The response of a harmonically forced premixed flame stabilized on a heat-conducting bluff-body

Type
Article

Authors
Kedia, Kushal S.
Ghoniem, Ahmed F.

KAUST Grant Number
KUS-11-010-01

Date
2015

Abstract
© 2014 The Combustion Institute. The objective of this work is to investigate the unsteady response of a bluff-body stabilized laminar premixed flame to harmonic inlet velocity excitation. A time series analysis was performed to analyze the physical sequence of events at a fixed longitudinal forcing frequency of 100 Hz for cases with (1) two different equivalence ratios and (2) two different thermal properties of the stabilizing bluff-body. It was observed that conjugate heat exchange between the heat conducting bluff-body and the surrounding reacting flow has a crucial impact on the dynamic response. The flame area and anchoring location, the net conjugate heat transfer and the total heat release underwent significant oscillations. The latter was mean shifted and had multiple frequencies. The burning velocity varied significantly along the flame length and the recirculation zone underwent complex changes in its shape and size during an unsteady cycle. The lower equivalence ratio case exhibited vortex shedding after an initial symmetric response with periodic flame extinction and re-ignition along its surface, unlike the higher equivalence ratio case. The metal/ceramic bluff-body showed a net heat transfer directed from/to the bluff-body, to/from the reacting flow during an unsteady cycle, resulting in a significantly different flame response for the two otherwise equivalent cases.

Citation
Kedia KS, Ghoniem AF (2015) The response of a harmonically forced premixed flame stabilized on a heat-conducting bluff-body. Proceedings of the Combustion Institute 35: 1065–1072. Available: http://dx.doi.org/10.1016/j.proci.2014.06.007.

Acknowledgements
This work was supported by King Abdullah University of Science and Technology (KAUST) award number KUS-11-010-01. We would like to acknowledge Dr. Habib Najm, Dr. Cosmin Safta and Dr. Jaideep Ray (Combustion Research Facility, Sandia National Laboratories, Livermore, CA, USA) for their major contribution towards the SAMR tool development.

Publisher
Elsevier BV

Journal
Proceedings of the Combustion Institute

DOI
10.1016/j.proci.2014.06.007

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