Influence of a bluff-body’s shape on the stabilization regime of non-premixed flames

Esquiva-Dano, Isabelle; Nguyen, Hong-Phuc; Escudié, Dany

doi:10.1016/s0010-2180(01)00318-2

Cited by 71 publications

(39 citation statements)

References 17 publications

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“…The transition of flame patterns in this work is similar to the description of Fig.10 from the Ref. [Esquiva et al (2001)], in which the fixed central gas jet is laminar (Re=1800) and bluff-body-stabilized non-premixed flames exhibit five characteristic modes: laminar flame, transition I, laminar ring flame, transition II, and recirculating flame. The former two modes are classified into the fuel-jet-dominant state.…”

Section: Flame Structures In Bluff-body Burnersupporting

confidence: 79%

“…The evolution of flame modes with γ is related to a displacement of stoichiometric mixture fraction [Esquiva et al (2001)]. Under differentγ conditions, the distributions of the mixture fraction exhibit complex changes as shown in Fig.…”

Section: Flame Structures In Bluff-body Burnermentioning

confidence: 99%

“…The flame structures multi-modally vary with the interaction of the fuel jet and air coflow behind the bluff-body, which are strongly related to the mixing process in the recirculation area [Chen et al (1998), Esquiva et al (2001)]. Vortex shedding and large-scale recirculation are known to keep flame stable in backward facing step and bluff-body wakes [Kim and Pitsch (2006)].…”

Section: Introductionmentioning

confidence: 99%

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The Effects of the Air-Fuel Velocity Ratio on Turbulent Non-Premixed Bluff-Body Flames

Yang

Zhang

2017

Volume 1: Boilers and Heat Recovery Steam Generator; Combustion Turbines; Energy Water Sustainability; Fuels, Combustion and Ma

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We reported the large-eddy simulations of a series of bluff-body flames varying air-fuel velocity ratio. The air-fuel ratio γ is defined by the ratio of external air velocity to central jet velocity, ranging from 0.05 to 0.50. The case of γ =0.32 is exactly same the Sydney bluff-body HM1e flame. Firstly, the mathematical model and numerical method were validated in details as the simulation results are all in good agreement with measurements in HM1e flame. Then the interaction between turbulence and thermochemistry is revealed. As γ increases, external coflow trends to dominant the flame behavior. The stoichiometric mixture fraction shifts from the area between recirculation zone and central jet to the area between external flow and recirculation zone. Corresponding, the flame changes from jet-like, columnar to hat-like flames. The different level of local extinction and reignition is also observed. Local extinction and reignition occurs in jet-like and columnar flames. As γ increases, local extinction becomes easier and reignition becomes harder.

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Section: Flame Structures In Bluff-body Burnersupporting

confidence: 79%

Section: Flame Structures In Bluff-body Burnermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Effects of the Air-Fuel Velocity Ratio on Turbulent Non-Premixed Bluff-Body Flames

Yang

Zhang

2017

Volume 1: Boilers and Heat Recovery Steam Generator; Combustion Turbines; Energy Water Sustainability; Fuels, Combustion and Ma

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“…Different techniques have been used to stabilize these flames at the nozzle exit. Examples of these techniques include the partially premixed flames [2][3][4][5], the swirl flame [6][7][8][9], the pilot flame for non-premixed [10,11]; premixed [12], and flame holder [13,14].…”

Section: Introductionmentioning

confidence: 99%

The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

Elbaz

Zayed

Samy

et al. 2016

Experimental Thermal and Fluid Science

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The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow KAUST Repository a b s t r a c tThe stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work. The stability map of partial premixed flames illustrates that the flames are stable between two extinction limits. A low extinction limit when partial premixed flames approach non-premixed flame conditions, and a high extinction limit, with the partial premixed flames approach fully premixed flame conditions. These two limits showed that the most stable flame conditions are achieved at a certain degree of partial premixed. The stability is improved by adding air co-flow. As the air co-flow velocity increases the most stable flames are those that approach fully premixed. The turbulent flow field of three flames at 0, 5, 10 m/s co-flow velocity are investigated using Stereo Particle Image Velocimetry (SPIV) in order to explore the improvement of the flame stability due to the use of air co-flow. The three flames are all at a jet equivalence ratio (U j ) of 2, fixed level of partial premixing and jet Reynolds number (Re j ) of 10,000. The use of co-flow results in the formation of two vortices at the cone exit. These vortices act like stabilization anchors for the flames to the nozzle tip. With these vortices in the flow field, the reaction zone shifts toward the reduced turbulence intensity at the nozzle rim of the cone. Interesting information about the structure of the flow field with and without co-flow are identified and reported in this work.

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“…The coflow air entrains a part of the central fuel jet into the low-speed recirculation zone in the wake of the bluff body, and then combustion mixing stabilizes the flame. With a bluff body, the flame characteristic changes from a pure diffusion flame, classically stabilized on the burner surface, to a partially premixed flame stabilized in the recirculation zone [1].…”

Section: Introductionmentioning

confidence: 99%

The Characteristic Modes and Structures of Bluff-Body Stabilized Flames in Supersonic Coflow Air

Kim

Yoon

Park

et al. 2012

International Journal of Aeronautical and Space Sciences

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The stability and structure of bluff-body stabilized hydrogen flames were investigated numerically and experimentally. The velocity of coflowing air was varied from subsonic velocity to a supersonic velocity of Mach 1.8. OH PLIF images and Schlieren images were used for analysis. Flame regimes were used to classify the characteristic flame modes according to the variation of the fuel-air velocity ratio, into jet-like flame, central-jet-dominated flame, and recirculation zone flame. Stability curves were drawn to find the blowout regimes and to show the improvement in flame stability with increasing lip thickness of the fuel tube, which acts as a bluff-body. These curves collapse to a single line when the blowout curves are normalized by the size of the bluff-body. The variation of flame length with the increase in air flow rate was also investigated. In the subsonic coflow condition, the flame length decreased significantly, but in the supersonic coflow condition, the flame length increased slowly and finally reached a near-constant value. This phenomenon is attributed to the air-entrainment of subsonic flow and the compressibility effect of supersonic flow. The closed-tip recirculation zone flames in supersonic coflow had a reacting core in the partially premixed zone, where the fuel jet lost its momentum due to the high-pressure zone and followed the recirculation zone; this behavior resulted in the long characteristic time for the fuel-air mixing.

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Influence of a bluff-body’s shape on the stabilization regime of non-premixed flames

Cited by 71 publications

References 17 publications

The Effects of the Air-Fuel Velocity Ratio on Turbulent Non-Premixed Bluff-Body Flames

The Effects of the Air-Fuel Velocity Ratio on Turbulent Non-Premixed Bluff-Body Flames

The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

The Characteristic Modes and Structures of Bluff-Body Stabilized Flames in Supersonic Coflow Air

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