ACTIVE CONTROL OF WAKE BLADE-ROW INTERACTION NOISE

This paper describes an analytical/computational approach for controll ing the noise generated by wake/blade-row interaction through the use of antisound actuators on the blade surfaces. A representative two-dim ensional section of a fan stage, composed of an upstream fan rotor and a downstream fan exit guide vane (FEGV), is exmained. An existing mod el for the wakes generated by the rotor is analyzed to provide realist ic magnitudes for the vortical excitations imposed at the inlet to the FEGV. The acoustic response of the FEGV is determined at multiples of the blade passing frequency by using the linearized unsteady flow ana lysis, LINFLO. An analysis then is presented to determine the complex amplitudes required for the control surface motions to best reduce the farfield noise. The effectiveness of the control is measured by the d ecrease in the circumferentially averaged sound pressure level, which is minimized by a standard least-squares procedure.