In several applications continuous combustion occurs, examples of which include gas turbines, afterburners, ramjets, and rocket motors. In many of these applications dynamic instability occurs which manifests as acoustic resonances. This resonance occurs due to coupling mechanisms between the underling acoustics, hydrodynamics, and heat-release. Not only is such a resonance undesired, but is of significant concern as it often is accompanied by observations by high burn rates, excessive vibrations, mechanical failures, and/or component melting.
This phenomenon has been studied for a long time in acoustics, experienced by gas turbine manufacturers at various operating conditions, with reports of a loud buzz, screech, or hum. This project pertains to a systematic dynamic model that captures the coupling between the underlying mechanics and builds on the underlying physics. This model-based approach in turn led to a suite of active control methods including time-delay, optimal, adaptive, and nonlinear ones. These active controllers have been implemented in a range of rigs from table-top combustors to large-scale industrial rigs. The plot above shows experimental results from a Rolls-royce scaled rig and the success of active control of combustion systems.