EXTRACTION FAN AND ROTOR
An extraction fan rotor including a hub and a plurality of vanes extending radially therefrom, wherein said vanes have an aerofoil profile in cross-section.
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The invention relates to the field of design and manufacture of extraction fans for domestic or commercial applications. In particular, the invention relates to an improved rotor blade configuration.
BACKGROUND OF THE INVENTIONAir extraction fans are used in a number of domestic and commercial applications, such as in extracting poisonous gases from fume hoods, or, most commonly, extracting odours and vapour from kitchens, bathrooms and the like.
Typically, these fans are mounted inside a duct and include a rotor, which is designed to impart mechanical energy to air inside the duct to impel air flow through the duct away from the room; and a stator downstream of the rotor which is designed to aid smooth airflow through the duct.
However, many existing designs are not particularly efficient in performing this task. Testing of many prior art designs reveals that domestic kitchen extraction fans are particularly inefficient in moving air through the duct. Very few designs actually maintain significant operational downstream pressure, or suction at the duct inlet, often doing little more than internally agitate the air. Often the fan does little more than suck in some air, agitate it, actually blow it back out of the inlet and then re-extract it again—effectively setting up a recycling stream wherein only a small portion of the agitated air is actually impelled through the duct.
Accordingly, it is an object of the invention to provide an extraction fan that efficiently meets the objective of such devices, by causing a substantially greater proportion of the air to be extracted from the source room and impelled away from the room to its target destination.
SUMMARY OF THE INVENTIONAccording to a first aspect of the invention, there is provided an extraction fan rotor, said rotor including a hub and a plurality of vanes extending radially therefrom, wherein said vanes have an aerofoil profile in cross-section.
The new and inventive use of an aerofoil profile for the vanes of an extraction fan provides a number of functional advantages. These include a significantly greater transfer of mechanical energy from the rotor to the air mass, thereby generating greater pressure and less noise. This is due mainly to the ability of a true aerofoil to maintain linear flow of air at the boundary layer along the vast majority of its surface.
Preferably, the profile of said aerofoil corresponds to a Selig SG6043 aerofoil profile.
Advantageously, the vanes are configured such that the angle of attack of the vanes increases with distance from the centre of the rotor. This appears to resemble a ‘twisting’ of the vane when viewed in a direction from the end of the vane toward the hub. This accounts for a different linear speed at each point of the vane and significantly improves the efficiency of the rotor.
The extraction fan rotor of any preceding claim, wherein the hub has a substantially hemispherical profile. This profile provides particularly good performance, and in particular, where the leading edges of the vanes are coplanar with the apex of the hemispherical profile of the hub.
According to another aspect of the invention, there is provided an extraction fan, said fan including a rotor according with that described above. It is advantageous if the rotor is couples with a downstream stator, wherein said stator includes a core and a plurality of vanes extending radially therefrom, and which make operative connection with the inner wall of a duct, in which the rotor and stator are housed.
Preferably, the cross-sectional profile of said hub is approximately parabolic, and is operably arranged such that the diameter of said hub decreases in the direction of air flow. This profile has been found by the inventors to enhance the ability of the extraction fan to impart energy to the movement of air through the duct. It is thought that the parabolic curvature of the stator helps to reduce turbulence in the air flowing through said duct.
Now will be described, with by way of a specific, non-limiting example, a preferred embodiment of the invention.
The invention provides an improved air extraction fan rotor which alleviates the problems of the prior art principally via a superior vane profile design, and which also features an improved hub and vane configuration.
The invention further provides an improved air extraction fan which incorporates said rotor and which advantageously further includes an improved stator design.
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The inventive rotor vane has been designed to minimise turbulence. As illustrated in the representation of computer-modelled flow path lines in
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However, the crucial difference is the particular profile of the core 115 in
It will be appreciated by those skilled in the art that the foregoing is merely one way in which the invention may be embodied. It will be understood by those skilled in the art that other embodiments may be conceived of which, while differing in some aspects, nevertheless fall within the scope of the invention and the claims appended hereto.
Claims
1. An extraction fan rotor, said rotor including a hub and a plurality of vanes extending radially therefrom, wherein said vanes have an aerofoil profile in cross-section.
2. The extraction fan rotor of claim 1, wherein said aerofoil corresponds to a Selig aerofoil profile.
3. The extraction fan rotor of claim 2, wherein said aerofoil corresponds to a Selig SG6043 aerofoil profile.
4. The extraction fan rotor of claim 1, wherein the angle of attack of the vane increases with distance from the center of the rotor.
5. The extraction fan rotor of claim 1, wherein the hub has a hemispherical profile.
6. The extraction fan rotor of claim 5, wherein the leading edges of the vanes are coplanar with the apex of the hemispherical profile of the hub.
7. An extraction fan comprising a rotor, said rotor including a hub and a plurality of vanes radially extending therefrom, wherein said vanes have an aerofoil profile in cross section.
8. The extraction fan of claim 7, said fan including a stator, wherein said stator includes a core and a plurality of vanes extending radially therefrom.
9. The extraction fan of claim 8, wherein a cross sectional profile of said hub is approximately parabolic, and is operably arranged such that the diameter of said hub decreases in the direction of air flow.
10. (canceled)
11. (canceled)
12. The extraction fan rotor of claim 2, wherein the angle of attack of the vane increases with distance from the center of the rotor.
13. The extraction fan rotor of claim 3, wherein the angle of attack of the vane increases with distance from the center of the rotor.
14. The extraction fan rotor of claim 2, wherein the hub has a hemispherical profile.
15. The extraction fan rotor of claim 3, wherein the hub has a hemispherical profile.
16. The extraction fan of claim 7, wherein said aerofoil corresponds to a Selig aerofoil profile.
17. The extraction fan of claim 7, wherein said aerofoil corresponds to a Selig SG6043 aerofoil profile.
18. The extraction fan of claim 7, wherein the angle of attack of the vane increases with distance from the center of the rotor.
19. The extraction fan of claim 7, wherein the hub has a hemispherical profile.
Type: Application
Filed: Sep 11, 2009
Publication Date: Sep 15, 2011
Applicant: HUNTER PACIFIC INTERNATIONAL PTY LTD (Dural)
Inventors: Philip Cedric Allen (New South Wales), David Glen Stocks (New South Wales), Liam Peter Keene (New South Wales)
Application Number: 13/062,368
International Classification: F01D 5/14 (20060101);