WO2017155417A1

WO2017155417A1 - Improvements in and relating to mixers

Info

Publication number: WO2017155417A1
Application number: PCT/NZ2017/050024
Authority: WO
Inventors: Bruce Hyndman Henley
Original assignee: Bruce Hyndman Henley
Priority date: 2016-03-10
Filing date: 2017-03-10
Publication date: 2017-09-14
Also published as: AU2017231596A1

Abstract

A dual impeller fluid mixer which includes a curved surface; a first impeller which creates from a first liquid source a first fluid stream moving over the curved surface along a first fluid path; a second impeller which creates from a second gas source a second fluid stream moving along a second fluid path; wherein the first and second fluid paths are directed to collide with one another at the outermost edge of the curved surface.

Description

Improvements in and Relating to Mixers

TECHNICAL FIELD

The present invention relates to improvements in fluid mixers and in particular to the mixing of fluids having different densities.

BACKGROUND ART

Methods and apparatus for mixing fluids vary greatly depending on the function they provide. One known mixing apparatus is a water aerator. Water aerators mix air into water in order to provide oxygenation of water allowing for biological oxidation reactions to take place.

One type of water aerator that is commonly used is a surface aerator. Surface aerators typically provide an axial suction flow which pulls water up from within a body of water. The axial flow is redirected at the surface of the water into a substantially radial discharge flow. Whilst the water is in flight it is able to adsorb air that is entrained by the discharge flow. As the discharge flow re-enters the body of water it carries the entrained air with it, thereby introducing bubbles into the body of water. Surface aerators create a circulating flow, carrying and mixing aerated water into a body of water.

The efficiency of a surface aerator is typically measured in kg of oxygen per kWh. Surface aerators rely on air-water contact to transfer oxygen, therefore a combination of a flatter and broader discharge flow and/or greater surface turbulence equate to greater aeration efficiency.

Whilst surface aeration systems are known they have not varied greatly in their design over time. Known systems rely on a combination of providing a broad flat radial discharge in combination with a degree of surface agitation. It would therefore be useful to have a system that includes additional mechanisms for aerating the water, thereby increasing the aeration efficiency.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the l common general knowledge in the art, in New Zealand or in any other country.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF THE INVENTION

The present invention generally relates to an impeller unit, a system and a method for mixing two fluids. In use portions of the impeller unit are positioned within each of the fluids to be mixed at a boundary of the fluids. The impeller unit drives the fluids together adjacent an edge of a curved surface of the impeller unit creating a predominantly radial flow relative to the axis of the impeller unit, wherein the first and second fluids are mixed together along the edge.

According to a first aspect of the present invention there is provided a dual impeller fluid mixer which includes: a curved surface; a first impeller which creates from a first liquid source a first fluid stream moving over the curved surface along a first fluid path; a second impeller which creates from a second gas source a second fluid stream moving along a second fluid path; wherein the first and second fluid paths are directed to collide with one another at the outermost edge of the curved surface.

Preferably the curved surface may provide an angular redirection of the first fluid of

substantially 90 degrees.

In use the first impeller is positioned within a first fluid. The impeller imparts an axial flow to the first fluid, this flow is redirected by the curved surface into a substantially radial flow and is mixed with the second fluid to provide a mixed flow of the first and second fluid that is parallel to a boundary layer between the first fluid and the second fluid.

In preferred embodiments the mixing edge is formed at an outer edge of the curved surface.

Prior to mixing the first fluid flow and the second fluid flow are separated from one another by the curved surface that provides redirection of the first fluid. Where the curved surface ends the separation between the first fluid and the second fluid is no longer present and the first and second fluid are driven into the same physical space. The edge of the curved surface acts a mixing zone as the first and second fluids are forced together.

In preferred embodiments the curved surface is the outer surface of a flared cone, wherein the first fluid flows along the outer surface of the cone from a narrow end to a flared end of the cone.

A flared cone provides redirection of an axial flow of fluid along the axis of the flared cone into a radial spread of the fluid. A further advantage of a flared cone is that the flared end of the cone provides a long mixing edge along which the first and second fluids can mix.

The curved surface may include a portion that extends substantially radially from its outer edge, the radially extending portion configured to provide substantially radial flow of fluids away from the outer edge of the surface.

In preferred embodiments the mixing edge is formed at an outer edge of the flared end of the cone.

The curved surface may be formed from any number of materials, such as metal, plastic or a composite material as such the material construction should not be seen as being limiting.

In preferred embodiments the first impeller is aligned coaxially with the axis of the flared cone.

The first impeller drives the first fluid axially with respect to the impeller drive axis and along the curved surface of the flared cone, the axial flow of the first fluid relative to the impeller is redirected into a substantially radial flow with respect to the axis of the drive impeller. Coaxial alignment of the first impeller with the flared cone is advantageous as this configuration results in the first fluid being pulled from a depth within a body of the first fluid. It should however be appreciated that the first fluid could be directed onto the flared cone by way of ducting or the like, allowing for the first impeller to be located some distance from the flared cone and not in coaxial alignment. The first impeller may take a number of different forms without departing from the scope of the present invention, non-limiting examples may include, helical screw, multiple blade screws, fixed pitch and variable pitch propellers.

The flared cone may take the form of a fixed deflector, or may be attached to one, or both, of the first impeller or second impeller.

In preferred embodiments the first impeller is formed along at least a portion of the surface of the flared cone.

Preferably the first impeller is formed at the narrow end of the flared cone.

In preferred embodiments the flared cone forms a drive shaft of the first impeller.

In preferred embodiments the first impeller is an axial screw impeller.

Preferably the flared cone attaches directly to a motor drive shaft. Forming the impeller on the surface of the flared cone provides simplicity and allows the impeller to be spun by rotation of the flared cone. This is advantageous in that the spinning cone further accelerates the flow of the first fluid as it is redirected across the rotating curved surface of the flared cone.

Preferably the second fluid mixes with the first fluid along the length of an outer edge of the flared cone.

Preferably the velocity imparted to the first fluid creates a lower pressure region immediately adjacent the mixing edge as the first fluid transitions across the mixing edge. In operation the lower pressure zone acts to pull the second fluid into the first fluid at the mixing edge.

In preferred embodiments the source of the second fluid is a second impeller of a pump. The pump may take any number of forms without departing from the scope of the present invention, for example the pump may be integrated with, or driven by, a drive unit of the first impeller, it may be a separate fluid pump that provides a flow of second fluid to the mixing edge, or the second impeller may be integrated with a portion of the first impeller.

In some preferred embodiments the second impeller may be driven by the same motor as the first impeller. In other embodiments separate motors may be provided for each impeller.

Preferred embodiments may include a second impeller that is attached to the drive shaft of the first impeller.

Driving the first and second impeller from the same drive motor, such as when the first and second impeller are driven by the same drive shaft, reduces cost and complexity. In particular the expense of a second drive motor is avoided and the requirement for additional ducting of the first and second fluids to the mixing edge may be eliminated.

In some preferred embodiments the second impeller may be attached to, or formed at, the flared end of the flared cone.

In preferred embodiments the second impeller drives the second fluid radially with respect to the axis of the flared cone.

At the edge of the flared cone both the first fluid and the second fluid are flowing substantially radially with respect to the axis of the flared cone, at the edge of the wide end of the flared cone the first and second fluids are flowing substantially in parallel and as they pass over the edge they are able to mix.

In preferred embodiments the first fluid is water.

In preferred embodiments the second fluid is air. According to a second aspect of the present invention there is provided an apparatus for mixing fluids, including:

• a support structure;

• a drive unit; and

• a dual impeller fluid mixer; wherein the drive unit is fixed to the support structure and is configured to impart rotational motion to the dual impeller fluid mixer; wherein the support structure is configured, in use, to position:

- the first impeller of the dual impeller fluid mixer within a source of the first fluid; and

- the second impeller of the dual impeller fluid mixer within a source of the second fluid of the dual impeller fluid mixer; wherein rotation the first impeller via the drive unit, in use, drives the first fluid onto the curved surface of the first impeller so as to produce an accelerating radial flow of the first fluid with respect to the axis of rotation of the first impeller; and wherein rotation of the second impeller pulls in the second fluid which is redirected to be driven into a collision with the first fluid at an outermost edge of the curved surface; and wherein the first fluid and the second fluid are atomised at the outermost edge of the curved surface. In preferred embodiments the drive unit is a motor attached to the support structure by a motor mount, the motor mount configured to space the motor away from the support structure so as to provide a gap through which a mixed first fluid and second fluid can be radially dispersed. In preferred embodiments a flow plate is positioned between the motor and the impeller unit, wherein a gap is provided between the motor and the top of the flow plate to allow the second fluid to pass there between.

Preferably the flow plate includes an aperture through which a drive shaft of the motor passes and attaches to the impeller unit. Preferably the flow plate includes an aperture there through for the second fluid to flow from the top of the flow plate to the impeller unit.

The aperture through the flow plates may be provided as a number of flow apertures, or may be provided by way of the aperture through which the drive shaft of the motor passes. Such where the diameter of the drive shaft aperture is sufficiently large to, allow the second fluid to pass between the drive shaft and the flow plate.

Some embodiments may include an impeller housing attached to the support structure into which the impeller unit is located.

In use the impeller housing constrains a first fluid flow in a substantially axial direction relative to the axis of the impeller unit. In preferred embodiments the support structure is one or more of:

• a float unit, or

• a framework.

According to a third aspect of the present invention there is provided a method of mixing two fluids, including the steps of: a) rotating a first impeller to drive a first fluid from a first inlet against a curved surface to produce a radial fluid flow with respect to the rotational axis of the first impeller; b) driving a second fluid from a source of the second fluid into the first fluid at a mixing edge of the curved surface, and c) mixing the radially flowing first fluid and the second fluid at a mixing edge of the curved surface.

According to a fourth aspect of the present invention there is provided a method of mixing two fluids comprising the steps of: accelerating a first fluid in the form of a liquid in a first direction to form a first fluid path; accelerating a second fluid in the form of a gas in a second radial direction to form a second fluid path; directing at least one fluid path to collide with the other fluid path so as to atomise the liquid in a radial direction.

According to a fifth aspect of the present invention there is provided a use of an air stream as a destructive force to atomise a liquid effluent stream to increase the surface area of the gas liquid interface to maximize oxygen transfer.

Preferred embodiments of the present invention may provide a number of advantages, including, but not limited to:

• Providing a system that provides an increase in oxygen transfer efficiency.

• Providing a system that provides radial mixing of two fluids.

• Providing a system that provides high efficiency mixing of fluids.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 Shows a profile view of an impeller unit for a fluid mixer in accordance with a preferred embodiment of the present invention;

Figure 2 Shows a top isometric view of the impeller of Figure 1 ;

Figure 3 Shows a top isometric view of the impeller of Figure 2 including a flow plate for the second impeller which has a section partially cut away along x-x;

Figure 4 Shows a profile view of a fluid mixer including the impeller unit of Figure 1 ;

Figure 5 Shows a top isometric view of the fluid mixer of Figure 4; Figure 6 Shows an in use depiction of the fluid mixer of figures 4 and 5;

Figure 7 Shows a more detailed view of the in use depiction of Figure 6; and

Figure 8 Shows a partial close up of what is generally shown in Figures 6 and 7 illustrating the method of the present invention in greater detail.

BEST MODES FOR CARRYING OUT THE INVENTION

Referring to Figures 1 , 2 and 3 there is shown a dual impeller fluid mixer as generally indicated by designator 1. The dual impeller fluid mixer 1 includes a curved surface in the form of flared cone 2 that tapers from a narrow end 2a to a wide end 2b. A first impeller in the form of dual start helical screw 3 is formed on the surface of the flared cone 2. The helical screw may be formed on the flared cone 2 in a number of ways without limitation, including welding, casting, bonding or fastening with rivets, screws or the like. As such the manner in which the helical screw 3 is formed on the flared cone 2 should not be seen as being limiting. In Figure 1 and Figure 2 the helical screw 3 is positioned near the narrow end 2a of the flared cone 2. It will be appreciated that the blades of the helical screw may be positioned at various locations along the length of the flared cone 2 and may vary in length and pitch without limitation. The helical screw impeller provides a flow path in a direction from the narrow end 2a to the wide end 2b of the flared cone 2. The flow path is predominantly axial at the narrow end 2a of the flared cone, this flow is redirected by the flare of the flared cone and becomes predominantly radial as it passes the mixing edge 5 at the wide end 2b.

The dual impeller fluid mixer 1 also includes a second impeller in the form of radial flow impeller 4 formed at the wide end 2b of flared cone 2, this is most clearly shown in Figure 2. The radial flow impeller includes vanes 6, each including an air grabbing portion 7 at an inner end thereof configured to pull air into the impeller, the air is then radially thrust relative to the axis of the impeller. The flow paths created by the helical screw impeller 3 and radial flow impeller 4 are separated initially by the flared end 2b of the flared cone 2, at the outermost edge 5 at the wide end 2b the flow paths collide and mix. The second impeller includes a flow plate 14 which sits above vanes 6, the top plate 30 is ring shaped to create central orifice (annulus) 15 through which air is sucked by the air grab portion 7. The top plate remains stationary whilst the second impeller is dynamic and rotates. Thus, the top plate 30 forms part of the housing of a compressor created by rotation of the vanes 6. The motion of the air is shown in greater detail in Figure 7 described below.

An attachment point 9 is provided to which a drive motor 10, shown in Figures 4 to 7, can be attached. In use the drive motor 10 rotates the entire impeller unit 1. It will however be appreciated that a non-unitary construction may be used where the first impeller, second impeller and curved surface are separate from one another. In such an embodiment the first impeller is driven by a drive shaft that passes through the centre of a fixed curved surface. A separate motor may be used for driving the second impeller.

Referring to Figure 4 and Figure 5 there is shown an apparatus for mixing fluids as generally indicated by designator 11. The apparatus includes a support structure in the form of a float chamber 12 to which a drive unit in the form of electric motor 10 is attached. The float chamber is illustrated with a section removed so that the detail of the impeller unit 1 is shown. The electric motor 10 is attached by motor mount 13. The motor mount spaces the motor away from the float chamber 12 so as to provide a gap 17 through which a mixed first fluid and second fluid can be radially dispersed. The motor mount 13 also includes a flow plate 14 which is positioned between the electric motor 10 and the impeller unit, adjacent the second impeller 4. A gap 19 is present between the motor 10 and the top of the flow plate 14 to allow a second fluid to pass there between. The flow plate 14 includes an orifice 15 through which the attachment point 9 of the first impeller is positioned and attached to the electric motor 10. The orifice 15 is larger than the diameter of the motor attachment point 9, thereby allowing the second fluid to flow from the top of the flow plate 16 through the orifice 15 and into the radial flow impeller 4. Attached below the float chamber 12 is an impeller housing 18, into which impeller unit 1 is located.

The following example is provided to clarify the invention and the manner in which it works, it should not be understood that the particular embodiment described is not an exhaustive description of the potential uses or implementation of the invention.

Referring to Figures 6, 7 and Figure 8 there is shown a dual impeller fluid mixer apparatus in the form of a water aerator, as generally indicated by designator 20. The water aerator 20 is positioned partially within a body of water 21 having a surface 22, and a body of air 23. The water aerator 20 includes float chamber 12 that floats on the surface 22. Above the surface 22 and attached to float chamber 12 by motor mount 13 is motor 10.

In use the motor 10 rotates the impeller unit 1. Rotation of the impeller unit 1 rotates helical screw impeller 3 creating an axial flow of water 24 along the axis of flared cone 2 from the narrow end 2a to the wide end 2b, the wide end 2b redirects the axial flow 24 into a radial flow 25. As the water flows through/over the flare of the flared cone the increasing diameter of the flared cone further accelerates the flow of water in a radial direction. At the same time axial flow impeller 4 sucks air 23 through aperture 15 in flow plate 14. The air 23 is radially accelerated in aperture 15 as shown by arrows 27 by the second impeller 4. The radial flow of water 25 and air 27 are initially separated from one another by a portion of the flared cone 2, however along mixing edge 5 the water flow 25 and the air flow 27 mix. The water flow 25 has a relatively high velocity due to the helical screw and flare of the first impeller. The motor mount 13 spaces the motor 10 from the float chamber 12 and provides a gap 17 through which an atomised mixture of water 25and air 27 can be radially dispersed.

In Figure 8 it can be more clearly seen that the flow plate 14 directs the atomised air/water mixture 28 and generates a substantially radial fluid path before entering the body of water 21 where turbulent mixing provides a final opportunity for air and water to mix. Figure 8 also usefully illustrates the method of the present invention whereby two fluids are mixed by:

- accelerating the first fluid in the form of water 23 in a first direction to form fluid path 24; and

- accelerating the second fluid in the form of air in a second direction to form fluid path 27; - directing the accelerated water fluid path 27 to collide with the accelerated air fluid path 27 to form an atomised water fluid path 28.

Figure 8 also serves to illustrate the effective use of an air stream 27 as a destructive force to atomise a liquid effluent stream 24 to increase the surface area of the gas liquid interface to maximize oxygen transfer.lt will be appreciated that in a traditional surface aerator it is only the stages where the radial flow of water is airborne and the subsequent turbulent mixing as the airborne water re-enters a body of water that air water mixing occurs.

Below the float chamber 12 impeller housing 18 constrains the water 25 flow in an axial direction drawing water from below the float and promoting a circulating flow 25 below surface 22. The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.

Reference to any prior art in this specification is not, and should not be taken as, an

acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world. The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Claims

WHAT WE CLAIM IS:

1. A dual impeller fluid mixer which includes: a curved surface; a first impeller which creates from a first liquid source a first fluid stream moving over the curved surface along a first fluid path; a second impeller which creates from a second gas source a second fluid stream moving along a second fluid path; wherein the first and second fluid paths are directed to collide with one another at the outermost edge of the curved surface.

2. A dual impeller fluid mixer as claimed in claim 1 wherein the curved surface provides an angular redirection of the first fluid of substantially 90 degrees.

3. A dual impeller fluid mixer as claimed in any one of the preceding claims wherein the

curved surface is the outer surface of a flared cone.

4. A dual impeller fluid mixer as claimed in any one of claims 1 to 3 wherein the first impeller is formed along at least a portion of the surface of the flared cone.

5. A dual impeller fluid mixer as claimed in any one of claims 1 to 4 wherein the flared cone forms a drive shaft of the first impeller.

6. A dual impeller fluid mixer as claimed in claim 1 wherein the second fluid collides with the first fluid along the length of an outer edge of the flared cone.

7. A dual impeller fluid mixer as claimed in any one of the preceding claims wherein the first impeller is an axial screw impeller.

8. A dual impeller fluid mixer as claimed in claim 5 wherein the second impeller is attached to the drive shaft of the first impeller.

9. A dual impeller fluid mixer as claimed in claim 4 wherein the curved surface is the outer surface of the flared cone and the second impeller is attached at the flared end of the flared cone.

10. A dual impeller fluid mixer as claimed in claim 8 wherein the second impeller drives the second fluid radially with respect to the axis of the flared cone.

1. An apparatus for mixing fluids, including: a support structure; a drive unit; and a dual impeller fluid mixer ; wherein the drive unit is fixed to the support structure and is configured to impart rotational motion to the dual impeller fluid mixer; wherein the support structure is configured, in use, to position: the first impeller of the dual impeller fluid mixer within a source of the first fluid; and the second impeller of the dual impeller fluid mixer within a source of the second fluid of the dual impeller fluid mixer; wherein rotation the first impeller via the drive unit, in use, drives the first fluid onto the curved surface of the first impeller so as to produce an accelerating radial flow of the first fluid with respect to the axis of rotation of the first impeller; and wherein rotation of the second impeller pulls in the second fluid which is redirected to be driven into a collision with the first fluid at an outermost edge of the curved surface; and wherein the first fluid and the second fluid are atomised at the outermost edge of the curved surface.

12. The apparatus for mixing fluids as claimed in claim 11 wherein the drive unit is a motor attached to the support structure by a motor mount, the motor mount configured to space the motor away from the support structure so as to provide a gap through which a mixed first fluid and second fluid can be substantially radially dispersed.

13. The apparatus for mixing fluids as claimed in any one of claims 11 to 12 including an

impeller housing having one or more curved inlet vanes that are configured to direct the first fluid into the impeller unit.

14. The apparatus for mixing fluids as claimed in claim 13 wherein the curved inlet vanes

impart a rotational velocity component to the incoming first fluid.

15. The apparatus for mixing fluids as claimed in any one of claims 11 to 14 wherein the

support structure is a float unit.

16. A method of mixing two fluids, including the steps of: a) rotating a first impeller to drive a first fluid from a first inlet against a curved surface to produce a radial fluid flow with respect to the rotational axis of the first impeller; b) driving a second fluid from a source of the second fluid into the first fluid at an

outermost edge of the curved surface, and c) mixing the radially flowing first fluid and the second fluid at an outermost edge of the curved surface.

17. A method of mixing two fluids comprising the steps of:

- accelerating a first fluid in the form of a liquid in a first direction to form a first fluid path;

- accelerating a second fluid in the form of a gas in a second radial direction to form a second fluid path; directing at least one fluid path to collide with the other fluid path so as to atomise the liquid in a radial direction.

18. A use of an air stream as a destructive force to atomise a liquid effluent stream to increase the surface area of the gas liquid interface to maximize oxygen transfer.