EP2735362A1 - Unit of a generator of gas bubbles in a liquid - Google Patents

Unit of a generator of gas bubbles in a liquid Download PDF

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Publication number
EP2735362A1
EP2735362A1 EP12199083.2A EP12199083A EP2735362A1 EP 2735362 A1 EP2735362 A1 EP 2735362A1 EP 12199083 A EP12199083 A EP 12199083A EP 2735362 A1 EP2735362 A1 EP 2735362A1
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European Patent Office
Prior art keywords
gas
vortex chamber
liquid
unit
chamber
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EP12199083.2A
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German (de)
English (en)
French (fr)
Inventor
Vaclav Tesar
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Institute of Thermophysics CAS
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Institute of Thermophysics CAS
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Publication of EP2735362A1 publication Critical patent/EP2735362A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03D—FLOTATION; DIFFERENTIAL SEDIMENTATION
    • B03D1/00—Flotation
    • B03D1/14—Flotation machines
    • B03D1/24—Pneumatic
    • B03D1/242—Nozzles for injecting gas into the flotation tank
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
    • B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
    • B01F23/23105—Arrangement or manipulation of the gas bubbling devices
    • B01F23/2312—Diffusers
    • B01F23/23121—Diffusers having injection means, e.g. nozzles with circumferential outlet
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F35/00—Accessories for mixers; Auxiliary operations or auxiliary devices; Parts or details of general application
    • B01F35/71—Feed mechanisms
    • B01F35/717—Feed mechanisms characterised by the means for feeding the components to the mixer
    • B01F35/71755—Feed mechanisms characterised by the means for feeding the components to the mixer using means for feeding components in a pulsating or intermittent manner

Definitions

  • the subject of this invention is a unit forming a part of a generator which produces in a liquid small bubbles of gas brought into the unit by a pipe or other cavities.
  • Small bubbles are required in a wide range of production processes, in particular those in which the supplied gas has to diffuse across the phase interface into the liquid.
  • An example is aeration of water to increase its oxygen content.
  • the small bubbles rise more slowly towards the liquid surface and this increases the total time over which the transport from the bubbles into the liquid takes place.
  • the simplest and most often used method of generating bubbles is bringing the gas into a device known as aerator.
  • This device is characterised by a large number of small orifices connected at one end to the common gas supply and at the other end open into the liquid.
  • the liquid is usually inside a vessel or tank and the aerator is submerged under the liquid level.
  • the bubbles are then formed by outflow of gas from the small orifices of the aerator.
  • the main problem is instability of parallel bubble formation. This is a direct consequence of the basic law governing bubble behaviour. According to this law, the pressure difference between the gas inside the bubble and the surrounding liquid is inversely proportional to the curvature radius of the bubble surface (the Young-Laplace law).
  • the gas pressure inside this larger bubble will be lower than in the neighbour bubbles supplied by the gas from the same gas source.
  • the gas then will flow, driven by the larger pressure difference, into the bubble that is already larger, at the expense of decreased or even stopped gas flow into the neighbour bubbles. They cease to grow, while the large bubble will reach an extremely large size, out of proportion to the size of the aerator orifice exits.
  • the fluidic oscillator to be used for the purpose was already earlier described in an article by authors Tesa V., Hung C.-H., and Zimmerman W.: "No-Moving-Part Hybrid-Synthetic Jet Actuator", Sensors and Actuators A, Vol. 125, pp. 159-169, 2006 .
  • This oscillator as it is also described in the Patent EP2081666 , consists of a fluidic diverter amplifier having no components that are moved or deformed in the course of amplifier operation - and from a feedback loop channel. The channel connects the two control terminals of the amplifier. The gas is supplied into the supply nozzle of the amplifier and leaves it as a gas jet into a space between two mutually opposed attachment walls.
  • the attachment of the jet to one of them is by means of the well-known Coanda phenomenon of fluid jet clinging to a solid wall.
  • the jet is actually held deflected at the wall by the low pressure which is acting also in the control nozzle on the same side of the amplifier. Since there is the feedback loop channel connected to the control terminals, the pressure difference arises between the ends of the feedback channel. This difference generates a flow in the channel. Gas leaving the low-pressure end of the feedback channel forms a control jet that acts on the supply jet and causes its separation from the attachment wall. The jet cannot remain straight and after the separation therefore attaches to the opposite attachment wall. These changes in the control nozzles generate in the feedback loop channel alternating-direction flow.
  • control actions in the amplifier produce alternating output flow in the two exit terminals of the diverter oscillator. Gas flow leaves one output terminal in first half of the cycle and the other terminal in the rest half of the cycle.
  • the subject of this invention is a unit of a generator of gas bubbles in a liquid connected to the inlet of the gas into the vessel containing the liquid that has the gas supply channel for the flow of the gas branched into at least two concurrent flowpaths each of which contains six components connected in series, namely a nozzle, pre-chamber, vortex chamber, central exit, distribution cavity, and a porous wall open into the vessel with the liquid where the nozzle is directed by its mouth into the pre-chamber and downstream from the nozzle is each flowpath inside the pre-chamber bifurcated into two alternative routes, namely a tangential and a radial route, both entering the vortex chamber, where the radial route is adjacent to an attachment wall directed towards the central exit while in the diverting location at the beginning of the two routes between the nozzle and the beginning of the attachment wall contains mouth of the connection channel leading between the first flowpath and the second flowpath.
  • the unit of a generator of gas bubbles in a liquid connected to the supply of the gas into the vessel containing the liquid may be also characterised by the fact that both the tangential route as well as the radial route lead from the pre-chamber to the axisymmetric vortex chamber through a single common orifice and the pre-chamber has opposite to the attachment wall a antipodal wall that is inclined to it by an angle ⁇ larger than 16 angular degrees and further that between the antipodal wall and the vortex chamber there is a protruding nose.
  • the purpose of this arrangement is simplification of manufacturing of the unit, especially if it is made from a stack of plates with cavities made by removal of the plate material.
  • the unit of a generator of gas bubbles in a liquid connected to the supply of the gas into the vessel containing the liquid may also have two orifices leading into the same vortex chamber, namely one orifice for the tangential route and another orifice for the radial route the said routes being formed each of them at a different side of the splitter.
  • This alternative layout may cause difficulties in the manufacturing process, but if the manufacturing problems are solved then this layout has the advantage of lower energetic losses, in particular for the radial route flow, because the flow through a closed conduit leads to lower pressure loss than a flow into which may be entrained the surrounding fluid.
  • the unit of a generator of gas bubbles in a liquid according to this invention may have inside the vortex chamber positioned a guiding blade shaped into an arch. It was demonstrated that the presence of the guiding blade has a favourable influence on the radial flow through the vortex chamber.
  • the unit of a generator of gas bubbles in a liquid connected to the supply of the gas into the vessel containing the liquid according to this invention may have, if the manufacturing aspects are solved, the upper wall of the vortex chamber and/or the bottom wall of the vortex chamber the shape of a cone.
  • Unit of a generator of gas bubbles in a liquid according to this invention may be advantageously made as a set of plates stacked on each other, containing the top plate provided with exit holes and under it a woven metal textile the part of which under the exit holes forms the porous wall of the distribution cavities where fastened to the top plate under the metal textile is the distribution plate to which is fastened partition containing central exits, the latter connected to the main plate to which is fastened the bottom plate and with advantage the carrying pipe connected to the top plate while the pre-chamber and the vortex chamber are mead in the main plate and the distribution cavities are made in the distribution plate.
  • the supporting ribs are placed between the exit holes in order to decrease the mechanical stressing of the metal textile caused by the gas pressure.
  • the basic manufacturing problem is the rather complex shape of internal cavities.
  • the unit according to this invention achieves new and higher effects than the previously known versions due to the fact that it is particularly suitable for being made in a very compact layout and with minimum spatial requirements, because it unites in a single solid body, submerged under the liquid level, the oscillator as well as two aerators immediately connected to the oscillator exits.
  • the most important fact, however, is easy achieving of low oscillation frequency of the oscillation due to the time delays which are due to gradual spin-up of the fluid motion in the vortex chambers during each cycle - and then equally slow stopping of the rotation in the subsequent part of the cycle.
  • the disadvantages are removed that are listed above as arising in known oscillators from the necessity to have the very long hoses for the feedback loops.
  • the unit according to this invention as shown in Figs. 1 to 4 is an example manufactured by the plate stack method.
  • the necessary cavities inside the unit body are manufactured by material removal separately in the plates. Operation of the unit - as is the case in all the examples of the unit discussed below - depends on oscillatory gas flow with the oscillation generated in cavities inside a solid body.
  • the cavities are made separately in each flat plate of the stack by the known methods like laser cutting or electric discharge machining.
  • the finished plates are stacked and held together. They may be welded together to form a single solid body - or they may be held by screws or similar fasteners allowing disassembling the unit.
  • the particular version presented the first four pictures is intended for producing air bubbles in waste water, such aeration being an important step in the wastewater processing. Without significant changes this unit may be used in other cases of aeration of a liquid.
  • the unit consists of five stainless-steel plates of equal outer shape and, in addition, there is also a thin mesh made by weaving from very thin stainless steel wires (in this particular case the wires are of 40 ⁇ m diameter).
  • This woven steel textile layer is of the same external shape as the other plates in the stack, inside which it is clamped between the uppermost plate and the plate immediately below.
  • the unit is in operation wholly submerged in the liquid, held from above by the carrying pipe 11 .
  • the plates forming the unit are held in a horizontal position horizontal.
  • the internal cavity of the carrying pipe 11 serves as the supply channel 1 bringing compressed air into the unit. In the form of bubbles, the air then leaves the unit into water through the above mentioned mesh.
  • the top plate 95 removed from the unit is shown in Fig. 1 .
  • the carrying pipe 11 (only a short segment of which is shown in Fig. 1 ) is welded to the top plate 95.
  • Apart from the nine screw holes 901 and two dowel holes 902 there are in the top plate 95 also fourteen exit holes 950 of roughly hexagonal shape. These exit holes 950 expose the metal-textile layer, which is held under the top plate 95 . Some areas of this layer, located under the exit holes 950 , thus form the porous walls 9a , 9b of the distribution cavities 8a , 8b made in the distribution plate 94.
  • both the top plate 95 and the metal textile layer are removed, which allows seeing the distribution plate 94. Also the screws and dowels are removed in Fig. 2 .
  • the distribution plate 94 Apart from the holes for these fastening components, there are in the distribution plate 94 two holes, made together with other material removal in a single manufacturing operation by programmed laser cutting. These two holes are star-shaped, with blunt tips of the star. At left this hole forms the first distribution cavity 8a and at right it forms the second distribution cavity 8b .
  • the distribution cavities 8a , 8b are each under the seven exit holes 950. The air from the distribution cavities 8a,b thus can escape upwards through the metal textile supported by the supporting ribs 951.
  • a round hole which is a part of the supply channel 1 .
  • FIG. 3 Shown on the next Fig. 3 is the unit with also the distribution plate 94 removed. This makes possible to see well the partition 93 . It is thinner than other plates, also made of stainless steel and with the same outer shape as the shape of other plates. Apart from the nine screw holes 901 and two dowel holes 902 there are in the partition 93 altogether five round holes. On top is again visible the hole that forms a part of the supply channel 1 . On the right-hand side there is the first central exit 7a and on the opposite left-hand side there is the second central exit 7b . Then there are also the interconnection holes 931 which in the assembled unit are each under one end of the interconnection channel 941 in the distribution plate 94 .
  • Fig. 4 In the top part of Fig. 4 is in the main plate 92 a hole which is a part of the supply channel 1 . Two concurrent flowpaths are branching from it, one at left and the other on the right-hand side.
  • the right-hand side air flow path leads through the first pre-chamber 4a into the first vortex chamber 6a - while, almost symmetrically, on the left-hand side there is connected to the supply channel 1 the second pre-chamber 4b and the second vortex chamber 6b.
  • Fig. 3 it is apparent that air may leave the first vortex chamber 6a through the first central exit 7a made in the partition 93 and, on the other side, air may leave the second vortex chamber 6b through the second central exit 7b in the partition 93 .
  • connection channel 20 which in the main plate 92 consist of two parts which both end, at the bottom of Fig. 4 , in those locations where the partition 93 (as seen in Fig. 3 ) has its interconnection holes 931. These holes make possible - together with the interconnection channel 941 in the distribution plate 94 - union of both parts of the connection channel 20 into a single continuous channel.
  • This connection through other plates is useful because it evades formation in the plates during their manufacturing of " islands" - the unsupported parts of the original plate that fall out in the material removal process and would necessitate expensive repositioning and fixing, a manual operation.
  • the gas flow is divided in pre-chambers 4a, 4b into two alternative flow routes, the tangential route 5a and radial route 5b .
  • Fig. 4 there are in the two flowpaths 2a, 2b two different flow conditions.
  • the gas follows the first tangential route 5aa while in the second pre-chamber 4b the gas takes the second radial route.
  • FIG.5 For description and explanation of the processes that take place inside the unit it is useful to note the schematic representation of the air flows in the following Fig.5 .
  • this is a diagram of topological structure which is the same in all cases of the unit according to this invebntion.
  • the vertical straight lines indicate some important locations.
  • At the left-hand side of the picture Fig. 5 there is the supply channel 1 where gas (air) enters the unit.
  • the illustration is oriented so that the gas (air) passes through the schematic representation from left to right.
  • Represented schematically at the right-hand side are thus the two location where the gas leaves the unit and enters the vessel containing the liquid in which the bubbles are produced.
  • first flowpath 2a is in the top part of the picture while in the bottom half is the second flowpath 2b . Both flowpath pass through nozzles.
  • the first flowpath 2a passes through the first nozzle 3a and the second flowpath 2b through the second nozzle 3b .
  • the two alternative routes downstream from this diverting locations 10a , 10b have different purposes and essentially should not be active simultaneously.
  • Shown in Fig. 5 is a particular phase of the oscillation in which the gas passing through the first flowpath 2a follows after leaving the first nozzle 3a the first tangential route 5aa through the pre-chamber 4a and into the first vortex chamber 6a.
  • the attachment of the gas to the second attachment wall 14b shown in the second flowpath 2b - and, on the other hand, the absence of such attachment to the first attachment wall 14a - is controlled by alternating flow in the connection channel 20 and its flow out from the second mouth 13b .
  • Decisive role is played by pressure distribution in the cavities of the unit.
  • Fig.6 and Fig. 7 are shown in identical perspective views the results of numerical flowfield computations showing trajectories of gas particles in the pre-chambers 4a, 4b and vortex chambers 6a , 6b .
  • the geometry of the chambers corresponds exactly to that shown in Fig. 4 .
  • the computations were made for everywhere the same depth of the cavities, equal to the thickness 4 mm of the main plate 92 and for the 70 mm diameter of the vortex chambers.
  • the width of the nozzle 3a, 3b in this case was 2.56 mm.
  • the gas leaving the first nozzle 3a follows the tangential route 5a while in Fig. 7 the gas follows the radial route.
  • FIG. 8 are presented parts of the first flowpath 2a consisting of_the first nozzle 3a , the first pre-chamber 4a as well as the first vortex chamber 6a.
  • the illustration shows some most important aspects of the planar geometry, which were found by computations with alternative geometric features. It is shown here, that if the first diverting location 10a into the first tangential route 5aa and the first radial route 5ba is to be as requested in the first pre-chamber 4a , then it is necessary do select a large angle ⁇ between the first attachment wall 14a and the first antipodal wall 15a .
  • first attachment wall 14a oriented so that the extension 214 of its end is directed exactly into the centre of the first vortex chamber 6a.
  • shaping of the nose 46 and a proper width of the first orifice 146a which in the case of Figs. 6 and 7 was equal to five widths of the exit from the first nozzle 3a.
  • For proper directing of the first radial route 5ba is was also important to form the shallow recession 206 in the wall of the first vortex chamber 6a.
  • Fig. 9 is demonstrated the asymmetry of the flowfield in the cavities arising despite the fact that their shape is symmetric relative to the symmetry axis 100.
  • the picture presents computed flow in the cavities of the main plate 92 in both flowpaths 2a, 2b at the extreme situation arising once in each oscillation cycle.
  • the computed trajectories of gas are coloured by the local pressure according to the scale at the left-hand side of the picture.
  • the monochromatic greyscale representation makes the pressure distribution less apparent.
  • Fig. 10 shows schematically the pressure conditions along the two flowpaths 2a , 2b .
  • the situation represented corresponds to the case in Fig. 9 : full rotation in the first vortex chamber 6a and the easy, essentially non-rotational flow in the second flowpath 2b .
  • Different pressure values in the two flowpaths 2a, 2b in the same locations are due to two factors. The first one is the intensity of the gas flow. The second is the effect of the large pressure drop on the first vortex chamber 6a with the rotation in it.
  • both nozzles 3a, 3b are geometrically the same, due to the easy character the flow rate in the second flowpath 2b is much larger - and, consequently, the pressure drop on the second nozzle 3b is much larger. On the other hand, due to the large pressure drop in the first vortex chamber 6a the flow rate through the first nozzle 3a is much smaller. In both flowpaths 2a, 2b a small pressure increase takes place in the upstream part of both pre-chambers 4a , 4b . This is an effect of pressure recovery in the slightly decelerating flow downstream from the exit from the nozzles 3a , 3b .
  • the air flow leaving the first nozzle 3a stops following the tangential route 5a and sooner or later attaches to the first attachment wall 14a.
  • the entrance flow into the first vortex chamber 6a will cease to be tangential.
  • the outflow from the second mouth 13b will cause the flow deflection away from the second attachment wall 14b .
  • the flow into the second vortex chamber 6b will cease to be radial.
  • the first flowpath 2a and the second flowpath 2b will exchange their respective roles. This, however, does not take place immediately.
  • the vortical motion in the first vortex chamber 6a will tend to keep its moment of momentum.
  • spinning up the rotation in the second vortex chamber 6b also takes some time.
  • the exchange of the radial route 5b and the tangential route 5a will be not instantaneous but will proceed with a time delay - despite the relative shortness of the connection channel 20.
  • the conditions will be a mirror image relative to the symmetry axis 100.
  • the air will rotate in the second vortex chamber 6a and will find an easy way out from the first vortex chamber 6b. This stops the previous flow in the connection channel 20 and then reverses the flow in it.
  • the roles of the vortex chambers 6a, 6b will exchange again - coming, after a certain delay, to the initial regime. The process then can start another cycle.
  • FIG. 11 is shown an alternative layout of the pre-chamber 4a, 4b.
  • the picture shows the first flowpath 2a and a part of the second flowpath 2b, which is of similar layout (it is a mirror image with respect to the symmetry axis 100, Fig. 9 ).
  • the geometry of cavities is very similar to the example presented in Fig. 4 .
  • the unit is a planar layout made from a stack of plates and what is shown in Fig. 11 is the main plate 92, made in a constant-thickness plate with laser-cut cavities.
  • the layout is very similar to Fig. 4 .
  • There is the supply channel 1 at left bifurcating into two flowpaths 2a, 2b - of the latter is drawn in Fig.
  • the first flowpath 2a leads through the first nozzle 3a and the second flowpath 2b leads through the second nozzle 3b.
  • Nozzles 3a, 3b have their exits open into the pre-chambers 4a, 4b.
  • One of the pre-chamber walls is the attachment wall 14a, 14b where there are the secondary bifurcations into the radial route 5b and the tangential route 5a, both leading into its vortex chamber 6a, 6b.
  • the radial route 5b in the first flowpath 2a is a direct continuation of the first attachment wall 14a of the first pre-chamber 4a and like in the layout shown in Fig.
  • the attachment of the air jet issuing from the first nozzle 3a is facilitated by the first nozzle 3a exit direction coinciding with the direction of the first attachment wall 14a.
  • the basic difference between the layouts in Fig. 4 and Fig. 11 is there is only one orifice between the first pre-chamber 4a and the first vortex chamber 6a in Fig. 4 while here in Fig. 11 there are two such orifices: the first orifice 146aa and the second orifice 146ba.
  • the tangential route 5a has its separate orifice for entry into the first vortex chamber 6a.
  • the gas jet leaving the first nozzle 3a is to be directed into the tangential route 5a - and this means, equally as in the configuration from Fig. 4 , that this jet must be separated from the first attachment wall 14a.
  • the sense of the rotation generated in the first vortex chamber 6a after this separation is opposite to the rotation sense in the case of Fig. 4 .
  • the tangential route 5a is separated from the radial route 5b by the splitter 50.
  • the straight flow through the orifice for the tangential route 5a is associated with lower hydraulic losses than in the case with the turning of the flow direction in Fig. 4 .
  • rapidly prototyping or also “three-dimensional printing”
  • three-dimensional printing offer an alternative to the manufacturing by the above described method of material removal from flat plates that are then stacked.
  • these alternative methods are based on three-dimensional computer-controlled addition of the material that forms cavity walls.
  • a typical case is, e.g., the stereolithography in which the walls are grown from a monomer liquid that solidifies - polymerises - upon laser light activation.
  • Another possibility is selective laser sintering in which the body of the unit is formed from powder added in thin layers to the wall locations after which the powder particles are fixed by heating them, by laser, up to the partial melting temperature.
  • the freedom offered by the stereolithography is used in this example to shape the vortex chambers 6a, 6b so that the requested change in the flow direction is by an angle less than by 90° .
  • Figure 12 shows a part of the first flowpath 2a involving the first pre-chamber 4a and the first vortex chamber 6a.
  • the cavities are shown in imagined meridian-plane section through the body of the unit.
  • the first vortex chamber 6a is of conical shape, decreasing in diameter towards the apex of the cone.
  • the necessary turning angle for entry into the first central exit 7a is only 45° rather than the full 90°.
  • Such a flow is easier, i.e. producing a lower hydraulic loss, which leads to a higher desirable pressure drop ⁇ P J that drives the flow in the connection channel 20.
  • the manufacturing methods known as "rapid prototyping” need not be generally accessible. They may also be costly and their special requirements on the character of the material easily polymerised from a liquid may be not compatible with the mechanical requirements of the body of the unit. After all, at present the methods are really used just to produce a prototype verifying the geometrical spatial conditions. In the cases where the "rapid prototyping" methods are not suitable, the complex internal cavities of the unit may be made by the classical method of "lost wax" casting.
  • the freedom offered by the stereolithographic manufacture is used even more.
  • the overall configuration of the unit corresponds to the schematic representation in Fig. 5 and the part that is shown in Fig. 13 shows a section through the body of the unit involving the first pre-chamber 4a and the first vortex chamber 6a. The difference is in the shape of the first central exit 7a. It is here not coaxial with the vortex chamber axis 101 as was the case in Fig. 12 but it is here inclined so that its axis is in line with the first radial route 5ba flow.
  • the nose 46 directs the gas to enter the first vortex chamber 6a tangentially, as is shown by the gas trajectory with arrows.
  • the conditions with the rotation do not differ very much from the conditions inside the cylindrical flat disk geometry in the previous examples Fig. 4 and Fig. 9 .
  • the centrifugal action makes the rotating flow difficult - and the inclined first central exit 7a makes the pressure drop even higher.
  • the straight flow following the first radial route 5ba causes much lower overall pressure drop.
  • the manufacturing method of selective laser sintering from powder makes possible making the manufactured product not only with solid walls, but also in a selected part of the manufactured object to make the cavity walls with tiny pores.
  • this is used for producing in a unit body simultaneously with making the solid walls also the porous walls 9a, 9b of the distribution cavity 8a , 8b , needed for generation of the gas bubbles.
  • the first porous wall 9a is shown arched inwards into the first distribution cavity 8a .
  • first porous wall 9a thinner and easier for the air to pass through it without unduly stressing the sintered first porous wall 9a in tension by the force action of the compressed air.
  • the dome-shaped first porous wall 9a is stressed by the acting pressure difference in compression, which it can better withstand.
  • Easier the entry from the vortex chamber 6a, 6b into the central exit 7a , 7b by the air in the regime with the flow following the radial route 5ba , 5bb may be achieved by alternative shapes of the cavities not necessary requesting unusual manufacturing methods.
  • the example presented in Fig. 15 achieves the desirable effect by the presence of the guiding blade 16 positioned inside the vortex chamber 6a, 6b not far from the central exit 7a , 7b .
  • the shape of the guiding blade 16 is derived from the shape of the air trajectories in the particular location inside the vortex chamber 6a, 6b in the regime with air rotation as shown in Fig. 6 .
  • the guiding blade 16 is very thin so that it does not in that regime produce a significantly large wake downstream from it.
  • FIG. 17 Another possibility how to force the gas to change its flow direction in the centre of the first vortex chamber 6a and induce it to enter the first central exit 7a is shown in Fig. 17 .
  • first pre-camber 4a considered in all alternatives discussed above, there are here many pre-chambers distributed evenly on the perimeter of the first vortex chamber 6a so that first radial routes 5ba leaving these pre-chambers collide.
  • first perimeter pre-chamber 4a1 on top at left
  • the second perimeter pre-chamber 4a2 on the left side below
  • the fourth perimeter pre-chamber 4a4 bottom right the fourth perimeter pre-chamber 4a4 bottom right.
  • Fig. 18 presents the layout of the first vortex chamber 6a in principle similar to the previous example in Fig. 17 where, however, the four perimeter pre-chambers 4a1, 4a2, 4a3, 4a4 are replaced by altogether sixteen inlets. All the air supplied by way of the first flowpath 2a into the sixteen first nozzles 3a is led into a single annular space so that the body in which in Fig. 17 are the pre-chambers is here in Fig. 18 disintegrated into sixteen bodies 1000. Each body 1000 has its first attachment wall 14a to which after leaving the first nozzles 3a attach the first radial routes 5ba directed towards the first central exit 7a.
  • each body 1000 has its first antipodal wall 15a the end of which is directed tangentially into the space that forms the first vortex chamber 6a. Since in the centre of the first vortex chamber 6a collide altogether sixteen radial inflows (of which only a single representative is shown in Fig. 18 ) the symmetry of flows is secured and with it also the low pressure drop across the first vortex chamber 6a in the regime with absence of rotation. As soon as air from the connection channel 20 starts to flow from the first mouths 13a, the air flow through the first nozzles 3a is separated from the first attachment walls 14a and follows the first antipodal wall 15a. These walls guide it - in a manner similar to the first tangential route 5aa presented in Fig. 11 - tangentially into the first vortex chamber 6a. Due to the large number of tangential inflows also this regime is characterised by welcome symmetry of the flowfield.
  • the first vortex chamber 6a arranged according to Fig. 18 has all prerequisites for high efficiency, i.e. on one hand the very low pressure drop in the radial flow regime and on the other hand very high pressure drop in the tangential flow regime with rotation.
  • the only disadvantage of this layout is the large diameter, especially with the system of the bodies 1000 on its outer circumference an, in addition, the annular space for air distribution into the first nozzle 3a.
  • Fig. 19 One solution is presented in Fig. 19 .
  • the radial layout of the bodies 1000 in Fig. 18 is here in Fig. 19 replaced by an axial layout.
  • the picture shows one from the two identical vortex devices in a unit.
  • At the left-hand side in Fig. 19 there is the entrance by axial first flowpath 2a which leaves, also axially, on the right-hand side.
  • the long conical diffuser (that improves the ratio of the pressure drops in the two regimes) is the first central exit 7a from the first vortex chamber 6a.
  • the first vortex chamber 6a is of flat cylindrical shape.
  • the first distribution cavity 8a with its first porous wall 9a connected directly to the first central exit 7a are not shown here.
  • the first vortex chamber 6a is here formed between the outer shell (only one half of which is shown, the other half being removed by imagined meridian section) and the axially symmetric central body 2000 similarly shown with one half removed.
  • the first flowpath 2a passes through the annular space between the outer shell and the central body 2000.
  • the spaces between the bodies 1000 form the first nozzles 3a.
  • Exit from the first nozzles 3a is directed axially, i.e. in parallel with the axis of the device.
  • one of the sides of the bodies 1000 forms the first attachment wall 14a.
  • the opposite first antipodal wall 15a wall of bodies 1000 is inclined and curved so as to lead into the first vortex chamber 6a tangentially. Between this wall and the attachment wall 14a is inserted the splitter 50 (similar as shown in Fig. 11 ).
  • first mouth 13a If a small pressure drop across the first vortex chamber 6a is requested, there is to be no air flow issuing from the first mouth 13a.
  • the air of the first flowpath 2a enters the first nozzle 3a , is accelerated there and directed to the first attachment wall 14a. This guides it axially and then, following the downstream side of the central body 2000 it is turned into the radial inflow into the first vortex chamber 6a where there is no rotation.
  • the pressure in the first mouth 13a is very low - and it is further decreased by the conversion taking place in the diffuser of the first central exit 7a.
  • This low pressure would induce an air flow into the connecting channel 20 (not drawn in Fig. 19 ) leading towards the first mouth 13a. from the second mouth 13b where the pressure is higher.
  • the flow in the connecting channel 20 gains momentum, it will assume a magnitude sufficient for separating the axial air flow from the first attachment wall 14a and switching it towards the first antipodal wall 15a thatg guides it into the tangential route 5a past the splitter 50.
  • This tangential inflow starts the rotation in the first vortex chamber 6a. Pressure difference across it increases. This is leads to flow direction reversal in the connecting channel 20 and subsequently to the next half of the pulsation cycle.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Biotechnology (AREA)
  • Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)
EP12199083.2A 2012-11-22 2012-12-21 Unit of a generator of gas bubbles in a liquid Withdrawn EP2735362A1 (en)

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CZ2012-822A CZ304314B6 (cs) 2012-11-22 2012-11-22 Jednotka generátoru plynových bublin v kapalině

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WO2016018504A1 (en) * 2014-07-29 2016-02-04 MikroFlot Technologies LLC Low energy microbubble generation by supplying pulsating gas to a porous diffuser
US9643140B2 (en) 2014-05-22 2017-05-09 MikroFlot Technologies LLC Low energy microbubble generation system and apparatus
SE2150045A1 (en) * 2021-01-18 2022-07-19 Valmet Oy Mixing device

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CZ2014903A3 (cs) * 2014-12-15 2016-07-20 Ústav termomechaniky Akademie věd České republiky v.v.i. Fluidický oscilátor

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Cited By (5)

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US9643140B2 (en) 2014-05-22 2017-05-09 MikroFlot Technologies LLC Low energy microbubble generation system and apparatus
WO2016018504A1 (en) * 2014-07-29 2016-02-04 MikroFlot Technologies LLC Low energy microbubble generation by supplying pulsating gas to a porous diffuser
SE2150045A1 (en) * 2021-01-18 2022-07-19 Valmet Oy Mixing device
WO2022154712A1 (en) * 2021-01-18 2022-07-21 Valmet Ab Mixing device
SE545007C2 (en) * 2021-01-18 2023-02-28 Valmet Oy Mixing device and method for mixing a fluid into a fiber pulp

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CZ304314B6 (cs) 2014-02-26

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