Patent Application
20070063076
1. Field of the Invention
This invention relates to liquid handling processes and apparatus. More particularly, this invention relates to new methods and apparatus for distributing the flow of liquid from a spray device.
2. Description of the Related Art
Fluidic inserts or oscillators are well known for their ability to provide a wide range of distinctive liquid sprays. The distinctiveness of these sprays is due to the fact that they are characterized by being oscillatory in nature, as compared to the relatively steady state flows that are emitted from standard spray nozzles.
A fluidic oscillator or insert is generally thought of as a thin, rectangular member that is molded or fabricated from plastic and has an especially-designed, uniform depth, liquid flow channel fabricated into either its broader top or bottom surface, and sometimes both (assuming that this fluidic insert is of the standard type that is to be inserted into the cavity of a housing whose inner walls are configured to form a liquid-tight seal around the insert and form an outside wall for the insert's boundary surface/s which contain the especially designed flow channels). See
Although it is more practical from a manufacturing standpoint to construct these inserts as thin rectangular members with flow channels in their top or bottom surfaces, it should be recognized that they can be constructed so that their liquid flow channels are placed practically anywhere (e.g., on a plane that passes though the member's center) within the member's body; in such instances the insert would have a clearly defined channel inlet and outlet.
Additionally, it should be recognized that these flow channels need not be of a uniform depth. For example, see U.S. Pat. No. 4,463,904 (Bray), U.S. Pat. No. 4,645,126 (Bray) and RE38,013 (Stouffer) for fluidic oscillators in which the bottom surfaces of these channels are discretely and uniformly sloped so as to impact the ways in which the sprays from these oscillators spread as the move away from the oscillator's outlet.
There are many well known designs of fluidic circuits that are suitable for use with such fluidic inserts. Many of these have some common features, including: (a) at least one power nozzle configured to accelerate the movement of the liquid that flows under pressure through the insert, (b) an interaction chamber through which the liquid flows and in which the flow phenomena is initiated that will eventually lead to the spray from the insert being of an oscillating nature, (c) an liquid inlet, (d) a pathway that connects the inlet and the power nozzle/s, and (e) an outlet or throat from which the liquid sprays from the insert.
Examples of fluidic circuits may be found in many patents, including U.S. Pat. No. 3,185,166 (Horton & Bowles), U.S. Pat. No. 3,563,462 (Bauer), U.S. Pat. No. 4,052,002 (Stouffer & Bray), U.S. Pat. No. 4,151,955 (Stouffer), U.S. Pat. No. 4,157,161 (Bauer), U.S. Pat. No. 4,231,519 (Stouffer), which was reissued as RE 33,158, U.S. Pat. No. 4,508,267 (Stouffer), U.S. Pat. No. 5,035,361 (Stouffer), U.S. Pat. No. 5,213,269 (Srinath), U.S. Pat. No. 5,971,301 (Stouffer), U.S. Pat. No. 6,186,409 (Srinath) and U.S. Pat. No. 6,253,782 (Raghu).
A key performance factor in many industrial applications for assorted spray devices, including fluidic oscillators, is the size of the area that the sprays from such devices can cover with liquid droplets—or alternatively, the lateral rate of spread of the fluid droplets as they proceed downstream. The degree of uniformity in the spatial distribution of these droplets can also be very important.
As one considers how to increase the lateral rate of spread of these liquid droplets and size of the area that they can cover, there is some prior art which is pertinent to this issue. For example, U.S. Pat. No. 4,151,955 (Stouffer), for what has come to be known as an “island” oscillator, discloses how one may cause the initial flow from a fluidic oscillator to take the form of a “sheet of liquid” or “sheet jet” that can be oscillated. This initial shape in the form of a sheet of liquid differs greatly from what normally is assumed to be the initially form of the flow from a fluidic oscillator—i.e., an essentially flat (i.e., very little thickness) but wide (i.e., large horizontal fan angle, φ) jet or spray of liquid droplets. See
Using the coordinate system shown in
U.S. Pat. No. 4,151,955 reveals that this “rectangular area” rather than “strip” wetting phenomena is achieved by controlling how the flow oscillator's sidewalls or boundaries are contoured downstream of a fluidic oscillator's throat.
As fluidic oscillators have continued to be used in more types of applications, the opportunity has arisen to re-examine and improve upon their design, especially changing the geometry of their exits or outlets and the use of structures downstream of an oscillator's throat, as a way to improve upon the spreading characteristics of the sprays they emit. The results of our research in this area and the inventions that have come from our work are described herein.
There has been summarized above, rather broadly, the prior art that is related to the present invention in order that the context of the present invention may be better understood and appreciated. In this regard, it is instructive to also consider the objects and advantages of the present invention.
It is an object of the present invention to provide the design for a new type of fluidic circuit that yields liquid sprays that are characterized by having enhanced thicknesses (i.e., the vertical rate of spread of such a spray's droplets is considerably greater than those of the usual “flat” sprays emitted by a wide range of fluidic circuits).
It is another object of the present invention to provide improvements in the design of the typical “island oscillator” so as to enable it to yield liquid sprays that are characterized by having enhanced thicknesses (i.e., the vertical rate of spread of such a spray's droplets is considerably greater than those of the usual “flat” sprays emitted by a wide range of fluidic circuits).
It is an object of the present invention to provide a liquid spray device that can enhance the rate of spread of the droplets that flow from such a spray device.
It is another object of the present invention to provide a liquid spray device that is especially well suited for cooling tower applications.
It is an object of the present invention to provide a clog-free, liquid spray device that is especially well suited for cooling tower applications.
It is a further object of the present invention to provide a liquid spray device that will provide clog-free performance in cooling tower applications while also providing equivalent or better cooling performance.
It is another object of the present invention to provide a liquid spray device that is especially well suited for cooling tower applications over a wide range of operating pressures (e.g., 1-5 psi) and flow rates (e.g., 10-90 gpm).
It is a still further object of the present invention to provide a liquid spray device that can uniformly spread liquid droplets over relatively large areas (4-8 sq. feet) located in close proximity (10-12 inches) to the device while operating at relatively large flow rates (25-85 gpm) and line pressures in the range of 0.5 to 6 psi.
It is an object of the present invention to provide a liquid spray device that can provide both horizontal and vertical rates of spread in the range of 70-120 degrees and 100-160 degrees, respectively, for the droplets that flow from such a spray device.
These and other objects and advantages of the present invention will become readily apparent as the invention is better understood by reference to the accompanying summary, drawings and the detailed description that follows.
Recognizing the need for the development of improved liquid spray devices, the present invention is generally directed to satisfying the needs set forth above and overcoming the disadvantages identified with prior art devices and methods.
In accordance with the present invention, an improved fluidic insert that operates on pressurized liquid flowing through it to generate a jet of liquid that flows into a surrounding gaseous environment and forms a spray of liquid droplets (in which the spray is characterized, in part, by its horizontal and vertical angles of spread) includes in a first preferred embodiment: (a) a member having top, front and rear outer surfaces and a centerline, (b) a fluidic circuit located within this top surface, with this fluidic circuit having an inlet, an outlet, a channel whose floor and sidewalls connect the inlet and outlet, and a barrier located proximate the outlet that rises from the channel floor, with the barrier configured such that: (i) it divides the channel in the region of the barrier into what are herein denoted as two power nozzles, (ii) each of the nozzles has a furtherest downstream portion whose cross section is characterized by a characteristic length L and the angle ζ that a centerline projecting normal to this cross section makes with the member's centerline, (iii) the barrier has a specified width that is characterized by the length W between the power nozzles' furtherest downstream portions, and (c) this is configured so as to control the lateral rate of spread of liquid droplets from the insert by specifying the parameters L, W and ζ.
In a second preferred embodiment, an improved fluidic spray device includes: (a) a body having an internal surface that includes a cavity that serves as a flow passage for the pressurized liquid, (b) an inlet that allows liquid to flows into the body, (c) an outlet that allows liquid flows from the body, (d) a first barrier within the cavity that serves to separate the flow passage into at least two flow passages, with each of these flow passages having an end section that terminates proximate the body's outlet, and wherein each of these flow passage end sections is configured so as to cause the liquid flowing from these sections to generate flow vortices behind the barrier which are swept out of the outlet in such a manner as to cause the direction of the spray flowing from the outlet to be oscillated back and forth so as to establish the spray's horizontal angle of spread, and (e) a second barrier having a flow-diversion section that is configured and oriented so as to cause the spray from the outlet to be diverted in such a manner as to help establish the spray's vertical angle of spread.
Thus, there has been summarized above, rather broadly, the present invention in order that the detailed description that follows may be better understood and appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims to this invention.
Before explaining at least one embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
The task of inventing a fluidic oscillator that can give spays of liquid droplets having large rates of lateral spread (i.e., wet a large surface area at a distance that is relatively close to the oscillator's exit) is quite outside the realm of the flows that have generally been seen or achieved with fluidic oscillators. For example, the spray requirements for many automotive windshield applications are on the order of: flow rates of 0.1 gpm, operating pressures of 9 psig, uniform coverage with spray droplets of a target area located approximately 10 inches in front of the sprayer and having a target area which has a width of approximately 30 inches, but a height of only about 1-2 inches; Area ˜0.09-0.2 ft.2, wherein the horizontal fan angles are approximately 70-120 degrees, and the thickness angles are only approximately 2-6 degrees.
For many showerhead applications, the spray requirements are on the order of: flow rates of 2.5 gpm or less, operating pressures of 10 psig, uniform coverage with 24 spray droplets of a target area located approximately 1 foot in front of the sprayer and having a target area of approximately 0.5 ft.2, wherein the droplets have a mean diameter of approximately 2 mm and a velocity of greater than 4 m/sec. and the oscillation frequency is in the range of 30-60 cps.
The first embodiment of the present invention, in the form of a new fluidic insert or oscillator 1 for generating “thicker” sprays, is shown in its top view in
A key distinction between the present invention and that of the “island oscillators” shown in
An inlet 4 that allows pressurized liquid to enter these circuits can be located anywhere (e.g., in the member's front face as shown in
The furtherest downstream ends 3ae, 3be of these power nozzles 3a, 3b have a perimeter that consists of the channel or power nozzle outer sidewalls 3as, 3bs, the gaps 3ag, 3bg from these outer sidewalls 3as, 3bs across the bottom of channels' floor at these ends and to the nearest sidewalls 5as, 5bs of the downstream end of the barrier 5. The distance between the points of the power nozzles' furtherest downstream sidewalls 3as, 3bs can be considered to define a throat for this fluidic circuit.
These power nozzle ends 3ae, 3be are defined, in part, by a characteristic length, L (e.g., the length of width of the gaps 3ag, 3bg). Similarly, the downstream end of the barrier 5 can be considered to be defined, in part, by a characteristic width, B (e.g., the distance between the barrier's furtherest downstream sidewalls 5as, 5bs) and an “interaction recess” depth, T. See
The discovery that led to the present invention is the finding that when the ratio of these the lengths, B/L or T/L, are in various ranges, the rate at which the spray that issues from such a fluidic circuit spreads vertically (i.e., in the x-z plane, see
For example, when the ratio B/L is in the range of 2-10 or the ratio T/L is in the range 0.5-4, and for a wide range of flow conditions, the vertical spread angles, θ, of the resulting sprays can be greatly increased (i.e., from 1-2 degrees to >10 degrees).
It has also been found that a spray's vertical spread angle can be influenced by the direction in which these power nozzles direct their flow with respect to the centerline of the fluidic. See the right hand, power nozzle 3be shown in
Power nozzle directional angles, ζ, of 10-80 degrees, when used in association with barriers having widths in the range of B/L equal 2-10, have been found to be especially effective in increasing the vertical spread angles, θ, of the sprays issuing from such fluidic oscillators.
In this embodiment, three portions of this throat 6 are seen to be comprised of the ends of the power nozzle sidewalls 3as, 3bs and the gap 3a-bg across the bottom of the channel which lies between these sidewalls 3as, 3bs. See
The expansion section 7 consists of sidewalls 7as, 7bs that are angled out from the member's centerline at a divergence angle of ψ. The length of this expansion section as measured along the member's centerline is denoted by the distance S. In trying to characterize this expansion section, it proves useful to describe it in terms of its length S and the outward directed angle of its sidewalls, ψ.
The outlet 8 for this member's flow passage is seen to lie in the member's front face. Three portions of this outlet include the ends 7ase, 7bse of the expansion section sidewalls 7as, 7bs and the gap 7a-bg across the bottom of the channel which lies between these sidewall ends 7ase, 7bse. The fourth and final portion of an enclosed-flow-passage outlet would be its upper portion that would be provided by the adjoining surface of the liquid-tight cavity of the housing into which the member would be inserted.
Experiments with variously shaped expansion sections have shown that extending the length of the expansion section too far, for a specified divergence angle ψ, can diminish the initial tendency of such sections to increase the thickness of the sprays coming from such fluidic oscillators. For example, when ψ is in the range of 20-80 degrees, then restricting the length of the expansion section such that the ratio S/L is in the range of 2-10 is seen, for a wide range of flow conditions, to yield sprays having increased vertical spread angles, θ (i.e., from 1-2 degrees to >10 degrees).
With an improved understanding of the effects of such fluidic oscillators' various geometric parameters on the spreading characteristics of the sprays that issue from them, it is now possible to design an assortment of fluidic oscillators to meet specialized operational needs. For example, to create at a flow rate of about 100 ml/min (˜25 gpm), what is referred to as a “barrier” spray (i.e., a relatively narrow, horizontal fan angle=30 degrees, but thick, vertical spread angle=10 degrees, spray, the fluidic oscillator shown in FIGS. 9A-B has proven to be a good choice when it is scaled such that L=0.4 mm, B/L=6, S/L=3.5, T/L=1.5, ζ=40 degrees and ψ=45-60 degrees.
As previously mentioned, it is possible to consider the fluidic circuits disclosed in FIGS. 8A-B and 9A-B as not being embedded in the top surface of a member that must be inserted into a housing's cavity, but as forming totally enclosed flow passages that are oriented around the centerline of a body that forms part of a fluidic device which has a clearly defined flow inlet and outlet.
The device shown in
In a cooling tower application of interest, water, that is hot because it's been used to take heat from a refrigerant and which is to be cooled in the tower, is sprayed or distributed over a media surface that has staggered/straight channels from which the water drips. A counter flow of air that's cooler than the hot water is induced through these channels by a fan. Within the channels, the water film on the media and air come in contact resulting in local evaporation at the air-water interface that serves to cool the water.
In order for the water to be cooled most efficiently, the water film on the media should be as uniform as possible. Heavy loading of water in some parts of the media and light loading in other parts will lead to inefficient cooling. More uniform water distributions on the media are achieved by spraying the water on the media by the use of nozzles.
In many cooling towers, the spray branches of nozzles are located above the 4 media. Depending on the nozzle design, nozzle flow rates may vary from 25-85 gallons per minute (gpm) and at line pressures of up to 6 pounds per square inch (psi). The nozzles are often required to spray relatively large areas (e.g., about 4-8 sq. ft) which are located only a comparatively short distance in front of the nozzles (e.g., in most cases: 10-12 inches, and in some: up to 22 inches). These operating conditions can make it very difficult to obtain a wide-angle, full-coverage and uniform distribution of spray on the media.
This device shown in
More information on possible alternative designs for the body's cavity and the configuration of the present embodiment's flow passages can be found in U.S. Pat. No. 6,253,782 which discloses a fluidic oscillator whose “fluidic circuit” can be considered to be “somewhat” similar to that shown in
The end sections 32, 34 of the passages or power nozzles of
In terms of the configuration of the outlet 20 of the present embodiment, it is seen to have a quite complex shape. Before trying to describe this shape, it proves useful to note, see
The outlet 20 has a perimeter that defines its boundary edge 40. This edge has a top 42 and a bottom 44 portion and two sidewall portions 46, 48. It should be noted that these sidewall portions 46, 48 are located at a further distance from the body's inlet than the top 42 and bottom 44 portions so as to promote the vertical spreading of the spray.
Additionally, it should be noted that the vertical spread of the spray can be further controlled by the addition of top 49a and bottom 49b plates which serve to further define the shape of the outlet's perimeter 40 in the x-y planes which lie fartherest from the spray's centerline.
To give a better idea of the geometry of this outlet 20, it can be noted that if the area of each flow passage end section 32, 34 is approximately shaped as a square whose side has a length of approximately L, then it has been experimentally determined that an appropriate distance to move the top 42 and bottom 44 portions of the outlet boundary edge upstream (so as to enhance the resulting spray's throw) is in the range of 0.2-2.0 L.
It should also be noted that we speak of these passage end sections 32, 34 as being “square,” although we note that their cross-sectional shape could take on any one of a number of geometric shapes. For example, they could be circular so as to maintain a minimum length scale and increase the velocity resulting in better low pressure performance.
To put some actual dimensions to the embodiment shown in
While this opening is relatively large, it should also be noted that the overall dimensions of this embodiment (e.g., with L=1 inch, the distance between the centerline of the inlet port 18 and the location of the flow-diversion section 38 is only about 4 inches, while the overall width of the body 10 is about 6 inches) are relatively small for the amount of water that can be pumped through such a nozzle (e.g., 85 gpm). Thus, one can conclude that this embodiment is of a compact design.
Downstream sidewalls 50, 52 also can be seen to be attached to each sidewall portion of the outlet's boundary edge. These sidewalls are sloped outwards so as to form an expansion section whose configuration serves to further control the horizontal spread of the spray. Slope angles that have proved useful for these sidewalls are in the range of 20-80 degrees. Meanwhile, the length of these sidewalls will generally be in the range of 0.2-8 L.
A closer examination of
An attempt to illustrate the flow phenomena associated with the fluidic oscillators or the present invention is shown in
It should be noted that the uniform wetting of such a large area cannot be achieved with any of the prior art spray devices. It is only the capability of the present embodiment to create a spray with such a large throw and then to uniformly spread it over such a relatively large width that allows for such wetting achievements.
In the installation shown in
It should also be noted, from
Pressurized liquid enters this insert through its inlet 70 and is sprayed from its outlet 72. The nature of the fluidic circuit for this device is similar to that shown in
However, it is notably different in that it has an expansion section 74 which, has a bottom surface 76 that slopes or tapers downward, at an angle ΔL, away from the device's centerline. Similarly, the top portion 62 also has an expansion section 78 which has a top surface 80 that is tapered or sloped away from the device's centerline at an angle ΔU.
Experimental results for such configurations have shown that these expansion section tapers serve to increase the thickness or throw of the resulting spray. The spray output from this device is seen to be much more three-dimensional. The area that it wets on a plane perpendicular to the device's centerline has a shape that is much more rectangular or even square-like than the typical thin, horizontal strip-shaped wetted area which is characteristic of the sprays from many fluidic oscillators.
An example of the use of these expansion section tapers can be seen in the design of a fluidic device which is to be used in what is commonly referred to a “trigger spray” container (e.g., a bottle of cleaning fluid which one applies by squeezing a trigger that issues a very small, flow rate spray of the liquid in the direction at which the bottle's nozzle is oriented). Assuming that a flow rate of about 0.05 gpm is desired, taper angles of about Δ=20 degrees in both the top and bottom portions have been shown to yield sprays that have a lateral vertical spread angle, θ, of almost this same degree (i.e., θ=ΔU+ΔL). In general, taper angles of 5-45 degrees have been found to be useful in controlling the shape of the emitted spray.
While the tapers in the above embodiment are shown as both being sloped away from the centerline, it is recognized that many other combinations of slopes (e.g., both sloped inward toward the centerline, one sloped inward & the other sloped outward) may be advantageous to control or modify the cross-sectional shape of the spray that is omitted from such a fluidic device. All of these combinations are considered to come within the scope of the present invention.
As previously mentioned, although it is more practical from a manufacturing standpoint to construct these inserts as thin rectangular members with flow channels in their top or bottom surfaces, it should be recognized that they can be constructed so that their liquid flow channels are placed practically anywhere (e.g., on a plane that passes though the member's center) within the member's body; in such instances the insert would have a clearly defined channel inlet and outlet.
The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, and because of the wide extent of the teachings disclosed herein, the foregoing disclosure should not be considered to limit the invention to the exact construction and operation shown and described herein. Accordingly, all suitable modifications and equivalents of the present disclosure may be resorted to and still considered to fall within the scope of the invention as hereinafter set forth in the claims.
