Numerical study of the effects of gravity on soot formation in laminar coflow methane/air diffusion flames under different air stream velocities

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DOIResolve DOI: http://doi.org/10.1081/13647830903342527
AuthorSearch for: ; Search for:
TypeArticle
Journal titleCombustion Theory and Modelling
Volume13
Issue6
Pages9931023; # of pages: 31
SubjectSoot formation; Laminar diffusion flame; Microgravity combustion; Thermal radiation; Coflow air velocity
AbstractNumerical simulations of laminar coflow methane/air diffusion flames at atmospheric pressure and different gravity levels were conducted to gain a better understanding of the effects of gravity on soot formation by using relatively detailed gas-phase chemistry and complex thermal and transport properties coupled with a semi-empirical twoequation soot model. Thermal radiation was calculated using the discrete-ordinates method coupled with a non-grey model for the radiative properties of CO, CO₂, H₂O, and soot. Calculations were conducted for three coflow air velocities of 77.6, 30, and 5 cm/s to investigate how the coflowing air velocity affects the flame structure and soot formation at different levels of gravity. The coflow air velocity has a rather significant effect on the streamwise velocity and the fluid parcel residence time, especially at reduced gravity levels. The flame height and the visible flame height in general increase with decreasing the gravity level. The peak flame temperature decreases with decreasing either the coflow air stream velocity or the gravity level. The peak soot volume fraction of the flame at microgravity can either be greater or less than that of its normal gravity counterpart, depending on the coflowair velocity.At sufficiently high coflowair velocity, the peak soot volume fraction increases with decreasing the gravity level. When the coflow air velocity is low enough, soot formation is greatly suppressed at microgravity and extinguishment occurs in the upper portion of the flame with soot emission from the tip of the flame owing to incomplete oxidation. The numerical results provide further insights into the intimate coupling between flame size, residence time, thermal radiation, and soot formation at reduced gravity level. The importance of thermal radiation heat transfer and coflow air velocity to the flame structure and soot formation at microgravity is demonstrated for the first time.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Institute for Chemical Process and Environmental Technology
Peer reviewedNo
NRC number51763
NPARC number14299049
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Record identifier2439f740-e877-4dce-a75f-5d3973edc79f
Record created2010-02-08
Record modified2016-05-09
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