Closed-loop Control System for Improved Combustor Stability and Performance

This proposal describes a novel active control system to improve the stability of low-NOx gas turbine combustors. The control scheme is based on using inlet fuel flow modulation to influence the unsteady mixing and heat release processes in the combustor to provide real-time control over combustion stability. In the proposed Phase I program, the control system will be adapted to an existing laboratory-scale spray combustor by installing a fast-response sensor and actuator coupled to a PC-based controller. An optical sensor will be fiber-optically coupled to the combustor to monitor luminous emission in the flame stabilization zone. The sensor will be used to detect combustion instability which is manifested in oscillatory burning. When combustion instability is sensed, the PC-based controller will send a control signal to an auxillary high-speed pulsed fuel injector to instantaneously increase mixing and combustion intensity in the flame stabilization region. This will lead to a local region of intense burning to stabilize the flame and reduce the combustion oscillation. The successful application of this control scheme to gas turbine engines will result in more stable, compact, and, efficient low NOx combustion systems.