Fan Flow Control for Improved Efficiency and Noise Reduction

Technology in Blacksburg (Techsburg) and the Vibrations and Acoustics Laboratory at Virginia Tech (VAL) are proposing an innovative flow control scheme for fan rotors designed to simultaneously increase fan loading and efficiency while reducing fan radiated noise. The technology uses blade embedded ejector pumps to provide suction and blowing on the suction surface of the rotor to prevent flow separation and significantly reduce wake size.The amount of work produced by a single compression stage is limited by the amount of diffusion that can occur without large-scale flow separation. Viscous losses within the separated region not only result in an efficiency penalty but also create a large wake behind each of the rotor blades which interact with the downstream exit guide vanes and stators. Left untreated, fan exhaust noise from this interaction is the most dominant perceived noise at takeoff and landing. By using flow control to eliminate separation and remove the boundary layer, both efficiency gains and noise reduction can be achieved.