defined as the normalized integral of the mass fraction of a product in the mixture fraction Z space and which expresses the progress of the chemical reaction. Calculation results reveal that the edge flame structure can be classified into three regions; fully burning flame, weakened flame with a low reaction rate, and a non-reacting preheat region. Under these conditions, and in terms of the energy balance, the edge flame structure is dependent on the Z-directional heat diffusion transport, heat consumption (given by the progress variable), and heat production by chemical reaction. It is found that each type of flame structure can be well characterized by three parameters; the mixture fraction, the stoichiometric scalar dissipation rate, and the progress variable. These three parameters are identified as important factors affecting the edge flame structure of nonpremixed flames with local extinction.

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Attachment mechanisms of diffusion flames

Cited by 79 publications

References 10 publications

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

On the similitude between lifted and burner-stabilized triple flames: a numerical and experimental investigation

Identification of Triple Flame Based on Numerical Data for Laminar Lifted Flames

Numerical Investigation of Edge Flame Structure of Counterflow Nonpremixed Flames with Local Extinction Due to Flame Stretch

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