Abstract:
An apparatus for treating a liquid includes a first flow generator having an outlet for generating a first flow stream and a reaction chamber positioned in proximity to the outlet of the first flow generator and having a cavity adapted to receive the first flow stream from the first flow generator and reverse its direction within the confined space of the cavity. The flow generator may be a cavitation generator for producing multiple cavitation bubbles in the first slow stream, or a nozzle for generating a flow stream devoid of cavitation bubbles. A method for treating a liquid includes directing the liquid into a first flow generator configured to generate a first flow stream of the liquid, and directing the first flow stream from the first flow generator into a cavity of a reaction chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATION   
       [0001]    This application claims priority to U.S. provisional patent application Ser. No. 61/076,241 filed on Jun. 27, 2008, the disclosure of which is expressly incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]    The invention relates to a liquid treatment apparatus for treating a liquid medium and, more particularly, to an apparatus and method for enhancing chemical reactions occurring in processes utilizing hydraulic cavitation. 
       BACKGROUND  
       [0003]    Many industrial processes rely on various chemical reactions in a liquid medium to achieve a certain end product. Accordingly, manufacturers and others that perform these industrial processes continually seek improvements to these processes so as to improve their efficiency and provide a cost benefit. By way of example, increasing the efficiency in chemical reactions occurring in a liquid medium may result in a decrease in processing time, which may lead to an increase in overall production and decrease in operating costs, and/or a decrease in chemical consumption in the liquid medium for achieving the desired result which may reduce operating costs. These are only exemplary and, depending of the specific application, many other benefits may be gained by improving the efficiency of various chemical reactions. 
         [0004]    One industrial application that may benefit from improved chemical reactions is in the treatment of liquid mediums using cavitation. For example, the use of cavitation in the treatment of contaminated water, e.g., wastewater, is documented. In these cavitation methods, the goal is to generate many fine bubbles, which upon their implosion create intense, but highly localized temperatures and pressures. This energy release then causes dissolution of the water molecules and the creation of free hydroxyl radicals. The potential of these powerful radicals for the beneficial treatment of the water has been well recognized for many years. However, the inefficiencies in the known processes for generating cavitation within a liquid (e.g., ultrasonic or jet cavitation) has restricted commercial acceptance of hydraulic cavitation. 
         [0005]    Recently, an apparatus for generating hydraulic cavitation within a liquid medium in an efficient manner has been proposed in U.S. Publication No. 2008/0099410, the disclosure of which is incorporated by reference herein in its entirety and which is assigned to the assignee of the present application.  FIGS. 1-4  of the present disclosure illustrate an exemplary embodiment of a modified cyclonette  10  for generating cavitation and a liquid treatment apparatus  12  that utilizes modified cyclonette  10  to treat a liquid medium, such as wastewater, using cavitation. 
         [0006]    In this regard, cyclonette  10  includes an insert  14  installed in the left hand end thereof and may be provided with an annular groove  16  into which an O-ring  18  may be seated. To the right of the O-ring  18 , a second annular groove  20  may be formed to receive a second O-ring  22  of more or less rectangular cross-sectional configuration. Interiorly of the cyclonette  10 , a flow path is provided by a throat portion  23 , an inwardly tapering flow channel  24 , and an outwardly tapering flow channel  26 . If the exiting fluid completely fills the flow channel at its minimum diameter at point  28 , the pressure within the upstream channel will be a function of the velocity head of the fluid at this point. If the absolute pressure at point  28  is at or below the vapor pressure of the fluid, or is low enough to cause dissolved gases to move out of solution, a mixed flow of gas and liquid will occur. 
         [0007]    As a result of the outwardly tapering flow channel  26  and the momentum of the fluid, there will be a tendency for the static pressure on the wall of the channel to be reduced which in turn will result in a lower pressure within the fluid. As the fluid moves beyond point  28 , the internal pressure within the gas bubbles will cause them to expand until pressure equilibrium is established. 
         [0008]    At its left-hand end, as seen in  FIG. 1 , the cyclonette  10  may be provided with an internally threaded socket  30  receiving the complementary external threads  32  of the insert  14 . The insert  14  has a straight sided internal bore  34  and captures and holds in place within cyclonette  10  a washer-shaped orifice plate  36  having a central orifice  37 . This embodiment has shown to be productive in the formation of multiple tiny bubbles, as the liquid being treated must first constrict from the larger diameter of the insert flow passage  34  to the restricted orifice  37  and then expand again into the throat of cyclonette  10 . Lastly, the cyclonette  10  may be provided with a passageway  38  extending through a wall of the cyclonette  10  into the throat portion  23 . The passageway  38  may be used for the addition of a flow of the liquid being treated or a chemical or physical modifying substance in either a tangential, radial, or substantially axial direction into the throat  23 . 
         [0009]    With reference now to  FIG. 2 , liquid treatment apparatus  12  includes a housing  40  having cylinders  42 , each having outwardly projecting annular flanges  44  to permit two or more cylinders  42  to be clamped together by bolts  46  to form a continuous, outer, annular chamber  68 . At its upper end, the annular outer chamber is capped by a closure plate  50  having a lifting ring  52 . The closure plate  50  is clamped to the upper end of the uppermost cylinder  42  in a manner similar to the clamping between adjacent cylinders by means of bolts  46 . 
         [0010]    With reference now to  FIGS. 2 and 3 , it will be seen that the lowermost cylinder  42  is attached at its lower end by means of bolts  46  to a manifold system  54 . At its upper end, the manifold system  54  has an outwardly projecting annular flange  56  to which the lower most cylinder  42  is clamped by the bolts  46  as shown in  FIG. 3 . The manifold system  54  comprises three concentric flow channels, namely, an outer feed channel  58 , a central, outwardly-flowing channel  60 , and an intermediate channel  62 , which may or may not be used. 
         [0011]    As seen in  FIG. 2 , positioned concentrically within the outer cylinders  42  are intermediate cylinders  64  and inner cylinders  66 , which are each superimposed upon each other and clamped by the clamping action between the outer cylinders, the top plate  50  and the lower annular rim  56  of the manifold system  54 . It will thus be apparent with reference to  FIGS. 2 and 3  that the outer and intermediate cylinders form the annular outer chamber  68  communicating with the outer feed manifold  58 , an inner or central chamber  70 , communicating with the manifold  60 , and an intermediate chamber  72  communicating with the manifold  62 . 
         [0012]    As best seen in  FIG. 4 , adjoining sets of intermediate and inner cylinders may be provided with annular grooves  74  and  76  to receive any convenient sealing means. Intermediate cylinders  64  are also provided with closely spaced openings  78  to receive modified cyclonettes which may be more or less of the type shown in  FIG. 1  or of various modified forms more fully disclosed in U.S. Publication No. 2008/0099410. In any case, the cyclonettes are secured in any convenient manner in the openings  78  with the opposite ends of the cyclonettes being received in openings  80  in the cylinders  66 . In  FIG. 4 , the openings  78  are shown as having internal threads, which could receive complementary external threads on the exterior of the cyclonettes. In this regard, O-rings, such as those shown at  16  and  20  in  FIG. 1 , may be utilized to create seals with the cylinders  64  and  66 , respectively. 
         [0013]    However, any convenient means may be utilized to secure the cyclonettes in the intermediate and interior cylinders  64  and  66 . In any case, the positioning of a cyclonette, regardless of its specific configuration, in the manner shown in  FIG. 4  permits the liquid delivered through the outer manifold  58  and into the annular outer chamber  68  to flow into an insert  14  and then into the upstream end of the cyclonette and out its downstream end where it is immersed in the liquid being treated, which is being collected in the inner or central cylindrical chamber  70  and then out through the manifold  60 . 
         [0014]    As seen in  FIG. 4 , it is contemplated that hundreds, perhaps even a thousand or more of cyclonettes, will be arrayed in a single housing  40  of liquid treatment apparatus  12 . Each cyclonette may be disposed opposite another, resulting in direct impingement of the flow from one cyclonette upon the opposite flow from an opposing cyclonette. 
         [0015]    In use, the manifold  58  is the feed manifold for the system, delivering the liquid to be treated to the upstream or left-hand end of the insert  14  from whence the flow is ejected in an axial jet out the orifice plate  36  of the insert  14  and into the flow channel  24 . This action results in the generation of shear zones that create a myriad of tiny bubbles, each of which, upon implosion, create highly localized areas of extreme pressures and temperatures. 
         [0016]    This in turn results in dissolution of the water molecules into, inter alia, aggressive hydroxyl radicals. While in its most straightforward form the passageway  38  in the upstream end of the cyclonette will not be utilized, alternatively, a supply of the liquid being treated may be fed via the intermediate manifold  62  and the intermediate chamber  72  into the passageways  36  to provide an additional flow and hence an intensifying of the shear zone to enhance the formation of the tiny bubbles as liquid flows through the flow channel  24  of the cyclonette  10 . 
         [0017]    The cyclonette  10  and/or apparatus  12  for generating and utilizing cavitation for the treatment of a liquid medium may find application in a host of additional industrial processes. By way of example, U.S. Publication No. 2008/0277264, the disclosure of which is incorporated by reference herein in its entirety and which is assigned to the assignee of the present application, discloses using liquid treatment apparatus  12  to generate cavitation in the production of ethanol. More particularly, as disclosed therein, certain benefits may be achieved by including one or more hydraulic cavitation processing steps in a conventional dry grind process, modified dry grind process, or a wet mill process. 
         [0018]    While the cyclonettes  10  and liquid treatment apparatus  12  as disclosed more fully in U.S. Publication No. 2008/0099410 are believed to be adequate for various applications, such as in ethanol production, there are some drawbacks. For example, while the designs disclosed in U.S. Publication No. 2008/0099410 focus on the design of the cyclonettes  10  so as to maximize cavitation generation, it may be desirable to design the liquid treatment apparatus  12  so as to optimize the collapse of the cavitation bubbles generated by cyclonettes  10 . In this regard, the liquid treatment apparatus  12  as disclosed in U.S. Publication No. 2008/0099410 discharges the fluid jet containing the cavitations bubbles into a large body of fluid (e.g., chamber  70 ) where the cavitation bubbles will eventually collapse. While such a method provides a certain level of effectiveness in generating hydroxyl radicals in the liquid medium, more efficient methodologies of bubble collapse are being sought. 
       SUMMARY  
       [0019]    An apparatus for treating a liquid includes a first flow generator having an outlet for generating a first flow stream of the liquid being treated and a reaction chamber positioned in proximity to the outlet of the first flow generator and having a cavity adapted to receive the first flow stream from the first flow generator. In one embodiment, the first flow generator includes a cavitation generator, such as, for example, a cyclonette, adapted to generate a first flow stream including multiple cavitation bubbles. In another embodiment, the first flow generator includes a nozzle adapted to generate a first flow stream substantially devoid of cavitation. In the former embodiment, the reaction chamber may be configured to facilitate bubble collapse and therefore enhance treatment of the liquid. In the latter embodiment, the reaction chamber may be configured to facilitate turbulence and mixing so as to enhance treatment of the liquid. 
         [0020]    The cavity in the reaction chamber may include a blind bore having at least one side wall and a base wall. The bore may have a relatively constant cross-sectional area along the length of the bore or alternatively, have a cross-sectional area that varies along the length of the bore, such as by having a tapered or arcuate side wall. By way of example, the cavity may include a blind bore configured as a cylindrical bore, a tapered bore, or a generally arcuate bore. 
         [0021]    In one embodiment, the apparatus may include a second flow generator having an outlet for generating a second flow stream of the liquid being treated. The second flow generator may be directly opposed to the first flow generator, such that the first and second flow streams intersect each other. In this embodiment, the cavity may include a first inlet adapted to receive the first flow stream and a second inlet adapted to receive the second flow stream, wherein the first and second flow streams intersect each other within the cavity. To this end, the cavity may include a first cavity portion and a second cavity portion in fluid communication with each other. In another embodiment utilizing opposed fluid generators, the cavity may include a flow channel defined by a side wall and having a first inlet adapted to receive the first flow stream and a second inlet adapted to receive the second flow stream, wherein the streams intersect within the cavity. A chamber is disposed in the side wall of the flow channel and is configured to receive the fluid streams after intersection thereof. In one embodiment, the chamber includes a multi-lobed configuration. 
         [0022]    In another embodiment, an apparatus for treating a liquid includes outer, intermediate and inner cylinders positioned concentrically with respect to each other so as to define an outer annular chamber, an intermediate chamber, and an inner, central chamber. A plurality of flow generators, each having a unidirectional flow channel extending therethrough from adjacent an upstream end to adjacent a downstream end, is mounted in the intermediate cylinder with the upstream ends communicating with the annular outer chamber and the downstream ends communicating with the inner, central chamber. The apparatus further includes an outer feed channel supplying liquid being treated to the outer annular chamber, and a central, outwardly-flowing channel receiving liquid from the flow generators and immersing downstream ends thereof in the liquid being treated. A reaction chamber insert is positioned in the inner, central chamber and includes a plurality of cavities, the insert is configured such that a cavity is positioned in proximity to the downstream end of a corresponding flow generator. 
         [0023]    In still another embodiment, a method for treating a liquid includes directing the liquid into a first flow generator configured to generate a first flow stream of the liquid, and directing the first flow stream from the first flow generator into a cavity of a reaction chamber. The first flow generator may be configured to generate cavitation bubbles in the first flow stream. The method may further include bringing the first flow stream to rest within the cavity, reversing the direction of the first flow stream within the cavity, and/or intersecting the first flow stream with itself. For example, in one embodiment, the first flow stream may be directed into a blind bore. In another embodiment, the method may include directing the liquid into a second flow generator configured to generate a second flow stream of the liquid, directing the second flow stream from the second flow generator into the cavity, and causing the first intersection of the first and second flow streams within the cavity resulting in a third flow stream, which may intersect itself or intersect at least one of the first or second flow streams. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0024]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention. 
           [0025]      FIG. 1 . is an enlarged cross-sectional view of an exemplary cavitation generator in the form of a modified cyclonette; 
           [0026]      FIG. 2  is an elevational view, partly in section, illustrating an array of cyclonettes modified to generate hydraulic cavitation; 
           [0027]      FIG. 3  is an elevational view of the lower end of the device of  FIG. 2  and with the cooperating inlet and outlet flow manifolds; 
           [0028]      FIG. 4  is a cross-sectional view of a portion of  FIG. 2  illustrating in greater detail the positioning of a modified cyclonette; 
           [0029]      FIG. 5  is a side elevational view of a liquid treatment apparatus, in partial cross section, incorporating a reaction chamber in accordance with one embodiment of the invention; 
           [0030]      FIG. 6  is a side elevational view of a liquid treatment apparatus, in partial cross section, incorporating a reaction chamber in accordance with another embodiment of the invention; 
           [0031]      FIG. 7  is a side elevational view of a liquid treatment apparatus, in partial cross section, incorporating a reaction chamber in accordance with another embodiment of the invention; 
           [0032]      FIG. 8  is a side elevational view of a liquid treatment apparatus, in partial cross section, incorporating a reaction chamber in accordance with another embodiment of the invention; 
           [0033]      FIG. 9  is a side elevational view of a liquid treatment apparatus, in partial cross section, incorporating a reaction chamber in accordance with another embodiment of the invention; 
           [0034]      FIG. 10  is a view similar to  FIG. 2  but including a reaction chamber insert; and 
           [0035]      FIG. 11  is a view similar to  FIG. 4  but including a reaction chamber insert. 
       
    
    
     DETAILED DESCRIPTION  
       [0036]    One approach to increase the efficiency of bubble collapse is to make the cavitation bubbles collapse in a more violent manner. It is believed that this will increase the localized temperature and pressures that occur during bubble collapse. This may be done, for example, by quickly increasing the pressure in the fluid that is exiting the cavitation generator. Moreover, because the fluid exiting the cavitation generator may be moving at a relatively high velocity (e.g., high velocity head), one approach is to use the fluids own energy to quickly increase the pressure in the fluid (e.g., the pressure head). Quickly bringing the fluid to rest or quickly changing the momentum of the fluid flow (e.g., direction of fluid flow) may do this, for example. When this is done, the velocity head decreases and the pressure head of the fluid increases to collapse the cavitation bubbles more efficiently. In this regard, for example, it is believed that as the rate of pressure rise within the bubble is increased, the time of bubble collapse is correspondingly decreased. This in turn reduces the time available for heat to be transferred to the surrounding fluid, resulting in higher vapor temperatures. Moreover, the rate of bubble collapse also influences the maximum pressure attained within the bubble. In this regard, it is believed that a high rate of momentum change increases the PV (pressure×volume) work done on the bubble. 
         [0037]    In addition to quickly increasing the pressure of the fluid, it may be beneficial if the fluid flow is quickly brought to rest or is subject to a quick change in momentum within a constrained space or volume. In this regard, constraining the region where the velocity head is transferred to pressure head limits the expansion of the fluid and results in a localized high pressure region within the constrained volume. Additionally, when bubbles collapse, shock waves are formed. When one bubble collapses near another bubble, the shock wave from the first bubble collapse has an interaction with the second bubble and may facilitate its collapse. Accordingly, constraining the volume may increase the fraction of bubbles that quickly collapse and increase interaction among them. Moreover, constraining the volume in the region of bubble collapse (e.g., with a reaction chamber as discussed below) focuses the energy from any pressure or shock waves generated within the flow stream so as to improve chemical or reaction kinetics. 
         [0038]    In accordance with an exemplary embodiment of the invention, an increase in the efficiency of cavitation bubble collapse may be achieved using a reaction chamber that facilitates a more violent collapse of cavitation bubbles. In reference to  FIG. 5 , a liquid treatment apparatus  100  includes a cavitation generator, shown schematically at  102 , and a reaction chamber  104  in proximity to cavitation generator  102 . In one embodiment, the cavitation generator  102  may be a modified cyclonette  10  as discussed above and more fully disclosed in U.S. Publication No. 2008/0099410. However, the invention is not so limited as other cavitation generators may be used. For instance, ultrasonic and/or other hydraulic cavitation generators may be used to generate a fluid flow with many cavitation bubbles therein. 
         [0039]    The reaction chamber  104  includes an external wall  106  having a cavity  108  formed therein. In one embodiment, and as shown in  FIG. 5 , the cavity  108  may be configured as a straight or right cylindrical blind bore  110  having a side wall  112  and a base wall  114 . The blind bore  110  may include a circular cross-sectional shape. However, other cross-sectional shapes, such as square, rectangular, triangular, etc., are also contemplated to be within the scope of the invention. Cavity  108  includes an inlet  116  adjacent a surface of external wall  106  that is positioned adjacent an outlet  118  of the cavitation generator  102  such that the fluid flow from generator  102  is directed through the inlet  116  and into the otherwise closed cavity  108 . 
         [0040]    The fluid stream from the outlet  118  of cavitation generator  102  generally includes a relatively large velocity head and a relatively low pressure head so as to, for example, facilitate bubble generation within the fluid. As illustrated schematically by the flow lines  120  in  FIG. 5 , the fluid flow from cavitation generator  102  flows through inlet  116  and interacts with the base wall  114  of cylindrical bore  110 . It is believed that the flow stream contacts the base wall  114  and is brought to rest such that the energy in the velocity head is transferred to the pressure head to cause a quick rise in the fluid pressure. The quick increase in fluid pressure causes the cavitation bubbles to collapse. Similar to fluid contacting a flat plate, the flow is deflected so as to flow in a generally radial direction. The fluid stream then contacts the side wall  112  and is redirected back toward the inlet  116  of bore  110 . In essence, the side wall  112  constrains the volume in which the transfer of energy from the velocity head to the pressure head takes place and results in a 180 degree reversal of the fluid flow, thus maximizing the change in momentum of the fluid flow. 
         [0041]    To accommodate the fluid flow entering and exiting the bore  110 , the cross-sectional area of the bore  110  should be greater than the cross-sectional area of the flow stream entering inlet  116  (which should correspond approximately to the cross-sectional area of the outlet  118  of cavitation generator  102 ). For example, in one embodiment, if the cross-sectional area of the fluid stream is given by A s =A l +A g , where A l  is the cross-sectional area of the liquid and A g  is the cross-sectional area of the gas bubbles, then the cross-sectional area of the bore  110  may be given by A b =2A l +A g . Such a relation would maximize the change in momentum. 
         [0042]    In addition, it may be desirable to achieve this change in momentum very rapidly. Accordingly, the length of the bore  110  should be relatively short, but yet provide a confined volume in which the change in momentum occurs. In this regard, it is believed that the more rapid the change in momentum, the higher the deceleration/acceleration of the fluid, and the higher the static pressure generated within the fluid stream (at least up to the point where the static pressure head equals the velocity head of the incoming fluid stream). By way of example, the length of the bore  110  may be correlated to the cross-sectional area of the liquid A l . In particular, if r c  is a hypothetical radius of a conduit having a cross-sectional area of A l  carrying only the liquid, then the length of the bore  110  should be greater than approximately 0.36r c . For example, a bore  110  having a length of approximately 0.5r c  may be used. Larger lengths may also be used but may decrease the rate of bubble collapse. Those of ordinary skill in the art will appreciate that other dimensions (e.g., cross-sectional area and/or length) may be utilized with reaction chamber  102  to increase the fluid pressure and facilitate collapse of the cavitation bubbles. 
         [0043]    The cylindrical bore  110  provides for a change in momentum, wherein the fluid is turned a full 180 degrees, within the constrained volume defined by the blind bore  110 . It is believed, therefore, that the rapid pressure rise that results will collapse the cavitation bubbles in the fluid flow stream in a more violent manner so as to provide the benefits discussed above. 
         [0044]    In an alternative embodiment shown in  FIG. 6 , wherein like reference numerals refer to like features shown in  FIG. 5 , the reaction chamber  104   a  includes cavity  108  defined by a blind bore  122  having a side wall  124  and a base wall  126 . Unlike the previous embodiment, wherein the bore  110  had a substantially constant cross-sectional area along the length of the bore  110 , the side wall  124  of bore  122  is tapered such that the cross-sectional area decreases in a direction from the inlet  116  and toward the base wall  126 . The bore  122  may have a circular cross-sectional shape but other shapes are also contemplated to be within the scope of the invention. 
         [0045]    The liquid treatment apparatus  100   a  utilizing the tapered bore  122  operates in a manner similar to that discussed above. In this regard, the inlet  116  to bore  122  is positioned adjacent the outlet  118  of cavitation generator  102  and the fluid flow therefrom is directed through inlet  116  and into the otherwise closed cavity  108 . The fluid flow from the cavity generator  102  includes a relatively large velocity head and a relatively low pressure head to facilitate bubble generation in the liquid. As illustrated schematically by flow lines  128 , the fluid flow from cavitation generator  102  flows through inlet  116  and interacts with base wall  126  of tapered bore  122 . It is believed that the flow stream contacts the base wall  126 , is brought to rest or nearly brought to rest, and is redirected back toward the inlet  116  of the bore  122 . The side wall  124  constrains the volume in which the transfer of energy from the velocity head to the pressure head takes place and, like the previous embodiment, results in a 180 degree reversal of the fluid flow and thus maximizes the change in momentum. 
         [0046]    Similar to the above, the cross-sectional area of the bore  122  at the inlet  116  should be greater than the cross-sectional area of the flow stream entering inlet  116  so as to accommodate fluid flow both entering and exiting the bore  122 . In one embodiment, the cross-sectional area of the bore  122  at the inlet  116  may be given by A i =2A l +A g . The length of the bore  110  should be relatively short, but yet provide a confined volume in which the transfer of energy from the velocity head to the pressure head occurs. By way of example, the length of the bore  110  may be the same as in the previous embodiment. Furthermore, the cross-sectional area of the base wall  126  is less than the cross-sectional area of the inlet  116  and may be approximately equal to the cross-sectional area of the incoming fluid stream. 
         [0047]    The tapered configuration of bore  122  provides an increased confinement of the fluid in the region where the energy is transferred from the velocity head to the pressure head, yet allows the liquid to escape from the bore  122  by forming the inlet  116  thereof larger than the incoming fluid stream. Moreover, it is believed that by tapering the side wall  124  of the bore  122 , the pressure on the fluid stream is increased at a greater distance from the base wall  126  as compared to a constant cross-sectional area bore. Accordingly, bubble collapse may start occurring away from base wall  126 , which for reasons explained in more detail below, may be desirable. Furthermore, by varying the taper angle of the side wall  124  and/or the length of bore  122 , better control of bubble collapse may be achieved. 
         [0048]    In any event, the tapered bore  122  provides for a change in momentum, wherein the fluid is turned a full 180 degrees, within the constrained volume defined by the blind tapered bore  122 . It is believed, therefore, that the rapid pressure rise that results will collapse the cavitation bubbles in the fluid flow stream in a more violent manner so as to provide the benefits discussed above. 
         [0049]    While the reaction chambers  104 ,  104   a  discussed above increase the efficiency in collapsing the cavitation bubbles generated by cavitation generator  102  to achieve certain benefits, it may also be desirable to increase the turbulence and mixing of the fluid. For example, increasing the turbulence or mixing of the fluid may enhance various chemical reactions taking place in the fluid. In the reaction chambers  104 ,  104   a,  the fluid flow is reversed a full 180 degrees such that the angle of incidence between the in flow and exit flow is approximately zero. It is believed that a low angle of incidence between the inlet and exit streams diminishes the amount of turbulence and mixing that might otherwise be achieved in the fluid. Therefore, it may be desirable to design a reaction chamber that not only provides for increased efficiency in bubble collapse, but also provides for enhanced turbulence and mixing of the fluid. 
         [0050]    A reaction chamber  104   b  designed to provide the benefits of reactions chambers  104 ,  104   a  discussed above and increase turbulence and mixing of the fluid is shown in  FIG. 7 , in which like reference numerals refer to like features in  FIG. 5 . In this embodiment, the reaction chamber  104   b  includes a cavity  108  defined by a generally arcuate (e.g., spherical, tear shaped, bulbous, etc.) blind bore  132  having smooth, arching side wall  134  and a base wall  136 . There may or may not be any discernible divide between the side wall  134  and base wall  134 . Additionally, the bore  132  may be characterized in that a maximum cross dimension of the bore  132  is intermediate the inlet  116  and the base wall  136 . Again, the bore  132  may have a circular cross-sectional shape, but other shapes are also contemplated to be within the scope of the invention. 
         [0051]    The liquid treatment apparatus  100   b  utilizing the generally arcuate bore  132  operates in a manner similar to that discussed above. In this regard, the inlet  116  to bore  132  may be positioned adjacent the outlet  118  of cavitation generator  102  and the fluid flow therefrom directed through inlet  116  and into the otherwise closed cavity  108 . The fluid flow from the cavity generator  102  includes a relatively large velocity head and a relatively low pressure head to facilitate bubble generation in the liquid. As illustrated schematically by flow lines  138 , the fluid flow from cavitation generator  102  flows through inlet  116  and interacts with base wall  136  of arcuate bore  132 . It is believed that the flow stream contacts the base wall  136 , is brought to rest or nearly brought to rest, and is redirected back toward the inlet  116  of the bore  132  along the side wall  134 . The side wall  134  constrains the volume in which the transfer of energy from the velocity head to the pressure head takes place and, like the previous embodiments, results in a reversal of the fluid flow toward the inlet  116  and a change in momentum. 
         [0052]    Unlike the previous embodiments, however, the side wall  134  is configured to direct the fluid flow which has interacted with base wall  136  (e.g., the return flow) so as to intersect the incoming fluid stream at a relatively large angle of incidence, as illustrated by angle α in  FIG. 7 . By way of example, the angle of incidence may be between approximately 30 degrees and 90 degrees. The relatively large angle of incidence between the inlet and exit streams provides for collisions between the fluid particles of the two streams that enhance turbulence and mixing within the fluid (e.g., inlet stream and return flow stream). Larger angles of incidence are expected to provide increased turbulence and mixing. 
         [0053]    In addition to the above, the reaction chamber  104   b  may provide additional benefits. For example, the configuration of arcuate bore  132  may increase the fraction of cavitation bubbles that collapse. In this regard, when the inlet fluid stream interacts with base wall  136 , the cavitation bubbles along the central portion of the incoming fluid stream are subjected to the largest transfer of energy from the velocity head to the pressure head and thus, are more likely to collapse. The cavitation bubbles along the outer portion of the incoming fluid stream may be deflected radially outward such that there is less of an energy transfer to the pressure head. Accordingly, a number of cavitation bubbles in this region may not collapse. As illustrated in  FIG. 7 , the return flow interacts with the incoming fluid stream along its outer region. When the fluid particles between the two streams collide, there is an increase in the localized pressure. This localized pressure rise may be sufficient to initiate bubble collapse in the incoming fluid stream, especially within the outer region thereof. Thus, cavitation bubbles that may otherwise not have collapsed through interaction with base wall  136  may collapse by directing the return flow to intersect the incoming fluid stream. Furthermore, directing the return flow to intersect the incoming fluid stream may initiate bubble collapse away from the base wall  136 , which for reasons discussed in more detail below may be desirable. 
         [0054]    As is well recognized, it may be undesirable to collapse bubbles near solid surfaces. As discussed above, the collapse of cavitation bubbles generate high, localized temperatures and pressures. In many cases, bubble collapse generally occurs in an asymmetric fashion, due to, for example, asymmetric pressure fields, resulting in the creation of high speed micro-jets of fluid. Impingement of the micro-jets on a solid surface in proximity to an asymmetric bubble collapse may result in erosion (pitting, cracking, etc.) of the solid surface. In some applications, the erosion of the solid surface may not be problematic. For example, it may be possible to replace an eroded solid surface with relative ease and without any significant burden (e.g., labor costs, material costs, downtime, etc.). In other applications, however, the burden of eroding or otherwise damaging a solid surface in proximity to collapsing bubbles may be appreciable. Therefore, it may be desirable to avoid or reduce the possibility of cavitation bubbles collapsing near a solid surface, such as base walls  114 ,  126 , and  136  of reaction chambers  104 ,  104   a,  and  104   b,  respectively. 
         [0055]      FIG. 8  illustrates an embodiment of a liquid treatment apparatus  200  having a reaction chamber that eliminates or reduces the possibility of bubble collapse near a solid wall and therefore avoids or diminishes erosion of the reaction chamber and the problems associated therewith. In this regard, liquid treatment apparatus  200  includes opposed first and second cavitation generators  202 ,  204 , and a reaction chamber  206  in proximity to the cavitation generators  202 ,  204 . In one embodiment, the cavitation generators  202 ,  204  may include modified cyclonettes  10  as discussed above, or may be other cavitation generators as known in the art. 
         [0056]    The reaction chamber  206  includes a wall  208  having a cavity  210  formed therein. The cavity  210  includes a first cavity portion  212  having an inlet  214  adjacent a surface of a first wall portion  216  that is positioned adjacent an outlet  218  of first cavitation generator  202 . In this way, the fluid flow from generator  202  is directed through the inlet  214  and into the first cavity portion  212 . The cavity  210  further includes a second cavity portion  220  having an inlet  222  adjacent a surface of a second wall portion  224  that is positioned adjacent an outlet  226  of second cavitation generator  204 . In this way, the fluid flow from the generator  204  is directed through the inlet  222  and into the second cavity portion  220 . The first and second cavity portions  212 ,  220  intersect each other, such as along a plane  228  (shown in dash in  FIG. 8 ), so that the fluid streams from the fluid generators  202 ,  204  intersect one another. By way of example, in one embodiment, the fluid streams may intersect each other at approximately 180 degrees (e.g., directly opposed to each other), as illustrated in  FIG. 8 . 
         [0057]    The first cavity portion  212  may be configured as a tapered bore  230  similar to that shown in  FIG. 6  and second cavity portion  220  may also be configured as a tapered bore  232 . However, instead of having a base wall that interacts with the incoming fluid stream, the base wall has been removed so that the incoming fluid streams react with each other. If the two fluid streams intersect at approximately 180 degrees and have similar fluid characteristics, including density and velocity, then the fluid streams respond or behave as if hitting a solid wall, but with no solid wall being present. Accordingly, the flow lines  234 ,  236  in first and second cavity portions  212 ,  220 , respectively, are each similar to flow lines  128  shown in  FIG. 6 . Moreover, the length of cavity  210  may be double the values of the cavities discussed above. Thus, in one embodiment, the length may be approximately r c . 
         [0058]    As a result of the configuration of reaction chamber  206 , the benefits afforded by tapered bores  230 ,  232  are similar to those discussed above with reference to  FIG. 6 , but the possibility of erosion of the reaction chamber  206  has been eliminated or significantly reduced. Additionally, turbulence and mixing may be enhanced using colliding fluid streams. As discussed below, this may be useful to improve chemical reaction kinetics. While the first and second cavity portions  212 ,  220  were configured as tapered bores, those of ordinary skill in the art will recognize that the right cylindrical bore  110  or generally arcuate bore  132  shown in  FIGS. 5 and 7 , respectively, may also be used to form cavity portions  212 ,  220 . 
         [0059]    The opposed fluid stream configuration illustrated in  FIG. 8  may provide additional benefits. For example, it is believed that replacing a stationary object (e.g., base wall) with a moving object (e.g., opposed fluid stream) increases the rate of bubble collapse within the fluid streams. As the maximum temperature and pressure achieved within the collapsing bubble are related to the rate of bubble collapse, providing for a quicker collapse results in higher temperatures and pressures. Quicker bubble collapse may also result in a lower fraction of heat loss to the surrounding fluid. The opposed fluid configuration may also reduce energy consumption. Additionally, if the fluid streams contain particles of higher density than their surrounding fluid medium, when the fluid streams intersect and reverse direction, the higher density particles tend to continue in their previous direction (e.g., straight direction) as compared to the less dense fluid particles which change direction. This introduces shear between the particles and the surrounding fluid which may result in improved chemical reaction kinetics. For example, it is believed that if the particles are being used to catalyze a reaction, the presence of mobile catalysts in a high shear zone where cavitation bubble collapse is occurring will further improve the reaction kinetics. Furthermore, cavitation bubble collapse would tent to “clean” the surface of catalyst particles and thus improve reaction kinetics. Still further, in some applications, it may be desirable to reduce the size of the particles. In such applications, it is believed that directing the fluid streams to meet in opposition to each other within a cavitation bubble collapse zone (e.g., within the cavity of the reaction chamber) will increase impact intensity and hence improve “milling” of the particles. 
         [0060]    Another embodiment that utilizes an opposed flow stream configuration to reduce or eliminate erosion of the reaction chamber is shown in  FIG. 9 . This embodiment also provides for enhanced turbulence and mixing of the fluid. In this regard, liquid treatment apparatus  300  includes first and second opposed cavitation generators  302 ,  304 , and a reaction chamber  306  in proximity to the cavitation generators  302 ,  304 . In one embodiment, the cavitation generators  302 ,  304  may include modified cyclonettes  10  as discussed above, or may be other cavitation generators as known in the art. 
         [0061]    The reaction chamber  306  includes a wall  308  having a cavity  310  formed therein. The cavity  310  includes a first inlet  312  adjacent a surface of a first wall portion  314  and a second inlet  316  adjacent a surface of a second wall portion  318 . The first and second inlets  312 ,  316  may include chamfers  320  to form a smooth transition between the cavity  310  and the first and second wall portions  314 ,  318 . Fluid flow from first cavitation generator  302  is directed through first inlet  312  and into cavity  310  and fluid flow from the second cavitation generator  304  is directed through second inlet  316  and into cavity  310  such that the fluid streams intersect one another. By way of example, in one embodiment, the fluid streams may intersect each other at approximately 180 degrees (e.g., directly opposed to each other), as illustrated in  FIG. 9 . 
         [0062]    The cavity  310  includes a side wall  322  that defines a channel  324  extending between the first and second inlets  312 ,  316 . In one embodiment, the channel  324  may include a generally constant cross-sectional area portion  326  extending inward from each of the inlets  312 ,  316 . A central portion of the channel  324  includes an outwardly extending (e.g., radially extending) chamber  328  disposed in side wall  322 . The chamber  328  includes an opening  330  in fluid communication with channel  324 . The chamber  328  has a multi-lobe configuration including a first lobe  332  and a second lobe  334 , which may be symmetrical about a central plane  336 , as shown in dash in  FIG. 9 . A flow divider  338  may be disposed in the chamber  328  for guiding or separating the flow stream into one of the lobes  332 ,  334 . 
         [0063]    The flow lines  340 ,  342  illustrate operation of the liquid treatment device  300 . In this regard, the fluid flow from first generator  302  enters inlet  312  and fluid flow from second generator  304  enters inlet  316  so as to intersect the first fluid stream generally along central plane  336 . The fluid particles collide thereat transferring the velocity head of the flows into pressure head. Accordingly, the internal pressure of the fluid rapidly increases thereby causing the cavitation bubbles to collapse. As explained above, the fraction of bubbles that collapse is generally the highest along the central part of the fluid flow streams and decreases toward the outer portion of the streams. 
         [0064]    As explained previously, the colliding streams behave in a manner similar to when contacting a perpendicular flat plate. Accordingly, the flow is directed generally radially outward and flows through the opening  330  in chamber  328 . The flow divider  338 , which may have a sharp point to reduce stagnation, divides the flow into a respective lobe  332 ,  334 . The fluid then flows along the generally arcuate wall  344  of the lobes  332 ,  334  so as to intersect the fluid flow stream entering the opening  330  in the chamber  328 . This intersection occurs at a relatively high angle of incidence (see  FIG. 7 ). The fluid then flows out of the chamber  328  adjacent the edges of the opening  330  and flows back toward the inlets  312 ,  316  along a region adjacent the side wall  322  of channel  324 . The flow then exits the reaction chamber  306  along the outer edges of inlets  312 ,  316 . 
         [0065]    The configuration shown in  FIG. 9  provides a number of benefits. As an initial matter, because the liquid treatment apparatus  300  utilizes an opposing fluid flow configuration, erosion of the reaction chamber  306  is eliminated or reduced. In this regard, a significant fraction of bubble collapse occurs along central plane  336  where the two fluid streams intersect. As the cross-sectional area of channel  324  is larger than the cross-sectional area of the fluid streams entering the cavity  310  (so as to accommodate both inlet and return flows), this collapse is away from side wall  322 . Moreover, any bubbles that do not collapse on impact between the two fluid streams, such as along the outer region of the streams, may be collapsed at the opening  330  of chamber  328  due to the intersection of the fluid stream with itself. As explained above, when the fluid particles collide as a result of the intersection, the internal pressure increases, which in turn may collapse any remaining cavitation bubbles along the outer region of the fluid streams. 
         [0066]    As explained above, a relatively large angle of incidence exists between the incoming and exiting fluid from chamber  328 . Thus, another benefit to the configuration shown in  FIG. 9  is that turbulence and mixing of the fluid is enhanced. In addition to these, the fluid flowing toward the inlets  312 ,  316  adjacent the side wall  322  provides a layer of fluid (for which the cavitation bubbles have already been collapsed) that further shields the reaction chamber  306  from erosion and other damage as a result of bubble collapse. 
         [0067]    Although not shown, in another embodiment, the chamber  328  may be configured to direct the fluid flow that enters the chamber  328  after the first and second fluid flow streams  340 ,  342  collide to intersect one of or both the incoming first and second fluid flow streams  340 ,  342  (such as along the outer portion thereof). It is believed that such a configuration would generally result in a greater fraction of cavitation bubbles in the outer regions of these streams collapsing. However, as compared to the configuration shown in  FIG. 9  (e.g., intersecting the radially moving flow after collision instead of the incoming flow), turbulence and mixing may be lessened. This may be due, at least in part, to the velocity of the return flow having a component in the direction of the inlets. 
         [0068]    In one aspect of the invention, the liquid treatment apparatus  12  as shown and described in  FIGS. 2-4  and more fully disclosed in U.S. Publication No. 2008/0099410 may be modified so as to receive the benefits afforded by a reaction chamber in accordance with one or more of the embodiments described above. As shown in  FIGS. 10 and 11 , in which like reference numerals refer to like features in  FIGS. 3 and 4 , liquid treatment apparatus  12  may include a generally cylindrical reaction chamber insert  400  disposed within the inner chamber  70  of apparatus  12 . In one embodiment, the reaction chamber insert  400  includes a plurality of blind bores  402  each in proximity to an outlet  118  of a corresponding modified cyclonette  10 . The apparatus  12  essentially operates in same manner as previously explained in U.S. Publication No. 2008/0099410, but with the inclusion of insert  400 , gets the benefit afforded by the use of a reaction chamber and described above. 
         [0069]    While the insert  400  is shown having the blind bores  402  configured as tapered bores, similar to that shown in  FIG. 6 , those of ordinary skill in the art will recognize that the blind bores  402  may be straight cylindrical bores and/or generally arcuate bores. Moreover, those of ordinary skill in the art will recognize that while insert  400  is shown as utilizing a blind bore configuration, the reaction chamber insert may also make use of the opposed fluid flow configuration described above. 
         [0070]    Aspects of the invention as described herein may be beneficial to a variety of industrial applications that rely on chemical reactions to achieve an end product. In particular, through a combination of cavitation and/or the use of a reaction chamber to accelerate/decelerate a bubble-laden medium, to constrain bubble collapse, and/or increase turbulence and mixing, chemical reactions may be enhanced. For example, it is believed that the chemical reactions may be accelerated potentially by orders of magnitude as compared to rates typically achieved in stirred tanks. By way of example, in one application it is believed that a starch oxidation process that normally takes between about 6-8 hours in a stirred tank batch reactor may be performed continuously using cavitation in combination with a reaction chamber. In another application, it is believed that the conversion of vegetable oil to biodiesel at room temperature, which may require several hours in a stirred tank, may also be performed continuously using cavitation in combination with a reaction chamber. 
         [0071]    The ability to convert batch type of chemical reaction into a continuous reaction has many benefits. For example, a continuous reaction provides improved quality control. In this regard, maintaining batch-to-batch consistency is often difficult and problematic. Continuous reactions, on the other hand, promote consistent quality upon maintaining the appropriate operating parameters. Additionally, continuous reactions are less susceptible to side chain reactions that may diminish quality. Still further, in continuous chemical reactions the amount of process tank volume is typically significantly reduced. This in turn, may provide for reduced inventory and capital costs. Moreover, in various food processes, reduced tank volumes reduce the risk of product contamination and continuous reactions reduce residence time for the growth of contaminating microorganisms. 
         [0072]    In addition to these, there may be other benefits. For example, it is believed that another benefit is that chemical consumption will be reduced when using cavitation in combination with a reaction chamber. In this regard, it is believed that the increased efficiency in collapsing the cavitation bubbles (and the resulting increases in pressure and temperatures) will require a lesser amount of chemical to achieve a similar result in the treated liquid. Less chemical consumption provides for cost savings in the chemicals themselves and may further reduce costs associated with handling of the chemicals either before or after treatment of a liquid. For example, in some applications, post chemical treatment processes may constitute a major portion of the costs of a manufacturing process. 
         [0073]    While embodiments described herein include both the use of cavitation and a reaction chamber, the invention is not so limited. For example, it is believed that the turbulence and mixing aspects of the reaction chamber may provide some increase in chemical reactions regardless of whether cavitation is used or not. Accordingly, the apparatus described above that facilitates turbulence and mixing (e.g.,  FIGS. 7 and 9 ) may include nozzle assemblies in place of the cavitation generators and attain at least some of the benefits described herein, including increased chemical reactions or enhanced mixing of the fluid itself. 
         [0074]    While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the various features of the invention may be used alone or in numerous combinations depending on the needs and preferences of the user.