Experimental and numerical study of a highly diluted turbulent diffusion flame close to blowout

Tacke, M.; Linow, Sven; Geiss, Stefan; Hassel, Egon; Janicka, J.; Chen, Jyh-Yuan

doi:10.1016/s0082-0784(98)80516-x

Cited by 20 publications

(32 citation statements)

References 18 publications

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“…1a-d, are typically characterized by an evolution in scalar structure, as revealed by plotting scatter data and conditional means for temperature and species mass fractions against mixture fraction, for example. Near the nozzle exit there may be strong effects of preferential diffusion on measured species mass fractions and temperature [75,80,82,83,149]. This is especially true when the jet exit Reynolds number is below about 15,000 and when H 2 is a component of the fuel stream.…”

Section: Preferential Molecular Diffusion Effectsmentioning

confidence: 99%

“…However, there are at least two examples of model calculations of jet flame that had to account for differential diffusion near the nozzle in order obtain reasonable agreement with experiments [133,149]. Consequently, it is important to quantify differential diffusion effects in laboratory-scale flames and understand how they might influence the interpretation of comparisons of measured and modeled results.…”

Section: Preferential Molecular Diffusion Effectsmentioning

confidence: 99%

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Laser diagnostics and their interplay with computations to understand turbulent combustion

Barlow

2007

Proceedings of the Combustion Institute

211

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Section: Preferential Molecular Diffusion Effectsmentioning

confidence: 99%

Section: Preferential Molecular Diffusion Effectsmentioning

confidence: 99%

Laser diagnostics and their interplay with computations to understand turbulent combustion

Barlow

2007

Proceedings of the Combustion Institute

211

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“…The concept of triple flames has been put forward by various researchers (Ruetsch et al, 1995;Buckmaster, 1996aBuckmaster, , 1996bDomingo and Vervisch, 1996;Plessing et al, 1998a;Tacke et al, 1998;Chen and Bilger, 2000) to be the key to understand the stabilization of lifted flames. According to this theory, gas expansion of the premixed flame front generates a normal velocity from the stabilization point into the unburnt mixture.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Flame Liftoff Height of Diffusion/Partially Premixed Jet Flames and Modeling of Mild Combustion Burners

Kumar

Paul

Mukunda

2007

Combustion Science and Technology

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In this article, a new flame extinction model based on the k=e turbulence time scale concept is proposed to predict the flame liftoff heights over a wide range of coflow temperature and O 2 mass fraction of the coflow. The flame is assumed to be quenched, when the fluid time scale is less than the chemical time scale (Da < 1). The chemical time scale is derived as a function of temperature, oxidizer mass fraction, fuel dilution, velocity of the jet and fuel type. The present extinction model has been tested for a variety of conditions: (a) ambient coflow conditions (1 atm and 300 K) for propane, methane and hydrogen jet flames, (b) highly preheated coflow, and (c) high temperature and low oxidizer concentration coflow. Predicted flame liftoff heights of jet diffusion and partially premixed flames are in excellent agreement with the experimental data for all the simulated conditions and fuels. It is observed that flame stabilization occurs at a point near the stoichiometric mixture fraction surface, where the local flow velocity is equal to the local flame propagation speed. The present method is used to determine the chemical time scale for the conditions existing in the mild= flameless combustion burners investigated by the authors earlier. This model has successfully predicted the initial premixing of the fuel with combustion products before the combustion reaction initiates. It has been inferred from these numerical simulations that fuel injection is followed by intense premixing with hot combustion products in the primary zone and combustion reaction follows further downstream. Reaction rate contours suggest that reaction takes place over a large volume and the magnitude of the combustion reaction is lower compared to the conventional combustion mode. The appearance of attached flames in the mild combustion burners at low thermal inputs is also predicted, which is due to lower average jet velocity and larger residence times in the near injection zone.

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“…Accordingly, we anticipate that models of turbulent combustion that account for differential diffusion at fuel/air interfaces will be more robust. As another example, the role of differential diffusion in stabilizing highly diluted turbulent flames near blowout has also been reported [24].…”

Section: Discussionmentioning

confidence: 93%

Investigation of differential diffusion in turbulent jet flows using planar laser Rayleigh scattering

Dibble

Long

2005

Combustion and Flame

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Experimental and numerical study of a highly diluted turbulent diffusion flame close to blowout

Cited by 20 publications

References 18 publications

Laser diagnostics and their interplay with computations to understand turbulent combustion

Laser diagnostics and their interplay with computations to understand turbulent combustion

Prediction of Flame Liftoff Height of Diffusion/Partially Premixed Jet Flames and Modeling of Mild Combustion Burners

Investigation of differential diffusion in turbulent jet flows using planar laser Rayleigh scattering

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