On liquid-fueled active combustion control - Instability suppression in dump combustors

摘要

An exploratory study on liquid-fueled active instability suppression was performed in a dump combustor to better understand the physical mechanisms involved and identify practical issues of importance. A timing-controlled pulsed fuel injection process and a vortex-droplet interaction mechanism were considered for regulating the heat release oscillations both in time and space. The analytical part of the study assessed the effect of fuel droplet size on combustion control effectiveness. In the experiments, fuel was pulsed directly into the flow vortical structures, and the injection timing was adjusted with respect to the shedding process to control their interaction. When the pulsed fuel injection process was properly timed using a feedback control loop, combustor sound pressure level was suppressed by up to 15 dB. In the ensuing scaling experiments, the critical amount of controlled fuel flux, which was required to maintain the control authority, was measured. The results showed that the critical fuel flux was a function of fuel droplet size; its dependence followed expected trends.