Structure and scalar correlation of ammonia/air turbulent premixed flames in the distributed reaction zone regime

Fan, Qingshuang; Liu, Xin; Cai, Xiao; Brackmann, Christian; Aldén, Marcus; Bai, Xue‐Song; Li, Zhongshan

doi:10.1016/j.combustflame.2022.112090

Cited by 22 publications

(4 citation statements)

References 44 publications

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“…For instance, Doan et al 74,75 have reported that eddies larger than 2 δ L contribute less than 10% to the total tangential strain rate computed along such a surface. It is worth stressing, however, that the PSR model requires a small ratio of Δ / δ L to resolve highly non-linear spatial variations of reaction rates, localized to narrow zones, 32–46 rather than to resolve wrinkles of the zone surface, created by small-scale turbulent eddies. The former task requires significantly better resolution.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, recent experimental and Direct Numerical Simulation (DNS) data reviewed elsewhere 32–34 show that, even in very intense turbulence, combustion can still be localized to narrow spatial zones, with magnitudes of fluctuations of temperature and mixture concentrations being, therefore, large, see also the latest measurements 35–38 and DNS 39–46 studies. Furthermore, as shown recently, 32 even the aforementioned Damköhler’s hypothesis is consistent with existence of thin reaction zones and, hence, with large fluctuations of temperature and species concentrations.…”

Section: Introductionmentioning

confidence: 96%

“…Furthermore, as shown recently, 32 even the aforementioned Damko¨hler's hypothesis is consistent with existence of thin reaction zones and, hence, with large fluctuations of temperature and species concentrations. In other words, (i) in order for the stirred reactor (thickened flame, or broken reaction zone) regime to exist (if any), turbulence should be much more intense than believed earlier and (ii) mixture non-uniformities can be significant even at small spatial scales under conditions of the cited studies, [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] thus, requiring very fine meshes when adapting the PSR model in RANS computations or LES of highly turbulent combustion.…”

Section: Introductionmentioning

confidence: 99%

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A priori test of perfectly stirred reactor approach to evaluating mean fuel consumption and heat release rates in highly turbulent premixed flames

Lipatnikov

2023

International Journal of Engine Research

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Unsteady three-dimensional Direct Numerical Simulation (DNS) data obtained earlier by Dave et al. ( J Fluid Mech 2020; 884: A46) from a statistically planar and one-dimensional, highly turbulent, moderately lean hydrogen-air flame propagating in a box are processed to perform a priori test of perfectly stirred reactor model. The test aims in particularly at estimating mesh resolution (or filter width within large eddy simulation framework) required to neglect variations in the temperature and mixture composition within a computational cell when evaluating mean (or filtered) fuel consumption and heat release rates. For this purpose, fuel consumption and heat release rates sampled directly from the DNS data and averaged over a cube of width [Formula: see text] are compared with fuel consumption and heat release rates calculated using the temperature and species concentrations averaged over the same cube. Moreover, turbulent burning velocities computed by integrating the former and latter rates are compared with one another. A ratio of [Formula: see text] to a laminar flame thickness [Formula: see text] is varied from 0.44 to 1.8. The obtained results indicate that the tested simple approach performs reasonably well (poor) if [Formula: see text] ([Formula: see text], respectively). This result is further supported by directly filtering fuel consumption rate in a laminar premixed flame. The values of the thickness [Formula: see text], calculated using detail chemical mechanisms for different fuels under elevated temperatures and pressures associated with combustion in piston engines, indicate that it is difficult to satisfy the constraint of [Formula: see text] in contemporary unsteady multidimensional numerical simulations of turbulent burning in such engines.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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A priori test of perfectly stirred reactor approach to evaluating mean fuel consumption and heat release rates in highly turbulent premixed flames

Lipatnikov

2023

International Journal of Engine Research

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“…They observed the coexistence of CH/HCO with OH or CH 2 O in the broken reaction zone regime, as a result of strong interaction between the fast vortex eddy and reactive fronts, which is quite different from radical distributions in the thin reaction zone regime. Fan et al [13] made ammonia/air LUPJ experiments in the conditions Ka = 247 ~ 4720, U'/S L =50 ~ 332, l t /δ L = 1.7, observing the evolutions of preheating and reaction zones by means of temperature and NH-PLIF imagings, which also con rmed the thickening of reaction zone layer (by 3-4 times) in the broken reaction zone mode.…”

Section: Introductionmentioning

confidence: 92%

DNS study of freely-propagating turbulent lean-premixed flames in the broken reaction zone regime

Zhang,

Kang,

et al. 2024

Preprint

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The novel engines nowadays featured with higher efficiency are operated under the superpressure, supercritical, supersonic, and near-limit combustion condition that is situated in the broken reaction zone regime. In the broken reaction zone regime, the turbulence Kolmogorov length is shorter than the reaction zone thickness and the fluctuating RMS velocity is higher than the propagating speed, as such small-scale vortex could tear up the continuous front surfaces and the combustion is dispersedly distributed, which is highly deviated off the flamelet theory assumption. Hence, the relevant study would provide some guiding implications for the refinement of turbulent premixed combustion models under the extreme conditions. In this article, the propagation and heat/radical diffusion physics of a high-pressure dimethyl ether (DME)/air turbulent lean-premixed flame with Ka = 200 are investigated numerically by DNS with detailed fuel chemistry and transport model. A wide range of statistical and diagnostic methods, including the Lagrangian fluids tracking, Joint Probability Density Distribution (JPDF), and chemical explosive mode analysis (CEMA) will be applied to reveal the deflagration front structure, the local combustion modes, dynamics evolution, as well as the roles of heat/mass transports and cool/hot flame interaction in the turbulent combustion regimes, which would be beneficial to the design of novel engines with high performances. It is found that in the broken reaction zone regime, the reacting front structure as well as its inner diffusion processes has changed significantly. The reaction zone thickness increases remarkably, and HRR and fuel consumption rate in the cool-flame zone are increased by 16% and 19% respectively. The diffusion effect not only enhances flame propagation, but also suppresses local HRR or fuel consumption. The strong turbulence interplaying with diffusive transports is the underlying physics for the enhancements in cool- and hot-flame fronts. In the turbulence field with strong flame folding and eddy mixing, it created intermixed reacting fronts with various progress variables; the heat/radical diffusions is the underlying mechanism for flame intensification/thickening phenomena. For the cool-flame front, diffusive transports of heat, CH2O, CH3OCH2O2, and CH3OCH3 are of the governing significances for the flame thickening and combustion enhancement. For the hot flame front, heat conductivity is most dominant and the diffusions of CH2O, H2O2, and CH3OCH3 are of less importance with an inhabitation impact.

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Simultaneous imaging of NO and NH in an ammonia-hydrogen-nitrogen flame using a single dye laser

Wang

Sheng²,

Roberts³

et al. 2022

Combustion and Flame

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Structure and scalar correlation of ammonia/air turbulent premixed flames in the distributed reaction zone regime

Cited by 22 publications

References 44 publications

A priori test of perfectly stirred reactor approach to evaluating mean fuel consumption and heat release rates in highly turbulent premixed flames

A priori test of perfectly stirred reactor approach to evaluating mean fuel consumption and heat release rates in highly turbulent premixed flames

DNS study of freely-propagating turbulent lean-premixed flames in the broken reaction zone regime

Simultaneous imaging of NO and NH in an ammonia-hydrogen-nitrogen flame using a single dye laser

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