Effects of CO2 dilution on turbulent premixed flames at high pressure and high temperature

Kobayashi, Haruo; Hagiwara, Hirokazu; Kaneko, Hiromasa; Ogami, Yasuhiro

doi:10.1016/j.proci.2006.07.159

Cited by 97 publications

(51 citation statements)

References 13 publications

(21 reference statements)

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“…The numerical results on intrinsic instability will be important information for the industrial application of premixed flames, e.g. premixed-type gas turbines, where combustion phenomena are strongly affected by intrinsic instability (Kobayashi et al, 2007;Ichikawa et al, 2011). Thus, we have to treat reactive flow in large space to obtain the useful knowledge on industrial applications.…”

Section: Introductionmentioning

confidence: 99%

The effects of unburned-gas temperature on the characteristics of cellular premixed flames generated by hydrodynamic and diffusive-thermal instabilities in large space: fractal dimension of cellular-flame fronts

Kadowaki

Washio²,

Aung³

et al. 2017

JTST

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The effects of unburned-gas temperature on the characteristics of cellular premixed flames generated by hydrodynamic and diffusive-thermal instabilities were numerically investigated. Two-dimensional reactive flow was calculated in large space, based on the compressible Navier-Stokes equations including a one-step irreversible chemical reaction. The dynamic behavior of cellular premixed flames, i.e. the coalescence and division of cells, appeared in large space owing to intrinsic instability. The behavior of flame fronts became more unstable with a decrease in unburned-gas temperature, even though the burning velocity of a planar flame reduced. This was due to the strength of thermal-expansion effects and to the enlargement of Zeldovich numbers. We found that the average burning velocity of a cellular flame normalized by that of a planar flame increased as the unburned-gas temperature became lower and the space size became larger. To elucidate the increase of burning velocity, we proposed the new model and showed that the normalized increment factor of burning velocity became larger under low unburned-gas temperature. In addition, we performed fractal analysis to consider the fractal dimension for three-dimensional flow. The obtained fractal dimension corresponding to laminar flames was nearly identical to the experimental and numerical results of turbulent flames.

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Section: Introductionmentioning

confidence: 99%

The effects of unburned-gas temperature on the characteristics of cellular premixed flames generated by hydrodynamic and diffusive-thermal instabilities in large space: fractal dimension of cellular-flame fronts

Kadowaki

Washio²,

Aung³

et al. 2017

JTST

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“…The successful implementation of oxy-fuel combustion in gas turbines depends on gaining better understanding of the differences that result from the replacement of N 2 with CO 2 . The effect of CO 2 dilution on flame characteristics has been extensively studied recently using Bunsentype turbulent premixed flames [4], counterflow non-premixed flame [5], and swirl-stabilized-flames [6]. Knowledge of the flame structure at the macro and microscales and their relation to dynamics and stability are essential for the safe operations of these systems.…”

Section: Introductionmentioning

confidence: 99%

“…Knowledge of the flame structure at the macro and microscales and their relation to dynamics and stability are essential for the safe operations of these systems. Studying the dynamics and stability in premixed CH 4 /O 2 /CO 2 flames is also important to achieve compact flames with lower CO and soot emissions. Recently, Shroll et al studied dynamic stability characteristics of premixed CH 4 /O 2 /CO 2 mixtures in the MIT swirl stabilized combustor, and found that the transition between instability modes correlated with the adiabatic flame temperature [6].…”

Section: Introductionmentioning

confidence: 99%

“…Studying the dynamics and stability in premixed CH 4 /O 2 /CO 2 flames is also important to achieve compact flames with lower CO and soot emissions. Recently, Shroll et al studied dynamic stability characteristics of premixed CH 4 /O 2 /CO 2 mixtures in the MIT swirl stabilized combustor, and found that the transition between instability modes correlated with the adiabatic flame temperature [6]. Further work in the same group [7,8] showed that the correlation between the flame structure and the dynamic mode, with flames stabilized on the inner shear layer around the inner recirculation zone being stable while flames stabilized in the inner shear layer as well as the outer shear layer being unstable.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impact of Equivalence Ratio on the Macrostructure of Premixed Swirling CH4/Air and CH4/O2/CO2 Flames

Watanabe

Shanbhogue

Ghoniem

2015

Volume 4B: Combustion, Fuels and Emissions

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Premixed CH 4 /O 2 /CO 2 flames (oxy-flames) and CH 4 /air flames (air-flames) were experimentally studied in a swirlstabilized combustor. For comparing oxy and air flames, the same equivalence ratio and adiabatic flame temperature were used. CO 2 dilution was adjusted to attain the same adiabatic temperature for the oxy-flame and the corresponding air-flame while keeping the equivalence ratio and Reynolds number (=20,000) the same. For high equivalence ratios, we observed flames stabilized along the inner and outer shear layers of the swirling flow and sudden expansion, respectively, in both flames. However, one notable difference between the two flames appears as the equivalence ratio reaches 0.60. At this point, the outer shear layer flame disappears in the air-flame while it persists in the oxy-flame, despite the lower burning velocity of the oxy-flame. Prior PIV measurements (Ref. 9) showed that the strains along the outer shear layer are higher than along the inner shear layer. Therefore, the extinction strain rates in both flames were calculated using a counter-flow premixed twin flame configuration. Calculations at the equivalence ratio of 0.60 show that the extinction strain rate is higher in the oxy than in the air flame, which help explain why it persists on the outer shear layer with higher strain rate. It is likely that extinction strain rates contribute to the oxy-flame stabilization when air flame extinguish in the outer shear layer. However, the trend reverses at higher equivalence ratio, and the cross point of the extinction strain rate appears at equivalence ratio of 0.64.

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“…Therefore the role of turbulence mixture motion becomes critically important for the diluted mixture like modern External Gas Recirculation (EGR) operation where burning rates are much lower than in the non-diluted mixture. The EGR operation in SI engines has the advantage of decreasing NOx emission because the dilution of the mixture by EGR gases decreases the flame temperature [18]. On the other hand, the strong EGR tends to enhance the possibility of misfiring and cyclic variation of the combustion in SI engines.…”

Section: Introductionmentioning

confidence: 99%

Study on Knocking Intensity under In-Cylinder Flow Field in SI Engines Using a Rapid Compression Machine

Hibi

Kohata

Tsumori

et al. 2013

JTST

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Knocking intensity under the in-cylinder flow field was investigated by using a rapid compression machine (RCM). The nitrogen diluted and non-diluted fuel-air mixtures were employed for the examination of the combustion characteristics under the in-cylinder flow field. The behaviors of flame propagation and the spontaneous ignition in end gas were observed. The analyses of the in-cylinder flow field and the dependency of the knocking intensity with considering the volume fraction for flame propagation and the heat release rate of the spontaneous ignition in end gas were carried out. As a result, the flame propagation velocity increased with heightening the turbulent intensity. The change of the flame propagation velocity provided the change of the volume fraction for flame propagation. The knocking intensity depended on the volume fraction for flame propagation and it reached a peak at about 0.6 in the volume fraction, when the heat release rate due to the spontaneous ignition was high enough. This agreed with the numerical prediction qualitatively. The combustion due to the spontaneous ignition in end gas was prolonged by the broader temperature variation by turbulence when the spontaneous ignition in end gas was delayed or turbulence was strong. In these cases, the knocking intensity was lowered with the prolongation of the combustion in end gas. It was to be expected that the dependency on the volume fraction for flame propagation remained the same even when the heat release rate due to the spontaneous ignition was lowered, by the numerical simulation.

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Effects of CO2 dilution on turbulent premixed flames at high pressure and high temperature

Cited by 97 publications

References 13 publications

The effects of unburned-gas temperature on the characteristics of cellular premixed flames generated by hydrodynamic and diffusive-thermal instabilities in large space: fractal dimension of cellular-flame fronts

The effects of unburned-gas temperature on the characteristics of cellular premixed flames generated by hydrodynamic and diffusive-thermal instabilities in large space: fractal dimension of cellular-flame fronts

Impact of Equivalence Ratio on the Macrostructure of Premixed Swirling CH4/Air and CH4/O2/CO2 Flames

Study on Knocking Intensity under In-Cylinder Flow Field in SI Engines Using a Rapid Compression Machine

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