CA2258582C

CA2258582C - Fluid extraction apparatus

Info

Publication number: CA2258582C
Application number: CA002258582A
Authority: CA
Inventors: Boon Pen Chua
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-06-20
Filing date: 1997-06-19
Publication date: 2003-06-17
Anticipated expiration: 2017-06-19
Also published as: CA2258582A1; ES2155002A1; DE19781857T1; WO1997048475A1; GB2329856B; AU3566097A; ES2155002B1; CN1226183A; BR9709874A; AU721217B2; HK1021514A1; US6331141B1; JP2000512894A; GB2329856A; CN1077445C; GB9827858D0; SG70574A1

Abstract

A fluid extraction apparatus comprises a passage (20) for the pumped flow therealong of a first fluid, for example air. A fluid flow area control devi ce in the form of an apertured plug (22) is present in the passage. An inlet (2 6) to the passage (20) is provided at or downstream of the downstream side of t he plug (22). When, in use, the first fluid is pumped along the passage through the aperture (23) of the plug (22) the fluid pressure at the inlet (26) is reduced causing a second fluid to be drawn into the passage (20) via the inl et (26) to flow with the first fluid towards the downstream end of the passage (20). The downstream end of the passage may be provided with a filter (6) in the form of a tank (8) containing an oil dissolving agent (10). The apparatu s has a particular application to a cooker hood assembly for extracting a gas from a cooker hood (2), without having to pass the gas through a pump (4), a nd then treating the extracted gas to remove pollutants such as water, oil droplets and smoke therefrom.

Description

CA 022~8~82 1998-12-16 FLUI~ EXTRACTION APPARATUS
The present inventlon relates to fluid extraction apparatus, particularly, but not exclusively, to apparatus for use in the pacification, purification or expulsion of a fluid, for example drawing a gas or liquid rrom a first area and transporting it to a second area at which it may optionally be treated. The present invention has particular application, but is not restricted, to use in the extraction and filtering of air ~ontaining impurities such as smoke, water vapour or oil vapour. Such an apparatus can be particularly useful in a cooking environment and could be employed in connection with a cooker hood above a cooking apparatus.
Normal extractor fans or cooker hoods generally use some ~orm of fan in the path of the air to be extracted.
Even if the fan is positioned downstream of a filter, oily impurities in the air can become deposited on the fan.
According to the present invention there is provided fluid extraction apparatus comprising:
a passage having an upstream end, a downstream end and a cross-sectional flow area for the pumped flow therealong of a first fluid in a downstream direction;
a fluid flow area control device having an upstream side and a downstream side and providing at said downstream side an increase in the available cross-sectional flow area of said passage between said upstream and downstream ends;
and an inlet to said passage at or downstream of said downstream side of said device;
whereby pumped flow of the first fluid along said passage past said device reduces the fluid pressure at said inlet to cause a second fluid to he drawn into said passage via said inlet to flow with the first fluid towards said downstream end.
Said fluid flow area control device advantageously provides an abrupt increase in the available cross-CA 022~8~82 1998-12-16 WO g7/48475 PCT/SG97/00028 sectional first ~luid r-low area o~ said passage at its downstream side.
In a preferred arrangement the passage downstream of the fluid flow area control d-vice is contained within a first conduit and a second conduit, for the supply of the second fluid to the inlet, branches into the first conduit at a branch junction.
The Cluid flow area control device may take the form of a plug situated in the first conduit, with the passage passing though at leas~ one aperture provided in the plug.
The device may further comprise a hollow extension pipe extending downstream from the downstream side of the plug, beyond the branch junction, with the passage passing through the plug's aperture and through the pipe.
In an alternative arrangement a downstream portion or the second conduit extends into the first conduit, beyond the branch ~unction, and extends in the downstream direction. The exterior surface of the downstream portion of the second conduit can be spaced from the surrounding interior surface of the first conduit to ~orm therebetween an annular space through which the passage passes. In this >. .
way thë downstream portion of the second conduit forms the fluid flow area control device.
The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a schematic sectional side view o~
apparatus according to a first embodiment of the present invention;
Figure 2 is a cross-section along the line II-II in Figure 1;
Figure 3 is a schematic sectional side view of apparatus according to a second embodiment of the invention;
Figure 4 is a schematic sectional side view of apparatus according to a third embodiment of the present CA 022~8~82 1998-12-16 W097/~75 PCT/SG97/00028 invention;
Figure 5 is a cross-section along line V-V in ~igure 4;
Figure 6 is a schematic sectional side view of apparatus according to a fourth embodiment of the invention; and Figure 7 is a cross-sectional view along the line VII-VII in Figure 6.
A schematic sectional side view of the rirst embodiment of apparatus in accordance with the present invention is shown in Figure 1. The embodiment is sectioned along the longitudinal axis of a first passage 20 and a second passage 24. For clarity, the thin wall materials of the conduits forming these passages, as well as other elements of the apparatus, have been shown schematically as having no thickness.
This first embodiment consists of a cooker hood 2, an air compressor 4, a filtering section 6, a control valve 12, a first passage 20, a fluid flow area control device 22 and a second passage 24.
In operation of this first embodiment the compressor 4, which may be a fan, pumps a first fluid (in this example, air) into the upstream, left hand end of the first passage 20. The amount of air passing through the passage 20 is controllable by a control valve 12. Downstream of the valve 12 the pumped air passes through a fluid flow area control device 22, past a branch junction 26 where the second passage 24 branches into the first passage 20 and along the downstream portion 28 of the first passage before passing into the filter section 6 at the downstream end of the first passage 20.
The fluid flow area control device 22 in the ~irst embodiment is a cylindrical plug with a small cylindrical aperture 23 provided along its central axis, coaxial with the longitudinal axis of the first passage 20, as shown in Figure 2. As the pumped air enters i~to the opening of the CA 022~8~82 1998-12-16 aperture 23 in the upstream side o~ the plug 22 the air will accelerate due to the decrease in the available cross-sectional flow area of the aperture 23, relative to the cross-section of the first passage 20 upstream o~ the upstream side o~ the plug. Upon exiting the aperture 23 at the downstream side of the plug 22 and passing into the wider cross-sectional flow area of the first passage 20 in the region of the branch junction 26 adjacent the inlet formed by the second passage 24, the high velocity of the pumped ~irst fluid (air) creates a low pressure region in the vicinity of the inlet o~ the second passage 24. In the illustrated embodiment the air pressure at the cooker hood will be approximately atmospheric pressure. The low pressure region thus draws a second fluid ~in this example, cooking fumes largely comprising air~ through the second passage 24 ~rom the cooker hood 2. This drawn air then flows with the pumped air along the remainder of the ~irs.
passage 20 to the filter sectio~ 6.
I~ the air in the cooker hood contains impurities such as smoke, air, steam or oil droplets, then these.can be readily removed at the filter section 6. In this embodiment the ~ilter section 6 has a tank 8 containing oil dissolving agents 10 into which the mixture of pumped and drawn air passes. In this way any oil droplets in the second fluid (air) can be removed. Other chemical or physical filters may be used instead of this tank or in addition to it. For instance, activated charcoal could be used to remove smoke and/or a desiccant could be used to remove water vapour. These other ~ilters could be provided within the downstream portion 28 of the ~irst passage or after the oil filter. The filters could be arranged in any effective order or in any suitable combination. The filters present could be matched to whatever impurities it is desired to remove from the incoming fluid.
The filter section is optional. If, for example, the mixture of pumped and drawn air was to be vented from CA 022~8~82 1998-l2-l6 downstream portion 28 direct to atmosphere, the filter section could be omitted.
By the time the air has passed through the filter section 6 it can be returned to the closed environment from which it came, for example a kitchen, or simply be expelled to atmosphere containing fewer impurities than if it had not been filtered.
In the illustrated embodiment of filter section 6, the end of the conduit forming the first passage 20 is surrounded by an outer pipe 14 of a greater diameter than the conduit. Holes 18 are provided in the perimeter of the lower end of this outer pipe which is in the tank and the air mixture passes through these into the oil dissolving agents. This arrangement reduces bubbling in the tank 8.
The small, central through-aperture 23 used in the fluid flow control element 22 has been found to be more effective than a simple gap between two halves of a ~ixed plug. The suction force generated at the downstream side of the flow control element 22 at branch junction 26 is greater for the same air pressure produced by the pump 4.
The diameter of the through-aperture 23 can be reduced to increase the suction at the inlet of the second passage 24. For a fixed first fluid flow rate, the smaller the size of the aperture 23, the greater will be the velocity of the first fluid when it exits the downstream side of the fluid flow area control device 22. In this illustrated embodiment the diameter of the aperture 23 is between 1 mm and 3 mm.
The entire portion of the first passage between the pump and the downstream side of the fluid flow area control device 22 can be provided with a constant cross-section that is reduced relative to the available flow cross-section downstream of said downstream side, so that the fluid flow area control device 22 simply acts to define an abrupt increase in the available cross-sectional flow area available to the first, pumped fluid at the downstream side CA 022~8~82 1998-l2-l6 W097/~475 PCT/SG97/00028 o~ the device 22. However, this can lead to excessive resistance to the flow of the ~irst fluid. Consequently, as in the illustrated embodiment, it is preferred for the fluid flow area control device 22 to be of restricted axial length, for example between about 20 mm and 100 mm. In this way the device 22 defines a reduction in the available cross-sectional flow area upstream of its upstream side as well as defining an abrupt increase in the flow area downstream of its downstream side.
In this illustrated embodiment the passages 20,24 are defined by conduits in the form of round pipes or between approximately 13-25 mm in diameter. The internal diameter of the conduit forming the first passage 20 matches the external diameter o,~ the cylindrical plug 22.
The control valve 12 is preferably, as shown, present in the conduit forming the first passage 20 after the air compressor 4 but before the upstream side of the fluid flow control element 22. The valve 12 can be used to control the air pressure in the apparatus, for example i- the bubbling action in the tank 18 becomes too great the air pressure may need to be reduced. Alternatively, the valve 12 can'be useful if the suction of the second fluid (air) is too great and the air causes too much noise. The use of the control valve 12 may be in addition to, or as an alternative to, controlling the power supplied to the air compressor 4.
The length or the conduit forming the second passage 24 between the hood 2 and the first passage 20 can be chosen to suit individual usage. For most effective results this conduit is typically no more than 2000 mm long; beyond that the effectiveness of the apparatus reduces.
In the first illustrated embodiment the cond~it forming the second passage 24 meets the conduit forming the first passage 20 at approximately right angles to form a branch junction. This centre of the branch junction may CA 022~8~82 1998-12-16 WO 97/48475 PCT/SGg7/00028 -- 7 -- .
advantageously be positioned between about 0 mm and 100 mm downstream of the downstream side of the fluid flow area control device 22. In this way the main high velocity flow of pumped first fluid (air) flowing through the aperture 23 in the plug 22 does not disperse sufficiently to rill the whole of the expanded cross-sectional area of the first passage 20 by the time that the inlet of the second passage 24 is r-ached at the branch junction.
In Figure 1 the downstream side of the plug 22 is shown as being spaced from the branch junction 26. The inlet ror the second ~luid, at which the first and second rluids are exposed to each other ~or the first time, is coincident with the branch junction 26 in this first embodiment. Consequently, the inlet is also spac-d downstream of the downstream side of the plug 22.
A second embodiment of apparatus in accordance with the present invention is shown in Figure 3. This embodiment is similar to that shown in Figure 1, except ~or the provision of an extension pipe 30. In this second embodiment the effectiveness or the apparatus is increased, i.e. the suction generated in the second passage 2~ is increased without requiring a corresponding increase in the air pressure supplied by the compressor 4. The ex.ension pipe 30 has an internal diameter similar to that or the aperture 23 in the plug 22 and is connected directly to the downstream end face of the plug 22 with its opening aligned with the plug aperture 23. It has been found that good results are achieved when the length of the extension pipe 30 is about 200 mm, with the branch junction between the first and second passages 20, 24 being approximately midway along the axial length of the pipe 30, as shown in Figure 3.
In this second embodiment the fluid flow area control device comprises both the apertured plug 22 and the extension pipe 30. The downstream side of the device, formed by the extreme right hand end ~f the pipe 35, is CA 022~8~82 1998-12-16 W097/~475 PCT/SG97/00028 positioned aowns_ream of the branch junction 26. In addition, the annular inlet 60 for the second ~luid, at which the first and second fluids are exposed to each other for the first ti~.e, is also positioned downstream of the branch junction 25.
A third e~odiment of apparatus is illustrated in Figures ~ and 5. The principle of operation of thls third embodiment is simila~ to that of the previous embodiments.
Where the same components exist in the third embodiment they have been g~ven the same reference numbers as in the previous embodim_nts.
The differe~ce between the third and first embodiments is in the form of the fluid flow control device 70. In the third embodiment this device comprises a solid, cylindrical plug ~ositioned coaxially in the conduit forming the rirst passage 20. The diameter of the plug 70 is such that the plug's exterior surface is spaced rrom the surrounding cylin~rical interior surface of the corduit to form therebetween a generally annular space through which the passage passes. In Figure 5 the plug 70 is shown as being supported in the conduit by three radially extending supports 72. Otner forms of support may be used. As with the first embodiment the plug 70 is oI restricted axial length, for example between abortt 20 mm and 100 mm.
In Fig. 4 the downstream side of the plug 70 is shown as being spaced from the branch junction 26. The inlet for the sëcond fluid, at which the first and second fluids are exposed to each other for the first time, is coincident with this branch junction 26. ~onsequently, in the third embodiment the inlet is also spaced downstream of the downstream side o~ the plug 70. The downstream side of the plug 70 may need not, however, be spaced from the branch junction 26 (not shown).
In the fourtn embodiment illustrated in Figures 6 and 3~ 7, a similar system is used to that shown in Figures 1 and 2. Where the sam- components exist in the fourth CA 022~8~82 1998-12-16 g embodiment they have been given the same re~erence -umbers 2S those in the ~irst embodiment.
In the Iourth embodiment the di~erences are in the form o~ the rluid Llow area control device and the inlet o_ , the second passage 42. As can be seen in Figure 4, the downstream end of a second passage 42 is ~ormed by a second conduit 52 that meets and passes at an angle into a ~irst conduit 62 ~orming the first passage 40 and continues coaxially within that first conduit 62. Thus the pumped air flowing within the first passage 40 must flow through a reduced cross-section annular passage 50 ~ormed betwQen the outside of the downstream portion o~ the second corauit 52 and the inside of the ~irst conduit 62 as ~ar as the end o~
the second conduit 52. At the extreme downstream end o_ the second conduit 52 the cross-sectional flow area available to the pumped first fluid increases abruptly.
In this fourth embodiment the downstream portion o~
the second conduit 52 acts as the fluid flow area control device, so that the available flow cross-section for the pumped fluid increases abruptly on exiting from the rQduced cross-section annular passage 50. As in the previous em~odiments, this increase in the ~1Ow cross-section available to the pumped ~luid creates a region o~ r2duced ~ressure at the downstream end o~ the ~luid flow ar_a control device, causing air from the cooker hood 2 to De drawn up along the second passage 42 into the first ~assage to thën pass downstream with the pumped air, as in the earlier em~odiments.
In this fourth embodiment the annular passage 50 around the extreme downstream (right hand) tip oI the second conduit 52 forms the inlet ~or the second ~luid, at which point the second ~luid is exposed to the pumped, ~irst ~luid for the first time.
To give good e~iciency, the annular passage 50 between the co-axial portion 44 of the second conduit 52 and the coaxial portion of the surrounding conduit 62 CA 022~8~82 1998-l2-l6 -- 10 -- ~
forming the first passage 40 is quite small and or corstant cross-sectional area. Setting this radial gap "h" (see Figure 7) to be between about 0.5 and 1.0 mm and making this co-axial region between about 20 mm and 100 mm long has been found to give particularly effective results.
Excessive increases in the length of the reduced cross-section annular passage 50 reduce the overall efriciency of the apDaratus The conduit 52 forming the second passage 42 branches into .he conduit forming the first passage 40 in the ~ourth embodiment at an angle. This helps to improve the efficiency over the two conduits branching together perpendicularly. However, a perpendicular branch is possible.
The described and illustrated embodiments can be used with a variety OL conduit or pipe sizes and shapes. The apparatus may be scaled up or down in size. Furthernore, the length of the different conduit portions can be changed. For example, the length of the condui. ~o~ming tke second passage 24, or the length of the main par~ o~
the conduit forming the first passage 20 after the ~irst and second conduits branch into one another can be varied.
The diameter of the first conduit can, for example, be increased above the preferred 13~25 mm range mentioned earlier. The capacity of the air compressor 4 may reed changing to match.
Although the conduits shown are pipes having circular cross-sections, conduits with other cross-sections are usable. Equally, the conduits do not need to be of constant cross-section or generally straight.
The illustrated and described embodiments are examples of the present invention being used with air as the pumped fluid and the drawn fluid. The apparatus is, however, operable with other gases or with liquids, for example water.

Claims

1. Fluid extraction apparatus comprising:
a passage having an upstream end, a downstream end and a cross-sectional flow area for the pumped flow therealong of a first fluid in a downstream direction;
a fluid flow area control device having an upstream side and a downstream side and providing at said down-stream side an increase in the available cross-sectional flow area of said passage between said upstream and down-stream ends; and an inlet to said passage at or downstream of said downstream side of said device;
whereby pumped flow of the first fluid along said passage past said device reduces the fluid pressure at said inlet to cause a second fluid to be drawn into said passage via said inlet to flow with the first fluid to-wards said downstream end.

2. An apparatus as claimed in claim 1, wherein said fluid flow area control device is arranged to provide an abrupt increase in the available cross-sectional first fluid flow area of said passage at said downstream side.

3. An apparatus as claimed in claim 1 or claim 2, wherein said fluid flow area control device also provides a decrease in the available cross-sectional first fluid flow area of said passage at said upstream side of said device.

4. Apparatus as claimed in claim 3, wherein said fluid flow area control device is arranged to provide an abrupt decrease in available cross-sectional first fluid flow area at said upstream side.

5. Apparatus as claimed in any one of claims 1 to 4, wherein the available cross-sectional first fluid flow area of said passage between said upstream and downstream sides of said fluid flow area control device remains gen-erally constant.

6. Apparatus as claimed in any one of claims 1 to 5, wherein said passage downstream of said fluid flow area control device is contained within a first conduit, and wherein a second conduit, for the supply of the second fluid to said inlet, branches into said first conduit at a branch junction.

7. Apparatus as claimed in claim 6, wherein said downstream side of said fluid flow area control device is spaced from said branch junction in the upstream direc-tion, such that said inlet is spaced downstream of said downstream side of said fluid flow area control device.

8. Apparatus as claimed in claim 6 or claim 7, wherein said fluid flow area control device is a plug situated in said first conduit, with said passage passing through at least one aperture provided in said plug.

9. Apparatus as claimed in claim 8, wherein said plug is provided with a single central aperture coaxially aligned with the longitudinal axis of said first conduit.

10. Apparatus as claimed in claim 6, wherein said downstream side of said fluid flow area control device is spaced from said branch junction in the downstream direc-tion, such that said inlet is positioned downstream of said branch junction at said downstream side of said de-vice.

11. Apparatus as claimed in claim 10, wherein said fluid flow area control device comprises an apertured plug, positioned in said first conduit entirely upstream of said branch junction, and a hollow extension pipe ex-tending downstream from said downstream side of said plug, beyond said branch junction, said passage passing through said aperture and through said pipe, whereby said down-stream side of said device and said inlet are positioned downstream of said branch junction.

12. Apparatus as claimed in claim 11, wherein said branch junction is positioned approximately midway along the axial length of said hollow extension pipe.

13. Apparatus as claimed in claim 11 or claim 12, wherein said hollow extension pipe has between approxi-mately 2 to 10 times the axial length of said plug.

14. Apparatus as claimed in any one of Claims 9 to 13 wherein the diameter of said aperture through said plug is between 1/100 and 3/20 of the axial length of said plug.

15. Apparatus as claimed in claim 6 or claim 7, wherein said fluid flow area control device is a plug situated in said first conduit, with said passage passing around the exterior surface of the plug.

16. Apparatus as claimed in claim 15, wherein said plug is coaxially aligned with the longitudinal axis of said first conduit.

17. Apparatus as claimed in claim 15 or claim 16, wherein the exterior surface of said plug is spaced from a surrounding interior surface of said first conduit to form therebetween a generally annular space through which said passage passes.

18. Apparatus as claimed in any one of claims 7 to 17, wherein said second conduit joins said first conduit at said branch junction at approximately a right angle to form a generally T-piece connection.

19. Apparatus as claimed in claim 6, wherein a downstream portion of said second conduit extends into said first conduit, beyond said branch junction, and ex-tends in the downstream direction such that said inlet is spaced downstream of said branch junction.

20. Apparatus as claimed in claim 19, wherein the exterior surface of said downstream portion of said second conduit is spaced from a surrounding interior surface of said first conduit to form therebetween a generally annu-lar space through which said passage passes, said annular space forming said inlet.

21. Apparatus as claimed in claim 20, wherein the length of said downstream portion of said second conduit is between 20 mm and 100 mm and said annular space has a radial thickness of between 0.5 mm and 1 mm.

22. Apparatus as claimed in claim 20 or claim 21, wherein at least part of said downstream portion of said second conduit extends coaxially with said surrounding first conduit.

23. Apparatus as claimed in any one of claims 19 to 22, wherein said fluid flow area control device is said downstream portion of said second conduit.

24. Apparatus as claimed in any one of claims 1 to 23, further comprising a pump for connection to said up-stream end of said passage to pump the first fluid along said passage.

25. Apparatus as claimed in any one of claims 1 to 24, wherein said passage is provided with a control valve for regulating the pumped flow of the first fluid.

26. Apparatus as claimed in any one of the preceding claims, further comprising filter means for positioning at said downstream end of said passage for filtering the first and second fluids to remove therefrom contaminants contained therein.

27. Apparatus as claimed in claim 26, wherein said filter means comprises a tank containing oil dissolving agent in which said downstream end of said passage is immersed, whereby the first and second fluids exiting said downstream end of said passage are required to pass through the oil dissolving agent.

28. Apparatus as claimed in any one of claims 1 to 27, wherein the first and second fluids are both gases and further comprising a hood having a collecting region which is arranged to be connected to said inlet whereby, in use, the drawing of the second fluid into said passage via said inlet will extract gas from said hood.