Feedback Control of Combustion Instabilities: A Case Study in Active AdaptiveControl of Complex Physical Systems

摘要

This program will address the following issues: Previous studies on small (1-kW),premixed, gas-fueled combustors have demonstrated suppression of longitudinal mode combustion instability using pressure (or heat release) feedback and loudspeaker modulation. Can the same results be achieved on a larger scale (200 kW), liquid-fueled combustor using a more practical actuation means. Owing to the high order and nonlinear nature of the processes involved, we would expect that a single, linear, time-invariant (LTI) controller would be capable of stabilizing the combustor over only a small range of airflows and equivalence ratios. To provide a research test bed, we will modify a 3-in by 3-in, premixed gas combustor to accept liquid fuel admitted through a high bandwidth, Moog servo valve. Fuel flow modulation will be tried first as a means of actuation. If necessary, a fuel pressure feedback loop will be closed around the valve to extend its bandwidth even further. We will then obtain a 'screech map' by measuring the combustor pressure power spectrum at several combinations of airflow rates and equivalence rations. Based on these measurements, and on our experience with the 1-kW combustor, we will select a screeching operating point at which to begin the control system design. (js)