Patent Publication Number: US-10315172-B2

Title: Rotor and stator device having bore holes for cavitational mixing

Description:
This application claims the benefit of U.S. provisional application Ser. No. 62/095,489 filed Dec. 22, 2014, the contents of which are incorporated herein in their entirety by reference. 
    
    
     FIELD 
     The present disclosure relates to a cavitational mixing device, and more particularly, a device for mixing fluids under controlled formation and collapse of cavitation bubbles in a fluid passing through the device. 
     BACKGROUND 
     In the field of cavitation mixing, various devices using rotors or other rotating members to generate hydrodynamic cavitation are known. Typical of the art are those devices disclosed in the following U.S. Pat. Nos. 5,188,090; 5,385,298; 5,957,122; 6,627,784; 6,857,774; 7,318,553; 7,357,566; 7,771,582 and 8,449,172. The devices disclosed in the aforementioned patents are useful for mixing dissimilar fluids. 
     To more efficiently mix fluids in rotor/stator type devices, the energy released from the cavitation bubbles generated in the bore openings and gap between the rotor and the stator can be enhanced. For this purpose, the cavitation generation flow path in which cavitation bubbles exist can be collapsed under high pressure. Accordingly, there is a need to improve cavitational mixing devices that result in poor efficiency and low energy release within the cavitational field. 
     SUMMARY 
     In a first aspect, there is a device for cavitational mixing, the device includes a housing having a chamber defined by a cylindrical wall having a longitudinal axis, the chamber further partially defined by a pair of end walls; a stator forming a portion of an end wall, the stator including a circumferential external surface facing the cylindrical wall and a first plurality of stator bore holes oriented perpendicular to the housing longitudinal axis; and a rotor mounted on a shaft, the rotor positioned within the housing chamber, the rotor including a circumferential internal surface facing the circumferential external surface of the stator, the circumferential internal surface of the rotor having a second plurality of rotor bore holes oriented perpendicular to the housing longitudinal axis, wherein the stator and the rotor are positioned such that the first plurality of stator bore holes are substantially in register to the second plurality of rotor bore holes, and when the rotor is rotated relative to the stator each of the second plurality of rotor bore holes passes a stator bore hole of the first plurality of stator bore holes, and wherein each of the bore holes in the second plurality of rotor bore holes and each of the bore holes in the first plurality of stator bore holes has substantially the same diameter. 
     In an example of aspect 1, the housing further including at least one inlet port for introducing fluid into a space between the circumferential internal surface of the rotor and the circumferential external surface of the stator. 
     In another example of aspect 1, the inlet port for introducing fluid is positioned in line with the center of the stator. 
     In another example of aspect 1, the housing further includes at least one outlet port for discharging fluid mixed in the device. 
     In another example of aspect 1, the rotor bore holes and the stator bore holes have a cylindrical shape. 
     In another example of aspect 1, the shaft is connected to a motive means to rotate the rotor. 
     In another example of aspect 1, the ratio of the depth of the stator bore holes to the depth of the rotor bore holes is less than 10:1. 
     In another example of aspect 1, the ratio of the depth of the stator bore holes to the depth of the rotor bore holes is greater than 1:1. 
     In another example of aspect 1, the stator includes two or more pluralities of stator bore holes, each plurality of the two or more plurality of stator bore holes includes bore holes arranged in a straight-line series and each stator bore hole of each plurality is equally spaced apart from one another; the rotor includes two or more pluralities of rotor bore holes, each plurality of the two or more pluralities of rotor bore holes includes bore holes arranged in a straight-line series and each rotor bore hole of each plurality is equally spaced apart from one another; the distance between each stator bore hole of each plurality or each rotor bore hole of each plurality is greater than the diameter of the stator bore holes and/or rotor bore holes. 
     In another example of aspect 1, the stator includes two or more pluralities of stator bore holes, each plurality of stator bore holes includes two or more stator bore holes. 
     In another example of aspect 1, the rotor includes two or more pluralities of rotor bore holes, each plurality of rotor bore holes includes two or more rotor bore holes. 
     In another example of aspect 1, the first plurality of stator bore holes has stator bore hole openings on the circumferential external surface of the stator and the second plurality of rotor bore holes has rotor bore hole openings on the circumferential internal surface of the rotor, the stator bore hole openings are spaced apart from the rotor bore hole openings at least 0.1 mm. 
     In another example of aspect 1, the stator bore holes of the first plurality have a cylindrical shape of constant diameter, the stator bore holes have an opening along the circumferential external surface of the stator and a flat closed end positioned within the stator. 
     In another example of aspect 1, the rotor bore holes of the second plurality have a cylindrical shape of constant diameter, the rotor bore holes have an opening along the circumferential internal surface of the rotor and a flat closed end positioned within the rotor. 
     In another example of aspect 1, the chamber has no more than two openings for introducing and discharging fluid through the housing for allowing the fluid to pass over the first plurality of the stator bore holes and the second plurality of the rotor bore holes. 
     The first aspect may be provided alone or in combination with any one or more of the examples of the first aspect discussed above. 
     The accompanying drawings are included to provide a further understanding of principles of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain, by way of example, principles and operation of the invention. It is to be understood that various features disclosed in this specification and in the drawings can be used in any and all combinations. By way of non-limiting example the various features may be combined with one another as set forth in the specification as aspects. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a longitudinal cross-sectional view of a cavitational mixing device. 
         FIG. 2  shows a cross-sectional view of the cavitational mixing device shown in  FIG. 1 , along the plane defined by line  2 - 2  in  FIG. 1 . 
         FIG. 3  shows a perspective view of a rotor for use in a cavitational mixing device. 
         FIG. 4  shows a perspective view of a stator for use in a cavitational mixing device. 
     
    
    
     DETAILED DESCRIPTION 
     Herein, when a range such as 5-25 (or 5 to 25) is given, this means preferably at least 5 and, separately and independently, preferably not more than 25. In an example, such a range defines independently not less than 5, and separately and independently, not less than 25. 
     A device has been developed for providing an efficient, high-energy way to mix fluids by generating cavitation within the device. The device allows for the controlled formation and collapse of cavitation bubbles in a fluid, for example, in one or more bore holes within the device. 
     In one embodiment,  FIG. 1  shows a cross-section of a device for cavitational mixing of a fluid or mixture of more than one fluid. As shown, the device  100  has a longitudinal axis denoted by the broken line running central to the inlet port  112  and shaft  109  of the rotor  108 . As shown, the inlet port  112  is in line with the center of the stator  105  along the longitudinal axis. 
     The device  100  includes housing  102  that partially defines chamber  101 . Housing  102  has an inner cylindrical or circumferential wall surface  102   a  parallel to and facing towards the longitudinal axis (“axis”) of the device and an adjacent end wall surface  102   b  facing perpendicular to the longitudinal axis of the device. Surfaces  102   a  and  102   b  are adjacent and connected to or integral with one another. Preferably, housing  102  is an integral component such that surfaces  102   a  and  102   b  are made of the same material. 
     Opposing surface  102   b  at a distance is stator  105  that, in part, forms the other end wall surface chamber  101 . A portion of stator  105  is perpendicular to the longitudinal axis of the device, which is also adjacent inner circumferential surface  102   a . As shown, stator  105  is mounted as an end wall on housing  102  with section  103  of the stator  105  being in direct contact and connected to housing  102  to secure the stator thereto. The stator  105  has a flat circular portion with an outer diameter portion  103  being in contact with housing  102 . The central portion of the circular portion of the stator has a protuberance section (shown in the shape of a ring) that extends inward into housing  102  and the chamber  101 . The protuberance section of the stator may be a hollow cylinder having an outer circumferential surface  105   b  facing towards the inner cylindrical or circumferential wall surface  102   a  of housing  102  and further includes a central opening defined by an inner circumferential surface  105   a  for accommodating fluid flowing into the device through the stator  105 . 
     The stator  105  has a plurality of stator bore holes  104 , for example a first plurality, in the protuberance section extending into housing  102  and chamber  101 . The plurality of bore holes  104  can be positioned in a series such as in a straight line as shown, in which there can be multiple groups of in-line series of bore holes equally spaced about outer circumferential surface  105   b  of the protuberance section. The stator bore holes  104  each have openings along outer or external circumferential surface  105   b  of stator  105 . The bore holes  104  extend inward into the stator  105  body, shown as the protuberance section in  FIG. 1 . The bore holes  104  terminate within the stator protuberance section and have a closed end, for example a flat end, positioned in the stator body. That is, bore holes  104  do not extend through the protuberance section such that the external circumferential surface  105   b  of stator  105  is in fluid connection with the inner circumferential surface  105   a  by passage through bore holes  104 . 
     The stator bore holes  104  can have any shape, for example, cylindrical or circular, and can have a uniform or substantially uniform cross section or diameter. In one example, the stator bore holes can have a diameter in the range of 5 to 60 mm, 10 to 40 mm or 15, 20, 25, 30 or 35 mm. The stator bore holes  104  can have any suitable depth, for example, the holes can have a depth in the range of 4 to 200 mm, 10 to 100 mm or 20, 40, 60 or 80 mm. 
     The central opening of stator  105  forms an inlet port  112 , for example a space defined by the inner circumferential surface  105   a  of the protuberance of the stator  105 , for introducing fluid or a mixture of fluids into chamber  101  of the device  100 . The diameter of the inlet port  112  formed by the inner circumferential surface  105   a  can be in the range of 5 to 300 mm. As shown, inlet port  1112  can optionally be connected to a pipe, flange, fitting or the like to accommodate fluid flow into the device and connect the device to a fluid source (e.g., a supply pipe) for passing fluid into and through the device. Fluid can enter the device by any suitable means, for example, by use of a pump, and can be at pressure in the range of 1 to 2,000, 5 to 1,500, 20 to 1,000, 50 to 800 or 100, 200, 300, 400, 500, 600 or 700 psi. Fluid flows through the inlet port  112  of stator  105  and contacts a central face  108   a  of rotor  108 , the surface of the face arranged perpendicular to the longitudinal axis, and continues into space  106  between the circumferential internal surface  108   b  of rotor  108  and the circumferential external surface  105   b  of stator  105 . The fluid passes over bore hole openings in the stator and rotor, preferably as the rotor rotates at a revolution rate capable of producing cavitation in the fluid, for example, fluid retained in the bore holes (e.g. stator bore holes). The fluid can further pass into and out of individual bore holes in the stator and rotor during operation. 
     The cavitated fluid forms a cavitation zone within the chamber. The cavitation bubbles in the cavitation zone, for example, in the bore holes (e.g.  104 ) or space  106  which includes the chamber area between the inner circumferential surface  108   b  of rotor  108  and the outer circumferential surface  105   b  of the stator  105 , are subsequently collapsed under pressure as the fluid is exposed to pressure generated by the rotation of the rotor or as it continues through chamber  101  and is discharged from the device  100 , e.g.,  114 . The cavitation zone can begin in the bore hole and extend into space  106 . Alternatively, the cavitation zone can extend downstream of space  106  as the fluid continues through chamber  101  and exits the device. 
     The device further includes rotor  108  that is positioned in chamber  101  formed in part by housing  102 . Rotor  108  extends into chamber  101  on shaft  109  and rotor  108  forms a portion of an end wall to the chamber in that shaft  109  to which it is attached fills and seals the opening in face  102   b  of housing  102 . Housing  102  fits around shaft  109  and conventional seal features for ensuring a fluid tight seal between shaft  109 , housing  102  and chamber  101  can be used as known in the art. The portion of rotor  108  extending into chamber  101  includes a cylindrical body open at one end and closed along rotor face  108   a  that is oriented perpendicular to the longitudinal axis of the device. The cylindrical body of rotor  108  is positioned in the device  100  such that it has the protuberance section of stator  105  and outer circumferential surface  105   b  having bore hole  104  openings nested in the open end of the cylindrical body of rotor  108 . As shown, the cylindrical body of rotor  108  has a circumferential internal surface  108   b  facing the circumferential external surface  105   b  of stator  105 , or space  106 . 
     The rotor  108  and shaft  109  can be connected to a motive means for rotating the rotor, for example, a motor. In an example, shaft  109  is connected to a motor for rotating rotor  108  at a desirable rate or rpm. The rotor  108  can be rotated at a rate in the range of 500 to 30,000 rpm, or at least 750, 1,000, 1,500, 2,000 or 2,500 rpm. 
     The circumferential internal surface  108   b  of rotor  108  can have a plurality of rotor bore holes  107 , for example a second plurality. The plurality of bore holes  107  can be positioned in a series such as in a straight line as shown. There can be multiple series of rotor bore holes spaced along and equally away from one another on the inner circumferential surface  108   b  of rotor  108 . The bore holes  107  extend inward from the circumferential internal surface  108   b  into the body of the rotor  108  as shown. The bore holes  107  terminate and have a closed end, for example a flat end, positioned in the rotor body. That is, the bore holes  107  do not extend through the rotor body such that the external circumferential surface or rotor  108  opposite surface  108   b  is in fluid connection with the inner circumferential surface  108   b  by passage through bore holes  107 . The openings of bore holes  107  are inward facing towards surface  105   b  of the stator and the opening of stator bore holes  104 . 
     The rotor bore holes  107  can have any shape, for example, cylindrical or circular, and can have a uniform or substantially uniform cross section or diameter. In one example, the rotor bore holes can have a diameter in the range of 5 to 60 mm, 10 to 40 mm or 15, 20, 25, 30 or 35 mm. The rotor bore holes  107  can have any suitable depth, for example, the holes can have a depth in the range of 2 to 150 mm, 10 to 100 mm or 20, 40, 60 or 80 mm. 
     In comparing the depth of the stator bore holes  104  to the depth of the rotor bore holes  107 , the ratio of depth of the stator bore holes to the rotor bore holes can be in the range 10:1 to 1:1, or less than 10:1, less than 8:1, less than 5:1, less than 4:1, less than 3:1, less than 2:1 or less than 1.5:1. Preferably, the depth of the stator bore holes is greater than the depth of the rotor bore holes. The depth of the bore holes is measured from the surface adjacent the opening of the bore holes (e.g.  105   b ,  108   b ) to the point along the closed end of the bore hole furthest away from the opening of the bore hole. 
     In one or more embodiments, stator bore holes  104  and rotor bore holes  107  are positioned such that a first plurality of holes  104  may be in register with a second plurality of hole  107  at one or more positions in the device as rotor  108  rotates around or relative to stator  105 . As rotor  108  rotates relative to stationary stator  105 , the second plurality of holes  107  passes over or by the first plurality of holes  104  at pre-determined positions, and at a point in time, are in register with or mirror holes  104 . 
     As shown in  FIG. 2 , along plane  2 - 2  of  FIG. 1 , stator  105  and rotor  108  are assembled such that stator bore holes  104  are aligned and in register with rotor bore holes  107 . As rotor  108  rotates relative to stator  105 , the bore holes become unaligned and not in register with one another until rotor  108  rotates far enough to align and bore holes  107  and  104  again. This bore hole alignment process is continually repeated as the rotor  108  rotates relative to stator  105 . The distance L between stator bore holes  104  is equal between each stator bore hole  104  and the distance L between rotor bore holes  107  is equal between each rotor bore hole  107  in the plurality of holes. The distance L between the stator bore holes  104  is less than the distance L between the rotor bore holes  107 . The space  106  between the outer circumferential surface of stator  105  and inner circumferential surface of rotor  108  can be in the range of 0.1 to 20 mm, 0.5 to 15 mm, or 1, 3, 5, 8, 10 or 12 mm. The open space between the outer circumferential surface of the rotor  108  and the inner surface of the housing  102  can be in the range of 0.3 to 20 mm, 0.5 to 15 mm, or 1, 3, 5, 8, 10 or 12 mm. 
     In one or more embodiments, one or more stator bore holes  104  can have the same or substantially the same diameter as one or more rotor bore holes  107 , for example, the first plurality of stator bore holes  104  can have the same or substantially the same diameter as the second plurality of rotor bore holes  107 . In the case the stator and rotor have additional bore holes or plurality of bore holes, the additional bore holes of each component can have the same or substantially the same diameter. In another embodiment, one or more stator bore holes can have a larger diameter than one or more rotor bore holes, or alternatively, one or more stator bore holes can have a smaller diameter than one or more rotor bore holes. 
     In one or more embodiments, the rotor  108  can have two or more pluralities of rotor bore holes. Each plurality of rotor bore holes can have bore holes arranged a series or straight line. The plurality of bore holes can be spaced equally apart from one another on surface  108   b . The distance between each plurality of rotor bore holes can be in the range of 30 to 250 mm, or at least 40, 50, 60, 80, 100, 150 or 200 mm. Each plurality can have two or more bore holes, for example, 3, 4 or 5 bore holes. In one example,  FIG. 3  shows a rotor  200  having multiple pluralities  212  of rotor bore holes arranged on the inner circumferential surface  206  of rotor  200  for housing the protuberance section of the stator. Each plurality of bore holes on the rotor  200  as shown includes 3 rotor bore holes  212  (shown as cylindrical holes) arranged in a straight line and spaced equally from one another in a longitudinal direction along the axis of device. The rotor bore holes  212  face inward away from surface  204 . It is appreciated that the rotor bore holes  212  can be different shapes than as shown. 
     The rotor  200  further include surface  208  that faces the protuberance section of the stator, wherein surface  208  on the surface opposite the stator area is connected to shaft  210  for rotating the rotor  200  relative to the stator during operation. Surface  208  or base portion has the raised rotor body in form of a circular disk or annular raised portion as illustrated and having an open section for accommodating a stator. The raised section can be in the shape of a ring having an inner circumference surface  206  and outer circumferential surface  204 . The area bound by the inner circumferential surface and surface  208  is shown as an empty cylindrical spaced for accommodating fluid and a stator. As noted above, rotation of rotor  200  body is facilitated by shaft  210 . The shaft is arranged to facilitate rotation of rotor  200  around an axis defined by a longitudinal line running along the length of shaft  210  through its center, for example, the center longitudinal line through the device and at the center of the inlet port to the device (not shown in  FIG. 3 ). Such an axis can also be referred as an axis of rotation for rotor  200 . 
     In one or more embodiments, the stator  105  can have two or more pluralities of stator bore holes. Each plurality of stator bore holes can have bore holes arranged a series or straight line. The plurality of bore holes can be spaced equally apart from one another on surface  105   b . The distance between each plurality of stator bore holes can be in the range of 30 to 250 mm, or at least 40, 50, 60, 80, 100, 150 or 200 mm. Each plurality can have two or more bore holes, for example, 3, 4 or 5 bore holes. In one example,  FIG. 4  shows a stator  300  having multiple pluralities  302  of stator bore holes arranged on the outer circumferential surface of the protuberance of the stator  300 . Each plurality of bore holes on the stator  300  includes 3 stator bore holes arranged in a straight line and spaced equally from one another in a longitudinal direction along the axis of the device. It is appreciated that the stator bore holes  302  can be different shapes than as shown. 
     The devices described herein generally provide for introduction of a fluid into rotating bore holes  107  and stationary bore holes  104  for the formation of cavitation bubbles in the fluid as it passes through the device. A vortex also may be formed in the bore holes,  107 ,  104 . Generally, the bore holes  107  and  104  are configured to alternate between at least two positions, for example, positions that can be described as a “closed position” and an “open position.” 
     “Closed position” used herein refers to the rotor bore holes  107  not being in line, in register or partially in line or in register with the stator bore holes  104 . That is, in a closed position, the stator bore holes  104  face outwardly towards a portion of the inner circumferential surface  108   b  of the rotor  108 , wherein the portion of surface  108   b  does not include a rotor bore hole  107  or a portion thereof. Similarly, in a closed position, the rotor bore holes  107  face inwardly towards a portion of the outer circumferential surface  105   b  of the stator  105 , wherein the portion of surface  105   b  does not include a stator bore hole  104  or a portion thereof. 
     “Open position” used herein refers to the rotor bore holes  107  being in line, in register or partially in line or in register with the stator bore holes  104 . That is, in an open position, the stator bore holes  104  face outwardly towards a portion of the inner circumferential surface  108   b  of the rotor  108 , wherein the portion of surface  108   b  includes a rotor bore hole  107  or a portion thereof. Similarly, in an open position, the rotor bore holes  107  face inwardly towards a portion of the outer circumferential surface  105   b  of the stator  105 , wherein the portion of surface  105   b  includes a stator bore hole  104  or a portion thereof. 
     In the “closed position,” the pressure in the rotor bore holes  107  increases and the pressure in the stator bore holes  104  decreases under the action of inertial forces caused by rotation of the components, for example, the rotor  108  relative to the stationary stator  105 . Due to this changing pressure condition, the fluid in the rotor bore holes  107  compresses and thereby stores energy in the fluid. Fluid in the stator bore holes  104  decompresses and cavitation bubbles are formed therein and around the bore holes  104  in space  106 . 
     In the “open position,” rotor bore holes  107  are opened and the stored compression energy is released as a hydraulic pressure pulse. This pressure pulse can be several orders of magnitude higher than the static pressure in the fluid within the device. Elevated hydraulic pulse pressure propagates through the stator bore holes  104  positioned opposite the rotor bore holes  107  and collapses the cavitation bubbles therein. Collapse of the cavitation bubbles releases energy into the fluid in the stator bore holes  104 . Elevated hydraulic pulse pressures are generally beneficial for greater energy releases from the cavitation bubbles during collapse. The power output, N, from the cavitation bubble collapse can be measured by the following equation: 
               N   =     4.60   ⁢           ⁢     R   2     ⁢         P   0   3     ρ           ,         
where R is the maximum radius the bubble has at the beginning of collapse, P 0  is hydraulic pulse pressure in surrounding fluid and initiated the bubble during collapse, and ρ is the fluid density.
 
     Although the present disclosure has applications in mixing, one skilled in the art would appreciate that the present disclosure may be utilized as a reactor to enhance and expedite chemical reactions. 
     It will be understood that this invention is not limited to the above-described embodiments. Those skilled in the art having the benefit of the teachings of the present invention as hereinabove set forth, can effect numerous modifications thereto. These modifications are to be construed as being encompassed with the scope of the present invention as set forth in the appended claims. 
     It will be apparent to those skilled in the art that many modifications, variations, substitutions, and equivalents for the features described above may be effected without departing from the spirit and scope of the invention as defined in the claims to be embraced thereby. A preferred embodiment has been described, herein. It will be further apparent to those skilled in the art that the above methods may incorporate changes and modifications without departing from the general scope of this invention. It is intended to include all such modifications and alteration in so far as they come within the scope of the appended claims or the equivalents thereof