Self-Noise and Wake Velocity of an Axial Fan for Different Operating Conditions
Aeroacoustic and hot-wire wake measurements have been made for rotating controlled diffusion blades configured as a three- and as a nine-blade axial fan. For each rotor, six different operating conditions (cases 1 to 6), ranging from very low pressure rise to blade stall and radial pumping, have been investigated. The experimental results include the wake flow patterns and the associated noise radiation. Fluctuation intensities and phase-averaged velocity magnitudes have been obtained in the downstream region of the fan to represent the basic flow features for each defined case. An array of microphones was used to measure the acoustic emissions created by the axial fan. A beamforming technique has been used to properly represent the fan acoustic emissions from the recorded acoustic data. Self-noise signatures of the propagated sound, corresponding to the defined cases, have been obtained in the range of 200–8000 Hz. Acoustic data and their links to 1) the physics of the flows, 2) aerodynamic loading, and ...