Inquiry into Discrete Frequency Noise Source of Cross Flow Fan (Reconstruction of Discrete Frequency Noise Propagation)

Abstract

Discrete frequency noise of a cross flow fan is generated by periodic flow fluctuation according to the rotation of an impeller. The interference of an impeller and a stabilizer is known as the main noise source. In this work, the discrete frequency noise source and the characteristics of the sound propagation of a cross flow fan were visualized according to operation points. The time sequential propagation of the sound wave was reconstructed by using an acoustic holography method. From the visualization of the discrete frequency noise, the following results were obtained. When the flow rate coefficient is large, the dominant discrete frequency noise source was observed at the contiguous area of an impeller and a stabilizer. And it shifts to the contiguously point of an impeller and a casing wall according to the decrease of the flow rate coefficient.