GB2515329A

GB2515329A - An axial fan for bi-directional air movement

Info

Publication number: GB2515329A
Application number: GB1311005.1A
Authority: GB
Inventors: Stephen Lilley; Robert Stephen Hudson
Original assignee: VISION VENTILATION LLP; Flakt Woods Ltd
Current assignee: VISION VENTILATION LLP; Flakt Woods Ltd
Priority date: 2013-06-20
Filing date: 2013-06-20
Publication date: 2014-12-24
Anticipated expiration: 2033-06-20
Also published as: GB201311005D0; GB2515329B

Abstract

An axial air movement fan suitable for a ventilation duct comprises a first, inner array of blades 2 which are contained within an encircling peripheral ring 3 and which define a section of a duct, and a second, outer array of blades 4 extending from the ring 3. The blades 2, 4 are oppositely disposed so that air is moved in one direction by the first set of blades 2 and is moved in a second, opposite direction by the second set of blades 4. The ring 3 may form part of the ventilation duct. A second ring may encircle the second array of blades 4. The fan may be driven by an electric motor. Alternatively, the fan may be driven by wind power, which may be provided by a wind-driven device 6 which rotates the fan in the required direction independent of wind direction. This device may comprise two oppositely-disposed wind bowls 18 projected radially from a vertical shaft 20 extending from the fan hub 1.

Description

An axial fan for bi-directional air movement The present invention relates to an axial air movement fan for use in an air movement duct, and particularly but not exclusively, relates to such a fan adapted for use in a ventilation turret or a rotatable roof cowl to move air bi-directionally in two opposing directions.

It is well known, particularly in natural ventilation solutions to venting closed spaces, such as buildings and shopping centres, to use ventilation turrets positioned on the outside of a roof of a building. Such turrets typically have a plurality of ouvres through which air from the interior of the closed space is vented to the exterior. In natural ventilation systems the air can flow out on the principle that hot air rises, to be a replaced by cooler air entering the space from lower down. In other arrangements, the interior of the space is pressurised slightly, for example by wind entering the building on one side, with the result that the pressurised air is vented to atmosphere through the turret, thus ventilating the building.

Such turrets or cowls also rely on wind to supply external air into the building. Such arrangements have disadvantages since the cooling capacity of natural ventilation is inherently limited and it is also extremely difficult to control the degree of ventilation particularly when reliance is placed on the exterior wind speed.

The present invention seeks to provide improved arrangements for the control of air movement in a ventilation system.

According to the present invention there is provided an axial air movement fan for use in an air movement duct, including: a first array of fan blades radially extending from a hub, the outer peripheries of the fan blades being contained within a peripheral ring secured for rotation with the fan blades and adapted to define a section of a duct, a second array of fan blades extending radially outwardly from the exterior of the peripheral ring, wherein upon rotation of the fan the first array of fan blades is adapted to move air in a first axial direction and the second array of fan blades is adapted to move ar in the opposite axial direction to said first axial direction.

In a preferred embodiment, the second array of blades is contained within an outer peripheral ring adapted to define part of an outer duct.

Preferably, aD of the blades of the first array of fan blades are secured to the peripheral ring.

In a further embodiment, the radially outer peripheries of all of the second array of fan blades are secured to an outer peripheral ring.

In a further embodiment of the invention there is provided an axial air movement fan, in combination with a ventilation turret or a rotatable cowl, which combination is adapted to ventUate an enclosed space, the turret or cowl having openings leading to said duct, through which external air passes to said enclosed space and further openings to exhaust air from said enclosed space. Preferably, said further openings are connected with said outer duct.

Preferably. an electric motor is provided to rotate the fan in a desired direction of rotation.

Alternatively, the combination may include a wind driven device adapted to rotate the fan in a desired direction whatever the direction of the wind.

The wind driven device may comprise at least two spaced vanes mounted on a rotatable shaft secured to the hub of the fan for rotation therewith. Preferably, the shaft is disposed vertically but may be disposed at an angle to the vertical depending upon the local air flow characteristics.

In a preferred embodiment, the spaced vanes each comprises a cup shaped element mounted at opposite ends of a bar secured to the shaft so as to lie in a radial plane, the cup shaped elements each having a wind engaging face, which two wind engaging faces are directed in circumferentially opposite directions.

Preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which:-Figure 1 shows an axial air movement fan, Figure 2 shows a sectional view through the fan iHustrated in Figure 1 in combination with a ventilation turret, Figure 3 shows a schematic perspective view of the apparatus shown in Figure 2, and Figure 4 shows a sectional view through a fan in combination with a ventilation turret.

Referring now to Figure 1, there is shown an axial air movement fan comprising a hub 1 having a first array of blades 2 extending generally radially outwardly from the hub. Five blades are shown but the precise number of blades will depend on the particular installation for which the fan is intended. The profile of the blades is inclined so that when the fan is rotated in a first direction air is driven by the fan in a first axial direction, for example in the embodiment of Figure 2, the air is driven downwardly. The radially outermost peripheries of the blades are secured to a peripheral ring 3 in the form of a cylindrical tube which forms part of a ventilation duct. It is not essential that all the blades are secured to the peripheral ring but preferably all of them are to make a more rigid structure.

On the exterior side of the peripheral ring, a second array of blades is secured to the ring and disposed about the ring with their profiles inclined to drive the air in the opposite axial direction to said first axial direction.

Referring now to Figures 2 and 3 there is shown in schematic form an axial fan in accordance with the present invention in combination with a ventilation turret 5 (shown in cross-section) and a wind driven device 6. The ventilation turret 5 is adapted to be mounted on the roof of a building, for example such as a factory, office, school, shop or shopping centre. The turret 5 as shown is circular in plan view but its precise shape will depend upon the particular installation and could be square, rectangular or even non-uniform. The turret 5 has a closed roof element 7 to prevent the ingress of rain and on all sides a plurality of louvres 8 to provide vents formed by passages between adjacent louvers 8 into the interior of the turret so that wind-driven air can enter the turret and hence the building to which the turret is attached regardless of the direction of the wind.

The turret contains a duct system 9 comprising a generally cylindrical duct 10 directed downwardly into the building. At its upper end the cylindrical part ba has an outwardly extending flange 11 which extends to the outer edge of the turret to thereby divide the louvres into an upper part forming an intake 12 and a Dower part forming an exit or extract 13. The fan as illustrated in Figure 1 is located in the duct passage 10 and is rotatably mounted on a bearing 14 mounted on the duct lOb by a bracket 15. The peripheral ring 3 of the fan is essentially the same diameter as the duct 10 and is located between the duct sections lOs and lOb with just a minimum clearance between the ring of 3 arid the duct sections, In this way the leakage of air through the gaps between the ring 3 and the dud sections is minimized. An extraction duct leading to the exit 13 is located by further ducting 16 to torn an outer duct passage 17. The outer array of fan blades 4 as located in this outer duct passage which is concentric with the duct 10.

In this embodiment, the fan is rotated by an air driven device consisting of a pair of vanes 18 disposed at the ends of a transverse bar 19 secured at its mid point to a shaft 20. The vanes 18 have on one side a wind engaging face and on an opposite side a wind deflecting face. The two wind engaging faces face in circumferentially opposite directions so that, whatever the direction of the wind, the shaft 20 is always turned in the same direction. The shaft 20 passes through a bearing 21 in the roof element of the turret and is secured to the hub 1 of the fan.

Although not shown, the flange 9 may extend outwardly beyond the lcuvres or a further shielding or air guide may be provided to extend the length of the extract passage away from the Iouvres to prevent or minimise the passage of air leaving the extract from re entering the intake and thus inadvertently recirculating stale air through the building.

Referring now to Figure 4 there is shown an alternative embodiment in which the fan is powered by an electric motor 22 mounted in the ducting 10 on mounting 15 to rotate the fan. In this embodiment the fan has an outer peripheral ring 23 in the form of a cylindrical tube section which forms part of the ducting defining an outer duct 24. In the same way as with the first embodiment, the gap between the peripheral ring 23 and the adjacent parts of the outer ducting 24 is kept as small as practical to minimise the leakage of air.

It will be appreciated that many variations may be made to the basic concept. For example the turret may be replaced by a rotating cowl which automatically rotates to take advantage of the prevailing wind. In such a case the ducting may be arranged so that the intake is on the side of the cowl facing the prevailing wind and the outlet or extract extends on the down side of the cowl to assist extraction. Although described in conjunction with a ventiiation turret, it wifl be understood that the fan could be incorporated in a norm& ducting arrangement in a building to combine both the air inlet and air outlet functions into a duct having a common cuter casing.

Claims

CLAIMS1 An axial air movement Ian for use in an air movement duct. including: a first array of fan blades radially extending from a hub: the outer peripheries of the fan blades being contained within a peripheral ring secured for rotation with the fan blades and adapted to define a section of a duct, a second array of fan blades extending radially outwardly from the exterior of the peripheral ring, wherein upon rotation of the fan the first array of fan blades is adapted to move air in a first axial direction and the second array of fan blades is adapted to move air in the opposite axial direction to said first axiai direction.

2. An axial air movement fan as claimed in claim 1 wherein the second array of blades is contained within an outer peripheral ring adapted to define part of an outer duct.

3. An axial air movement Fan according to claim one or claim 2, wherein all ol the blades of the first array of fan blades are secured to the periDheral ring.

4. An axial air movement fan according to claim 2 or 3 when dependent thereon, wherein the radiaHy outer peripheries of all of the second array of Ian blades are secured to the outer peripheral ring.

5. An axial air movement fan according to any one of the preceding claims, in combination with a ventilation turret or a rotatable cowl, adapted to ventilate an enclosed space, the turret or cowl having openings leading to said duct, through which external air passes to said enclosed space and further openings to exhaust air from said enclosed space.

5. An axial air movement fan according to claim 5 wherein said further openings are connected with said outer duct.

7. An axial air movement fan including an electric motor to rotate the fan in a desired direction of rotation.

8. An axial air movement fan as claimed in claim 5 016 including a wind-driven device adapted to rotate the fan in a desired direction whatever the direction the wind is blowing.

9. An axial air movement fan as claimed in claim S wherein the wind driven device comprises 2 spaced vanes mounted on a rotatable shaft secured to the hub of the fan for rotation therewith.

10. An axial air movement fan as claimed in claim 9, wherein the shaft is disposed verticaUy.

11. An axial air movement fan as claimed in claim 9 or 10 wherein the spaced vanes each comprises a cup shaped element mounted at opposite ends of a part secured to the shaft so as to lie in a radial planes, the cup shaped elements each having a wind engaging face which two wind engaging faces are directed in circumferentially opposite directions..

12. An axial air movement fan as claimed in any one of claims 2 to 11 wherein the peripheral ring comprises a cylindrical tube forming part of the first duct.

13. An axial air movement fan as claimed in any one of claims 2 to 12 wherein the outer peripheral ring comprises a cylindrical tube forming part of an outer duct.

14. An axial air movement fan substantially as described herein with reference to and as illustrated in the accompanying drawings.

15. An axial air movement fan in combination with a ventilation turret or cowl, substantially as described herein with reference to and as illustrated in the accompanying drawings.