Kouji Matsunaga

Flow Analysis of Low-frequency Noise in Air-Conditioner Centrifugal Blower

Much progress has been made in recent years in reducing the noise from air conditioner centrifugal blowers used in automobiles. There is particularly great demand to reduce the noise in the frequencies 50-300 Hz generated in the high-pressure operation area. Therefore, the mechanism by which the low-frequency noise is generated was analyzed and measures for reducing blower noise were studied.To analyze the noise generating mechanism, flow visualization and fluid measurement were used. The flow visualization method was to inject and adjust the tracer from two locations and clearly visualize the flow at the interference section, which was the cause of the noise. For fluid measurement, SI and a hot-wire flow velocity meter were used to investigate the relationship with the noise. It was found that the causes of the low-frequency noise are fluctuating flow and periodic vortex generation at the blower intake side.