Development of High Performance Aircraft Bleed Air Temperature Control System With Reduced Ram Air Usage

Conventional aircraft engine bleed air temperature regulation system is inefficient due to unnecessary ram air usage in cooling the bleed air, which in turn causes unnecessary drag and fuel consumption. This paper proposes an aircraft bleed air temperature control system, aiming at minimizing the ram air usage to reduce drag and fuel consumption while maintaining fast temperature control response. To achieve both of the objectives, a new control system configuration is developed to control both ram air and bypass flows in such a way that the bypass bleed air flow is automatically controlled at a small level that is just sufficient to maintain fast regulation of the flow temperature at the load. Analytical equations describing the system dynamics and linearized model are derived and utilized in the overall bleed air temperature control design and analysis. PI control and optimal output feedback are investigated. Computer simulations and experiments have been conducted, and the proposed control system is shown to be effective in reducing ram air usage and maintaining fast temperature control response in the meantime.