Effects of oxidant stream composition on non-premixed laminar flames with heated and diluted coflows

Evans, Michael J.; Medwell, Paul R.; Tian, Zhao Feng; Ye, Jingjing; Frassoldati, Alessio; Cuoci, Alberto

doi:10.1016/j.combustflame.2016.12.023

Cited by 19 publications

(29 citation statements)

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“…The hot and diluted coflows of JHC flames suppress the formation of soot (Medwell et al, 2008;de Joannon et al, 2012;Ye et al, 2016Ye et al, , 2017Evans et al, 2017bEvans et al, , 2019b. Soot may be suppressed for typically sooty fuels such as ethylene under MILD combustion conditions (Medwell et al, 2008;Evans et al, 2017b). In clean flames, thermometry may be performed using Rayleigh scattering.…”

Section: Thermography In Gaseous Soot-free Flamesmentioning

confidence: 99%

“…Fundamental studies of these flames have not only provided significant insight into autoignition processes, but have been used to generate extensive datasets in simplified configurations for validating turbulence-chemistry interaction models for numerical modeling of combustion systems. Fundamental studies of laminar and turbulent jet flames issuing into high temperature, low oxygen environments have been undertaken in jet in hot coflow (JHC) burners (Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Oldenhof et al, 2010Oldenhof et al, , 2011Oldenhof et al, 2012;Medwell and Dally, 2012a;Sepman et al, 2013;Ye et al, 2016Ye et al, , 2017Ye et al, , 2018Evans et al, 2017bEvans et al, , 2019aKruse et al, 2019), hot cross-flow burners (Sidey and Mastorakos, 2017), vitiated coflow burners (VCBs) (Cabra et al, 2002(Cabra et al, , 2005Gordon et al, 2008Gordon et al, , 2009Macfarlane et al, 2018Macfarlane et al, , 2019Ramachandran et al, 2019), and partially premixed jet burners (PPJBs) (Dunn et al, 2007a;Dunn et al, 2009), as have spray flames in hot coflow burners (Correia Rodrigues et al, 2015a,b;Wang et al, 2019b). In each case, fresh fuel issues from a jet into a stream of hot gas generated by lean premixed flames, resulting in 15% O 2 (by vol.).…”

Section: Introductionmentioning

confidence: 99%

“…Such improved understanding these transitions-and the structure of the upstream flames leading to their formation-may be achieved through targeted laser-diagnostics studies and subsequently validated, complementary numerical modeling. The high fidelity data that laser diagnostics can provide allows for the detailed study of reactive structures across the broad range of spatial and temporal scales in different optically-accessible JHC burners and reactors (Plessing et al, 1998;Cabra et al, 2002Cabra et al, , 2005Dally et al, 2002;Medwell et al, 2007Medwell et al, , 2008Gordon et al, 2008Gordon et al, , 2009Oldenhof et al, 2010Oldenhof et al, , 2011Oldenhof et al, 2012;Medwell and Dally, 2012a;Sepman et al, 2013;Sorrentino et al, 2015Sorrentino et al, , 2016Ye et al, 2016Ye et al, , 2017Ye et al, , 2018Evans et al, 2017bEvans et al, , 2019aSidey and Mastorakos, 2017;Macfarlane et al, 2018Macfarlane et al, , 2019Kruse et al, 2019;Ramachandran et al, 2019). Laser diagnostics a provide means to investigate the small-scale and distributed reaction zones in macroscopically-near-homogeneous MILD combustion conditions.…”

Section: Introductionmentioning

confidence: 99%

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Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Evans

Medwell

2019

Front. Mech. Eng.

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There is a wealth of existing experimental data of flames collected using laser diagnostics. The primary objective of this review is to provide context and guidance in interpreting these laser diagnostic data. This educational piece is intended to benefit those new to laser diagnostics or with specialization in other facets of combustion science, such as computational modeling. This review focuses on laser-diagnostics in the context of the commonly used canonical jet-in-hot-coflow (JHC) burner, although the content is applicable to a wide variety of configurations including, but not restricted to, simple jet, bluff body, swirling and stratified flames. The JHC burner configuration has been used for fundamental studies of moderate or intense low oxygen dilution (MILD) combustion, autoignition and flame stabilization in hot environments. These environments emulate sequential combustion or exhaust gas recirculation. The JHC configuration has been applied in several burners for parametric studies of MILD combustion, flame reaction zone structure, behavior of fuels covering a significant range of chemical complexity, and the collection of data for numerical model validation. Studies of unconfined JHC burners using gaseous fuels have employed point-based Rayleigh-Raman or two-dimensional Rayleigh scattering measurements for the temperature field. While the former also provides simultaneous measurements of major species concentrations, the latter has often been used in conjunction with planar laser-induced fluorescence (PLIF) to simultaneously provide quantitative or qualitative measurements of radical and intermediary species. These established scattering-based thermography techniques are not, however, effective in droplet or particle laden flows, or in confined burners with significant background scattering. Techniques including coherent anti-Stokes Raman scattering (CARS) and non-linear excitation regime two-line atomic fluorescence (NTLAF) have, however, been successfully demonstrated in both sooting and spray flames. This review gives an overview of diagnostics techniques undertaken in canonical burners, with the intention of providing an introduction to laser-based measurements in combustion. The efficacy, applicability and accuracy of the experimental techniques are also discussed, with examples from studies of flames in JHC burners. Finally, current and future directions for studies of flames using the JHC configuration including spray flames and studies and elevated pressures are summarized.

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Section: Thermography In Gaseous Soot-free Flamesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Evans

Medwell

2019

Front. Mech. Eng.

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“…It is worth mentioning that a recently presented new MILD combustion definition, based on an equivalent activation energy [69] and further observations [70], suggested that DJHC flames do not fully meet criteria for MILD combustion.…”

Section: The Test Case and Boundary Conditionsmentioning

confidence: 99%

“…Moreover, Evans et al [70] [14] with Gran and Magnussen [13] in two cases: when mean or surrounding value is used as the inflow condition to the PSR. The fifth simulation represents the case when the mean value is used but the factor (1 − γ λ ) −1 is not introduced.…”

Section: Reacting Fraction χmentioning

confidence: 99%

Analysis of the Eddy Dissipation Concept formulation for MILD combustion modelling

Lewandowski

Ertesvåg

2018

Fuel

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Performance of the Eddy Dissipation Concept (EDC) in the regime of Moderate and Intense Low-oxygen Dilution (MILD) combustion is investigated. The special MILD features, where chemical and turbulence time scales are comparable (Damköhler number close to unity), have led several researchers to suggest modifications of EDC, mainly by changing model constants. EDC with standard and modified constants are compared, and the importance of each effect is outlined. Different fine-structure reactor models and their inflow/initial conditions are discussed and found to play a significant role. The reacting fraction of fine structures, which in virtually all other numerical studies is set to unity, is also discussed and found to be important. We observe better agreement with experiment when the reacting fraction is reduced below unity, which is also described by the original EDC. The results obtained with the variable reacting fraction are found to improve both the temperature distributions and the lift-off height predictions. The calculations are carried out with the use of open source software OpenFOAM. The main test case was the Delft Jet-in-Hot-Coflow burner emulating MILD regime at three different flow conditions (jet Reynolds numbers of 2500, 4100 and 8800).

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Reverse water gas shift (RWGS) over Ni – Spatially-resolved measurements and simulations

Benzinger

Daymo²,

Hettel

et al. 2019

Chemical Engineering Journal

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Effects of oxidant stream composition on non-premixed laminar flames with heated and diluted coflows

Cited by 19 publications

References 105 publications

Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Understanding and Interpreting Laser Diagnostics in Flames: A Review of Experimental Measurement Techniques

Analysis of the Eddy Dissipation Concept formulation for MILD combustion modelling

Reverse water gas shift (RWGS) over Ni – Spatially-resolved measurements and simulations

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