Book Description

This study investigated the feasibility of active control of combustion instabilities in liquid fueled combustors using a liquid fuel injector actuator and adaptive control of combustion instabilities. Two different liquid fuel injector actuators were developed and their performance was investigated in open and closed loop active control tests. The open loop tests have shown that these actuators can effectively produce coherent, large amplitude, heat release oscillations with nearly constant phase over a wide range of frequencies, thus indicating that they could be employed to damp combustion instabilities. Furthermore, cold and reactive flow tests have shown that the performance of the liquid fuel actuators depends upon the injector's design and the characteristics of its spray. In parallel efforts, an adaptive control approach that does not require apriori knowledge of the open loop response of the control system is being investigated. The system "forces" the unstable combustor with a controlled, slowly varying, disturbance and uses the measured response of the combustor to determine the optimum control system phase and gain. Initial results obtained with this system are promising. This study also investigated the use of piezoelectric actuators to drive the fuel injector actuators in an effort to reduce their size and weight.