The behavior of a laboratory-scale pulsed combustor is shown to undergo a global bifurcation as the equivalence ratio of the propane-air mixture is reduced toward the lean flammability limit. At near-stoichiometric and moderately lean conditions, the acoustically driven combustion oscillations exhibit small, stochastic cycle-to-cycle variations. At very lean conditions, the available fuel inventory is rapidly consumed and slowly restocked resulting in a high degree of variability in combustion quality over a span of several acoustic cycles. This mode of operation is very unstable and often leads to misfire and flameout of the combustor. A feedback control strategy is applied which occasionally applies small, appropriately timed injections of supplemental fuel to hasten the restocking process and push the trajectory of the system toward the more stable operating mode. Emission levels of unburned hydrocarbons and NOx are monitored to demonstrate the effectiveness of feedback control. Possible improvements for the control strategy are recommended.
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Updated: 2001-06-23 ceaf