Noise generation by vacuum cleaner suction units: Part II. Effect of vaned diffuser on noise characteristics

Noise emitted by a vacuum cleaner suction unit has aerodynamic, mechanical and electromagnetic noise origins. The aerodynamically generated noise within the blower mostly prevails in the total emitted noise at design and off-design operations. The vaned diffuser built into the blower has an important effect on the aerodynamically generated noise and its spectra. Therefore, in this part of the paper, the effects of the vaned diffuser on the performance and noise characteristics have been measured and analysed at the design and off-design operation. Analysis of measurement results have shown that the built-in vaned diffuser has numerous disadvantages, including: increase in the rotational noise, increase in the non-rotational turbulent noise, especially at off-design operation, increase in production costs and reduction of the flow rate. Therefore, and due to variable operating conditions of the suction units built into a vacuum cleaner, it could be omitted or replaced by a vaneless one.     

Noise generation by vacuum cleaner suction units: Part I. Noise generating mechanisms - An overview

Among all household appliances, the vacuum cleaner is the most powerful source of noise. The built-in suction unit, consisting of an electric motor and a centrifugal blower, represents the main source of noise; this is partially aerodynamic, mechanical and electromagnetic in origin. The contribution of the particular origin of noise generation to the total noise level depends on the geometry of the suction unit and operating conditions. The operating point of a suction unit built into a vacuum cleaner depends on the amount of dust particles in the dust bag and is constantly changing during operation until it reaches a zero flow rate. There are differences in noise generation at different operating conditions as well as between the suction units having a blower without and with a vaned diffuser. In this part of the paper, an overview of aerodynamic, mechanical and electromagnetic noise origins at different operating conditions is given.