Abstract: Both aerodynamic and aeroacoustic performance of collateral axial flow fan system inside outdoor unit of air-conditioner is investigated by particle imaging velocimetry measurement and CFD simulation. The discrete noise frequency is not equal to the upside blade passing frequency, nor the downside rotor, but equal to the integral times of BPF differences between upside and downside rotors. No obvious flow field interaction has been found between upside and downside rotor. Vortex shedding noise prediction model is proved to be effective, with predicted total sound pressure level error less than 3 dBA.

Key words: Aerodynamic noise, Air-conditioner, Axial flow fan, Particle imaging velocimetry