IMPROVED FLUID INDUCTOR

Abstract: An inductor for drawing one fluid into another (e.g. air into fish-pond water) comprises an insert (12) located in a duct (10) to define narrowing (15, 16) and widening (19, 20) passages on either side. The first fluid flows along theses passages and draws the second fluid into it via egress holes (24). A valve (25) can be moved in the duct to vary the size of the narrowing passages (15, 16).

Description: IMPROVED FLUID INDUCTOR Background of the Invention 1. Field of the Invention This invention relates to an _mproved fluid inductor intended to draw one fluid into a low of a second f; sid moving in a duct. In this specification the term "fluid" is used to cover liquids and/or gases. The invention has particular, but not exclusive, utility in the aeration of water for marine life ponds. 2. Description of Related Art GB-A-1580211 and GB-A-1362789 both disclose an inductor for creating fine gas bubbles in a liquid flowing along a duct but in neither case is there any facility for varying the cross-sectional area available for liquid flow past the inductor to allow control to be exercised over the ratα at which gas is drawn into the flowing liquid. Summary of the Invention In its simplest embodiment the invention comprises an insert in a duct containing a flowing first fluid, the insert including an upstream portion causing a progressive reduction in cross-sectional area available for first fluid flow and a downstream portion causing a progressive increase in cross-sectional area available for first fluid flow, means to feed a second fluid to at least one second fluid egress hole in the downstream portion of the insert through which at least one hole the second fluid is drawn into the flowing first fluid by the pressure changes induced therein by the insert, and adjustable means to vary at least one of said cr * s-sectional areas available for first fluid flow past sa..j. insert. Conveniently the insert, or at least the downstream portion thereof, is hollow and the second fluid is fed to the hollow insert or hollow portion thereof. Preferably the flow varying means acts on the cross-section available for first fluid flow past the upstream portion of the insert. The flow varying means can, in one embodiment, be a valve sleeve located upstream of the insert and movable axially of the duct to reduce the area available for first fluid flow past the upstream portion of the insert as the sleeve is moved towards the insert. In a second embodiment, the relative width of the insert in the duct can be made adjustable in the upstream portion or in both of its upstream and downstream portions. The insert can be moulded or cut from foamed plastics material, can be a hollow body made from sheet metal, but is preferably a hollow body moulded from plastics material. A plurality of egress holes are preferably provided and these can conveniently be located close to the upstream end of the downstream portion. An insert which extends completely across the duct in a central plane of the duct, which is symmetrical about said central plane and which smoothly reduces the cross-sectional area available on each side of" the insert for fluid flow at least over the upstream portion is preferred. An adjustable valve means that acts to simultaneously vary the cross-sectional area on each side of the insert is particularly preferred. The insert can be provided with an upstream portion movable axially of the duct relative to the downstream portion, the upstream portion having wings on each side thereof which are spread outwardly towards the wall(s) of the duct to reduce the cross-sectional areas available to first fluid flow on each side of the insert as the upstream portion is moved towards the downstream portion and to reduce said cross-sectional areas as the upstream portion is moved away from the downstream portion. In a further arrangement, a laterally expansible upstream portion of the insert is provided adjacent to a stationary hollow downstream portion which cont ins a plurality of second fluid egress holes fed from a second fluid supply communicating only with the downstream portion of the ins t. A sharp discontinuity betwee the upstream and downstream portions may be desirable with a plurality of egress holes located close to the discontinuity. An insert with a generally diamond shaped configuration is particularly preferred. Brief Description of Drawings Some embodiments of inductor in accordance with this invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic horizontal sectional view on the line I-I of Figure 2 of a first embodiment of ho. " ow insert located in a duct of circular cross-section provided with an axially movable valve sleeve, Figure 2 is an end view of the duct as viewed in the direction of the arrow A in Figure 1, Figure 3 is an end view of the duct viewed generally in the direction opposite τ .> the arrow A in Figure 1, Figure 4 is a schematic view of the duct of Figures 1 to 3 shown installed as an aerator for pond water, Figure 5 is a schematic horizontal sectional view on the line V-V of Figure 6 of a second moulded insert located in a duct of circular cross-section, Figure 6 is an end view of the duct as viewed in the direction of the arrow B in Figure 5, Figure 7 is a sectional view from above of a third embodiment having a modified form of insert whose width is adjustable within a rectangular section of duct, Figure 8 is a partly sectioned side elevation of the duct and insert of Figure 7, Figure 9 is a schematic horizontal cross-sectional view of a fourth embodiment of insert located in a duct, Figure 10 is a side view of the duct of Figure 9, Figure 11 is an isometric view of the downstream portion of the insert of Figure 9, Figure 12 is a view similar to Figure 9 of a fifth embodiment of insert located in a duct, and Figures 13 and 14 are views of a fifth embodiment of insert in opened out and folded-up conditions, respectively. Description of Preferred Embodiments A circular duct 10 shown in Figures 1 to 3 carries a flow of water moving past a hollow insert 12 which has an upstream portion 14 creating narrowing water passages 15, 16 on each side thereof. From the widest region of the insert (marked by the line 17) a downstream portion 18 creates a pair of widening passages 19, 20 for the water leading to the downstream end 21 of the insert where the full bore of the duct 10 is restored. The insert 12 extends completely across the bore of the duct 10 from top to bottom thereof. An air inlet pipe 22 penetrates the wall of the duct 10 and leads to the hollow interior of the insert 12 which is sealed to the inside wall of the duct 10. Egress holes 24 are formed in the wall of the insert over a part of the downstream portion 18. The interaction between the flowing water and the stationary insert 12 causes the pressure in the water to rise to above ambient pressure in the passages 15 and 16 but to drop below ambient in the upstream parts of the passages 19 and 20 so that the natural pressure changes caused in the water flow by the presence of the insert 12, draws air into the hollow interior of the insert 12 from the pipe 22 and causes it to flow out from the insert 12 into the water flow as streams of bubbles leaving the insert through the egress holes 24. Air and water flow on together downstream of the insert 12. In a convenient arrangement the end of the pipe 22 is threaded, passes through a clearance hole in the wall of the duct 10 and is screwed into a threaded hole provided in the insert 12. This simple arrangement provides secure location of the insert 12 in the duct 10 and an air-tight connection between the pipe 22 and the insert 12 yer allows for easy removability for cleaning of the insert 12 when required. In order to adjust the cross-sectional areas available for flow of water past the insert 12 on each side thereo: . a tubular valve sleeve 25 is provided in the duct 10 on the upstream side of the insert 12. The sleeve 25 is slidable axially within the duct 10 between a fully retracted position (shown in full lines) in which its downstream ends 26 are roughly aligned with the upstream tip of the insert 12, to a fully inserted position (showr in dashed lines) in which its downstream ends 26 are slightly downstream of the line 17. The sleeve 25 has triangular cut-outs 27 in its upper and lower surfaces to accommodate the insert 12 and has a bore which first narrows and then widens in the direction towards the downstream ends 26. The upstream end of the sleeve 25 has an internal pipe thread 27 provided therein to allow it to be connected to a supply pipe for water fed to the duct 10 and the upstream end of the duct 10 has a captive locking ring 28 which is turnable on the outside of the duct 10 and is provided with a cam surface 29 which can deflect a tongue 30 cut in the wall of the duct 10 inwardly to frictionally engage the sleeve 25 and lock the same in a chosen axial position relative to the duct 10. 5 With the valve sleeve 25 in its fully retracted position, the cross-sectional area available for water to flow past each side of the insert 12 is set by the spacing between the insert 12 and the inner wall of the duct 10. In its fully inserted position the ends 26, being located 10 between the widest part of the insert 12 and the duct 10 at the line 17, restrict the flow of water past the insert 12 thus throttling the water flow to some extent and altering the pressure effects induced by the water flows. Accordingly, the proportion of air added to the water 15 flowing through the duct 10 can be varied depending on the axial setting of the valve sleeve 25. Figure 4 shows an aerator for a fish pond 30 based on the arrangement shown in Figures 1 to 3. A pump 31 draws pond water through a filter 32 and passes it through piping 20 33 leading to the duct 10 of Figures 1 to 3. The duct 10 includes spigots 34 extending outwardly of the duct 10 to permit its angle to the horizontal to be set as required depending on the siting of the pond 30 and the duct 10. In practice the outlet of the duct 10 would be submerged below 25 the level of the free surface of water in the pond 30. In a typical case the outlet of the duct would be between some 5 to 20 cms below the water surface, the depth of insertion preferably being a variable under the control of the user. The presence of the insert causes large volumes of air 30 to be drawn through the pipe 22 into the flowing water stream this bubbling up over an area 34 of the surface of the pond adjacent to the outlet of the duct 10 and perturbing the surface of the pond over an area which can exceed one metre square. Control over the amount of air drawn into the pond can be exercised by a) varying the depth of submersion of the outlet of the duct 10, b) varying the rate of flow of water through the duct 10 and c) varying the position of the sleeve 25 in the duct 10. Thus action can be taken with a given pump 31 to compensate for the loss of oxygen in a biological filter 32, changes in atmospheric pressure, the temperature of the water in the pond and the stocking level of fish in the pond 30. In one particular example using a pump 31 having a low settling (1) providing 4000 litres(900 gallons)/hour, a mid- setting (2) providing 6000 litres(1300 gallons)/hour and a high setting (3) providing 8200 litres(1800 gallons)/hour and with a duct 10 of some 35 mm bore discharging into the pond at a depth of some 20 cms the following performance was noted as the valve sleeve 25 was moved between fully retracted (FR) and fully inserted (FI) positions. For each setting of the pump and valve sleeve a rating of the turbulence of the water over the perturbed surface area 34 of the pond was expressed on a scale of 0 to 10. Turbulence level 0 had many small air bubbles breaking the surface of the pond but no significant change in water level over the area 34. Turbulence level 10, on the other hand, showed extremely violent water movements with large air bubbles constantly breaking the surface and a central region of the perturbed surface where the rising flows of air and water created a mound of water rising on occasions some 10 to 15 cms above the still level of water in the pond. The intermediate levels between 0 and 10 given in the following Table were my assessment of the different degrees of turbulence obtained for the different conditions noted. TABLE Pump Valve Sleeve Noted Setting Setting Turbulence Level 1 FR 0 - 1 2 FR 3 - 4 3 FR 5 - 6 1 FI 1 - 2 '■ =- 2 FI 5 - 6 3 FI 9 - 10 Figures 5 and 6 show a second embodiment of the invention in which the same reference numerals used in Figures 1 to 3 with the addition of 100 are used to represent components in the second embodiment which are similar to those shown in the first embodiment. In this embodiment the -insert 112 is a body of foamed plastics material having a sharp discontinuity at the line 117 caused by vertical grooves 50 extending from top to bottom of the duct 110. . The minimum water flow area created on the line 117 by the tips 52 can be enlarged by cutting away plastics material at the tips and this allows for easy adjustment of the pressure drop caused by the insert 112. This embodiment lacks the facility for continuous adjustment but is useful for some applications. Figures 7 and 8 show a third embodiment in which the same reference numerals with the addition of 200 are used to represent components of the third embodiment which are similar to those shown in the first embodiment. Referring to Figures 7 and 8, the insert 212 comprises two hollow half sections 212a, 212b hinged together at a film hinge 212c located at the upstream end of the insert and separately fed with air from an air tube 222. Air exits from each half section 212a, 212b via air egress holes 224 formed in each downstream portion of each half section. The insert 212 is located in a region 210a of a duct 210 which is of rectangular seicion so that (as seen in Figure 8) the insert extends fully across the duct 110 from top to bottom. Circular sections 210b, 210c of the duct 210 are provided upstream and downstream of the central region 210a. Located between the half sections 212a, 212b is an adjustment screw 51 having a tapered lower end 52 which bears against internal walls of each half section. The screw 51 is accessible from outside the duct 210 and can be moved up or down relative to the duct by means of its screw- threaded engagement in a boss 53 which provides a water- tight seal to the duct wall. Screwing the screw 51 further intc the duct forces the half sections apart restricting the cross-sectional area available for water flow on each side of the insert 210 while unscrewing the screw 51 in the boss 53 allows the half sections 212a, 212b to close together increasing said areas available for liquid flow past the insert. A further modification would be to have a fixed insert (e.g. like the member 10 in Figure 1) but to provide an external clamp to squeeze the wall of the uct inwardly at the location of the line 17 to reduce the minimum cross- sectional area available for water flow on each side of the insert. Figures 9, 10 and 11 show a further form of adjustable insert 312 which has axially adjustable upstream and downstream portions. The downstream portion 318 is fixed in a rectangular duct section 310a by an air supply pipe 322 and contains arrays of small air egress holes 324 close to its widest part (see Figure 10) . The upstream portion 314 of the insert 312 has a shaft 370 slidably received in a bore 372 of the downstream portion, a rack 374 in the shaft 370 engaging a cog 376 on a turnable adjusting screw 351 which is accessible from 5 outside the ' duct 310. Extending outwardly from the shaft 370 are two wings 360 which ride on side regions 362 of the downstream portion 318 and extend from top to bottom of the duct section 310a. Figure 9 shows the upstream portion 314 in its rearward 10 (or fully retracted) position where each wing 360 is nested close to the side regions 362 providing the maximum available cross-sectional area for water to flow on each side past the insert 312. Turning the screw 351 anticlockwise in Figure 9 draws the shaft 370 into the bore 15 372 forcing the wings 360 outwardly to reduce the available cross-sectional areas for water flow. Figure 12 shows a still further form of adjustable insert 412 which has a downstream portion 418 fixed in place in a rectangular duct section 410a by an air supply pipe 20 422. Air egress holes 424 communicate with the pipe 422. The upstream end of the portion 418 has an arcuate form which is engaged by the downstream ends of two flaps 480 which are hinged together at their upstream ends 482 and can be spread apart by an adjusting screw 451 having a tapered 25 lower end which is inserted between the flaps 480. By screwing the screw 451 into the duct 410 the flaps are splayed apart to reduce the cross-sectional areas available for water flow past the two sides of the insert 412. A yet further form of adjustable insert is illustrated 30 in Figures 13 and 14. In this embodiment a folded-up insert 512 is employed located in a cavity 510a of rectangular cross-section in a water duct 510. The insert extends from top to bottom of the cavity 510a and is folded up from a strip shown in Figure 13 having a pair of hinged-together first or upstream blades 512a, 512b which can be of solid plastics material and a pair of hollow downstream blades 512c, 512d which include air supply tubes 522a, 522b that can turnably engage one in the other when the strip is folded up into the shape shown in Figure 14. Tube 522a communicates with the interior of blade 512c and tube 522b communicates with the interior of blade 512d each hollow blade 512c, 512d having an array of egress holes 524 formed over an area adjacent to the hinge joint between blades 512a and 512c and the hinge joint between blades 512b and 512d. In this way air supplied to the conjoined tubes 522a, 522b will be drawn out into the stream of water flowing in the duct 510. Conveniently the sum of the areas of all the holes 524 in both blades 512c and 512d is approximately equal to the cross-section of the air passage in the pipe 522 feeding the tube 522b and the tubes 522a and 522b are arranged to distribute the air supplied by pipe 522 roughly equally to the two hollow blades 512c and 512d. By virtue of the hinge joints between the blades, the insert 512 formed from the folded-up strip can have its geometry varied from a maximum width shown in full lines in Figure 14 to a minimum width shown in dash lines. Various mechanisms can be used to cause the change of shape of the insert but a currently preferred one is to locate pegs 90 in a V-shaped groove in a drive plate that can be moved axially of the cavity 510a, e.g. by means of a knob driving a spiral track in which a projection of the drive plate locates. To stabilise the insert 512 in the cavity 510a it is convenient to pass the pegs 90 through inwardly inclined slots in a closure plate of the cavity and to engage the ends of the pegs 90 projecting through the slots in the closure plate in the V-shaped groove in the drive plate. Although described with reference to aerating water in a duct 10, 110, 210, 310, 410 and 510 the invention can be used to add any second fluid drawn into the pipe 22, 122, 222, 322, 422 and 522 into a propellant fluid flowing in the duct 10, 110, 210, 310, 410 and 510. Thus any gas can be added to any liquid, one liquid to any other liquid, one gas to any other gas or one liquid to any gas. There are three main components to the devices illustrated, these being the insert 12, 112, 212, 312, 412, 512, the duct or tubular housing 10, 110, 210, 310, 410, 510 and the pick-up pipe 22, 122, 222, 322, 422 and 522. In one example of the embodiment of Figures 1 to 3, the insert 12 is a composite unit manufactured in a mouldable plastics material. Incorporated in this composite moulding is a series of induction holes 24, connecting to a central induction inlet, which is threaded for connection with the air pick-up pipe 22. Each duct 10, 110, 210, 310, 410, 510 is conveniently manufactured from B.S. plastic pipe. The pick-up pipe 22, 122, 222, 322, 422, 522 may be threaded at one end and also manufactured from B.S. plastic pipe. The ducts 210, 310, 410, 510 can be made in two parts separable in the central region 210a, 310a, 410a, 510a to permit insertion of the insert 212, 312, 412, 512 therein.

Claims: CLAIMS 1. A fluid inductor comprising an insert in a duct containing a flowing first fluid, the insert including an upstream portion causing a progressive reduction in cross- sectional area available for first fluid flow and a downstream portion causing a progressive increase in cross- sectional area available for first fluid flow, means to feed a second fluid to at least one second fluid egress hole in the downstream portion of the insert through which at least one hole the second fluid is drawn into the flowing first fluid by the pressure changes induced therein by the insert, and adjustable means to vary at least one of said cross- sectional areas available for first fluid flow past said insert. 2. An inductor as claimed in claim 1, in which at least the downstream portion of the insert i∑. iiollow and the second fluid is fed to the hollow portion thereof. 3. An inductor as claimed in claim 1 or claim 2, in which the insert extends completely across the duct and provides areas for first fluid flow on each side thereof. 4. An inductor as claimed in any one preceding claim, in which the flow varying means acts on the cross-section available for first fluid flow past the upstream portion of the insert. 5. An inductor as claimed in any one preceding claim, in which the flow varying means is a valve sleeve located upstream of the insert and movable axially of the duct to reduce the area available for first fluid flow past the upstream portion of the insert as the sleeve is moved towards the insert. 6. An inductor as claimed in any one of claims 1 to 4, in which the relative width of the insert in the duct is adjustable at least in the upstream portion thereof. 7. An inductor as claimed in any one of claims 1 to 4, in which the insert is provided with an upstream portion movable axially of the duct relative to the downstream portion, the upstream portion having wings on each side thereof which are spread outwardly towards the wall(s) of the duct to reduce the cross-sectional areas available to first fluid flow on each side of the insert as the upstream portion is moved towards the downstream portion and to reduce said cross-sectional areas as the upstream portion is moved away from the downstream portion. 8. An inductor as claimed in any one of claims 1 to 4, in which the insert has a laterally expansible upstream portion located adjacent to a stationary hollow downstream portion which contains a plurality of second fluid egress holes fed from a second fluid supply communicating only with the downstream portion of the insert. 9. An inductor as claimed in any one preceding claim, in which the insert extends completely across the duct in a central plane of the duct, is symmetrical about said central plane and smoothly reduces the cross-sectional area available on each side of the insert for fluid flow over the upstream portion, an adjustable valve means acting to simultaneously vary the cross-sectional area on each side of the insert. 10. An inductor as claimed in claim 9, in which a sharp discontinuity is provided between the upstream and downstream portions with a plurality of egress holes located close to the discontinuity. 11. An inductor as claimed in claim 10, in which the insert has a generally diamond shaped configuration. 12. An inductor as claimed in claim 6, in which the insert is made from folded-up blades the downstream ones of which are hollow, include the egress holes and are fed with second fluid through conjoined tube parts turnable, one relative to the other, as the width of the insert in the duct is adjusted. 13. An aerator for a fish pond including an inductor as claimed in any one preceding claim.

Inventors: SHORT DAVID RICHARD MARTIN, SHORT, DAVID, RICHARD, MARTIN
Applicants: SHORT DAVID RICHARD MARTIN, SHORT, DAVID, RICHARD, MARTIN
Application year: 1993
Main classification: B01F3
IPC codes: B01F5, C02F3, F04F5