Pulsed air jets control flow over wings
Particularly during take-off and landing, the wing must provide enough lift at low speed. Complex systems of leading and trailing edge (TE) flaps can provide high lift but they increase the overall weight, fuel consumption and emissions of the aircraft. Active flow control systems that sense and respond to flight conditions can be quite effective in enhancing lift and stability and in reducing drag. However, although much research has been devoted to flow control actuator concepts, none has reached the maturity to be considered for civil aviation.EU-funded scientists undertook an intensive research and development campaign within the project DT-FA-AFC to deliver a system with such potential. They emphasised the flow control system and the control hardware rather than the aerodynamic effects of flow control, taking on an area of research somewhat neglected. The end result is a robust and compact aircraft-scale fluidic actuator system with no moving or electrical parts.The system delivers high-amplitude pulsed air jets to delay or avoid flow separation. Preventing or delaying separation of the smooth flow of air over a body from its surface and the subsequent transition to turbulent flow increases the operating range. A single-element fluidic actuator was designed in cooperation with external organisations to fulfill technical specifications and to fit in the TE flap. Elements were then combined in a large array of actuators together with the necessary driving stage. The aircraft-scale system was tested for pressures, flow rates and frequencies, and was then down-scaled for wind tunnel testing. System performance as evaluated in bench-top experiments demonstrated the necessary control in the relevant frequency range to be considered for integration in a civil aeroplane.Active separation control via pulsed blowing from the flap shoulder is expected to have major impact on reaching the Advisory Council for Aeronautics Research in Europe (ACARE) Vision 2020 goals. This is achieved through reduced mechanical complexity, required space and weight and thus reduced fuel consumption and emissions. DT-FA-AFC is slated to deliver a fluidic actuator system of high industrial relevance and the first with the potential to be considered for integration in civil aircraft.>
Keywords
Active flow control, fluidic actuator system, pulsed air jet, flow separation, low speed, high lift