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Journal ArticleDOI

Numerical investigation of flame–vortex interactions in laminar cross-flow non-premixed flames in the presence of bluff bodies

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...
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

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

References
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Journal ArticleDOI
01 Jan 1989
TL;DR: In this paper, the separation of separated flow in the presence of obstructions to the flow and surface blowing as encountered in many practical heat transfer and heterogeneous combustion problems is investigated, and experimental simulation in two-dimensional geometry has enabled the estimation of heat transfer rates to the wall as well as flow visualization.
Abstract: The separated flow in the presence of obstructions to the flow and surface blowing as encountered in many practical heat transfer and heterogeneous combustion problems is investigated. The experimental simulation in two-dimensional geometry has enabled the estimation of heat transfer rates to the wall as well as flow visualization. The measured heat transfer coefficients and the observed flow patterns reveal, a relation between the two even in this complex flow configuration wherein a two-vortex pattern dominates. The observations made in reactive and nonreactive flow conditions exhibit many common features indicating that the rather rigid flame at the boundary of the primary vortex results in the same heat transfer trends as would an equally hot core flow.

13 citations


"Numerical investigation of flame–vo..." refers methods in this paper

  • ...Experimental studies on flame stabilisation were reported by Raghunandan and Yogesh [5] using a diaphragm and by Rohmat et al. [6] using a backward facing step and a rectangular cylinder....

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  • ...Experimental studies on flame stabilisation were reported by Raghunandan and Yogesh [5] using a diaphragm and by Rohmat et al....

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Journal ArticleDOI
TL;DR: In this paper, an experimental study of scalar mixing in a laminar vortex is presented for vortices generated between two gas streams flowing parallel to each other in a rectangular flow channel.
Abstract: An experimental study of scalar mixing in a laminar vortex is presented for vortices generated between two gas streams flowing parallel to each other in a rectangular flow channel. An isolated line vortex is initiated on demand by momentarily increasing one stream velocity in relation to the other using an electromagnetically actuated piston. The temporal piston motion profile is tailored to generate vortices of different strengths corresponding to vortex Reynolds numbers, Re≡Γ/2πν=130–210. Evolution of mixing is monitored by laser-induced fluorescence of acetone vapor premixed into one of the gas streams as the vortex structure evolves with increasing downstream distance from its point of origin. Vortex is generated by pulsing either of the gas streams (seeded or unseeded stream). Vortex initiation process affects the abundance of the gas in the vortex core from the pulsed stream. Spatial mixing statistics are obtained by determining scalar concentration probability density functions (pdf) and the mean mixed fluid concentrations obtained from these pdfs. It is found that the interfacial area generation as a result of vortex kinematics and molecular diffusion along this interface are principally responsible for mixing. The mean mixed fluid concentration in the vortex interaction region scales with the product of vortex circulation and the elapsed time of interaction. These results are similar to those found in liquid mixing experiments, but the rate of mixing is significantly higher due to higher diffusivity of gases.

9 citations


"Numerical investigation of flame–vo..." refers background in this paper

  • ...Cetegen [18] conducted experimental studies on the enhancement in the mixing of parallel gas streams in the presence of a laminar line vortex....

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Journal ArticleDOI
TL;DR: In this article, a numerical model with a multi-step chemical kinetics mechanism, variable thermo-physical properties, multi-component species diffusion and a radiation sub-model is employed for this purpose.
Abstract: Numerical investigation of laminar diffusion flames established on a flat plate in a parallel air stream is presented. A numerical model with a multi-step chemical kinetics mechanism, variable thermo-physical properties, multi-component species diffusion and a radiation sub-model is employed for this purpose. Both upward and downward injection of fuel has been considered in a normal gravity environment. The thermal and aerodynamic structure of the flame has been explained with the help of temperature and species contours, net reaction rate of fuel and streamlines. Flame characteristics and stability aspects for several air and fuel velocity combinations have been studied. An important characteristic of a laminar boundary layer diffusion flame with upward injection of fuel is the velocity overshoot that occurs near the flame zone. This is not observed when the fuel is injected in the downward direction. The flame standoff distance is slightly higher for the downward injection of fuel due to increase in dis...

7 citations


"Numerical investigation of flame–vo..." refers background in this paper

  • ...Though multi-step chemistry was considered for a similar problem in a recent study [23], an unsteady analysis was not attempted as the primary focus was to simulate flames stabilised using backward facing steps....

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Journal ArticleDOI
TL;DR: In this article, a computational study of soot formation and transport in a laminar acetylene diffusion flame perturbed by a convecting line vortex was performed, and the topology of the soot contours resulting from flame vortex interactions was investigated.

6 citations


"Numerical investigation of flame–vo..." refers methods in this paper

  • ...A computational study was reported by Mishra, Santhosh and Basu [20] of the interaction of a laminar diffusion flame with a convective line vortex....

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