Local flame structure in the well-stirred reactor regime

Tanahashi, Mamoru; Nada, Yuzuru; Ito, Yoshikazu; Miauchi, Toshio

doi:10.1016/s1540-7489(02)80249-8

Cited by 68 publications

(35 citation statements)

References 11 publications

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“…However, it is worth noting that significant advances have been made in recent years towards simulating systems burning practically relevant fuels together with detailed and accurate models for both the chemical and transport phenomena [14][15][16]. Thanks to the rapid growth of computational capabilities, adequate numerical predictions of the turbulent burning velocity have been provided [17,18] up to laboratory scale configurations [19,20] using high fidelity DNS. Such numerical studies have shown that turbulence enhances the flame speed with a rate faster than the growth in flame surface area, which is consistent with earlier studies conducted with simple models.…”

Section: Introductionmentioning

confidence: 99%

Impact of Turbulence Intensity and Equivalence Ratio on the Burning Rate of Premixed Methane–Air Flames

Fru¹,

Thévenin²,

Janiga³

2011

Energies

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Direct Numerical Simulations (DNS) have been conducted to study the response of initially laminar spherical premixed methane-air flame kernels to successively higher turbulence intensities at five different equivalence ratios. The numerical experiments include a 16-species/25-step skeletal mechanism for methane oxidation and a multicomponent molecular transport model. Highly turbulent conditions (with integral Reynolds numbers up to 4 513) have been accessed. The effect of turbulence on the physical properties of the flame, in particular its consumption speed S c , which is an interesting measure of the turbulent flame speed S T has been investigated. Local quenching events are increasingly observed for highly turbulent conditions, particularly for lean mixtures. The obtained results qualitatively confirm the expected trend regarding correlations between u ′ /S L and the consumption speed: S c first increases, roughly linearly, with u ′ /S L (low turbulence zone), then levels off (bending zone) before decreasing again (quenching limit) for too intense turbulence. For a fixed value of u ′ /S L , S c /S L varies with the mixture equivalence ratio, showing that additional parameters should probably enter phenomenological expressions relating these two quantities.

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Section: Introductionmentioning

confidence: 99%

Impact of Turbulence Intensity and Equivalence Ratio on the Burning Rate of Premixed Methane–Air Flames

Fru¹,

Thévenin²,

Janiga³

2011

Energies

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“…All of these 3D studies were based on simplified chemistry. More recently Tanahashi et al [10,11] performed simulations of this type for turbulent premixed hydrogen flames with detailed hydrogen chemistry. Bell et al [12] performed a similar study for a turbulent methane flame.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of Lewis number effects on lean premixed turbulent flames

Bell

Cheng

Day

et al. 2007

Proceedings of the Combustion Institute

122

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A dominant factor in determining the burning rate of a premixed turbulent flame is the degree to which the flame front is wrinkled by turbulence. Higher turbulent intensities lead to greater wrinkling of the flame front and an increase in the turbulent burning rate. This picture of turbulent flame dynamics must be modified, however, to accommodate the affects of variations in the local propagation speed of the flame front. Classical flame analysis characterizes these local variations in propagation speed by the Markstein number which represents the response of the flame front to curvature and strain. In this paper, we consider lean premixed flames for three different fuels having widely varying fuel Lewis numbers corresponding to widely varying Markstein numbers. In particular, we present numerical simulations of premixed turbulent flames for lean hydrogen, propane and methane mixtures in two dimensions. Each simulation is performed at turbulence conditions similar to those found in laboratory-scale experiments and is performed using detailed chemical kinetics and transport properties. We discuss the effect of Lewis number on the overall flame morphology and explore the dependence of local flame propagation speed on flame curvature. We also explore the relationship between local flame speed and experimentally accessible variables such as OH concentration. Finally, we focus on the low Lewis number case, hydrogen, in which the flame front is broken indicating local extinction.

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“…From 2D DNS of turbulent premixed flames (44), (45) , local extinction in small scales has been reported. However, for 3D turbulent premixed flame, although local extinction in small scale has not been observed from DNS, an unexpected flame structure, whcih is called as double-layer structure, has been reported (3) .…”

Section: Local Flame Structure Of Turbulent Premixed Flamesmentioning

confidence: 97%

DNS and Combined Laser Diagnostics of Turbulent Combustion

Tanahashi

Sato

Shimura

et al. 2008

JTST

Self Cite

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With the developments of computer technologies, three-dimensional direct numerical simulations (DNS) of turbulent combustion have been realized with a detailed or reduced kinetic mechanism. The 3D DNS gives detailed information about turbulent flames, while there are few experimental techniques which have high accuracy enough to compare with DNS. In this paper, after showing summary of recent DNS of turbulent premixed flames, newly-developed laser diagnostics are presented. Simultaneous CH-OH planar laser induced fluorescence (PLIF) and stereoscopic particle image velocimetry (PIV) are used to investigate the local flame structure of the turbulent premixed flames. From CH-OH PLIF and PIV measurements, flame fronts are identified, and the curvature of the flame front and the tangential strain rate at the flame front are evaluated. The experimental results are compared with 3D DNS of hydrogen-air and methane-air turbulent premixed flames. The flame displacement speeds in turbulent premixed flames have been measured directly by the CH double-pulsed PLIF. Since the time interval of the successive CH PLIF can be selected arbitrarily, both of the large scale dynamics and local displacement of the flame front can be obtained. As an application of laser diagnostics for development of high-efficient and low-emission combustors, reconstruction of 3D flame structure is shown by using multiple-plane OH PLIF.

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Local flame structure in the well-stirred reactor regime

Cited by 68 publications

References 11 publications

Impact of Turbulence Intensity and Equivalence Ratio on the Burning Rate of Premixed Methane–Air Flames

Impact of Turbulence Intensity and Equivalence Ratio on the Burning Rate of Premixed Methane–Air Flames

Numerical simulation of Lewis number effects on lean premixed turbulent flames

DNS and Combined Laser Diagnostics of Turbulent Combustion

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