Model-Based Self-Tuning Multiscale Method for Combustion Control

Abstract

A Multi-Scale representation of the combustor dynamics was used to create a self-tuning, scalable controller to suppress multiple instability modes in a liquid-fueled aero engine-derived combustor operating at engine-like conditions. Its self-tuning features designed to handle the uncertainties in the combustor dynamics and time-delays are essential for control performance and robustness. The controller was implemented to modulate a high-frequency fuel valve with feedback from dynamic pressure sensors. This scaleable algorithm suppressed pressure oscillations of different instability modes by as much as 90 percent without the "peak-splitting" effect. The self-tuning logic guided the adjustment of controller parameters and converged quickly toward phase-lock for optimal suppression of the instabilities. The forced-response characteristics of the control model compare well with those of the test rig on both the frequency-domain and the time-domain.

Aircraft Turbine Engine Control Research at NASA Glenn Research Center

“…In order to achieve closed-loop suppression of the combustion instability, two alternative control methods were developed (Kopasakis et al 2004;Le et al 2005). These control methods were formulated to deal with the large wideband combustor noise, severe time delay, and randomness in phase associated with the combustor thermoacoustic pressure oscillations.…”

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“…Multivariable control methods provide the ability to optimize the performance of the whole system 19 and/or the performance of individual components. 20,21 …”

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“…Aircraft engines are complex, nonlinear systems with significant interaction between components. Multivariable control methods provide the ability to optimize the performance of the whole system [11] and/or the performance of individual components [12,13].…”