Buoyant Tsuji diffusion flames: global flame structure and flow field

This article presents the results of computations on pilot-based turbulent methane/air co-flow diffusion flames under the influence of the preheated oxidizer temperature ranging from 293 to 723 K at two operating pressures of 1 and 3 atm. The focus is on investigating the soot formation and flame structure under the influence of both the preheated air and combustor pressure. The computations were conducted in a 2D axisymmetric computational domain by solving the Favre averaged governing equation using the finite volume-based CFD code Ansys Fluent 19.2. A steady laminar flamelet model in combination with GRI Mech 3.0 was considered for combustion modeling. A semi-empirical acetylene-based soot model proposed by Brookes and Moss was adopted to predict soot. A careful validation was initially carried out with the measurements by Brookes and Moss at 1 and 3 atm with the temperature of both fuel and air at 290 K before carrying out further simulation using preheated air. The results by the present computation demonstrated that the flame peak temperature increased with air temperature for both 1 and 3 atm, while it reduced with pressure elevation. The OH mole fraction, signifying reaction rate, increased with a rise in the oxidizer temperature at the two operating pressures of 1 and 3 atm. However, a reduced value of OH mole fraction was observed at 3 atm when compared with 1 atm. The soot volume fraction increased with air temperature as well as pressure. The reaction rate by soot surface growth, soot mass-nucleation, and soot-oxidation rate increased with an increase in both air temperature and pressure. Finally, the fuel consumption rate showed a decreasing trend with air temperature and an increasing trend with pressure elevation.

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The effect of flame structure on soot-particle inception in diffusion flames

Fuel and Energy Abstracts ◽

10.1016/0140-6701(95)80616-4 ◽

1995 ◽

Vol 36 (3) ◽

pp. 206

Keyword(s):

Soot Particle ◽

Diffusion Flames ◽

Flame Structure

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Non-premixed swirl-type tubular flames burning liquid fuels

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.248 ◽

2018 ◽

Vol 846 ◽

pp. 210-239

Author(s):

Vinicius M. Sauer ◽

Fernando F. Fachini ◽

Derek Dunn-Rankin

Keyword(s):

Flow Field ◽

Swirling Flow ◽

Flame Structure ◽

Flow Analysis ◽

Liquid Fuels ◽

Reacting Flow ◽

Surface Mass ◽

Surface Mass Transfer ◽

Incompressible Viscous Flow ◽

Porous Walls

Tubular flames represent a canonical combustion configuration that can simplify reacting flow analysis and also be employed in practical power generation systems. In this paper, a theoretical model for non-premixed tubular flames, with delivery of liquid fuel through porous walls into a swirling flow field, is presented. Perturbation theory is used to analyse this new tubular flame configuration, which is the non-premixed equivalent to a premixed swirl-type tubular burner – following the original classification of premixed tubular systems into swirl and counterflow types. The incompressible viscous flow field is modelled with an axisymmetric similarity solution. Axial decay of the initial swirl velocity and surface mass transfer from the porous walls are considered through the superposition of laminar swirling flow on a Berman flow with uniform mass injection in a straight pipe. The flame structure is obtained assuming infinitely fast conversion of reactants into products and unity Lewis numbers, allowing the application of the Shvab–Zel’dovich coupling function approach.

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Flame stability limits of premixed low-swirl combustion

Advances in Mechanical Engineering ◽

10.1177/1687814018790878 ◽

2018 ◽

Vol 10 (9) ◽

pp. 168781401879087 ◽

Cited By ~ 1

Author(s):

Yinli Xiao ◽

Zhibo Cao ◽

Changwu Wang

Keyword(s):

Flow Field ◽

Vortex Breakdown ◽

Flame Structure ◽

Field Measurements ◽

Operating Conditions ◽

Oh Radicals ◽

Flame Stability ◽

Atmospheric Conditions ◽

Swirl Burner ◽

Stability Limits

The objective of this study is to gain a fundamental understanding of the flow-field and flame behaviors associated with a low-swirl burner. A vane-type low-swirl burner with different swirl numbers has been developed. The velocity field measurements are carried out with particle image velocimetry. The basic flame structures are characterized using OH radicals measured by planar laser-induced fluorescence. Three combustion regimes of low-swirl flames are identified depending on the operating conditions. For the same low-swirl injector under atmospheric conditions, attached flame is first observed when the incoming velocity is too low to generate vortex breakdown. Then, W-shaped flame is formed above the burner at moderate incoming velocity. Bowl-shaped flame structure is formed as the mixture velocity increases until it extinct. Local extinction and relight zones are observed in the low-swirl flame. Flow-field features and flame stability limits are obtained for the present burner.

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Effect of Diluent on the Blowout Limits of Jet Diffusion Flames

Part A: Combustion and Alternative Energy Technology; Computers in Engineering; Drilling Technology; Environmental Engineering Technology; Composite Materials Design and Analysis; Manufacturing and Services ◽

10.1115/etce2001-17018 ◽

2001 ◽

Author(s):

N. Papanikolaou ◽

I. Wierzba ◽

V. W. Liu

Keyword(s):

Carbon Dioxide ◽

Experimental Investigation ◽

Flow Field ◽

Diffusion Flames ◽

Jet Fuel ◽

Field Structure ◽

Jet Diffusion Flames ◽

Air Stream ◽

Lifted Flames

Abstract The paper will describe the results of an experimental investigation on the effect of diluents premixed with either the jet or co-flowing air stream on the blowout limits and flow field structure of jet diffusion flames. Experiments were conducted for a range of co-flowing air stream velocities with methane as the primary jet fuel, and nitrogen and carbon dioxide as diluents in the jet fuel; carbon dioxide was also used in the co-flowing air stream. The addition of a diluent to the surrounding air stream had a much stronger effect on the blowout limits than the addition of the diluent to the jet fuel. The effect of partially premixing air with the jet fuel on the blowout limits was also investigated. The addition of air (to up to 30%) to the methane jet significantly reduced the blowout limits of lifted flames, but it had little effect on the blowout limits of attached flames, which was rather unexpected.

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The effect of changes in the flame structure on the formation and destruction of soot and NOx in radiating diffusion flames

Symposium (International) on Combustion ◽

10.1016/s0082-0784(96)80044-0 ◽

1996 ◽

Vol 26 (2) ◽

pp. 2181-2189 ◽

Cited By ~ 27

Author(s):

A. Atreya ◽

C. hang ◽

H.K. Kim ◽

T. Shamim ◽

J. Suh

Keyword(s):

Diffusion Flames ◽

Flame Structure

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Flow Field Derived Equivalent Reactor Networks for Accurate Chemistry Simulation in Gas Turbine Combustors

Volume 2: Combustion, Fuels and Emissions ◽

10.1115/gt2009-59861 ◽

2009 ◽

Author(s):

Scott A. Drennan ◽

Chen-Pang Chou ◽

Anthony F. Shelburn ◽

Devin W. Hodgson ◽

Cheng Wang ◽

...

Keyword(s):

Flow Field ◽

Gas Turbine ◽

Flame Structure ◽

Cost Effective ◽

Fuel Injector ◽

Accurate Analysis ◽

Detailed Chemistry ◽

Reactor Networks ◽

Detailed Kinetics ◽

Time Required

A method has been developed in which the flow field predicted by Computational Fluid Dynamics (CFD) is automatically condensed into an Equivalent Reactor Network (ERN), composed of well stirred reactors, allowing rapid and accurate analysis of emissions. This paper presents the effectiveness of utilizing an ERN that is a direct abstraction of the computational flow field for combustion analysis. The CFD results are divided into reactors using various filters on flow-field variables to construct an ERN that represents the 3-D combustor flow field and flame structure. Detailed kinetics can then be used in ERN simulations to analyze effects of fuel composition and operating condition on emissions. The technique is applied to a commercial industrial gas turbine combustor fuel injector and compared against experimental emissions results. Sensitivity of emissions predictions to different parameters in the network extraction is also presented. Parameter variations in fuel flow rate are applied to the ERN to obtain relative impacts of fuel-air ratio on the emissions of NOx without requiring new CFD solutions. This automatic approach has been found to reduce the time required to construct and analyze flow field derived ERNs with detailed chemistry by 90%. A local calculation of Damko¨hler number, important for stability analysis, is also presented. This calculation also uses abstracted information from the CFD flow field and detailed-kinetics simulations for more accurate, cost-effective analysis.

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