Effects of the cone angle on the stability of turbulent nonpremixed flames downstream of a conical bluff body

Ata, Alper; Özdemir, I. Bedii

doi:10.1007/s00231-019-02789-6

Cited by 4 publications

(7 citation statements)

References 41 publications

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“…Ma and Harn [25], working on a conical bluff body with a large cone angle, showed that the large diameters caused an increase in the spread of the wake flow and, therefore, a shorter recirculation length results. In a similar study [26,27], it was pointed out that as the flame holder becomes wider, the residence time increases, leading to a sooty flame, and this was also shown experimentally by Ata and Ozdemir [2] in their work on the conical bluff bodies.…”

Section: Introductionmentioning

confidence: 58%

“…The flame length is also known to be another parameter influenced by the co-flow velocity. Contrary to the widespread belief, in that increasing the co-flow decreases the flame length [36,37,42,43], it was experimentally shown [2,44,45] that, under certain circumstances (such as the co-flows velocities up to 3 m/s or the bluff body diameters smaller than 18mm) flames can elongate by the increasing the co-flow. In addition to these three parameters, the velocity and the momentum flux ratios of the fuel and air streams were found to have indirect effects on the recirculation strength [11,21] through the vortex formation mechanisms.…”

Section: Introductionmentioning

confidence: 85%

“…Figure 1 presents the experimental rig schematically, whose details were described in our recent publications [2,44]. The flame was formed downstream of a non-premixed burner with a conical stabilizer.…”

Section: Experimental Configurationmentioning

confidence: 99%

“…Dally et al [39] and Yen et al [37] are rare examples with temperature measurements made up to 15 bluff body diameters. This paper is the outcome of an ongoing investigation on the conical bluff bodies [2,44] and aims to map the thermal characteristics of the conical bluff body flames up to the full length, which was approximately 55D. Hence, the data set of this study serves as a piece of complementary information to our earlier research on such flames.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, appliances with nonpremixed flames are still in use in industrial systems due to the need for higher temperature regimes in the applications, such as steam boilers and furnaces for various production processes. Flame stabilization with bluff bodies is an efficient design method used in the non-premixed forced draught burners [2][3][4][5][6][7], where the flow downstream of the complex flame holders can be perceived as an axial gaseous fuel jet through a central bluff body and a peripheral co-flowing stream of air [8][9][10][11][12][13][14][15][16]. This is why single bluff body flames have been systematically investigated in various aspects of fundamental issues.…”

Section: Introductionmentioning

confidence: 99%

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Stability Characteristics of a Turbulent Nonpremixed Conical Bluff Body Flame

Ata¹,

Özdemir²

2021

IJHT

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The thermal characteristics of turbulent non-premixed methane flames were investigated by four burner heads with the same exit diameter but different heights. The fuel flow rate was kept constant with an exit velocity of 15 m/s, while the co-flow air speed was increased from 0 to 7.6 m/s. The radial profiles of the temperature and flame visualizations were obtained to investigate the stability limits. The results evidenced that the air co-flow and the cone angle have essential roles in the stabilization of the flame: An increase in the cone angle and/or the co-flow speed deteriorated the stability of the flame, which eventually tended to blow off. As the cone angle was reduced, the flame was attached to the bluff body. However, when the cone angle is very small, it has no effect on stability. The mixing and entrainment processes were described by the statistical moments of the temperature fluctuations. It appears that the rise in temperature coincides with the intensified mixing, and it becomes constant in the entrainment region.

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Section: Introductionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 85%

Section: Experimental Configurationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stability Characteristics of a Turbulent Nonpremixed Conical Bluff Body Flame

Ata¹,

Özdemir²

2021

IJHT

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Flame Stability in Swirling and Bluff-Body Burners: A Review

Shakir Mahmood,

Saleh

2023

Jurnal Teknologi

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Flame stability is one of the main challenges facing the different combustion applications. A lot of undesirable phenomena such as blow-off and flashback may occur according to the instability of the flame causing damage to the overall combustion system. Therefore, it is necessary to develop methods which help improve the combustion process and obtain wider flame stable regions. Among these methods, swirling flows and bluff-bodies are the most commonly used in flame stabilization. These may create central recirculation zones (CRZ’s) that, in turn, recirculate the heat and active chemical species to the root of flame, improving the reactants mixing and as a result, flame stability. Hence, the current article presents an overview of flame stability mechanisms and the operation map using swirling flows and bluff-bodies. The effect of the swirl number (S) and burner’s geometry, as well as the influence of the bluff-body shape, size and position on the flame stabilization mechanisms are discussed.

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Study on the Effects of Cone Height on the Turbulent Nonpremixed Flames Downstream of a Conical Bluff Body

Ata

Özdemir

2020

Journal of Thermal Science and Engineering Applications

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Flow, thermal and emission characteristics of turbulent nonpremixed CH4 flames were investigated for three burner heads of different cone heights. The fuel velocity was kept constant at 15 m/s, while the coflow air speed was varied between 0  7.4 m/s. Detailed radial profiles of the velocity and temperature were obtained in the bluff body wake at three vertical locations of 0.5D, 1D, and 1.5D. Emissions of CO2, CO, NOx, and O2 were also measured at the tail end of every flame. Flames were digitally photographed to support the point measurements with the visual observations. Fifteen different stability points were examined, which were the results of three bluff body variants and five coflow velocities. The results show that a blue-colored ring flame is formed, especially at high coflow velocities. The results also illustrate that depending on the mixing at the bluff-body wake, the flames exhibit two modes of combustion regimes, namely jet- and coflow-dominated flames. In the jet-dominated regime, the flames become longer compared to the flames of the coflow-dominated regime. Emissions were largely reduced due to the excess air dilution, surpassing their production.

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Effects of the cone angle on the stability of turbulent nonpremixed flames downstream of a conical bluff body

Cited by 4 publications

References 41 publications

Stability Characteristics of a Turbulent Nonpremixed Conical Bluff Body Flame

Stability Characteristics of a Turbulent Nonpremixed Conical Bluff Body Flame

Flame Stability in Swirling and Bluff-Body Burners: A Review

Study on the Effects of Cone Height on the Turbulent Nonpremixed Flames Downstream of a Conical Bluff Body

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