CN110892159B

CN110892159B - Axial flow fan of cooling tower with hollow disc/annular structure

Info

Publication number: CN110892159B
Application number: CN201880030912.XA
Authority: CN
Inventors: L·马蒂尼; D·施特劳斯; R·德·阿劳约·佩雷拉·安德雷德
Original assignee: Evapco Inc
Current assignee: Evapco Inc
Priority date: 2017-04-21
Filing date: 2018-04-23
Publication date: 2022-05-03
Anticipated expiration: 2038-04-23
Also published as: CN110892159A; EP3612731A1; EP3612731A4

Abstract

A cooling tower fan hub having a ring and a disk with a hollow and open groove in the ring and/or disk to reduce the natural frequency of the fan and avoid increasing several loads affecting the fan during operation. The number, size and shape of the hollows can be adjusted so that the natural frequency of the fan remains around the original value.

Description

Axial flow fan of cooling tower with hollow disc/annular structure

Background

Technical Field

The invention relates to a cooling tower fan.

Disclosure of Invention

The present invention relates to cooling tower axial flow fans, typically between 60 and 156 inches in diameter. These fans typically have a central boss, a hub and a number of evenly distributed blades. A common problem for these fans is the occurrence of high vibrations and even structural failures in the case of certain rotational frequencies/rotational speeds at which the fan cannot operate for a long time (called "locked rotation"). That is, using a variable frequency drive, the speed of the fan can be increased between 0RPM and its rated value. At a certain frequency, the resulting resonance can lead to high displacements and strong stresses into the several parts that make up the wind turbine. Typically, the end result of resonance is fatigue failure of the component.

The inventors of the present invention have aimed at providing a cooling tower without locked rotation. For the purposes of this invention, the cooling tower fan will operate at acceptable (customer-defined) vibration levels throughout the range of rotational speeds (0RPM to its rated or maximum safe rotational speed).

The present invention is a hub for a cooling tower fan comprised of a disk bolted to a central boss, in which a plurality of hollows and grooves (either laser cut or water cut) are opened to reduce the natural frequency of the fan and avoid increasing several loads affecting the fan during operation. The number, size and shape of the hollows can be adjusted so that the natural frequency of the fan remains around the original value. The present invention includes a structure according to which the hollow and the groove "overlap" each other, thereby forming a star-shaped rotor. According to another embodiment, the rotor can be constituted by a hollow without grooves only. The ring may similarly be modified using only grooves. The grooves in the annular member may have the same or opposite concave orientation as the corresponding grooves into the disc. In each of the configurations of the present invention, a sealing disk is provided to avoid backflow.

Accordingly, in accordance with the present invention, there is provided a cooling tower axial fan hub comprising a first disk configured to be connected to a central boss; a second disk bolted to the first disk by a connecting element of the plurality of fan blades, the connecting element being sandwiched between the first disk and the second disk; a sealing disk attached to the second disk to inhibit backflow; wherein the first disk is an annular outer ring connected to an inner ring by a plurality of spokes, wherein the spokes define a plurality of hollow spaces in the first disk, the inner ring configured to connect to the central boss; wherein the second disc consists only of an annular ring having an inner diameter and an outer diameter, wherein the outer diameter of the annular ring is substantially equal to the outer diameter of the annular outer ring of the first disc (fig. 1-4).

According to the present invention, there is also provided a cooling tower axial fan hub wherein the first and second disks have a constant outer diameter with no notches or grooves at their peripheral edges (fig. 2).

According to the present invention there is also provided a cooling tower axial fan hub wherein the second disc annular ring has a constant inner diameter with an inner peripheral edge free of notches or grooves (fig. 3).

According to the present invention, there is also provided a cooling tower axial fan hub wherein the first disk has an outer peripheral edge with regularly spaced notches (fig. 1 and 2).

According to the present invention, there is also provided a cooling tower axial fan hub wherein the second disc comprises only an annular ring of constant outer diameter, an outer peripheral edge without notches or grooves and an inner peripheral edge with regularly spaced notches (fig. 1 and 2).

According to the present invention, there is also provided a cooling tower axial fan hub having a first star plate configured to be connected to a central boss; a second star plate bolted to the first plate by a connecting element of the plurality of fan blades, wherein the connecting element is sandwiched between the first plate and the second plate; a sealing disk attached to the second disk to inhibit backflow; wherein the first and second disks are characterized by: a plurality of corresponding and regularly spaced fan blade attachment sections/spokes, a first disk section/spoke extending distally an equal distance from the central boss attachment and the second disk section/spoke extending distally an equal distance from the open central core, each pair of adjacent spokes defining a V-shaped space therebetween (fig. 5 and 6).

Drawings

Fig. 1 shows a perspective view of the top of a first embodiment of the invention.

Fig. 2 shows a perspective view of the bottom of the first embodiment of the invention.

Fig. 3 shows a perspective view of the top of a second embodiment of the invention.

Fig. 4 shows a perspective view of the bottom of the first embodiment of the invention.

Fig. 5 shows a perspective view of the top of a third embodiment of the invention.

Fig. 6 shows a perspective view of the bottom of a third embodiment of the invention.

Detailed Description

Fig. 1 and 2 show a cooling tower fan with blades 3 connected to a hub 5, which hub 5 in turn is connected to a central boss 7. The hub 5 comprises a disc 9 and a ring 11, the disc 9 preferably being bolted to the central boss 7. The connecting portions 13 of the blades 3 are attached to the hub 5, preferably sandwiched between the disc 9 and the ring 11. The disc 9 and ring 11 are planar elements having a thickness between 5/32 inch (4mm) and 3/4 inch (19mm) and a diameter between 20 inch (510mm) and 72 inch (180 mm). The ring 11 is generally annular in shape, having a preferably circular outer periphery 15 and an inner periphery 17, the outer periphery 15 having a constant outer diameter, the inner periphery 17 being defined by grooves or notches 19 regularly spaced around the inner periphery 17. The inner periphery 17 of the ring 11 defines an opening 18 that is free of any annular structure.

The disc 9 comprises a central portion 21 configured to be bolted to the central boss 7. The central portion 21 is connected to the outer annular portion 23 by a plurality of spokes 25. The outer disc ring portion 23 has a constant inner diameter with spokes 25 inserted therein. The outer periphery 29 of the annular portion 23 of the disc 9 is generally circular but is characterised by grooves or recesses 19 regularly spaced around the outer periphery 29 of the annular portion. The plurality of spokes 25 define hollow or open spaces 26 in the disk 9, which hollow or open spaces 26 are devoid of any disk structure. As mentioned above, the fan hub 5 (comprising the ring 11 and the disk 9) is connected to the central boss 7 at the central portion 21 of the disk 9. The fan blades 3 are bolted between the ring 11 and the outer annular portion 23 of the disk 9. A sealing disk 31 may be attached to the ring 11 (see fig. 3) to inhibit backflow.

In fig. 3 and 4 different embodiments are shown, wherein the outer and inner peripheries (15 and 17 respectively) of the ring 11 have a constant diameter, i.e. do not have grooves or recesses, and the outer periphery 15 of the ring-shaped part of the disc 9 likewise has a constant diameter and does not feature grooves or recesses. In other respects, the hub 5 comprising the disc 9 and the ring 11 is connected to the central boss 7 and the fan blades 3 in the same way as in fig. 1 and 2.

Fig. 5 and 6 show a sector hub 5 with a star ring 11 and matching a star disk 9. According to the present embodiment, both the ring 11 and the disk 9 have a plurality of star spokes 33 corresponding to the number of attached fan blades. Neither the ring 11 nor the disc 9 has an annular outer ring. Instead, the distal end portion of the spoke is connected to the fan blade attachment portion 13. The disc 9 has a central portion configured to be bolted to a central boss. The ring 11 defines a circular central opening 35. As shown in fig. 6, a sealing disk 31 may be attached to the disk to prevent backflow.

Claims

1. A cooling tower axial flow fan hub comprising:

a first disk configured to be connected to a central boss;

a second disk bolted to the first disk by a connecting element of a plurality of fan blades, the connecting element sandwiched between the first disk and the second disk;

a sealing disk comprising an annular ring having an inner diameter and an outer diameter and attached to the second disk;

the first disk comprises two concentric annular rings interconnected by a plurality of spokes defining a plurality of hollow spaces in the first disk, the two concentric annular rings comprising an annular outer ring and an annular inner ring configured to connect to the central boss;

the second disk includes only an annular ring having an inner diameter and an outer diameter, the annular ring of the sealing disk being sized to cover the open area between the second disk annular ring inner diameter and the central boss.

2. The cooling tower axial fan hub of claim 1, wherein said first and second disks have a constant outer diameter with a peripheral edge that is free of notches or grooves.

3. The cooling tower axial flow fan hub of claim 2, wherein said second disk annular ring has a constant inner diameter with an inner peripheral edge that is free of notches or grooves.

4. The cooling tower axial fan hub of claim 1, wherein said first disk has an outer peripheral edge with regularly spaced notches.

5. The cooling tower axial fan hub of claim 4, wherein said second disk comprising only an annular ring has a constant outer diameter and an outer peripheral edge without notches or grooves, and an inner peripheral edge with regularly spaced notches.

6. A cooling tower axial flow fan hub comprising:

a first disk configured to be connected to a central boss;

the first disk includes a plurality of corresponding and regularly spaced fan blade connection sections that each extend distally an equal distance from the central boss connection and the second disk fan blade connection sections extend distally an equal distance from the open central core, each pair of adjacent first disk fan blade connection sections defining a V-shaped hollow space and each pair of adjacent second disk fan blade connection sections defining a V-shaped hollow space, the annular ring of the sealing disk being sized to cover each V-shaped hollow space defined by each pair of adjacent second disk fan blade connection sections.