Active Control of Discrete-Frequency Turbomachinery Noise Using a Rotary-Valve Actuator

Abstract

Turbomachine discrete-frequency tones, a significant environmental concern, are generated by rotor-stator interactions. Specific spatial modes are generated, but not all generated modes propagate to the far field. It is the propagating spatial modes generated by rotor-stator interaction that represent the community-disturbing far field discrete-frequency noise. Fundamental active airfoil source discrete-frequency noise control experiments are performed, with the active airfoil source control optimized to generate propagating spatial modes to cancel the propagating spatial modes generated by the rotor-stator interaction. These experiments demonstrate the viability and effectiveness of rotary-valve discrete-frequency noise control. Specifically, the active noise control system combines the active airfoil source control with in-duct spatial mode measurement. In this unique design, the active airfoils of the stator vane row are driven by a remote centerbody-mounted rotary-valve system. Propagating spatial mode reductions of 5 dB and 9 dB upstream and downstream with negligible modal spillover are demonstrated. [S0742-4795(00)02702-2]