Multiply conditioned analyses of stratification in highly swirling methane/air flames

Sweeney, Mark; Hochgreb, Simone; Dunn, Matthew J.; Barlow, Robert S.

doi:10.1016/j.combustflame.2012.10.017

Cited by 55 publications

(52 citation statements)

References 37 publications

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“…A number of previous analyses concentrated on flame propagation in stratified mixtures based on experimental (Anselmo-Filho et al, 2009;Balusamy et al, 2014;Grune et al, 2013;Kang and Kyritsis, 2005;Mulla and Chakravarthy, 2014;Renou et al, 2004;Samson, 2002;Sweeney et al, 2013;Zhou et al, 1998Zhou et al, , 2013 and direct numerical simulations (DNS) (Cruz et al, 2000;Haworth et al, 2000;Hélie and Trouvé, 1998;Jiménez et al, 2002;Malkeson and Chakraborty, 2010;Patel and Chakraborty, 2014;Pera et al, 2013;Swaminathan et al, 2007) data. These studies demonstrated that the flame propagation statistics are strongly affected by the local gradient of equivalence ratio.…”

Section: Introductionmentioning

confidence: 99%

Effects of Mixture Distribution on Localized Forced Ignition of Stratified Mixtures: A Direct Numerical Simulation Study

Patel

Chakraborty

2016

Combustion Science and Technology

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The influences of initial mixture distribution on localized forced ignition of globally stoichiometric stratified mixtures have been analyzed using three-dimensional compressible direct numerical simulations. The globally stoichiometric mixtures (i.e., hϕi ¼ 1:0) for different root-meansquare (rms) values of equivalence ratio (i.e., ϕ 0 = 0.2, 0.4, and 0.6) and the Taylor micro-scale lϕ of equivalence ratio ϕ variation (i.e., lϕ=l f ¼ 2.1, 5.5, and 8.3 with l f being the Zel'dovich flame thickness of stoichiometric mixture) have been analyzed for different initial rms values of turbulent velocity u 0 . The equivalence ratio variation is initialized following both Gaussian and bi-modal distributions for a given set of values of ϕ 0 and lϕ=l f in order to analyze the effects of mixture distribution. The localized forced ignition is accounted for by considering a source term in the energy conservation equation that deposits energy for a stipulated time interval. It has been demonstrated that the initial equivalence ratio distribution has significant effects on the extent of burning of stratified mixtures following successful localized forced ignition. It has been found that an increase in u 0 =S b ϕ¼1 ð Þ (ϕ 0 ) has adverse effects on the burned gas mass, whereas the effects of lϕ=l f on the extent of burning are nonmonotonic and dependent on ϕ 0 for initial bi-modal mixture distribution. The initial Gaussian mixture distribution exhibits an increase in burned gas mass with decreasing lϕ=l f , but these cases are more prone to flame extinction for high values of u 0 than the corresponding bi-modal distribution cases. Detailed physical explanations have been provided for the observed mixture distribution, ϕ 0 , u 0 , and lϕ=l f dependences on the extent of burning following localized forced ignition of stratified mixtures. ARTICLE HISTORY

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Section: Introductionmentioning

confidence: 99%

Effects of Mixture Distribution on Localized Forced Ignition of Stratified Mixtures: A Direct Numerical Simulation Study

Patel

Chakraborty

2016

Combustion Science and Technology

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“…Each PLIF image was corrected for the pixel-response before background subtraction. To improve SNR, we applied a wavelet adaptive thresholding (WATR) technique for de-noising [17]. A previously developed 1D wavelet de-noising algorithm [17] was extended to two dimensions, with the primary modifications being the use of bi-orthogonal 2D wavelet-functions [18] and a 2D stationary wavelet transform.…”

Section: High-speed-stereo-piv and Acetone-plif Setupmentioning

confidence: 99%

“…To improve SNR, we applied a wavelet adaptive thresholding (WATR) technique for de-noising [17]. A previously developed 1D wavelet de-noising algorithm [17] was extended to two dimensions, with the primary modifications being the use of bi-orthogonal 2D wavelet-functions [18] and a 2D stationary wavelet transform. The CMOS camera-noise data necessary for the de-noising algorithm to statistically characterize the noise processes were determined using dark and Ulbricht Sphere measurements.…”

Section: High-speed-stereo-piv and Acetone-plif Setupmentioning

confidence: 99%

Investigation of flame propagation in a partially premixed jet by high-speed-Stereo-PIV and acetone-PLIF

Weinkauff

Trunk

Frank

et al. 2015

Proceedings of the Combustion Institute

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This paper presents an experimental study of flame propagation through a partially-premixed flow following ignition. A combination of simultaneous high-speed acetone planar laser induced fluorescence (PLIF) and stereoscopic particle image velocimetry (SPIV) was utilized for time-resolved measurements of mixture fraction, flow field and flame position. This provides access to the major quantities needed to characterize non-premixed flames. High quality mixture fraction measurements with signal-to-noise ratios up to 120 for unity mixture fraction were made feasible using a combination of a conventional high-speed laser at 10 kHz for LIF excitation and a wavelet based de-noising algorithm to reject camera noise. It was observed that flame propagation in the far-field of a partially-premixed jet takes place in a premixed mode, with the flame propagating through highly stratified mixtures until it approaches locations containing mixtures outside the flammability limits. In these areas the flame recedes and further propagation is controlled by mixing processes of air and fuel. Even though flame propagation is then mixing-controlled, the flame is not observed to switch into a non-premixed mode. Instead, mixing ahead of the flame takes place until locally premixed flammable mixtures are recovered for subsequent flame propagation.

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“…computation of gradients, conditioned analyses) has been conducted by using both experiments and simulations to obtain deeper insight (e.g. [5][6][7][8]). …”

Section: Introductionmentioning

confidence: 99%

A Numerical Study of the Flame Stabilization Mechanism Being Determined by Chemical Reaction Rates Submitted to Heat Transfer Processes

Kuenne

Euler²,

Ketelheun³

et al. 2014

Zeitschrift Für Physikalische Chemie

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Large Eddy Simulations of a turbulent lean premixed stratified burner are conducted in order to determine the physical mechanisms that dominate the flame stabilization close to burner walls. The purpose of this work is both to provide insight into the underlying physics as well as to check whether the deficiencies found in previous simulations are related to an inappropriate heat transfer treatment. The simulation utilizes a three-dimensional detailed chemistry database in order to capture the chemical reaction rates based on local mixing and thermal conditions. The study is supplemented by very accurate wall temperature measurements to remove the large uncertainty revealed in the past for this configuration. The results obtained from the simulations are evaluated by means of a qualitative illustration of the different flame stabilizations and comparisons with experimental data.

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Multiply conditioned analyses of stratification in highly swirling methane/air flames

Cited by 55 publications

References 37 publications

Effects of Mixture Distribution on Localized Forced Ignition of Stratified Mixtures: A Direct Numerical Simulation Study

Effects of Mixture Distribution on Localized Forced Ignition of Stratified Mixtures: A Direct Numerical Simulation Study

Investigation of flame propagation in a partially premixed jet by high-speed-Stereo-PIV and acetone-PLIF

A Numerical Study of the Flame Stabilization Mechanism Being Determined by Chemical Reaction Rates Submitted to Heat Transfer Processes

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