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Abstract
The flow of premixed reactants in a duct with flames stabilized on a sudden expansion and an open downstream end gave rise to combustion oscillations of low frequency due to extinction and relight and high frequency due to longitudinal acoustic modes. This paper quantifies the flammability and stability limits and their temperature dependence; considers the nature of oscillations, their coupling and modulation effects with methane, propane and ethylene; and describes the extent to which they can be reduced in amplitude by oscillations imposed at discrete frequencies with and without active phase control and with the addition of small quantities of fuel close to the expansion.
This research was carried out with financial support from the U.S. Office of Naval Research and the U.S. Army under Grant N000014-02-1-0664 and Contract N68171-00-C-9019, respectively. Useful discussions, advice, and practical assistance with and from Drs. S. Fletcher, H. McDonald, A. M. Marquis, G. Roy, S. Sampath, and S. Sivasegaram and the earlier contributions of Drs. S.R.N. De Zilwa, and J.H. Uhm and I. Emiris are gratefully acknowledged.
Notes
Flame speed and maximum adiabatic flame temperature; φ = 1.0 at standard temperature and pressure.