Inflow Ducting in High-Volume-Flow Subsonic Anechoic Chambers.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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When studying the aeroacoustic performance of fluid moving machinery, spacial and temporal disturbances in the supply flow may induce otherwise nonexistent noise characteristics in the test device. To control these incoming disturbances, inlet screens, honeycombs, and other wind tunnel configurations have been used. To investigate whether an aeroacoustic test facility could be designed which would utilize neither a wind tunnel configuration nor an inlet control structure at the test device inlet, a one-sixth-scale model of a proposed high-volume-flow subsonic anechoic chamber was evaluated. An experimental investigation of inlet-flow controlling walls with combined anechoic and aerodynamic capabilities was carried out. Aerodynamic performance was measured in the plane of a proposed test fan rotor. Data from several inlet wall configurations give guidance in the design of inflow ducting configurations for high-volume-flow subsonic anechoic chambers. The results indicate that substantial reduction of axial turbulence intensities and steady-state spacial disturbances can be achieved without degradation of the anechoic capability of the inlet wall. Because inflow control is no longer needed near the test device inlet, the acoustical characteristics of the test device should match those of a free-field device.