Note: Descriptions are shown in the official language in which they were submitted.
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AXIAL FAN ASSEMBLY
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application claims priority on United
States Provisional Patent Application No. 60/601,615, filed
on August 16, 2004, and on United States Patent Application
No. 11/124,286, filed on May 9, 2005, both by the present
applicant.
BACKGROUND OF THE INVENTION
1. Field of the Invention
to 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
2o 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.
z5 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,
3o the rotor including a hub rotatably engaged with the shaft
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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
to 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
i5 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,
2o 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
25 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
3o 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
35 with another embodiment of the present invention;
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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
s 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;
to 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
15 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
2o 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 adj acent to a stator 16 . All rotors 14 and
25 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
3o 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
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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
to 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
zo 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
3o 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.
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It is also contemplated to provide each stage 12
with its own casing portion, such that an axial fan assembly
could be made up of modular end-to-end stages.
Such a configuration is advantageous in that the
5 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
l0 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
i5 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
3o 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
3s 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.
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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
to 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
zo a pair of cover plates 108 on the rotor 102 will lessen any
turbulence in the axial fan assembly 100.
Referring to Fig. 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
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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
s 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
to 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
15 is intended to embrace all such alternatives, modifications
and variances which fall within the scope of the appended
claims.
