Effect of turbulence–chemistry interactions on chemical pathways for turbulent hydrogen–air premixed flames

Dasgupta, Debolina; Sun, Wenting; Day, Marc; Lieuwen, Tim

doi:10.1016/j.combustflame.2016.09.029

Cited by 38 publications

(24 citation statements)

References 20 publications

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“…The contribution of the same reaction increases by ~50% with decreasing PSR residence time. This observation is very different from that observed in the case of lighter fuels, such as hydrogen [2] and methane [9], wherein the variation between the contribution of a given reaction for stretched flame and for PSR was within ~20%. Considering next the turbulent flame results in Figure 3(c), the plot shows that the dominant heat release reactions here are the same as those identified for stretched flames and PSR.…”

Section: Resultscontrasting

confidence: 85%

“…Since the volumetric statistics are integrated normal to the flame, they are generally insensitive to the precise isotherm used. Details of the integration procedure and the subsequent averaging are detailed in Dasgupta et al [2]. A corresponding procedure was performed on unstretched premixed flame (using PREMIX [19]), a stretched, premixed laminar flames (using OPPDIF [20]) and perfectly stirred reactor (using PSR [21]) to compare the turbulent flame-chemistry interaction with simple laminar models.…”

Section: Methodsmentioning

confidence: 99%

“…Additionally, LTC studies for n-heptane flames by Savard et al [8] suggest fuel oxidation for cool flames occur through the same chemical pathways in laminar and turbulent flames. Similarly, studies of H 2 /air [2,6] and CH 4 /air [9] flames have shown relatively minor changes in the spatially integrated dominant chemical pathways. For example, the contribution of H+O 2 (+M)®HO 2 (+M) (the primary heat releasing reaction) to the total heat release for H 2 /air flames changed by 20% between unstretched laminar flame and Ka=36 turbulent flames and changed by only 5% between Ka=1 to Ka=36 for the turbulent flames.…”

Section: Introductionmentioning

confidence: 98%

“…The objective of this paper is to consider the extent to which chemical pathways vary with turbulence levels. A detailed discussion of the potential mechanisms through which turbulence could alter reaction pathways is given in our previous study [2], and is briefly summarized here.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of chemical pathways and flame structure for n-dodecane/air turbulent premixed flames

Dasgupta

Sun

Day

et al. 2019

Combustion and Flame

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This paper analyzes turbulence-chemistry interactions for an n-dodecane-air flame, focusing on the degree to which fuel oxidation pathways change in turbulent flames relative to their corresponding laminar flames. This work is based on a lean ( =0.7) ndodecane-air flame DNS database from Aspden et al. (Proc. Combust. Institute, 36 (2017) 2005. The relative roles of dominant reactions that release heat and produce/consume radicals are examined at various turbulence intensities and compared with stretched flame calculations from counterflow flames and perfectly stirred reactors.These results show that spatially integrated (i.e. integrated heat release or radical production rate metrics averaged over the entire flame) chemical pathways are relatively insensitive to turbulence intensity and mimic the behavior of stretched flames. In other words, the contribution of a given reaction to heat release or radical production, integrated over the entire flame, is nearly independent to turbulence. Localized analysis conditioned on topological feature of the flame and on temperature is also performed.The former analysis reveals that much larger alteration of pathways occurs in the positively-curved regions of the flame. The latter localized analysis shows that peak activity in the low temperature (i.e. below 1200K) region shift towards higher temperatures with increases in Karlovitz number. This result is particularly interesting given that prior work with lighter fuels showed the opposite behavior suggesting a disparate response of the reactions involved in the fuel oxidation process to increased turbulence.

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Section: Resultscontrasting

confidence: 85%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of chemical pathways and flame structure for n-dodecane/air turbulent premixed flames

Dasgupta

Sun

Day

et al. 2019

Combustion and Flame

Self Cite

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“…On the one hand, the invoked simplifications are very strong and make the studied problem substantially different from the problem of propagation of a premixed flame in a turbulent flow, because Lewis number and preferential diffusion, thermal expansion, complex chemistry and other effects can play an important role in the latter case, as reviewed, e.g., in Refs. [36][37][38][39] or shown in recent papers [40,41]. Accordingly, from purely numerical perspective, the present simulations are inferior to modern DNS studies that allow for both thermal expansion and complex chemistry in intense (u /S L 1) turbulence, e.g., [41][42][43][44][45][46][47].…”

Section: Statement Of the Problemmentioning

confidence: 80%

A DNS Study of Sensitivity of Scaling Exponents for Premixed Turbulent Consumption Velocity to Transient Effects

Lipatnikov

2018

Flow Turbulence Combust

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3D Direct Numerical Simulations of propagation of a single-reaction wave in forced, statistically stationary, homogeneous, isotropic, and constant-density turbulence, which is not affected by the wave, are performed in order to investigate the influence of the wave development on scaling (power) exponents for the turbulent consumption velocity U T as a function of the rms turbulent velocity u , laminar wave speed S L , and a ratio L 11 /δ F of the longitudinal turbulence length scale L 11 to the laminar wave thickness δ F. Fifteen cases characterized by u /S L = 0.5, 1.0, 2.0, 5.0, or 10.0 and L 11 /δ F = 2.1, 3.7, or 6.7 are studied. Obtained results show that, while U T is well and unambiguously defined in the considered simplest case of a statistically 1D planar turbulent reaction wave, the wave development can significantly change the scaling exponents. Moreover, the scaling exponents depend on a method used to compare values of U T , i.e., the scaling exponents found by processing the DNS data obtained at the same normalized wave-development time may be substantially different from the scaling exponents found by processing the DNS data obtained at the same normalized wave size. These results imply that the scaling exponents obtained from premixed turbulent flames of different configurations may be different not only due to the well-known effects of the mean-flame-brush curvature and the mean flow non-uniformities, but also due to the flame development, even if the different flames are at the same stage of their development. The emphasized transient effects can, at least in part, explain significant scatter of the scaling exponents obtained by various research groups in different experiments, thus, implying that the scatter in itself is not sufficient to reject the notion of turbulent burning velocity. Keywords Premixed turbulent combustion • Burning velocity • Consumption velocity • Turbulent flame development • DNS Nomenclature a heat diffusivity of a mixture c combustion progress variable

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RANS Simulations of Premixed Turbulent Flames

Lipatnikov

2017

Energy, Environment, and Sustainability

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The paper aims at assessing a hypothesis that resolution required to evaluate fuel consumption and heat release rates by directly (i.e., without a subgrid model of unresolved influence of small-scale turbulent eddies on the local flame) processing filtered fields of density, temperature, and species mass fractions should be significantly finer than resolution required to directly compute flame surface density by processing the same filtered fields. For this purpose, box filters of various widths Δ are applied to threedimensional Direct Numerical Simulation data obtained earlier by Dave et al. (Combust. Flame 196 (2018) 386-399) from a statistically one-dimensional and planar, moderately lean H2/air complexchemistry flame propagating in a box under conditions of sufficiently intense small-scale turbulence (Karlovitz number is larger than unity and a ratio of laminar flame thickness δL to Kolmogorov length scale is about 20). Results confirm this hypothesis and show that the mean flame surface density and area can be predicted with acceptable accuracy by processing filtered combustion progress variable fields computed using a sufficiently wide filter, e.g., ∆⁄δL=4⁄3. Such an approach does not require a model of the influence of subgrid turbulent eddies on flame surface density provided that ∆ and δL are of the same order of magnitude. Good performance of this approach is attributed to inability of smallscale (when compared to δL) turbulent eddies to substantially change the local flame structure, which, nevertheless, is significantly perturbed by larger turbulent eddies that strain the local flame.

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Effect of turbulence–chemistry interactions on chemical pathways for turbulent hydrogen–air premixed flames

Cited by 38 publications

References 20 publications

Analysis of chemical pathways and flame structure for n-dodecane/air turbulent premixed flames

Analysis of chemical pathways and flame structure for n-dodecane/air turbulent premixed flames

A DNS Study of Sensitivity of Scaling Exponents for Premixed Turbulent Consumption Velocity to Transient Effects

RANS Simulations of Premixed Turbulent Flames

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