WO1989011926A1

WO1989011926A1 - Ventilating system for mechanical local exhaustion

Info

Publication number: WO1989011926A1
Application number: PCT/DK1989/000144
Authority: WO
Inventors: Niels Raagaard
Original assignee: Hansen & Raagaard Aps
Priority date: 1988-06-08
Filing date: 1989-06-08
Publication date: 1989-12-14
Also published as: DK312288D0; AU3839389A

Abstract

In order to be able to perform an effective mechanical local exhaustion with simple means, according to the invention there is used a system with an airstream (4) which has a substantially uniform speed at the same distance from the injection, and which cannot be mixed with a central upwardly-directed column of exhaust air (11). This is achieved by positioning the injection nozzles (5, 8), possibly in concentric rings, around the exhaust channel (6, 7), and by allowing the injection and the exhausting to take place in the same plane, and by allowing the direction of injection to run tangentially to the airstream (4). By means of a compact and simple system, a stable flow is hereby ensured over relatively great distances.

Description

VENTILATING SYSTEM FOR MECHANICAL LOCAL EXHAUSTION

The invention relates to a ventilating system for mechanical local exhaustion of gases such as vapour, steam, airborne suspensions and the like, said system partly comprising a number of injection nozzles and/or blowers which give the air a downwards flow, and partly one or more exhaustion channels which, from above, suck out around the axis of the flow.

Mechanical local exhaustion of this kind is used wherever there is a need for the exhaustion of a spatially limited zone, without such exhaustion giving rise to inconveniences in the form of draught in the room. In order to achieve this, a cyclone effect is utilized to generate a column of air which moves from the zone area and upwards along a perpendicular line and directly out through an ejection channel. Alternatively, the cyclone effect is used to create the possibility of filtration of the air.

There is hereby achieved an economically satisfactory exhaustion and cleaning by means of simple means.

From SE document no. 419,830 and DE PS no. 3249664 a system is known for the exhaustion of polluted air, whereby the flow of air introduced via nozzles generates a co-stream of air which is thereafter sucked into a cylinder where it creates a rotating air space with the cyclone effect. The co-stream is utilized to remove the polluted air.

However, this method has the disadvantage that the system must be placed either at the side of or partly under the source of the pollution, whereby there arises a considerable limitation in the work area, and also there will be a limitation in the height of the influx of air, which can be a drawback where the polluted air has a strongly upwardly-directed speed, such that a risk will arise that a greater or smaller amount of polluted air will remain in the room.

In order to avoid these disadvantages, it is known from DE PS 2837543 to use a system where the injection takes place from above via guide plates, and where the exhaustion is effected through a centrally located channel. The injected air will be conducted primarily in an axial direction, and for reasons of the shield's construction there will be a risk of inwardly-directed flow, and herewith of being influenced by the upwardly-directed flow. The stability of the skirt created by the outflow thus becomes very poor, and the suction distance and hereby the capacity is thus limited. Correspondingly, there is no guarantee that the exhaust flow is brought to rotate around its axis in achieving of the cyclone effect for reasons of this merging of oppositely-directed flows.

The object of the invention is to overcome these disadvantages and inconveniences of the known systems, and this is achieved according to the invention by a system in which the nozzles and/or blowers are mounted around one or more centrally- located exhaust channels, and which disembogue in the same plane as said channels, and such that the direction of injection is tangential in relation to the flow.

In a simple manner, there is hereby achieved a hitherto unattainable characteristic, i.e. that the local exhaustion can be ensured over a hitherto unknown great distance. This is due first and foremost to the fact that the injection and the exhaustion take place in the same plane, and such that the injection is effected tangentially, in that it is hereby possible to achieve a very stable cyclone effect. In practice, it has thus been determined that a positive and stable local exhaustion can be achieved over a distance which is greater than the outside diameter of the ventilation shroud. It has also been found that when the injection and the exhaust are effected in the same plane, there is no tendency for the flow created by the injection to reduce its radius and thereby risk being mixed with the upwardly-directed exhaustion column.

As disclosed in claim 2, by mounting two or more concentric rings of nozzles or blowers around the exhaust channel, one is able to further ensure the stability of the flow and hereby make the local exhaustion less vulnerable to disturbing streams of air in the room, and thus reduce the risk of escape of pollution from the cyclone.

As disclosed in claim 3, by allowing the nozzle to consist of inclined guide-plates, it is possible to achieve a uniform distribution of the initial flow over the whole circumference.

Finally, as disclosed in claim 4, it is expedient to make the guide-plates adjustable, in that it is possible hereby to adjust the positioning of the outflow, its volume and direction in accordance with the conditions existing in the room.

In the following, the invention will be described in more detail with reference to the drawing, in which

fig. 1 shows a longitudinal section through a system with overlying nozzles seen in direction I-I in fig. 2,

fig. 2 shows a cross-section through this system seen in direction II-II in fig.l,

fig. 3 shows a part-section through a second embodiment seen in direction III-III in fig. 4.

fig. 4 shows a cross-section through this embodiment seen in direction IV-IV in fig.

3,

fig. 5 shows a cross-section through a third embodiment seen in direction V-V in fig. 6,

fig. 6 shows a section through this third embodiment seen in direction VI-VI in fig. 5, and fig. 7 shows a section through one of the nozzles seen in direction VII-VII in fig. 6.

In figs. 1 and 2 is shown an embodiment for the ventilating system which is suspended or mounted in such a manner that the direction of exhaustion is from below and up into the system around a centreline 3. In practice this means that the centreline 3 of the system must cut through the zone 12 illustrating the polluting object or the polluting source.

The system itself comprises an annular shroud 13, which in a suitable manner is suspended or mounted around the remaining parts. These parts comprise a number of air nozzles 5 which are mounted in such a manner that the direction of the injected air 1 is tangential in relation to the spiral formation 4 which is desired to be created.

In order to stabilize the injection of air, a further annular shroud 14 is mounted, whereby the injection takes place in an annular chamber. This stabilizes the inflowing air 2. Downwardly, the shrouds 13 and 14 are terminated on the same plane, so that the blowing out through the nozzles 5 takes place at the same level.

In the example shown there are four nozzles, but there will be able to be more or less all depending on requirements, merely providing that these are evenly distributed along the circumference of the spiral. The number will thus depend greatly on the diameter of the desired spiral, and herewith on the desired exhaustion capacity.

When air 1 is injected through the nozzles 5, a downwardly-moving spiral-formed flow 2 is created. This is indicated in its entirety by the arrow 4. When the flow 4 has reached a limitation, for example the object to be worked, the working surface or the like, the downwardly-directed flow ceases and the air will assume a direction towards the core of the spiral where, as a column as indicated by the arrow 11, it will follow a direction towards the exhaust channels. The exhaust channels consist partly of the central exhaust channel 6, but can possibly be supplemented with further secondary exhaust channels 7, which can be necessary in order to ensure an effective exhaustion of an air column 11 around the centre axis 3 where this has a large diameter.

The exhaust channels 6, 7 open out on the same plane as the air injection nozzles, which ensures that the influx of air 4 does not mix with the exhaust air 11.

In figs. 3 and 4 is shown an example of a second embodiment where the injection takes place through slots 8, which are formed between radially-mounted plates 9 extending between the two annular shrouds 13 and 14. The advantage with this form of nozzle is that a large number of injections 2 are created for the stabilization of the flow 4, which therefore assumes a very stable initial movement and subsequent flow.

The injection is effected via one or more channels 15, which disembogue above the plates 9 in a chamber 16, while the exhausting of the column 11 takes place through the central exhaustion channel 6. This construction is very space-saving, and thus the construction height of the system is kept as low as possible.

Finally, in figs. 5 - 7 is shown a third embodiment. The object of this is to avoid that the air flowing out of the nozzle is not sucked directly into the exhaust column around the centreline 3.

This is achieved by mounting nozzles 8 in two or more concentric rings around the centreline 3. The nozzles 8 are configured in the bottom of the pressure chamber 16, and are further provided with an intermediate shroud 14 on the underside of the pressure chamber, said shroud 14 terminating in the same plane as the outer shroud 13.

One can hereby achieve a downwardly-directed flow which is so strong that it develops into a stable spiral, which can neither wholly nor partly be mixed with and sucked out by the exhaust nozzles 6.

The common pressure chamber 16 also ensures that the system becomes as compact as possible.

As will appear from the drawing, the guide-plate 9 is formed by an opening cut in the bottomplate, so that the slot 8 is formed by bending down the plate part 9. This is a simple and effective way in which to configure the nozzles, and it enables the nozzle opening 9 to be adjusted by bending the plate part 9 inwards or outwards, and which can therefore be adjusted from a completely closed nozzle to a fully open nozzle.

In the above, the invention has been explained and shown with air injection through nozzles. However, in certain cases it is possible to achieve a greater stability by using one or more blowers, either alone or in combination with nozzles, hereby enabling compensation to be made for possible external disturbances in the airstream.

In order to avoid draught, it is advantageous if the amount of air injected substantially corresponds to the amount of air exhausted.

In accordance with requirements, in the exhaust channels of the embodiments shown can be mounted various forms of filters which will be able to clean the air effectively for reasons of the uniform flow and the relatively high concentration of pollution in the exhaust air.

Claims

C A I M S

1. Ventilating system for mechanical local exhaustion of gases such as vapour, steam, airborne suspensions and the like, said system partly comprising a number of injection nozzles and/or blowers which give the air a downwards flow, and partly one or more exhaustion channels which, from above, suck out around the axis of the airstream, c h a r a c t e r i z e d in that the nozzles (5, 8) and/or the blowers are mounted around one or more centrally located exhaust channels (6, 7) and disembogue in the same plane as these, and such that the direction of injection is tangential in relation to the flow (4).

2. Ventilating system according to claim 1, c h a r a c t e r i z e d in that the injection nozzles (8) and/or blowers are mounted in two or more preferably concentric rings around the exhaust channel or channels (6).

3. Ventilating system according to claims 1 and 2, c h a r a c t e r i z e d in that the nozzles consist of openings (8) between inclined guide-plates (9).

4. Ventilating system according to claim 3, c h a r a c t e r i z e d in that the guide-plates

(9) are adjustable for regulation of the size of the opnenings (8).