Structure and stabilization of hydrogen jet flames in cross-flows

Steinberg, Adam M.; Sadanandan, Rajesh; Dem, Claudiu; Kutne, Peter; Meier, Wolfgang

doi:10.1016/j.proci.2012.06.026

Cited by 73 publications

(57 citation statements)

References 20 publications

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“…The mean and instantaneous heat release rate fields in Fig. 2 show that there are two intense heat releasing regions similar to those observed in experiments [29]. These two regions correspond to the flame edges of the two branches.…”

Section: Flame Stabilization Characteristicssupporting

confidence: 72%

“…The upstream zone is located inside the LW sampling region and the second zone is located further downstream, spanning both the windward and leeward sides. The upstream explosive zones exist primarily on the lean side characterized by a lean partially premixed flame in a conventional lee-stabilized branch [29], while the intense heat release rate regions (see Q • = 0.8, 0.7 contour line in Fig. 3) in the flame base exist slightly on the rich side.…”

Section: Flame Stabilization Characteristicsmentioning

confidence: 98%

“…Using advanced laser diagnostics a previous experimental study [29] revealed the existence of two flame branches in a JICF configuration: a persistent branch located upstream and referred to as a "lee-stabilized" branch and a second more intermittent branch located downstream on the windward side, referred to as a "lifted" branch. Based on the description in Ref.…”

Section: Flame Stabilization Characteristicsmentioning

confidence: 99%

“…As for mixture preparation, in the near field of the JICF the intense fine scale turbulence increases micro-mixing rates and provides a sufficiently homogeneous mixture resulting in flame stabilization via partially premixed combustion [15,16]. Accordingly, if turbulent mixing, which scales with the momentum flux ratio R m , is kept constant, the laminar flame speed S L would have a dominant influence on flame stabilization [29,30]. Indeed, the fluid velocity component normal to the flame base is scaled by S L in JICF configurations [17].…”

Section: Flame Stabilization Characteristicsmentioning

confidence: 99%

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Effect of fuel composition and differential diffusion on flame stabilization in reacting syngas jets in turbulent cross-flow

Minamoto

Kolla

Grout

et al. 2015

Combustion and Flame

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a b s t r a c tThree-dimensional direct numerical simulation results of a transverse syngas fuel jet in turbulent cross-flow of air are analyzed to study the influence of varying volume fractions of CO relative to H 2 in the fuel composition on the near field flame stabilization. The mean flame stabilizes at a similar location for CO-lean and CO-rich cases despite the trend suggested by their laminar flame speed, which is higher for the CO-lean condition. To identify local mixtures having favorable mixture conditions for flame stabilization, explosive zones are defined using a chemical explosive mode timescale. The explosive zones related to flame stabilization are located in relatively low velocity regions. The explosive zones are characterized by excess hydrogen transported solely by differential diffusion, in the absence of intense turbulent mixing or scalar dissipation rate. The conditional averages show that differential diffusion is negatively correlated with turbulent mixing. Moreover, the local turbulent Reynolds number is insufficient to estimate the magnitude of the differential diffusion effect. Alternatively, the Karlovitz number provides a better indicator of the importance of differential diffusion. A comparison of the variations of differential diffusion, turbulent mixing, heat release rate and probability of encountering explosive zones demonstrates that differential diffusion predominantly plays an important role for mixture preparation and initiation of chemical reactions, closely followed by intense chemical reactions sustained by sufficient downstream turbulent mixing. The mechanism by which differential diffusion contributes to mixture preparation is investigated using the Takeno Flame Index. The mean Flame Index, based on the combined fuel species, shows that the overall extent of premixing is not intense in the upstream regions. However, the Flame Index computed based on individual contribution of H 2 or CO species reveals that hydrogen contributes significantly to premixing, particularly in explosive zones in the upstream leeward region, i.e. at the preferred flame stabilization location. Therefore, a small amount of H 2 diffuses much faster than CO, creating relatively homogeneous mixture pockets depending on the competition with turbulent mixing. These pockets, together with high H 2 reactivity, contribute to stabilizing the flame at a consistent location regardless of the CO concentration in the fuel for the present range of DNS conditions.Published by Elsevier Inc. on behalf of The Combustion Institute.

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Section: Flame Stabilization Characteristicssupporting

confidence: 72%

Section: Flame Stabilization Characteristicsmentioning

confidence: 98%

Section: Flame Stabilization Characteristicsmentioning

confidence: 99%

Section: Flame Stabilization Characteristicsmentioning

confidence: 99%

See 2 more Smart Citations

Effect of fuel composition and differential diffusion on flame stabilization in reacting syngas jets in turbulent cross-flow

Minamoto

Kolla

Grout

et al. 2015

Combustion and Flame

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“…The jet-in-crossflow (JICF) configuration studied here finds applications in an array of engineering problems and therefore has been studied extensively over the past years in nonreacting and reacting flows [3,[13][14][15][16]. JICFs exhibit highly strained regions of non-uniform mixing, reaction rate, and temperature, and therefore mimic conditions of technical relevance.…”

Section: Introductionmentioning

confidence: 99%

Autoignition of hydrogen/nitrogen jets in vitiated air crossflows at different pressures

Fleck

Griebel

Steinberg

et al. 2013

Proceedings of the Combustion Institute

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Autoignition of hydrogen/nitrogen jets in crossflows of vitiated air has been experimentally studied at conditions relevant for gas turbine combustor operation, including practical pressures (5, 10, 15 bar), crossflow temperatures (T cf = 1185 K and 1143 K), crossflow velocities (u cf = 200 and 300 m/s), and jet momentum ranges. Experiments were performed in an optically accessible duct, in which the appearance of autoignition events was investigated using high-speed imaging. At the different crossflow parameters, the H 2 mole fraction X H2 in the fuel jet was incrementally increased until autoignition created a stable flame. During this process, the autoignition kernel and subsequent flame dynamics were recorded at a rate of 30 kHz. In order to compare the experimental autoignition characteristics of the partially premixed, turbulent system to a homogeneous system, kinetic simulations of homogenous systems were conducted for pressures, temperatures, and vitiated air compositions corresponding to the experiments. The ignition delay times estimated from the experiment were considerably shorter than those from the kinetic simulations, and exhibited a different pressure dependency. These differences suggest that, in the current flow configuration, autoignition is strongly affected by turbulent mixing and flow field characteristics.

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