Axial fan assembly

Abstract

An axial fan assembly comprises a rotating shaft adapted to be actuated in rotation and axial fan assembly sections. Each assembly section has one rotor, the rotor including a hub rotatably engaged with the shaft and a plurality of blades radially extending from the hub; and one stator in proximity and downstream of each rotor. The stator includes an inner ring rotationally receiving the shaft. A plurality of vanes radially are connected the inner ring, such that a swirl of a flow of air produced by the rotor is reduced when the flow of air goes through the stator. An end-to-end configuration is provided between the axial fan assembly sections so as to increase a static pressure at the outlet of the axial fan assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority on U.S. Provisional Patent Application No. 60/601,615, filed on Aug. 16, 2004, by the present applicant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fan assemblies, particularly to axial exhaust fans.

2. Background Art

Exhaust systems usually comprise a number of elements causing resistance to the airflow, such as dampers, filters, coils, etc. Exhaust fans (a.k.a., axial fans) thus need to be able to produce an airflow at a great pressure in order to overcome such resistance. Because they are able to overcome a greater static pressure, centrifugal fans are typically used as exhaust fans. However, centrifugal fans are substantially more expensive to manufacture than axial fans and take more space.

SUMMARY OF INVENTION

It is therefore an aim of the present invention to provide an improved axial exhaust fan.

Therefore, in accordance with the present invention, there is provided an axial fan assembly comprising a rotating shaft adapted to be actuated in rotation; at least a first and a second axial fan assembly section, each assembly section having: at least one rotor, the rotor including a hub rotatably engaged with the shaft and a plurality of blades radially extending from the hub; and one stator in proximity and downstream of each rotor, the stator including an inner ring rotationally receiving the shaft, an outer ring concentric with the inner ring, and a plurality of vanes radially connecting the inner ring and the outer ring, such that a swirl of a flow of air produced by the rotor is reduced when the flow of air goes through the stator; and an end-to-end configuration between the axial fan assembly sections so as to increase a static pressure at the outlet of the axial fan assembly.

Further in accordance with the present invention, there is provided an axial fan assembly comprising a rotating shaft; at least one rotor, the rotor including a hub rotatably engaged with the shaft and a plurality of blades radially extending from the hub; and one stator in proximity and downstream of each rotor, the stator including an inner ring rotationally receiving the shaft, an outer ring concentric with the inner ring, and a plurality of vanes radially connecting the inner ring and the outer ring, the vanes having a cross-section becoming progressively more arcuately curved toward the outer ring, such that a swirl of a flow of air produced by the rotor is reduced when the flow of air goes through the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof and in which:

FIG. 1 is a longitudinal section view of an axial fan assembly in accordance with an embodiment of the present invention, with a belt drive;

FIG. 2 is an exploded view of the axial fan assembly of FIG. 1;

FIG. 3 is a plan view of a stator in accordance with another embodiment of the present invention;

FIG. 4 is a sectional view of the stator, taken along cross-section lines IV-IV of FIG. 3;

FIG. 5 is a longitudinal section view of an axial fan assembly in accordance with another embodiment of the present invention, with a belt drive;

FIG. 6 is an exploded view of the axial fan assembly of FIG. 5;

FIG. 7 is a plan view of a rotor of the axial fan assembly of FIG. 5;

FIG. 8 is a longitudinal sectional view of the rotor of FIG. 7 taken along sectional line VIII-VIII of FIG. 7; and

FIG. 9 is an enlarged sectional view of an interconnection between a hub and a blade of the rotor of FIG. 7, with a cover plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1 and 2, an axial fan assembly generally indicated at 10 is composed of a plurality of stages 12 assembled in an end-to-end configuration. The fan assembly preferably includes at least two or three stages 12 (i.e., axial fan assembly sections), as the embodiment illustrated herein does (three stages 12). Each stage 12 is composed of a rotor 14 located upstream of and adjacent to a stator 16. All rotors 14 and stators 16 are aligned, with a common rotating shaft 18 passing through the center of each of the rotors 14 and stators 16. A direction of flow of fluid through the axial fan assembly 10 is illustrated as A.

Each rotor 14 comprises a hub 30 which is rotationally engaged with the shaft 18. The hub 30 supports a plurality of radially extending blades 32, so that rotation of the shaft 18 causes a rotation of the blades 32. Each blade 32 defines a leading edge 34, a trailing edge 36 and a blade tip 38. The blades 32 preferably have an appropriate airfoil profile, as is known in the art. The blades 32 also preferably have a twist.

Referring to FIGS. 3 and 4, each stator 16 comprises an inner ring 50 in which the shaft 18 is free to rotate, and may have an outer ring 52 concentric with the inner ring 50, with the direction of flow illustrated as A. A plurality of vanes 54 extend between the inner ring 50 and the outer ring 52 and are attached thereto. The vanes 54 each have a leading edge 56 and a trailing edge 58. The vanes 54 have a curve (as seen in FIG. 4) from the leading edge 56 to the trailing edge 58. As best seen in FIG. 1, the vane leading edges 56 are located in close proximity to the blade trailing edges 36.

By adding more stages 12 (i.e., axial fan assembly sections) to the fan 10 in the end-to-end configuration, the static pressure produced can be increased without increasing the blade tip speed. Since, in a preferred embodiment, each stator 16 cancels the swirl of the airflow caused by the preceding upstream rotor 14, increasing the number of stages will increase the airflow pressure.

As best seen in FIG. 2, the fan assembly 10 has a pair of shells 60, which are assembled to enclose the rotors 14, stators 16 and the shaft 18, thereby defining the tunnel of the axial fan assembly 10.

Moreover, the shells 60 define an enlarged intake 62 for the fan assembly 10. By the presence of a belt 64 for a belt drive, and associated components such as the motor 66, the shaft pulley 68, and the covers 70, some tunnel volume is lost, whereby the flaring shaft shape of the enlarged intake 62 compensates for this loss of volume.

The shells 60 are also provided with access doors 72. The access doors 72 facilitate access to an interior of the fan assembly 10, for maintenance. Accordingly, maintenance interventions, such as the replacement of a bearing, is facilitated by the presence of access doors 72.

It is also contemplated to provide each stage 12 with its own casing portion, such that an axial fan assembly 10 could be made up of modular end-to-end stages.

Such a configuration is advantageous in that the axial fan assembly 10 is modular, whereby additional rotor 14/stator 16 assemblies may be added to the axial fan assembly 10 for the assembly 10 to overcome greater static pressures.

Although not illustrated, the axial fan assembly 10 may be actuated by a motor directly on the shaft 18, as an alternative to the belt drive.

Referring now to FIG. 5 to 9, an axial fan assembly in accordance with another preferred embodiment is generally shown at 100 (FIG. 5). A plurality of components are similar in both the axial fan assembly 10 and the axial fan assembly 100, whereby like numerals will represent like components.

Referring to FIG. 5 to 9, a rotor used with the axial fan assembly 100 is generally shown at 102. The rotor 102 of the preferred embodiment is used in a configuration similar to that illustrated in FIG. 1, in which a sequence of rotors and stators are axially positioned in a cylindrical housing so as to define an axial fan assembly.

For instance, the rotor 102 has a hub 104 by which the rotor 102 is mounted to the shaft 18 of the axial fan assembly 100 (FIG. 5), such that actuation of the shaft 18 will cause a rotation of the rotor 102 about a longitudinal axis of the shaft.

The rotor 102 has a plurality of blades 106 projecting radially from the hub 104. It is best seen from FIGS. 6 and 7 that axial cover plates 108 are provided on both sides of the rotor 102, in such a way that only a portion of the blades 106 extends beyond an outer periphery of the axial cover plates 108. This is also visible in FIG. 5, in which the axial fan assembly 100 shows only a portion of the blades 106, as a remainder of the blades 106 is hidden behind the axial cover plates 108.

The axial cover plates 108 are provided in order to increase the static pressure of the axial fan assembly 100. More specifically, it is known that the tangential velocity of any point on any one of the blades 106 increases from a center of the rotor 102 to a tip of the blades 106. Accordingly, the downstream pressure induced by the rotor 102 is greater opposite the tip of the blades 106 than opposite the center of the rotor 102.

Considering that the pressure differential is nonnegligible, a back flow of air occurs near the center of the hub 104. The use of the axial cover plates 108 reduces the back flow passage area at the rotor 102, due to the fact a central portion of the hub 104 is covered by the axial plates 108. Therefore, the axial fan assembly 100 will produce a greater static pressure with the cover plates 108 than without the cover plates 108.

Moreover, although two cover plates 108 are illustrated on the rotor 102, it is contemplated to provide only one of the cover plates 108. However, the presence of a pair of cover plates 108 on the rotor 102 will lessen any turbulence in the axial fan assembly 100.

Referring to FIGS. 8 and 9, it is illustrated how the blades 106 can be connected to the hub 104 in view of the presence of the axial cover plates 108. More specifically, the blades 106 are shown having a blade connector 110. A securing ring 112 cooperates with the hub 104 to grasp the blade connectors 110, whereby the blades 106 are secured to the hub 104. Fasteners 114 are used to connect the securing ring 112 to the hub 104 with the blades 106 held therebetween. The axial cover plates 108 are also retained to the hub 104 by way of the fasteners 114.

It is contemplated to use the rotor 102 with an associated stator, such as the stator 120, in an axial fan assembly. However, to optimize the operation of the axial fan assembly 100, cover plates similar to those illustrated at 108 in FIG. 6 can be provided for the stators used in combination with the rotors 102. Accordingly, an annular tunnel is defined to facilitate air flow through the axial fan assembly 100.

Additional rotor/stator pairs can be added in a sequence similar to the axial fan assembly 10 of FIG. 1, so as to increase the static pressure resulting from the operation of the axial fan assembly. The axial fan assembly of FIG. 5 is shown in a belt-drive configuration. Other types of drives, such as a direct drive, can be used.

The embodiments of the invention described above are intended to be exemplary. Those skilled in the art will therefore appreciate that the foregoing description is illustrative only, and that various alternatives and modifications can be devised without departing from the spirit of the present invention. Accordingly, the present is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

Claims

1. An axial fan assembly comprising:

a rotating shaft adapted to be actuated in rotation;

at least a first and a second axial fan assembly section, each assembly section having: at least one rotor, the rotor including a hub rotatably engaged with the shaft and a plurality of blades radially extending from the hub; and one stator in proximity and downstream of each rotor, the stator including an inner ring rotationally receiving the shaft, and a plurality of vanes radially connected to the inner ring, such that a swirl of a flow of air produced by the rotor is reduced when the flow of air goes through the stator; and an end-to-end configuration between the axial fan assembly sections so as to increase a static pressure at the outlet of the axial fan assembly.

2. The axial fan assembly according to claim 1, wherein the vanes have a cross-section becoming progressively curved from a trailing edge to a leading edge.

3. The axial fan assembly according to claim 1, wherein the fan assembly comprises at least three of the axial fan assembly section in the end-to-end configuration.

4. The axial fan assembly according to claim 1, wherein the swirl is eliminated by the stator.

5. The axial fan assembly according to claim 1, wherein the rotor vanes are defined so as to have a curve.

6. The axial fan assembly according to claim 1, wherein each of the rotor has at least one cover plate covering a central portion of the rotor to reduce a back flow passage area through the rotor.

7. The axial fan assembly according to claim 6, wherein each of the rotor has one of the cover plates on each side thereof.

8. The axial fan assembly according to claim 6, wherein each of the stator has at least one cover plate covering a central portion of the stator, whereby a flow passage in the fan assembly has an annular cross-section.

9. The axial fan assembly according to claim 8, wherein each of the rotor has one of the cover plates on each side thereof.

10. The axial fan assembly according to claim 6, wherein each of the blades has a connector end so as to be connected to the hub of the rotor.

11. The axial fan assembly according to claim 10, wherein the connector end is retained between a securing ring and the hub.

12. The fan assembly according to claim 11, wherein a set of fasteners secure both the securing ring and the cover plates to the hub.

13. The axial fan assembly according to claim 1, wherein the axial fan assembly sections are enclosed in a tunnel consisting of a pair of longitudinal shells.

14. The axial fan assembly according to claim 13, wherein an intake portion of the tunnel has a flared shape.

15. The axial fan assembly according to claim 13, wherein at least one access door is provided in any one of the longitudinal shells, to provide access to an interior of the tunnel.