Houseless fan with rotating tip ring as silencer

Abstract

The stationary housing of a conventional fan assembly is replaced with a rotating tip ring. The rotating tip ring has a shaped cross-sectional profile to enhance performance and eliminate tonal noise associated with the fundamental (or blade passing) frequency and its harmonics.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates generally to an axial flow fan and in particular to a fan impeller having improved noise characteristics.[0002]Conventional fans typically comprise a motor and an impeller coupled to the motor. The impeller includes a hub to which a set of fan blades are attached. The hub is connected to the rotor of the motor. Existing fan designs typically include a stationary housing to house the fan. The housing is a common source of fan noise in such designs.[0003]Every rotating fan radiates noise. Noise is function of a number of factors which include fan speed, size, and blade shape. Most of the acoustic energy reveals itself as frequencies or tones (referred to as “tonal noise”) which contain most of the acoustic power, and are thus annoying to the listener. These tonal modes are the harmonics; the first being the fundamental frequency (f, or the blade passing frequency), the second being 2f, the third is 3f, and so on. In other ...

AI Technical Summary

Benefits of technology

[0007]An advantage of the present invention is the elimination, minimization, or otherwise reduction of noise during operation of the fan, particularly tonal noise. An axial fan according to the present invention exhibits increased performance. An axial fan according to the present invention is cheaper to produce due to a reduced parts count; i.e., there is no housing. The tip ring prevents or otherwise reduces the occurrence of fan stall.

[0008]The invention provides a rotating tip ring attached to the tip of the blades of an axial fan impeller which replaces classical housing structures, and which acts as a silencer by eliminating noise created by rotation of the impeller, particularly tonal noise. To enhance performance, an embodiment of the tip ring is constructed as a circular-arc which starts upstream of the leading edge and which ends downstream of the trailing edge.

Problems solved by technology

The housing is a common source of fan noise in such designs.

Every rotating fan radiates noise.

Most of the acoustic energy reveals itself as frequencies or tones (referred to as “tonal noise”) which contain most of the acoustic power, and are thus annoying to the listener.

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