Experimental Demonstration of Active Flow Control to Reduce Unsteady Stator-Rotor Interaction

An experimental investigation is conducted to reduce the unsteady stator-rotor interaction in a turbofan simulator using active flow control. The fan rotor of a 1/14-scale turbofan propulsion simulator is subjected to circumferentially periodic inlet flow distortions, generated by four stators that support a centerbody in the inlet mounted onto the simulator. These wakes are reenergized by injecting air from the trailing edge of each stator through discrete blowing holes. The flow rate through each blowing hole is controlled by an individual microelectro-mechanical system based microvalve. The microvalve actuation signal voltage is generated by a proportional-integral-derivative controller and is a function of the wake velocity defect. To determine the successful reenergizing of the wakes, far-field sound pressure level at the blade passing frequency without and with blowing is measured in an anechoic chamber. The active control experiments are performed for two simulator speeds of 29,500 and 40,000 rpm. In addition, the feasibility and advantage of active control is demonstrated by the ability of the system to respond to changes in the inlet flow velocity.