Structure and propagation speeds of turbulent premixed flames—A numerical study

This paper presents a numerical study of the sound generated by turbulent, premixed flames. Direct numerical simulations (DNS) of two round jet flames with equivalence ratios of 0.7 and 1.0 are first carried out. Single-step chemistry is employed to reduce the computational cost, and care is taken to resolve both the near and far fields and to avoid noise reflections at the outflow boundaries. Several significant features of these two flames are noted. These include the monopolar nature of the sound from both flames, the stoichiometric flame being significantly louder than the lean flame, the observed frequency of peak acoustic spectral amplitude being consistent with prior experimental studies and the importance of so-called ‘flame annihilation’ events as acoustic sources. A simple model that relates these observed annihilation events to the far-field sound is then proposed, demonstrating a surprisingly high degree of correlation with the far-field sound from the DNS. This model is consistent with earlier works that view a premixed turbulent flame as a distribution of acoustic sources, and provides a physical explanation for the well-known monopolar content of the sound radiated by premixed turbulent flames.

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Numerical Study on Counter-Gradient Transport Phenomenon in Turbulent Premixed Flames

21st AIAA International Space Planes and Hypersonics Technologies Conference ◽

10.2514/6.2017-2220 ◽

2017 ◽

Author(s):

Fang Chen ◽

Dali Yu ◽

Wenxuan Huang ◽

Hong Liu

Keyword(s):

Transport Phenomenon ◽

Numerical Study ◽

Premixed Flames ◽

Turbulent Premixed Flames ◽

Turbulent Premixed

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Statistical behaviour of dissipation rate of turbulent kinetic energy in turbulent premixed flames

Proceeding of THMT-12. Proceedings of the Seventh International Symposium On Turbulence, Heat and Mass Transfer Palermo, Italy, 24-27 September, 2012 ◽

10.1615/ichmt.2012.procsevintsympturbheattransfpal.430 ◽

2012 ◽

Author(s):

Nilanjan Chakraborty ◽

M. Hudson ◽

R.S. Cant

Keyword(s):

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Dissipation Rate ◽

Premixed Flames ◽

Turbulent Premixed Flames ◽

Turbulent Premixed

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Modelling of Conditional Scalar Dissipation Rate in Turbulent Premixed Combustion

Computation ◽

10.3390/computation9030026 ◽

2021 ◽

Vol 9 (3) ◽

pp. 26 ◽

Cited By ~ 1

Author(s):

Shokri Amzin ◽

Mariusz Domagała

Keyword(s):

Dissipation Rate ◽

Premixed Flames ◽

Moment Closure ◽

Navier Stokes ◽

Scalar Dissipation ◽

Flame Surface ◽

Scalar Dissipation Rate ◽

Turbulent Premixed Flames ◽

Conditional Moment ◽

Turbulent Premixed

In turbulent premixed flames, for the mixing at a molecular level of reactants and products on the flame surface, it is crucial to sustain the combustion. This mixing phenomenon is featured by the scalar dissipation rate, which may be broadly defined as the rate of micro-mixing at small scales. This term, which appears in many turbulent combustion methods, includes the Conditional Moment Closure (CMC) and the Probability Density Function (PDF), requires an accurate model. In this study, a mathematical closure for the conditional mean scalar dissipation rate, <Nc|ζ>, in Reynolds, Averaged Navier–Stokes (RANS) context is proposed and tested against two different Direct Numerical Simulation (DNS) databases having different thermochemical and turbulence conditions. These databases consist of lean turbulent premixed V-flames of the CH4-air mixture and stoichiometric turbulent premixed flames of H2-air. The mathematical model has successfully predicted the peak and the typical profile of <Nc|ζ> with the sample space ζ and its prediction was consistent with an earlier study.

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