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Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames

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Summary, in English

The stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime,significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.

Publishing year

2011

Language

English

Publication/Series

Proceedings of the 17th Mediterranean Combustion symposium, MCS 7

Document type

Conference paper

Publisher

Combustion Institute

Topic

  • Fluid Mechanics and Acoustics
  • Atom and Molecular Physics and Optics

Conference name

17th Mediterranean Combustion Symposium

Conference date

2011-09-11 - 2011-09-15

Conference place

Chia Laguna, Cagliari, Sardinia, Italy

Status

Published

ISBN/ISSN/Other

  • ISBN: 978-88-88104-12-6