A Model for Flame Extinction in Turbulent Flow

Byggstøyl, S.; Magnussen, Bjørn F.

doi:10.1007/978-3-642-69996-2_31

Cited by 37 publications

(31 citation statements)

References 10 publications

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“…Figures 5 and 6 show the flame liftoff height predictions carried out with a constant time scale of 8.5 ms. Flame liftoff heights are overpredicted at low velocities and under-predicted at high velocities-near the blow-off limit. Flame liftoff predictions are independent to the fuel jet diameter compared to the predictions of Byggstoyl and Magnussen (1985) which are based on a fine structure time scale C(n=e) 1=2 . It is clear from Figures 5 and 6 that k=e based fluid time scale and flame liftoff height do not increase at the same rate for turbulent jet flames.…”

Section: Lifted Propane Jet Flames At Ambient Temperature and Pressurementioning

confidence: 98%

“…Energy and species conservation equations related to the particular fuel are solved in the computational domain. Mean reaction rate is modeled using the eddy dissipation concept (EDC) model with multi-step skeletal kinetics (Byggstoyl and Magnussen, 1985).…”

Section: The Computational Geometrymentioning

confidence: 99%

“…It has been found that the prediction of flame liftoff height is in excellent agreement with the experimentally measured values as shown in Figure 12. 1=2 based time scale proposed by Byggstoyl and Magnussen (1985). All the values of the chemical time scale used for the present computations are derived using the parameters listed in Table 1.…”

Section: Diluted Propane Flamesmentioning

confidence: 99%

“…The extinction model proposed by Byggstoyl and Magnussen (1985) assumes that both fuel and air are essentially premixed at the base of the flame. According to this model, extinction occurs when this time scale matches the chemical time scale for extinction based on C(n=e) 1=2 parameter.…”

Section: Introductionmentioning

confidence: 99%

“…This method has been used to predict liftoff height of diluted methane flames and compared with the experimental measurements of Horch (1978). However, the proposed C(n=e) 1=2 based extinction criterion depends explicitly on the diameter of the fuel jet, a feature acknowledged by the authors themselves (Byggstoyl and Magnussen, 1985).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

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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Section: Lifted Propane Jet Flames At Ambient Temperature and Pressurementioning

confidence: 98%

Section: The Computational Geometrymentioning

confidence: 99%

Section: Diluted Propane Flamesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Multiscale modeling of turbulent combustion and NO_x emission in steam crackers

2007

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in Wiley InterScience (www.interscience.wiley.com).A 3D RANS simulation of lean premixed turbulent combustion in an industrial scale steam cracking furnace is performed. Turbulence is represented by a renormalization group (RNG) k 2 e model, while combustion is modeled with a skeletal mechanism. The eddy dissipation concept (EDC) model is used to account for turbulence/combustion interaction. The turbulent combustion regime is identified as a ''thin flame regime with pockets'' or a ''corrugated flamelet regime''. A weighted sum of gray gases model (WSGGM) is used to account for the gas radiative properties. The radiative transfer equation is solved using the P-1 and discrete ordinates method in the conservative finite volume formulation. NO x calculations are performed as a postprocessing step, with the flow field, temperature, and species concentrations fixed. The formation of NO through thermal, prompt, and N 2 O intermediate mechanisms is considered. The in situ adaptive tabulation technique is used to decrease the computational time required to treat the combustion chemistry. The effect of radiation models on the predicted furnace wall, tube skin, and flue gas temperature profiles and heat fluxes toward the reactor tubes, as well as on the predicted species and NO concentration profiles and structure of the furnace flames under normal firing conditions, is discussed.

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