A DNS study of the physical mechanisms associated with density ratio influence on turbulent burning velocity in premixed flames

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Lipatnikov, Andrei,1961Chalmers tekniska högskola,Chalmers University of Technology (författare)

A DNS study of the physical mechanisms associated with density ratio influence on turbulent burning velocity in premixed flames

Artikel/kapitelEngelska2018

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2017-10-30
Informa UK Limited,2018

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LIBRIS-ID:oai:research.chalmers.se:c0167d33-d4c1-4e41-9e74-e0de63750cfa
https://research.chalmers.se/publication/500472URI
https://research.chalmers.se/publication/501088URI
https://research.chalmers.se/publication/500801URI
https://doi.org/10.1080/13647830.2017.1390265DOI

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Språk:engelska
Sammanfattning på:engelska

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Data obtained in 3D direct numerical simulations of statistically planar, 1D weakly turbulent flames characterised by different density ratios σ are analysed to study the influence of thermal expansion on flame surface area and burning rate. Results show that, on the one hand, the pressure gradient induced within a flame brush owing to heat release in flamelets significantly accelerates the unburned gas that deeply intrudes into the combustion products in the form of an unburned mixture finger, thus causing largescale oscillations of the burning rate and flame brush thickness. Under the conditions of the present simulations, the contribution of this mechanism to the creation of the flame surface area is substantial and is increased by σ, thus implying an increase in the burning rate by σ. On the other hand, the total flame surface areas simulated at σ = 7.53 and 2.5 are approximately equal. The apparent inconsistency between these results implies the existence of another thermal expansion effect that reduces the influence of σ on the flame surface area and burning rate. Investigation of the issue shows that the flow acceleration by the combustion-induced pressure gradient not only creates the flame surface area by pushing the finger tip into the products, but also mitigates wrinkling of the flame surface (the side surface of the finger) by turbulent eddies. The latter effect is attributed to the high-speed (at σ = 7.53) axial flow of the unburned gas, which is induced by the axial pressure gradient within the flame brush (and the finger). This axial flow acceleration reduces the residence time of a turbulent eddy in an unburned zone of the flame brush (e.g. within the finger). Therefore, the capability of the eddy for wrinkling the flamelet surface (e.g. the side finger surface) is weakened owing to a shorter residence time.

Ämnesord och genrebeteckningar

TEKNIK OCH TEKNOLOGIER Maskinteknik Energiteknik hsv//swe
ENGINEERING AND TECHNOLOGY Mechanical Engineering Energy Engineering hsv//eng
TEKNIK OCH TEKNOLOGIER Maskinteknik Strömningsmekanik och akustik hsv//swe
ENGINEERING AND TECHNOLOGY Mechanical Engineering Fluid Mechanics and Acoustics hsv//eng
Darrieus–Landau mechanism
density ratio
modelling
premixed turbulent flame
DNS

Biuppslag (personer, institutioner, konferenser, titlar ...)

Chomiak, Jerzy,1934Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)comb (författare)
Sabelnikov, Vladimir,1946Office national d'etudes et de recherches aerospatiales (ONERA) (författare)
Nishiki, Shinnosuke,1981Kagoshima University (författare)
Hasegawa, Tatsuya,1956Nagoya University (författare)
Chalmers tekniska högskolaOffice national d'etudes et de recherches aerospatiales (ONERA) (creator_code:org_t)

Sammanhörande titlar

Ingår i:Combustion Theory and Modelling: Informa UK Limited22:1, s. 131-1551364-78301741-3559

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Av författaren/redakt...: Lipatnikov, Andr ...; Chomiak, Jerzy, ...; Sabelnikov, Vlad ...; Nishiki, Shinnos ...; Hasegawa, Tatsuy ...

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TEKNIK OCH TEKNOLOGIER: TEKNIK OCH TEKNO ...; och Maskinteknik; och Energiteknik

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Av lärosätet: Chalmers tekniska högskola

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