CUED Publications database

Scalar dissipation rate and scales in swirling turbulent premixed flames

Kamal, M and Coriton, B and Zhou, R and Frank, J and Hochgreb, S (2016) Scalar dissipation rate and scales in swirling turbulent premixed flames. Proceedings of the Combustion Institute, 36. pp. 1957-1965. ISSN 1098-6596

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Simultaneous Rayleigh scattering and OH-PLIF imaging measurements of temperature and OH were used to investigate the properties of turbulent premixed flames, including the nature of the 2D thermal structures and scalar dissipation rate in the Cambridge/Sandia swirling bluff body stabilized flames, with and without the effect of swirl. Swirl creates enhanced turbulence as well as outer flow entrainment, and disrupts the pre-flame zone significantly, whilst the high temperature reaction zone as marked by OH remains relatively intact. In particular, the temperature at the location of maximum OH gradient shows very low variance across the flame region. The 2D image analysis of OH and temperature shows that the corresponding 2D gradients are aligned up to a distance of half the laminar flame thickness away from the flame front, deviating significantly in the case of swirling flames beyond that region. As in previous investigations in diffusion flames, the mean width of the observed thermal structures increases from 300 to 600 microns near the flame, with a main mode around the laminar flame thermal width in the unswirled case. The correlation between 2D thermal fluctuation gradients and variance extracted from the images shows a direct proportionality, with a slope which agrees well with theory in the region of high turbulence away from the base. At the base of the flame where turbulence is low, the local scalar dissipation becomes a function of the local temperature via the thermal diffusivity.

Item Type: Article
Uncontrolled Keywords: turbulent premixed flame scalar dissipation rate dissipative structures swirl burner 2D Rayleigh scattering
Divisions: Div A > Energy
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 20:03
Last Modified: 07 Aug 2018 03:22