Noise reduction and control in a propeller fan

초록

A new design technique for the propeller fan in an outdoor unit of air-conditioner was applied to satisfy requirements of aerodynamic and aeroacoustic performance, which employs the intersection method of two cylinders for mean camber line. Three proto-types of propeller fan including Palm-Shaped, Highly-Swept (PSHS) fan (proto III) were designed not only to provide low fit forces for dipole sound, but also to reduce the organised tip vorticies interacting with the fan guide causing narrow-banded rotating instabilities. The performance and noise characteristics were measured using ANSI test plenum for air-moving devices (AMDs) as a test apparatus. Detailed measurements were made to study flow noise source characteristics for three proto-type fans designed. The cross-correlations between a microphone at far field and a hot-wire sensor at near field show that the flow near hub region of proto III fan are less organized and the flow structure especially at high flow rate coefficients for proto III fan are less correlated with noise generated than those of other proto-type fans. For the purpose of reduction and control of the noise from the propeller fan, an inlet guide of wavy wall was deliberately designed, and their performance was tested and discussed.