Open-loop active control of combustion dynamics on a gas turbine engine

Combustion dynamics is a prominent problem in the design and operation of low-emission gas turbine engines. Even modest changes in fuel composition or operating conditions can lead to damaging vibrations in a combustor that was otherwise stable. For this reason, active control has been sought to stabilize combustors that must accommodate fuel variability, new operating conditions, etc. Active control of combustion dynamics has been demonstrated in a number of laboratories, single-nozzle test combustors, and even on a fielded engine. In most of these tests, active control was implemented with closed-loop feedback between the observed pressure signal and the phase and gain of imposed fuel perturbations. In contrast, a number of recent papers have shown that open-loop fuel perturbations can disrupt the feedback between acoustics and heat release that drives the oscillation. Compared to the closed-loop case, this approach has some advantages because it may not require high-fidelity fuel actuators, and could be easier to implement. This paper reports experimental tests of open-loop fuel perturbations to control combustion dynamics in a complete gas turbine engine. Results demonstrate the technique was very successful on the test engine and had minimal effect on pollutant emissions.