Title:
Local exhaust ventilator with rotating swirler
Kind Code:
A1


Abstract:
The present invention relates to a local exhaust ventilator which has a rotating swirler to make a swirl flow for increasing exhaust efficiency by expanding an exhaust region. Disclosed is a local exhaust ventilator with a simplified structure, wherein noise due to interference of turbulence is reduced and exhaust gas is removed at a wide area. The local exhaust ventilator includes a disk-shaped swirler rotatably mounted at an exhaust tube, a wing installed at the swirler perpendicular thereto to form a swirl flow, and a driving unit installed at the exhaust tube to rotate the swirler.



Inventors:
Lee, Sang Min (Busan-city, KR)
Lee, Jin Won (Kyungsangbuk-do, KR)
Application Number:
11/026233
Publication Date:
07/28/2005
Filing Date:
12/30/2004
Assignee:
POSTECH Foundation (Kyungsangbuk-do, KR)
Primary Class:
International Classes:
F24F7/00; F04D25/16; F04D29/28; F24F7/02; (IPC1-7): F24F7/007
View Patent Images:
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Primary Examiner:
PROBST, SAMANTHA A
Attorney, Agent or Firm:
K&L Gates LLP-Charlotte (CHARLOTTE, NC, US)
Claims:
1. A local exhaust ventilator comprising: a disk-shaped swirler rotatably mounted at an exhaust tube; a wing installed at the swirler perpendicular thereto to form a swirl flow; and a driving unit installed at the exhaust tube to rotate the swirler.

2. The local exhaust ventilator of claim 1, wherein the wing has a linear structure.

3. The local exhaust ventilator of claim 1, wherein the wing has a curved structure bent toward the central axis of the swirler.

4. The local exhaust ventilator of claim 1, wherein the angle between the rotation axis of the swirler and an inclined side of the swirler is in the range from 60° to 120°.

5. The local exhaust ventilator of claim 4, wherein the wing is spaced apart from the exhaust tube by a predetermined distance, and is elongated outwardly such that the length of the wing is enlarged.

6. The local exhaust ventilator of claim 1, wherein the driving unit has a structure where the swirler is rotatably fitted to the outer circumference of the exhaust tube via a bearing with a circular rack mounted along the top thereof, and a pinion gear is installed at the rotation shaft of a driving motor provided external to the exhaust tube while being coupled to the rack.

7. A local exhaust ventilator comprising: a swirler comprising an annular plate which is placed near an inlet of an exhaust pipe and which rotates about an axis of the exhaust pipe, and a plurality of blades which are placed along an outer rim of the annular plate, each blade being fixed in the radial direction on the annular plate while protruding toward the exhaust pipe; a driving unit installed within the exhaust pipe and having a shaft of the swirler attached thereto for rotating the swirler.

8. The local exhaust ventilator of claim 7, further comprising a swirler cover comprising a ring-shaped top cover which covers a top of the blades and provides a first gap between an outer surface of the exhaust pipe and an inner rim of the top cover, and a ring-shaped bottom cover which covers a bottom of the blades and is positioned apart from the top cover by a second gap.

9. The local exhaust ventilator of claim 8, wherein the swirler cover forms a gap space between the top cover and the bottom cover such that the gap space decreases in height as the distance from the rotational axis of the swirler increases in a radial direction.

10. The local exhaust ventilator of claim 8, wherein the top cover has a hole with a diameter larger than the outer diameter of the exhaust pipe, and the bottom cover has a hole with a diameter close to the inner diameter of the exhaust pipe.

11. The local exhaust ventilator of claim 8, wherein each blade is in a streamlined shape of which the height decreases as a distance from the rotational axis of the swirler is increased in a radial direction.

12. The local exhaust ventilator of claim 11, wherein the top cover of the swirler cover is formed in a shape contoured to the shape of the blade of the swirler.

13. The local exhaust ventilator of claim 8, wherein the outer portion of the blade extends in a radial direction beyond the outer rim of the annular plate.

14. The local exhaust ventilator of claim 8, wherein each blade of the swirler is straight in a radial direction.

15. The local exhaust ventilator of claim 8, wherein each blade of the swirler is curved toward the perimeter of the annular plate.

16. The local exhaust ventilator of claim 8, wherein each blade of the swirler is fixed perpendicular to the surface of the annular plate.

17. The local exhaust ventilator of claim 8, wherein the driving unit comprises a driving motor which is mounted inside the exhaust pipe by brackets, and a driving rod of the driving motor which is fixed at the center of rotation of the swirler and which rotates the swirler.

Description:

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to an exhaust ventilator, and, in particular, to a local exhaust ventilator which has a rotating swirler to produce a swirl flow for increasing exhaust efficiency by expanding an exhaust region.

(b) Description of the Related Art

Generally local exhaust ventilators are utilized in homes, restaurants, and factories that generate pollutants, and, in particular, they can be used where local pollutants are produced far from a main ventilator, where the ventilator is not easily installed near the source of the pollutants, and where the pollutants are produced momentarily.

However, conventional local exhaust ventilators for these purposes have some shortcomings, as follows. The capture speed necessary for the removal of the pollutants decreases rapidly along the axial direction so that the conventional local exhaust ventilators are not effective to eliminate pollutants occurring far from the exhaust pipe, and, therefore, the exhaust pipe needs to be installed as near to the source of the pollutants as possible. The near-installed exhaust pipe, however, can be an obstacle to a working line, and is inefficient for pollutant removal due to workers moving around near the exhaust pipe.

In order to overcome these shortcomings of the conventional local exhaust ventilators, swirl flow has been introduced to an exhaust ventilator, which blows a similar amount of air to that of the exhausted air into the surrounding space. The blown air produces a swirl flow that increases the exhaust efficiency by using the concentrated swirl flow in the intake process of the exhaust ventilator.

Such an exhaust ventilator, however, makes noises resulting from the turbulence generated by the interference between the flow being drawn and the flow being blown in the narrow area under the exhaust pipe, and raises the possibility of spreading the pollutants farther in the space by the blown flow. Also, additional facilities, such as a flow pipe, a filter, and a blower, are required to generate the swirl flow.

SUMMARY OF THE INVENTION

In accordance with the present invention, a local exhaust ventilator is provided that reduces noise due to turbulence-induced interference and removes exhaust gas over a larger area.

Further in accordance with the present invention, a local exhaust ventilator is provided that involves a simplified structure, an economic production cost, and easy installation, maintenance, and repair.

The present invention discloses a local exhaust ventilator comprising a disk-shaped swirler rotatably mounted at an exhaust tube, a wing installed at the swirler perpendicular thereto to form a swirl flow, and a driving unit installed at the exhaust tube to rotate the swirler.

The wing may have a linear structure or a curved structure bent toward the central axis of the swirler.

The angle between the rotation axis of the swirler and an inclined side of the swirler may be in the range from 60° to 120°. The wing may be spaced apart from the exhaust tube a predetermined distance, and be elongated outwardly such that the length of the wing is enlarged.

The driving unit may have a structure where the swirler is rotatably fitted to the outer circumference of the exhaust tube via a bearing with a circular rack mounted along the top thereof, and a pinion gear may be installed at the rotation shaft of a driving motor provided external to the exhaust tube while being coupled to the rack.

In accordance with one form of the present invention, a local exhaust ventilator is provided that increases exhaust efficiency by radial swirl flow entraining air from above an exhaust pipe. A swirler, which is an annular plate with blades, is installed in an exhaust pipe and rotates inside a swirler cover having a peripheral gap along the outer surface of the exhaust pipe and another peripheral gap along the outer rim of the swirler cover.

Further in accordance with one form of the present invention, a local exhaust ventilator is provided in which a protective cover for the rotating swirler secures the safety of workers moving around under the system. In another exemplary embodiment of the present invention, a local exhaust ventilator includes a swirler, a swirler cover, and a driving unit.

The swirler may include an annular plate positioned near an inlet of an exhaust pipe and which rotates about the axis of the exhaust pipe, and a plurality of blades which are placed along an outer rim of the annular plate, each blade being fixed in the radial direction on the annular plate while protruding toward the exhaust pipe.

The swirler cover may include a ring-shaped top cover which covers a top of the blades and provides a first gap between an outer surface of the exhaust pipe and inner rim of the top cover, and a ring-shaped bottom cover which covers a bottom of the blades and is positioned apart from the top cover by a second gap.

The driving unit may be installed within the exhaust pipe and rotates the swirler by way of a swirler shaft attached thereto.

The gap space between the top cover and the bottom cover of the swirler cover may decrease in height as the distance from the rotational axis of the swirler increases in a radial direction.

Also, with a swirler cover, the top cover has a hole larger than the outer diameter of the exhaust pipe, and the bottom cover has a hole with a diameter close to the inner diameter of the exhaust pipe.

Each blade may be formed in a streamlined shape with the height of each swirler blade decreasing as the distance from the rotational axis of the swirler increases in a radial direction, and the top cover of the swirler cover may be formed in a shape contoured to the shape of the swirler blade.

The outer portion of the swirler blade can extend in a radial direction beyond the outer rim of the annular plate. Each swirler blade may be straight in a radial direction or curved toward the perimeter of the annular plate. Each blade of the swirler can be fixed perpendicular to the surface of the annular plate.

The driving unit may include a driving motor mounted inside the exhaust pipe by brackets, and a driving rod of the driving motor fixed at the center of rotation of the swirler and which rotates the swirler.

According to one form of the local exhaust ventilator of the present invention, the swirler is operated with the instant generation of a local contamination source, thereby enhancing the energy efficiency. Furthermore, a tornado-like flow is induced due to the interaction thereof with the ground surface, thereby removing the contamination source generated at the ground in an effective manner.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present invention will become more apparent by describing embodiments thereof in detail with reference to the accompanying drawings, in which:

FIG. 1 is a schematic longitudinal sectional view of a local exhaust ventilation system according to an embodiment of the present invention;

FIG. 2 is a schematic longitudinal sectional view of a local exhaust ventilation system according to another embodiment of the present invention;

FIG. 3 illustrates a swirler installed at the local exhaust ventilator according to an embodiment of the present invention;

FIG. 4 illustrates a variant of the swirler shown in FIG. 3;

FIG. 5 is a perspective external view of a swirler with a protection unit;

FIGS. 6A and 6B illustrate the operational state of the local exhaust ventilator according to an embodiment of the present invention, depending upon the rotation speed of the swirler;

FIGS. 7A and 7B illustrate the operational state of the local exhaust ventilator according to an embodiment of the present invention, depending upon the angle of the swirler;

FIG. 8 is a longitudinal sectional view of a local exhaust ventilator according to an exemplary embodiment of the present invention;

FIG. 9 is a transverse sectional view of a local exhaust ventilator according to an exemplary embodiment of the present invention; and

FIG. 10 is a transverse sectional view of a local exhaust ventilator according to another exemplary embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments of the invention are shown.

As shown in FIG. 1, the local exhaust ventilator includes a swirler 10 installed at an exhaust tube 50 to form a swirl flow, and a driving unit for rotating the swirler 10.

Swirlers are largely classified into an inner drive type and an outer drive type. With the inner drive type shown in FIG. 1, the driving unit is formed with a driving motor 20 fixed to the inner circumference of the exhaust tube 50 via a bracket 21. The swirler 10 rotates around the rotation shaft of the driving motor 20 extended external to the exhaust tube 50 while being fixed thereto.

Furthermore, with the outer drive type shown in FIG. 2, the swirler 10 is installed at the outer circumference of the exhaust tube 50 via a bearing 30 such that it can be rotated. A circular rack 31 is mounted on the top of the swirler 10. A driving motor 32 is installed external to the exhaust tube 50, and a pinion gear 33 is provided at the rotation shaft of the driving motor 32 and coupled to the rack 31.

With the above structure, the driving power of the driving motor 32 is transmitted to the swirler 10 via the rack 31 and the pinion gear 33 to thereby rotate the swirler 10.

The outer drive type is more preferable than the inner drive type in that the swirler, the bearing, and the motor can be modulated in a simplified manner while being attached to the common exhaust tube 50, and motor failure due to the contamination source can be minimized.

The driving unit is not limited to the above structure, but may bear any other structure provided that the swirler 10 can rotate around the central axis of the exhaust tube 50.

The swirler 10 rotates around the exhaust tube 50 to generate a swirl flow. The swirler 10 is formed with a disk body and a wing 11 vertically installed at the bottom of the disk body.

The wing 11 substantially generates the swirl flow when the swirler 10 is rotated. The swirl flow characteristic is varied depending upon the installation direction or location of the wing 11 with respect to the swirler 10. The wing 10 may be installed distant from the central axis of the swirler 10, or close thereto with a linear or curved structure.

FIG. 3 illustrates the curved structure of the wing 11 bent toward the central axis of the swirler 10, and FIG. 4 illustrates the linear structure thereof.

Furthermore, the driving speed (the rotation speed) of the swirler 10 influences the air flow around the exhaust tube 50. It is preferable to rotate the swirler 10 at 1300˜1700 rpm.

A protection cover may be installed external to the swirler to protect the facility, and prevent possible safety failures due to the high speed rotation of the swirler.

As shown in FIG. 5, the cover has a disk-shaped top cover 60 installed at the exhaust tube 50 while being extended to the backside of the swirler 10, a donut-shaped bottom cover 61 placed forward of the wing 11 of the swirler 10, and supports 62 vertically installed at the frontal end of the top cover 60 while being spaced apart from each other by a predetermined distance to support the bottom cover 61.

The swirler 10 and the wing 11 are protected by the top cover 60 and the bottom cover 61, and the lateral side of the wing 11 disposed between the bottom cover and the top cover opens to blow the air for forming the swirl flow.

The operation principle of the local exhaust ventilator according to the present invention will be now explained.

When the swirler 10 is rotated with the exhaust operation shown in FIG. 6A, the air flow made below the swirler 10 is simultaneously influenced by the centrifugal force and the centripetal force due to the exhaust operation so that it is not moved in the radial direction, but is rotated by the rotation speed of the swirler 10. In this case, the flow not moved in the radial direction is like an imaginary flux wall (air curtain).

The local exhaust ventilator is operated while constantly maintaining the amount of exhaust gas so that it takes in the air below the air curtain rather than the air external to the air curtain. The air expelled to the outside by the swirler 10 is introduced to the location of the intake air, and is directed toward the exhaust tube 50. Based on such an operation principle, as shown in FIG. 6A, a secondary swirl flow 40 is formed below the swirler 10 while being rotated in the direction perpendicular to the rotation direction of the swirler 10. Of course, the secondary swirl flow is a part of the primary swirl flow (air curtain) rotated around the axis of the exhaust tube 50.

The secondary swirl flow 40 continually receives the required energy by the swirler 10, and rotates at a predetermined speed so that it has a role of intruding the air below the secondary swirl flow 40 into the exhaust tube 50. In this way, the influential area of the exhaust flow is amplified downwards while enlarging the ventilating area.

The formation location of the secondary swirl flow 40 is varied depending upon the rotation speed of the swirler 10. As shown in FIG. 6B, when the rotation speed of the swirler increases, the effect of the centrifugal force increases so that the secondary swirl flow 40 is generated at the area more distant from the swirler.

With the lower rotation speed of the swirler 10, the secondary swirl flow 40 is formed below the swirler so that a complicated and strong turbulence is formed below the swirler with increased noise. Furthermore, as the contaminants are diffused within the turbulence, the contamination source in the exhaust flow is liable to be diffused. By contrast, when the secondary swirl flow 40 is formed distant from the swirler, the noise is diminished due to the clear isolation of the secondary swirl flow 40 from the exhaust flow, and the diffusion possibility of the contamination source due to the swirler is removed. Furthermore, a wide ventilating area is formed due to the secondary swirl flow 40 spread external to the swirler.

The flow characteristic is influenced by the shape of the swirler, that is, the size and axial angle thereof. As the radius of the swirler is increased, the swirl flow becomes stronger, and the exhaust depth becomes enlarged at the same rotation speed. As shown in FIG. 6A, the swirler 10 commonly proceeds perpendicular to the axis thereof.

As shown in FIG. 7A, when the angle θ between the rotation axis and the inclined side of the swirler 10 is in the range from 60° to 90°, the secondary swirl flow 40 can be brought downwards close to the ground. As shown in FIG. 7B, the angle θ between the rotation axis and the inclined side of the swirler 10 is in the range from 90° to 120°, the exhaust depth is decreased compared to the case where the inclined side is angled at 90°, but the secondary swirl flow 40 is stabilized so that the noise is reduced and the exhaust flow is also formed in a stable manner.

It is also preferable to shape the wing 11 attached to the swirler 10 correctly. With the rotation of the swirler 10, the flow around the swirler is rotated due to the Wing 11 attached to the swirler. Therefore, with a larger sectional area of the wing, the amount of flow to be rotated is increased. As the rotation speed of the swirler is higher with the larger radius, the outer length of the wing should be elongated. Furthermore, in order to prevent the contamination source from being diffused due to the swirler, the wing should be attached to the swirler while being spaced apart from the exhaust tube 50 by a predetermined distance. In order to extrude a larger amount of flow to the outside, it may be considered to make a linear wing as well as a curved wing.

FIG. 8 is a longitudinal sectional view of a local exhaust ventilator according to an exemplary embodiment of the present invention, and FIG. 9 is a transverse sectional view of a local exhaust ventilator according to an exemplary embodiment of the present invention.

According to the embodiment, a local exhaust ventilator 60 includes a swirler 70 which is installed in the vicinity of an inlet of the exhaust pipe 62 and produces a swirl flow while rotating, a swirler cover 80 which covers the top and the bottom of the blades 77 of the swirler 70, and a driving unit 90 which is mounted within the exhaust pipe 62 and rotates the swirler 70.

The swirler 70 includes an annular plate 73 which is placed near the end of the exhaust pipe 62 and rotates about the axis of the exhaust pipe 62, and a plurality of blades 77 which are placed along the outer rim of the annular plate 73 and are attached vertically in a radial direction on the annular plate 73. Each blade 77 protrudes toward the exhaust pipe 62.

The annular plate 73 has a hole of at least the same size as the inner diameter of the exhaust pipe 62, and the outer diameter of the annular plate 73 is larger than that of the exhaust pipe 62. The annular plate 73 has a plurality of spokes 75 connecting the center of rotation 71 of the swirler 70 to the inner rim of the annular plate 73. Because the spokes 75 are positioned at the inlet of the exhaust pipe 62, about three spokes, as seen in FIG. 8 and FIG. 9, are preferable, in order not to block the incoming flow through the inlet of the exhaust pipe 62.

The blades 77 placed around the outer rim of the annular plate 73 are preferably fixed vertically on the top surface of the annular plate 73, with the outer portion of the blades extending in the radial direction beyond the outer rim of the annular plate 73. Each blade 77, as seen in FIG. 8, has a streamlined shape of which the height decreases with an increase in the distance from the rotational axis. Because the blade 77 serves as a working part of the swirler 70 for producing the swirl flow, the blade 77 with the streamlined shape can draw a large quantity of air from above the inlet of the exhaust pipe 62 and then exhaust it in a radially outward direction.

Also, each blade 77 is straight in the radial direction as seen in FIG. 9.

The swirler cover 80 includes a top cover 82 covering the top of the blade 77, and a bottom cover 86 covering the bottom of the blade 77.

The top cover 82 is in a ring shape which has a hole larger than the outer diameter of the exhaust pipe 62, and is positioned to form a first gap I between the outer surface of the exhaust pipe 62 and the inner rim of the top cover 82. And, the bottom cover 86 is in a ring shape which has a hole with a diameter similar to the inner diameter of the exhaust pipe 62, and is positioned apart from the top cover 82 to form a second gap II between the outer rims of both the bottom cover 86 and the top cover 82.

In particular, the top cover 82 is in a rounded shape contoured to the shape of the blades 77 such that the height of the top cover 82 increases as the distance from a center of rotation 71 of the swirler 70 decreases, and the height of the top cover 82 decreases as the distance from the center of rotation 71 of the swirler 70 increases. The bottom cover 86 is formed in a flat shape, and therefore the gap space between the top cover 82 and the bottom cover 86 decreases as the distance from the rotational axis of the swirler decreases in the radial direction. Due to this particular shape, the swirler cover 80 makes the air drawn by the swirler 70 accelerate through the radially contracted space and produces the strong swirl flow when the air is expelled to the outside.

The swirler cover 80 also protects the blade 77 by covering both the top and bottom of the blade 77.

The top cover 82 is mounted on the outside of the exhaust pipe 62 by a plurality of supporting rods 58. In order to not block the air flow through the first gap I between the outer surface of the exhaust pipe 62 and the top cover 82, the supporting rods 58 are preferably positioned equidistant to each other, and four or six supporting rods may be used.

A plurality of guide blades 84 connect the top cover 82 to the bottom cover 86 at the outer portions of both the top cover 82 and bottom cover 86. The guide blade 84 positioned in the radial direction along the perimeter is attached vertically to both the top cover 82 and the bottom cover 86. It is preferable for the guide blades 84 to be uniformly placed equidistantly. Each of the guide blades 84 may be placed at a position corresponding to each blade 77, and the number of guide blades 84 may be the same as the number of the blades 77. However, there is no restriction in the number and the position of the guide blades 84 with respect to the blades 77. Therefore, each of the guide blades 84 seen in FIG. 9 is straight in the radial direction in the illustrated embodiment.

The swirler 70 is rotated by a driving unit, as illustrated in FIG. 8, including a driving motor 93 which is mounted inside the exhaust pipe 62 by brackets 91, and a driving rod 95 of the driving motor 93 that extends to the end of the exhaust pipe 62 and is fixed at the center of rotation 71 of the swirler 70. However, the driving unit 90 of the present invention does not necessarily have this configuration only, and it can have any configuration such that it can rotate the swirler about the axis of the exhaust pipe.

On the other hand, the swirler 70, the swirler cover 80 and the driving unit 90, as described above, can be assembled in a single module which can be attached to an existing exhaust pipe directly and used immediately.

As seen in FIG. 10, the local exhaust ventilator of the illustrated embodiment is the same as that of the previous embodiment except for the shapes of the blades 102 attached vertically to the annular plate 73 and of the guide blades 104 connecting the top cover 82 to the bottom cover 86 around the outer rims thereof and forming a gap between them.

The blades 102 of the swirler in the illustrated embodiment are curved toward the perimeter of the annular plate 73, and the guide blades 104 are also curved toward the perimeter of the bottom cover 86. It is preferable that the curvature of the blades 102 is opposite to that of the guide blades 104. The opposite curvature plays a role in helping the air accelerated by the swirler 70 to have a strong swirl flow.

Following is the working principle of the local exhaust ventilator of the present invention.

Under the proper working state, as illustrated in FIG. 8, the flow a above the inlet of the exhaust pipe 62 is pulled by the rotating swirler 70 through the first gap I to the inside of the swirler cover 80, and is pushed radially by the swirler blade 77 to the outside through the second gap II while forming the swirl flow b. At this time, the air is accelerated and expelled by the swirler cover 80 and the guide blade 84 while maintaining the swirl component. The flow below the inlet of the exhaust pipe 62 is divided into two kinds of flow by the accelerated outgoing swirl flow: one flow c is pushed radially outward; and the other flow d is entrained by the exhaust ventilator 60 toward the axis of the exhaust pipe 62. Because the flow rate of the exhaust ventilator 60 is kept constant under the working state, the exhaust ventilator 60 exhausts an additional volume of air which is the same amount as the air pushed in the radial direction. Therefore, the interaction between these two kinds of flow expands the exhaust region in the axial direction.

The radially pushed swirl flow c and d moves toward the axis of the exhaust pipe 62 because of the exhausting process, and forms the secondary swirl flow e under the swirler 70. The secondary flow e keeps rotating at a constant speed with the energy supplied by the swirler 70, and plays a role in pushing the air under the secondary swirl flow into the exhaust pipe 62. By this principle, the air is accelerated toward the inlet of the exhaust pipe 62 so that the exhaust region expands.

Also, as the swirl flow that is widely spread in the radial direction is entrained toward the axis of the exhaust pipe 62 by the exhausting process, the rotation of the swirl flow becomes more vigorous by the conservation of the angular momentum. This causes a low pressure distribution under the exhaust pipe 62 which strongly boosts the exhaust flow.

As explained above, the local exhaust ventilator using the swirler of the present invention can enhance the performance of exhaust ventilation by making a radial swirl flow which is produced by a swirler, a swirler cover, and air entrained from above the inlet of an exhaust pipe. Also, it can prevent pollutants from being rebroadcast and can make it possible for the efficient removal of the pollutant occurring in a local area.

Since the swirler, the swirler cover, and the driving unit can be assembled in a single module which can be simply attached to an existing exhaust pipe, there is no need for further investment in the facility.

In addition, the safety of workers near the local exhaust ventilator can be secured by the swirler cover which surrounds the swirler blades that rotate at a high speed.

Although various embodiments of the present invention have been described in detail hereinabove, it should be dearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the art will still fall within the spirit and scope of the present invention, as defined in the appended claims.