Optimization of Bleed-Flow-Control for an Aggressive Serpentine Duct

Abstract

A procedure for designing flow-control-enabled aggressive serpentine duct shapes as part of an Integrated Total Aircraft Power Systems (ITAPS TM ) study is presented. Some military aircraft are driven towards serpentine shaped inlet designs to increase survivability through reduction in engine visibility. Maintaining the engine inflow quality with low total pressure losses and low engine face total pressure distortions generally requires a relatively long duct. Long ducts, significantly increase the size and the weight of the overall air vehicle system result in limitations to the vehicle’s overall performance. Without boundary layer control, a shorter (more aggressive) inlet is not a viable solution due to massive flow separation resulting in high total pressure losses and inlet distortion along with overall low system performance. Flow control has the potential to eliminate flow separation in these aggressive ducts and was included in the present study as an enabling technology. However, for the overall system performance, flow control by itself may not be a viable solution due to penalties associated high actuation requirements, power, weight and flow source or sink. In addition, the robustness of the flow control in an aggressive serpentine duct must be considered since it has to be maintained for all possible mission conditions. The present methodology consists of a novel approach of integrating a simple inlet bleed-flow control actuation with the aircraft Environmental Control System (ECS), thus providing a viable robust inlet design with impr oved system performance while supplying the flow required by the ECS. A new inlet optimization tool, OPDUCT, was created and used to design a flow-control-enabled aggressive serpentine duct and evaluate its performance. It employs a hierarchy of high and low fidelity models that allow for optimizing duct geometry to yield high inlet total pressure recovery and low distortion. The resulting inlet total pressure recovery and distortion were then assessed to capture the impact on engine operability and aircraft performance.