Chaos in an imperfectly premixed model combustor

Kabiraj, L., Saurabh, A., Karimi, N. , Sailor, A., Mastorakos, E., Dowling, A. P. and Paschereit, C. O. (2015) Chaos in an imperfectly premixed model combustor. Chaos: An Interdisciplinary Journal of Nonlinear Science, 25(2), 023101. (doi: 10.1063/1.4906943) (PMID:25725637)

Abstract

Spontaneous feedback coupling between the flame and chamber acoustics in a combustor can have disastrous consequences. Hence, thermoa- coustic instability, as this phenomenon is tech- nically referred to, is a critical issue for indus- tries dependent on combustor technology. Ther- moacoustic instability also is an interesting case of nonlinear time-delayed coupling. A recent de- velopment in the research on thermoacoustic in- stability is the identification of chaotic dynamics and chaotic scenarios in simple model combus- tors running on laminar flames. As the flame is an inherent part of the instability, one could expect clean chaotic transitions to be specific to simple laminar systems. We will show here that this is not the case. This article is a report on the nonlinear analysis of thermoacoustic instabil- ity in a more realistic combustor configuration. We conducted experiments on a combustor op- erating on imperfectly premixed, turbulent com- bustion with equivalence ratio as the control pa- rameter for bifurcation analysis. Imperfectly pre- mixed combustion is the preferred mode of oper- ation in real systems due to its advantages over the premixed mode. Of the several variables in a combustor, the fuel-air or equivalence ratio is the most likely to vary. We calculate and ana- lyze dynamical measures of chaos and complexity from the phase space reconstructed from experi- mental data while varying the control parameter. Results demonstrate that a well-defined route to chaos is followed by the instability in the com- bustor even in the presence of several complexi- ties that are absent in laminar flame combustors. The main development over recent results that this article presents is to demonstrate that even in a practical configuration, the thermoacoustic sys- tem exhibits deterministic chaotic dynamics and a well-defined route to chaos, which has been ob- served in several other nonlinear systems. These results uncover a new aspect of the instability and will motivate the incorporation of new approaches based on dynamical systems theory for the model- ing and control of thermoacoustic instability. The study also introduces a naturally occurring phe- nomenon that is of technical relevance to the class of nonlinear systems exhibiting rich dynamics.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Karimi, Dr Nader
• Authors: Kabiraj, L., Saurabh, A., Karimi, N., Sailor, A., Mastorakos, E., Dowling, A. P., and Paschereit, C. O.
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: Chaos: An Interdisciplinary Journal of Nonlinear Science
• Publisher: American Institute of Physics
• ISSN: 1054-1500
• ISSN (Online): 1089-7682
• Copyright Holders: Copyright © 2015 American Institute of Physics
• First Published: First published in Chaos: An Interdisciplinary Journal of Nonlinear Science25(2):023101
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher.