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Journal ArticleDOI

Numerical investigation of laminar cross-flow non-premixed flames in the presence of a bluff-body

TL;DR: In this article, a detailed numerical study of laminar cross-flow non-premixed methane-air flames in the presence of a square cylinder is presented, where flow, temperature, species and reaction fields have been predicted using a comprehensive transient three-dimensional reacting flow model with detailed chemical kinetics and variable thermo-physical properties.
Abstract: A knowledge of flame stability regimes in the presence of cylindrical bluff-bodies of various dimensions is essential to design non-premixed burners. The reacting flow field in such cases is reported to be three-dimensional and unsteady. In the literature, only a few experimental investigations with limited measurements are available. Therefore, in this work, a detailed numerical study of laminar cross-flow non-premixed methane–air flames in the presence of a square cylinder is presented. The flow, temperature, species and reaction fields have been predicted using a comprehensive transient three-dimensional reacting flow model with detailed chemical kinetics and variable thermo-physical properties, in order to get a good insight into the flame stabilisation phenomena. Further, analyses of quantities such as local equivalence ratio, cell Damkohler number, species velocity, net consumption rate of methane, which are not easily obtained through experiments even with detailed diagnostics, have been carried ou...
Citations
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Journal ArticleDOI
01 Jul 2018-Fuel
TL;DR: In this paper, the stability of cross-flow non-premixed flames is studied systematically, where biogas is injected through a horizontal porous plate and air is blown parallel to the fuel injector.

12 citations

Journal ArticleDOI
TL;DR: In this paper, the characteristics of laminar cross-flow methane-air diffusion flames in the presence of bluff bodies have been analyzed by using a high-definition digital camera.

6 citations

Book ChapterDOI
04 Jan 2018
TL;DR: In this paper, an unstructured grid finite volume method was used and simulations were carried out to simulate a two-dimensional laminar transient flow past a cylindrical bluff body.
Abstract: A two-dimensional, laminar transient flow past a cylindrical bluff body, with methane injection perpendicular to the direction of the free stream flow, i.e. the cross-flow arrangement, is numerically studied. An unstructured grid finite volume method is used and simulations were carried out. The methane mass fraction and the injection velocity of methane injected from the slotted cylinder are altered simultaneously, and their effects on the combustion, flame characteristics, and fluid mechanics are investigated. The flame is anchored right in front of the cylinder and is stabilized by the wake of the bluff body. The current investigation illustrates the qualitative aspects of the vortex shedding phenomena. A particular case of injection velocity and mass fraction is studied in detail and its vortex shedding phenomena are analysed minutely. The non-reacting flow exhibits 2P mode of vortex shedding while the reacting flow exhibits the more common 2S mode. Fast Fourier transform analysis of the temporally fluctuating lift coefficient is performed for the different cases carried out in the present study.

3 citations

Journal ArticleDOI
TL;DR: Shijin et al. as discussed by the authors investigated the regimes of flame stabilisation of non-premixed laminar flames established in a cross-flow combustor in the presence of a square cylinder.
Abstract: Flame stabilisation in a combustor having vortices generated by flame holding devices constitutes an interesting fundamental problem. The presence of vortices in many practical combustors ranging from industrial burners to high speed propulsion systems induces vortex–flame interactions and complex stabilisation conditions. The scenario becomes more complex if the flame sustains after separating itself from the flame holder. In a recent study [P.K. Shijin, S.S. Sundaram, V. Raghavan, and V. Babu, Numerical investigation of laminar cross-flow non-premixed flames in the presence of a bluff-body, Combust. Theory Model. 18, 2014, pp. 692–710], the authors reported details of the regimes of flame stabilisation of non-premixed laminar flames established in a cross-flow combustor in the presence of a square cylinder. In that, the separated flame has been shown to be three dimensional and highly unsteady. Such separated flames are investigated further in the present study. Flame–vortex interactions in sepa...

2 citations


Cites background or methods from "Numerical investigation of laminar ..."

  • ...[24] investigated the characteristics of cross-flow diffusion flames in the presence of a square cylinder bluff body....

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  • ...A C1 mechanism [25] with 18 species and 43 reaction steps is selected for the present study after comparing the predictions of different mechanisms and establishing the adequacy of the C1 mechanism [24]....

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  • ...Details of the solution methodology, reaction mechanism, radiation sub-model, grid discretisation and validation exercise have been reported in a previous work by the authors [24]....

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Journal ArticleDOI
TL;DR: In this paper , the ANSYS Fluent model was used to evaluate the flame characteristics of laminar cross-flow non-premixed biogas-air flames established in a boundary layer.
Abstract: This study presents the flame characteristics of laminar cross-flow non-premixed biogas-air flames established in a boundary layer using ANSYS Fluent. The validated numerical model is comprehensive enough to include variable thermo-physical properties, multi-component diffusion, short chemical kinetics mechanism, and optically thin approximation-based radiation model. Fuel is injected at a uniform velocity and the air is supplied perpendicular to it. Predicted and the in-house experimental biogas flames are qualitatively compared in terms of flame extents. The fuel flow rate has been varied from 0.02 m/s to 0.04 m/s to study the effects of power rating on the flame characteristics. At a given fuel flow rate, the airflow rate is incremented in steps to study the effects of forced convection on the characteristics and stability of the flames. Furthermore, the effects of the length of the flat plate upstream of the leading edge of the fuel injector plate on the flame anchoring location have been studied. The structure and characteristics of the reactive boundary layer are explained by using fields of temperature, velocity, mass fractions of major species, stoichiometric equivalence ratio, and Damköhler number. The reactive boundary layer fueled by methane is compared with that of biogas.
References
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ReportDOI
01 Mar 1990
TL;DR: The Chemkin general-purpose chemical kinetics package uses a data base that contains polynomial fits to specific heats, standard state enthalpies, and standard state entropy as mentioned in this paper.
Abstract: The Chemkin general-purpose chemical kinetics package uses a data base that contains polynomial fits to specific heats, standard state enthalpies, and standard state entropies The fourteen coefficient fits are in the same form as used in the NASA Complex Chemical Equilibrium Program (Gordon and McBride, 1971) This report represents a compilation of the data that is currently in use at Sandia National Laboratories 16 refs

579 citations


"Numerical investigation of laminar ..." refers methods in this paper

  • ...The molecular weights, standard state enthalpies, standard state entropies and Lennard–Jones parameters of all the species are taken from CHEMKIN TM [16]....

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Book
01 May 1993
TL;DR: In this article, an introduction to the up-to-date technology used in reducing kinetic mechanisms especially for combustion systems is presented, as well as the most recent methods for modelling a variety of systems.
Abstract: This book is an introduction to the up-to-date technology used in reducing kinetic mechanisms especially for combustion systems. However, it can also be used as a handbook, in that it presents the most recent methods for modelling a variety of systems. In addition it presents existing software for reducing mechanisms and flame calcualtions for mixed and pre-mixed flames and fuels ranging from hydrogen to propane, and it defines a format for general flamelet libraries. Details are thoroughly compared with experimental data. This volume addresses scientists, graduate students and chemical engineers in industry and environmental research.

577 citations

Journal ArticleDOI
TL;DR: In this article, the authors used Raman scattering and laser-induced fluorescence to measure temperature, the major species (N2, O2, CH4, CO2, H2O, CO, and H2), OH, and NO in steady laminar opposed-flow partially premixed flames of methane and air.

495 citations


"Numerical investigation of laminar ..." refers methods in this paper

  • ...Therefore, thermal radiation absorbed by CH4, CO2, H2O and CO species are modelled using a radiation sub-model based on the optically thin approximation proposed by Barlow, Karpetis, Frank and Chen [18]....

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  • ...Chen and T’ien [13] studied laminar diffusion flames numerically, using a two-dimensional model and a single-step chemical reaction, over a wide range of Damköhler numbers....

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  • ...The heat loss due to radiation, calculated using Planck’s mean absorption coefficient [18], is accounted for using a source term in the energy equation and implemented in FLUENT R © using a User Defined Function (UDF), which is a C++ program....

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Journal ArticleDOI
TL;DR: In this article, the authors examined and partially solved the problem of controlling the rate of combustion in large droplets, where the heat transfer and diffusion processes will have removed the chemical reaction zone far enough from the droplet to where it is less sensitive to the effects of the droplets itself.
Abstract: Fur Tropfchen, die groser als, sagen wir, 10−1 Zoll sind, entfernen Warmeleitungs- und Diffusionsprozesse die chemische Reaktionszone weit genug vom Tropfchen dorthin, wo sie fur die Effekte des Tropfchens selbst weniger sensibel ist, und daher die Verbrennungsgeschwindigkeit von den Warmeleitungs- und Massenprozessen selbst gesteuert wird. Dieses Problem wird in dieser Arbeit untersucht und teilweise gelost. For larger droplets - than say 10−1 inches - the heat transfer and diffusion processes will have removed the chemical reaction zone far enough from the droplet to where it is less sensitive to the effects of the droplet itself and hence the control of the rate of combustion will be the heat and mass transfer processes themselves. It is this problem that will be examined and partially solved in this paper.

257 citations


"Numerical investigation of laminar ..." refers background in this paper

  • ...Many theoretical and experimental investigations on laminar boundary layer diffusion flames over a flat plate have been reported after Emmons [1] gave a similarity solution for the two-dimensional boundary layer over a flat plate with fuel evaporation, diffusion and reaction [2–6]....

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Journal ArticleDOI
TL;DR: In this article, the conditions under which there are significant effects of buoyancy on a forced-convection, boundary-layer flow along a flat plate were determined and it was found that lowPrandtl number fluids are more sensitive to buoyancy effects.

120 citations