Device and method for generating micro bubbles in a liquid using hydrodynamic cavitation

A device and method for generating micro bubbles in a liquid. The method includes the steps of: providing a flow-through channel containing at least two local constrictions of flow therein; passing the liquid at a velocity of at least at least 12 m/sec through a first local constriction of flow to create a first hydrodynamic cavitation field downstream from the first local constriction of flow; introducing a gas into the liquid in the first local constriction of flow, thereby creating gas-filled cavitation bubbles; collapsing the gas-filled cavitation bubbles formed in the first hydrodynamic cavitation field to dissolve the gas into the liquid, thereby forming a gas-saturated liquid; passing the gas-saturated liquid through a second local constriction of flow to create a second hydrodynamic cavitation field downstream from the second local constriction of flow; and extracting the dissolved gas from the gas-saturated liquid, thereby generating micro bubbles in the liquid.

BACKGROUND

The present invention relates to a device and process for generating micro bubbles in a liquid using hydrodynamic cavitation.

Because micro bubbles have a greater surface area than larger bubbles, micro bubbles can be used in a variety of applications. For example, micro bubbles can be used in mineral recovery applications utilizing the floatation method where particles of minerals can be fixed to floating micro bubbles to bring them to the surface. Other applications include using micro bubbles as carriers of oxidizing agents to treat contaminated groundwater or using micro bubbles in the treatment of waste water.

DETAILED DESCRIPTION

Illustrated inFIG. 1is a longitudinal cross-section of one embodiment of a hydrodynamic cavitation device10for generating micro bubbles in a liquid. The device10includes a wall15having an inner surface20that defines a flow-through channel or chamber25having a centerline CL. For example, the wall15can be a cylindrical wall that defines a flow-through channel having a circular cross-section. It will be appreciated that the cross-section of flow-through channel25may take the form of other geometric shapes such as square, rectangular, hexagonal, or any other complex shape. The flow-through channel25can further include an inlet30configured to introduce a liquid into the device10along a path represented by arrow A and an outlet35configured to exit the liquid from the device10.

With further reference toFIG. 1, in one embodiment, the device10can further include multiple cavitation generators that generate a cavitation field downstream from each cavitation generator. For example, the device10can include two stages of hydrodynamic cavitation where a first cavitation generator can be a first baffle40and a second cavitation generator can be a second baffle45. It will be appreciated that any number of stages of hydrodynamic cavitation can be provided within the flow-through channel25. Furthermore, it will be appreciated that other types of cavitation generators may be used instead of baffles such as a Venturi tube, nozzle, orifice of any desired shape, or slot.

In one embodiment, the second baffle45is positioned within the flow-through channel downstream from the first baffle40. For example, the first and second baffles40,45can be positioned substantially along the centerline CLof the flow-through channel25such that the first baffle40is substantially coaxial with the second baffle45.

To vary the degree and character of the cavitation fields generated downstream from the first and second baffles40,45, the first and second baffles40,45can be embodied in a variety of different shapes and configurations. For example, the first and second baffles40,45can be conically shaped where the first and second baffles40,45each include a conically-shaped surface50a,50b,respectively, that extends into a cylindrically-shaped surface55a,55b,respectively. The first and second baffles40,45can be oriented such that the conically-shaped portions50a,50b,respectively, confront the fluid flow. It will be appreciated that the first and second baffles40,45can be embodied in other shapes and configurations such as the ones disclosed in U.S. Pat. No. 5,969,207, issued on Oct. 19, 1999, which is hereby incorporated by reference in its entirety herein. Of course, it will be appreciated that the first baffle40can be embodied in one shape and configuration, while the second baffle45can be embodied in a different shape and configuration.

To retain the first baffle40within the flow-through channel25, the first baffle40can be connected to a plate60via a shaft65. It will be appreciated that the plate60can be embodied as a disk when the flow-through channel25has a circular cross-section, or the plate60can be embodied in a variety of shapes and configurations that can match the cross-section of the flow-through channel25. The plate60can be mounted to the inside surface20of the wall15with screws or any other attachment means. The plate60can include a plurality of orifices70configured to permit liquid to pass therethrough. It will be appreciated that that a crosshead, post, propeller or any other fixture that produces a minor loss of liquid pressure can be used instead of the plate60having orifices70. To retain the second baffle45within the flow-through channel25, the second baffle45can be connected to the first baffle40via a stem or shaft75or any other attachment means.

In one embodiment, the first and second baffles40,45can be configured to be removable and replaceable by baffles embodied in a variety of different shapes and configurations. It will be appreciated that the first and second baffles40,45can be removably mounted to the stems65,75, respectively, in any acceptable fashion. For example, each baffle40,45can threadly engage each stem65,75, respectively.

In one embodiment, the first baffle40can be configured to generate a first hydrodynamic cavitation field80downstream from the first baffle40via a first local constriction85of liquid flow. For example, the first local constriction85of liquid flow can be an area defined between the inner surface20of the wall15and the cylindrically-shaped surface55aof the first baffle40. Also, the second baffle45can be configured to generate a second hydrodynamic cavitation field90downstream from the second baffle45via a second local constriction95of liquid flow. For example, the second local constriction95can be an area defined between the inner surface20of the wall15and the cylindrically-shaped surface55bof the second baffle45. Thus, if the flow-through channel25has a circular cross-section, the first and second local constrictions85,95of liquid flow can be characterized as first and second annular orifices, respectively. It will be appreciated that if the cross-section of the flow-through channel25is any geometric shape other than circular, then each local constriction of flow may not be annular in shape. Likewise, if a baffle is not circular in cross-section, then each corresponding local constriction of flow may not be annular in shape.

In one embodiment, the size of each local constriction85,95is sufficient to increase the velocity of the fluid flow to a minimum velocity necessary to achieve hydrodynamic cavitation (hereafter the “minimum cavitation velocity”), which is dictated by the physical properties of the fluid being processed (e.g., viscosity, temperature, etc.). For example, the size of each local constriction85,95, or any local constriction of fluid flow discussed herein, can be dimensioned in such a manner so that the cross-section area of each local constriction of fluid flow would be at most about 0.6 times the diameter or major diameter of the cross-section of the flow-through channel. The minimum cavitation velocity of a fluid is about 12 m/sec. On average, and for most hydrodynamic fluids, the minimum cavitation velocity is about 18 m/sec.

With further reference toFIG. 1, the flow-through channel25can further include a port97for introducing a gas into the flow-through channel25along a path represented by arrow B. For example, the gas can be air, oxygen, nitrogen, hydrogen, ozone, or steam. In one embodiment, the port97can be disposed in the wall15and positioned adjacent the first local constriction85of flow to permit the introduction of the gas into the liquid in the first local constriction85of flow. For example, the gas can be introduced into the liquid in a region of reduced liquid pressure in the first local constriction85of flow. It will be appreciated that the port97can be disposed in the wall15anywhere along the axial length first local constriction85of flow. Furthermore, it will be appreciated that any number of ports can be provided in the wall15to introduce gas into the first local constriction85or the port97can be embodied as a slot to introduce gas into the first local constriction85.

In operation of the device10illustrated inFIG. 1, the liquid enters the flow-through channel25via the inlet30and moves through the orifices70in the plate60along the fluid path A. The liquid can be fed through the flow-through channel25and maintained at any flow rate sufficient to generate a hydrodynamic cavitation field downstream from both the first and second baffles40,45. As the liquid moves through the flow-through channel25, the gas is introduced into the first local constriction85via the port97, thereby mixing the gas with the liquid as the liquid passes through the first local constriction85. The gas can be introduced into the liquid in the first local constriction85and maintained at a flow rate that is different from the liquid flow rate and sufficient to control the collapse of cavitation bubbles formed in the hydrodynamic cavitation field. For example, a ratio between the gas volumetric flow rate and the liquid volumetric flow rate is about 0.1 or less. In other words, the ratio between the liquid volumetric flow rate and the gas volumetric flow rate can be at least about 10.

While passing through the first local constriction85, the velocity of the liquid increases to the minimum cavitation velocity for the particular fluid being processed. The increased velocity of the liquid forms the first hydrodynamic cavitation field80downstream from the first baffle40, thereby generating cavitation bubbles that grow when mixed with the gas to form gas micro bubbles. Upon reaching an elevated static pressure zone, the gas micro bubbles can be partially or completely collapsed (or squeezed) thereby dissolving the gas into the liquid to form a gas-saturated liquid.

Once the gas micro bubbles are generated after the first stage of hydrodynamic cavitation, the gas-saturated liquid continues to move towards the second baffle45. While passing through the second local constriction95, the velocity of the gas-saturated liquid increases to a minimum cavitation velocity of the liquid. The increased velocity of the gas-saturated liquid, forms the second hydrodynamic cavitation field90downstream from the second baffle45thereby generating cavitation bubbles. Upon reaching an elevated static pressure zone, a vacuum is created in the second hydrodynamic cavitation field90to extract the dissolved gas from the gas-saturated liquid, thereby generating micro bubbles. These micro bubbles are smaller in size and more uniform than the micro bubbles produced after the first stage of hydrodynamic cavitation. The liquid and micro bubbles then exits the flow-through channel25via the outlet35.

Illustrated inFIG. 2is a longitudinal cross-section of another embodiment of a hydrodynamic cavitation device200for generating micro bubbles in a liquid. The device200includes a wall215having an inner surface220that defines a flow-through channel or chamber225having a centerline CL. For example, the wall215can be a cylindrical wall that defines a flow-through channel having a circular cross-section. It will be appreciated that the cross-section of flow-through channel225may take the form of other geometric shapes such as square, rectangular, hexagonal, or any other complex shape. The flow-through channel225can further include an inlet230configured to introduce a liquid into the device200along a path represented by arrow A and an outlet235configured to exit the liquid from the device200.

With further reference toFIG. 2, in one embodiment, the device200can further include multiple cavitation generators that generate a cavitation field downstream from each cavitation generator. For example, the device200can include two stages of hydrodynamic cavitation where a first cavitation generator can be a first plate240having an orifice245disposed therein to produce a first local constriction of liquid flow and a second cavitation generator can be a second plate250having an orifice255disposed therein to produce a second local constriction of liquid flow. It will be appreciated that any number of stages of hydrodynamic cavitation can be provided within the flow-through channel225. Furthermore, it will be appreciated that other types of cavitation generators may be used instead of plates having orifices disposed therein such as baffles. As discussed above, the size of the local constrictions of flow are sufficient to increase the velocity of the liquid flow to the minimum cavitation velocity for the fluid being processed.

Each plate240,250can be mounted to the wall215with screws or any other attachment means to retain each plate240,250in the flow-through channel225. In another embodiment, the first and second plates240,250can include multiple orifices disposed therein to produce multiple local constrictions of fluid flow. It will be appreciated that each plate can be embodied as a disk when the flow-through channel225has a circular cross-section, or each plate can be embodied in a variety of shapes and configurations that can match the cross-section of the flow-through channel225.

In one embodiment, the second plate250is positioned within the flow-through channel downstream from the first plate240. For example, the first and second plates240,250can be positioned substantially along the centerline CLof the flow-through channel225such that the orifice245in the first plate240is substantially coaxial with the orifice in the second plate250.

To vary the degree and character of the cavitation fields generated downstream from the first and second plates240,250, the orifices245,255can be embodied in a variety of different shapes and configurations. The shape and configuration of each orifice245,255can significantly affect the character of the cavitation flow and, correspondingly, the quality of crystallization. In one embodiment, the orifices245,255can have a circular cross-section. It will be appreciated that each orifice245,255can be configured in the shape of a Venturi tube, nozzle, orifice of any desired shape, or slot. Further, it will be appreciated that the orifices245,255can be embodied in other shapes and configurations such as the ones disclosed in U.S. Pat. No. 5,969,207, which is hereby incorporated by reference in its entirety herein. Of course, it will be appreciated that the orifice245disposed in the first plate240can be embodied in one shape and configuration, while the orifice255disposed in the second plate250can be embodied in a different shape and configuration.

In one embodiment, the orifice245disposed in the first plate240can be configured to generate a first hydrodynamic cavitation field260downstream from the orifice245. Likewise, the orifice255disposed in the second plate250can be configured to generate a second hydrodynamic cavitation field265downstream from the orifice255.

With further reference toFIG. 2, the flow-through channel225can further include a port270for introducing a gas into the flow-through channel225along a path represented by arrow B. For example, the gas can be air, oxygen, nitrogen, hydrogen, ozone, or steam. In one embodiment, the port270can be disposed in the wall215and extended through the plate240to permit the introduction of the gas into the liquid in the first local constriction of flow. For example, the gas can be introduced into the liquid in a region of reduced liquid pressure in the first local constriction of flow. It will be appreciated that the port270can be disposed in the wall215anywhere along the axial length of the orifice245disposed in the first plate240. Furthermore, it will be appreciated that any number of ports can be provided in the wall215to introduce gas into the orifice245disposed in the first plate240or the port270can be embodied as a slot to introduce gas into the orifice245disposed in the first plate240.

In operation of the device200illustrated inFIG. 2, the liquid is fed into the flow-through channel225via the inlet230along the path A. The liquid can be fed through the flow-through channel225and maintained at any flow rate sufficient to generate a hydrodynamic cavitation field downstream from both the first and second plates240,250. As the liquid moves through the flow-through channel225, the gas is introduced into the orifice245disposed in the first plate240via the port270thereby mixing the gas with the liquid as the liquid passes through the orifice245disposed in the first plate240. The gas can be introduced into the liquid in the orifice245disposed in the first plate240and maintained at a flow rate that is different from the liquid flow rate and sufficient to control the collapse of cavitation bubbles formed in the hydrodynamic cavitation field. For example, a ratio between the volumetric gas flow rate and the volumetric liquid flow rate is about 0.1 or less. In other words, the ratio between the volumetric liquid flow rate and the volumetric gas flow rate can be at least about 10.

While passing through the orifice245disposed in the first plate240, the velocity of the liquid increases to a minimum cavitation velocity for the particular liquid being processed. The increased velocity of the liquid forms the first hydrodynamic cavitation field260downstream from the first plate240, thereby generating cavitation bubbles that grow when mixed with the gas to form gas micro bubbles. Upon reaching an elevated static pressure zone, the gas micro bubbles can be partially or completely collapsed (or squeezed), thereby dissolving the gas into the liquid to form a gas-structured liquid.

Once the gas micro bubbles are generated after the first stage of hydrodynamic cavitation, the gas-saturated liquid continue to move towards the second plate250. While passing through the orifice255disposed in the second plate250, the velocity of the gas-saturated liquid increases to the minimum cavitation velocity of the liquid. The increased velocity of the gas-saturated liquid forms the second hydrodynamic cavitation field265downstream from the second plate250, thereby generating cavitation bubbles. Upon reaching an elevated static pressure zone, a vacuum is created in the second hydrodynamic cavitation field265to extract the dissolved gas from the gas-saturated liquid thereby generating micro bubbles. These micro bubbles are smaller in size and more uniform than the micro bubbles produced after the first stage of hydrodynamic cavitation. The liquid and micro bubbles then exits the flow-through channel225via the outlet235.

Illustrated inFIG. 3is a longitudinal cross-section of another embodiment of a hydrodynamic cavitation device300for generating micro bubbles in a liquid. The device300includes a wall315having an inner surface320that defines a flow-through channel or chamber325having a centerline CL. The flow-through channel325can further include an inlet330configured to introduce a liquid into the device300along a path represented by arrow A and an outlet335configured to exit the liquid from the device300.

With further reference toFIG. 3, in one embodiment, the device300can further include multiple cavitation generators that generate a cavitation field downstream from each cavitation generator. For example, the device300can include two stages of hydrodynamic cavitation where a first cavitation generator can be a baffle340and a second cavitation generator can be a plate345having an orifice350disposed therein to produce a local constriction of liquid flow. It will be appreciated that the plate355can be embodied as a disk when the flow-through channel325has a circular cross-section, or the plate355can be embodied in a variety of shapes and configurations that can match the cross-section of the flow-through channel325. Further, it will be appreciated that any number of stages of hydrodynamic cavitation can be provided within the flow-through channel325. As discussed above, the size of the local constrictions of flow are sufficient to increase the velocity of the fluid flow to a minimum cavitation velocity for the fluid being processed.

In one embodiment, the plate345is positioned within the flow-through channel downstream from the baffle340. For example, the baffle340and the plate345can be positioned substantially along the centerline CLof the flow-through channel325such that the baffle340is substantially coaxial with the orifice350disposed in the plate345.

To retain the baffle340within the flow-through channel325, the baffle340can be connected to a plate355via a stem or shaft360. It will be appreciated that the plate355can be embodied as a disk when the flow-through channel325has a circular cross-section, or the plate355can be embodied in a variety of shapes and configurations that can match the cross-section of the flow-through channel325. The plate355can be mounted to the inside surface320of the wall315with screws or any other attachment means. The plate355can include a plurality of orifices365configured to permit liquid to pass therethrough. To retain the plate345within the flow-through channel325, the plate345can be connected to the wall315with screws or any other attachment means.

In one embodiment, the baffle340can be configured to generate a first hydrodynamic cavitation field370downstream from the baffle340via a first local constriction375of liquid flow. For example, the first local constriction375of liquid flow can be an area defined between the inner surface320of the wall315and an outside surface of the baffle340. Also, the orifice350disposed in the plate345can be configured to generate a second hydrodynamic cavitation field380downstream from the orifice350.

With further reference toFIG. 3, the flow-through channel325can further include a port385for introducing a gas into the flow-through channel325along a path represented by arrow B. In one embodiment, the port385can be disposed in the wall315and positioned adjacent the first local constriction375of flow to permit the introduction of the gas into the liquid in the first local constriction375of flow. For example, the gas can be introduced into the liquid in a region of reduced liquid pressure in the first local constriction of flow. It will be appreciated that the port385can be disposed in the wall315anywhere along the axial length first local constriction375of flow. Furthermore, it will be appreciated that any number of ports can be provided in the wall315to introduce the gas into the first local constriction375or the port385can be embodied as a slot to introduce the gas into the first local constriction375.

In operation of the device300illustrated inFIG. 3, the liquid enters the flow-through channel325via the inlet330and moves through the orifices365in the plate360along the path A. The liquid can be fed through the flow-through channel325and maintained at any flow rate sufficient to generate a hydrodynamic cavitation field downstream from both the first and second cavitation generators. As the liquid moves through the flow-through channel325, the gas is introduced into the first local constriction375via the port385thereby mixing the gas with the liquid as the liquid passes through the first local constriction375. The gas can be introduced into the liquid in the first local constriction375and maintained at a flow rate that is different from the liquid flow rate and sufficient to control the collapse of cavitation bubbles formed in the hydrodynamic cavitation field. For example, a ratio between the gas volumetric flow rate and the liquid volumetric flow rate is about 0.1 or less. In other words, the ratio between the liquid volumetric flow rate and the gas volumetric flow rate can be at least about 10.

While passing through the first local constriction375, the velocity of the liquid increases to a minimum cavitation velocity for the particular liquid being processed. The increased velocity of the liquid forms the first hydrodynamic cavitation field370downstream from the baffle340, thereby generating cavitation bubbles that grow when mixed with the gas to form gas micro bubbles. Upon reaching an elevated static pressure zone, the gas micro bubbles can be partially or completely collapsed (or squeezed), thereby dissolving the gas into the liquid to form a gas-saturated liquid.

Once the gas micro bubbles are generated after the first stage of hydrodynamic cavitation, the gas-saturated liquid continues to move towards the plate350. While passing through the orifice350disposed in the plate345, the velocity of the gas-saturated liquid increases to the minimum cavitation velocity of the liquid. The increased velocity of the gas-saturated liquid forms the second hydrodynamic cavitation field380downstream from the plate345, thereby generating cavitation bubbles. Upon reaching an elevated static pressure zone, a vacuum is created in the second hydrodynamic cavitation field380to extract the dissolved gas from the gas-saturated liquid, thereby generating micro bubbles. The micro bubbles are smaller in size and more uniform than the micro bubbles produced after the first stage of hydrodynamic cavitation. The liquid and micro bubbles then exit the flow-through channel325via the outlet335.

Illustrated inFIG. 4is a longitudinal cross-section of another embodiment of a hydrodynamic cavitation device400for generating micro bubbles in a liquid. The device400includes a wall415having an inner surface420that defines a flow-through channel or chamber425having a centerline CL. The flow-through channel425can further include an inlet430configured to introduce a liquid into the device400along a path represented by arrow A and an outlet435configured to exit the liquid from the device400.

With further reference toFIG. 4, in one embodiment, the device400can further include multiple cavitation generators that generate a cavitation field downstream from each cavitation generator. For example, the device400can include two stages of hydrodynamic cavitation where a first cavitation generator can be a plate440having an orifice445disposed therein to produce a local constriction of liquid flow and a second cavitation generator can be a baffle450. It will be appreciated that the plate455can be embodied as a disk when the flow-through channel325has a circular cross-section, or the plate455can be embodied in a variety of shapes and configurations that can match the cross-section of the flow-through channel325. Further, it will be appreciated that any number of stages of hydrodynamic cavitation can be provided within the flow-through channel425. As discussed above, the size of the local constrictions of flow are sufficient to increase the velocity of the fluid flow to a minimum cavitation velocity for the fluid being processed.

In one embodiment, the plate440is positioned within the flow-through channel upstream from the baffle450. For example, the plate440and the baffle450can be positioned substantially along the centerline CLof the flow-through channel425such that the baffle450is substantially coaxial with the orifice445disposed in the plate440.

To retain the plate440within the flow-through channel425, the plate440can be connected to the wall415with screws or any other attachment means. To retain the baffle450within the flow-through channel425, the baffle450can be connected to a plate455via a stem or shaft460. It will be appreciated that the plate455can be embodied as a disk when the flow-through channel425has a circular cross-section, or the plate455can be embodied in a variety of shapes and configurations that can match the cross-section of the flow-through channel425. The plate455can be mounted to the inside surface420of the wall415with screws or any other attachment means. The plate455can include a plurality of orifices465configured to permit liquid to pass therethrough.

In one embodiment, the orifice445disposed in the plate450can be configured to generate a first hydrodynamic cavitation field470downstream from the orifice245. Also, the baffle450can be configured to generate a second hydrodynamic cavitation field475downstream from the baffle450via a local constriction480of liquid flow. For example, the local constriction475of liquid flow can be an area defined between the inner surface420of the wall415and an outside surface of the baffle450.

With further reference toFIG. 4, the flow-through channel425can further include a port485for introducing a gas into the flow-through channel425along a path represented by arrow B. In one embodiment, the port485can be disposed in the wall415and extended through the plate440to permit the introduction of the gas into the liquid in the local constriction480of flow. For example, the gas can be introduced into the liquid in a region of reduced liquid pressure in the first local constriction480of flow. It will be appreciated that the port485can be disposed in the wall415anywhere along the axial length of the orifice445disposed in the plate440. Furthermore, it will be appreciated that any number of ports can be provided in the wall415to introduce gas into the orifice445disposed in the plate440or the port485can be embodied as a slot to introduce gas into the orifice445disposed in the plate440.

In operation of the device400illustrated inFIG. 4, the liquid is fed into the flow-through channel425via the inlet430along the path A. The liquid can be fed through the flow-through channel425and maintained at any flow rate sufficient to generate a hydrodynamic cavitation field downstream from both the first and second cavitation generators. As the liquid moves through the flow-through channel425, the gas is introduced into the orifice445disposed in the plate440via the port485thereby mixing the gas with the liquid as the liquid passes through the orifice445. The gas can be introduced into the liquid in the orifice445disposed in the plate440and maintained at a flow rate that is different from the liquid flow rate and sufficient to control the collapse of cavitation bubbles formed in the hydrodynamic cavitation field. For example, a ratio between the gas volumetric flow rate and the liquid volumetric flow rate is about 0.1 or less. In other words, the ratio between the liquid volumetric flow rate and the gas volumetric flow rate can be at least about 10.

While passing through the orifice445disposed in the plate440, the velocity of the liquid increases to a minimum cavitation velocity for the particular liquid being processed. The increased velocity of the liquid forms the first hydrodynamic cavitation field470downstream from the plate440, thereby generating cavitation bubbles that grow when mixed with the gas to form gas micro bubbles. Upon reaching an elevated static pressure zone, the gas micro bubbles can be partially or completely collapsed (or squeezed), thereby dissolving the gas into the liquid to form a gas-saturated liquid.

Once the gas micro bubbles are generated after the first stage of hydrodynamic cavitation, the gas-saturated liquid continues to move towards the baffle450. While passing through the local constriction480of flow, the velocity of the gas-saturated liquid increases to the minimum cavitation velocity of the liquid. The increased velocity of the gas-saturated liquid forms the second hydrodynamic cavitation field475downstream from the baffle450, thereby generating cavitation bubbles. Upon reaching an elevated static pressure zone, a vacuum is created in the second hydrodynamic cavitation field475to extract the dissolved gas from the gas-saturated liquid thereby generating micro bubbles. These micro bubbles are smaller in size and more uniform than the micro bubbles produced after the first stage of hydrodynamic cavitation. The liquid and micro bubbles then exit the flow-through channel425via the outlet435.

Illustrated inFIG. 5is a longitudinal cross-section of another embodiment of a hydrodynamic cavitation device500for generating micro bubbles in a liquid. The device500includes a wall515having an inner surface520that defines a flow-through channel or chamber525having a centerline CL. The flow-through channel525can further include an inlet530configured to introduce a liquid into the device500along a path represented by arrow A and an outlet535configured to exit the liquid from the device500.

With further reference toFIG. 5, in one embodiment, the device500can further include multiple cavitation generators that generate a cavitation field downstream from each cavitation generator. For example, the device500can include two stages of hydrodynamic cavitation where a first cavitation generator can be a first baffle540and a second cavitation generator can be a second baffle345. It will be appreciated that any number of stages of hydrodynamic cavitation can be provided within the flow-through channel525.

In one embodiment, the first baffle545is positioned within the flow-through channel525downstream from the first baffle540. For example, the first and second baffles540,545can be positioned substantially along the centerline CLof the flow-through channel525such that the first baffle540is substantially coaxial with the second baffle545.

To vary the degree and character of the cavitation fields generated downstream from the first and second baffles540,545, the first and second baffles540,545can be embodied in a variety of different shapes and configurations. It will be appreciated that the first and second baffles540,545can be embodied in other shapes and configurations such as the ones disclosed in U.S. Pat. No. 5,969,207, issued on Oct. 19, 1999, which is hereby incorporated by reference in its entirety herein. Of course, it will be appreciated that the first baffle540can be embodied in one shape and configuration, while the second baffle545can be embodied in a different shape and configuration.

To retain the first baffle540within the flow-through channel525, the first baffle540can be connected to a plate550via a stem or shaft555. The plate550can be mounted to the inside surface520of the wall515with screws or any other attachment means. The plate550can include at least one orifice560configured to permit liquid to pass therethrough. To retain the second baffle545within the flow-through channel525, the second baffle545can be connected to the first baffle540via a stem or shaft565or any other attachment means.

In one embodiment, the first baffle540can be configured to generate a first hydrodynamic cavitation field570downstream from the first baffle540via a first local constriction575of liquid flow. For example, the first local constriction575of liquid flow can be an area defined between the inner surface520of the wall515and an outside surface of the first baffle540. Also, the second baffle545can be configured to generate a second hydrodynamic cavitation field580downstream from the second baffle545via a second local constriction585of liquid flow. For example, the second local constriction585can be an area defined between the inner surface520of the wall515and an outside surface of the second baffle545. As discussed above, the size of the local constrictions575,585of flow are sufficient to increase the velocity of the fluid flow to a minimum cavitation velocity for the fluid being processed.

With further reference toFIG. 5, the flow-through channel525can further include a fluid passage590for introducing a gas into the flow-through channel525along a path represented by arrow B. In one embodiment, the port590can be disposed in the wall515to permit the introduction of the gas into the liquid in the first local constriction575of flow. For example, the gas can be introduced into the liquid in a region of reduced liquid pressure in the first local constriction575of flow. Beginning at the wall515, the fluid passage590extends through the plate550, the stem555, and at least partially into the first baffle540. It will be appreciated that the fluid passage595can be embodied in any shape or path. In the first baffle540, the fluid passage terminates into at least one port595that extends radially from the CLof the first baffle540and exits in the first local constriction575of flow. Furthermore, it will be appreciated that the port595can be disposed in the first baffle540anywhere along the axial length of the first local constriction575of flow. Furthermore, it will be appreciated that any number of ports can be provided in the first baffle to introduce gas into the first local constriction575of flow or the port595can be embodied as a slot to introduce gas into the first local constriction575of flow.

In operation of the device500illustrated inFIG. 5, the liquid enters the flow-through channel525via the inlet530and moves through the at least one orifice560in the plate550along the path A. The liquid can be fed through the flow-through channel525and maintained at any flow rate sufficient to generate a hydrodynamic cavitation field downstream from both the first and second baffles540,545. As the liquid moves through the flow-through channel525, the gas is introduced into the first local constriction575via the port590and the passage595thereby mixing the gas with the liquid as the liquid passes through the first local constriction575. The gas can be introduced into the liquid in the first local constriction575and maintained at a flow rate that is different from the liquid flow rate and sufficient to control the collapse of cavitation bubbles formed in the hydrodynamic cavitation field. For example, a ratio between the gas volumetric flow rate and the liquid volumetric flow rate is about 0.1 or less. In other words, the ratio between the liquid volumetric flow rate and the gas volumetric flow rate can be at least about 10.

While passing through the first local constriction575, the velocity of the liquid increases to a minimum cavitation velocity for the particular liquid being processed. The increased velocity of the liquid forms the first hydrodynamic cavitation field580downstream from the first baffle540, thereby generating cavitation bubbles that grow when mixed with the gas to form gas micro bubbles. Upon reaching an elevated static pressure zone, the bubbles can be partially or completely collapsed (or squeezed), thereby dissolving the gas into the liquid to form a gas-saturated liquid.

Once the gas micro bubbles are generated after the first stage of hydrodynamic cavitation, the gas-saturated liquid continues to move towards the second baffle545. While passing through the second local constriction585, the velocity of the gas-saturated liquid increases to the minimum cavitation velocity of the liquid. The increased velocity of the gas-saturated liquid forms the second hydrodynamic cavitation field580downstream from the second baffle545, thereby generating cavitation bubbles. Upon reaching an elevated static pressure zone, a vacuum is created in the second hydrodynamic cavitation field580to extract the dissolved gas from the gas-saturated liquid, thereby generating micro bubbles. The micro bubbles are smaller in size and more uniform than the micro bubbles produced after the first stage of hydrodynamic cavitation. The liquid and micro bubbles then exit the flow-through channel525via the outlet535.

The following examples are given for the purpose of illustrating the present invention and should not be construed as limitations on the scope or spirit of the instant invention.

The following example of a method of generating micro bubbles in liquid was carried out in a device substantially similar to the device200as shown inFIG. 2, except that the device included only one stage of hydrodynamic cavitation. Water was fed, via a high pressure pump, through the flow-through channel225, at a velocity of 30.12 meters per second (m/sec) and a flow rate of 5.68 liter per minute (l/min). Air was introduced, via a compressor, into the flow-through channel225via the port270in the first local constriction of flow245at a flow rate of 0.094 standard liters per minute (sl/min). Accordingly, the volume ratio of the air flow rate to the water flow rate was 0.017. The combined water and air then passed through the local constriction of flow245creating hydrodynamic cavitation to thereby effectuate the generation of micro bubbles. The resultant bubble size of the micro bubbles was between 5,000 and 7,000 microns.

The following example of a method of generating micro bubbles in liquid was carried out in a device substantially similar to the device200as shown inFIG. 2, which included two stages of hydrodynamic cavitation. Water was fed, via a high pressure pump, through the flow-through channel225, at a velocity of 30.12 m/sec and a flow rate of 5.68 l/min. Air was introduced, via a compressor, into the flow-through channel225via the port270in the first local constriction of flow245at a flow rate of 0.566 sl/min. Accordingly, the volume ratio of the air flow rate to the water flow rate was 0.100. The combined water and air then passed through the first and second local constrictions of flow245,255creating hydrodynamic cavitation to thereby effectuate the generation of micro bubbles. The resultant bubble size of the micro bubbles was between 200 and 300 microns.

The method above was repeated in the device200, except that the gas flow rate was changed. The results are illustrated in Chart 1 below.

The following example of a method of generating micro bubbles in liquid was carried out in a device substantially similar to the device200as shown inFIG. 2, except that the device included only one stage of hydrodynamic cavitation. Water was fed, via a high pressure pump, through the flow-through channel225, at a velocity of 46.21 m/sec and a flow rate of 8.71 l/min. Air was introduced, via a compressor, into the flow-through channel225via the port270in the first local constriction of flow245at a flow rate of 0.212 standard sl/min. Accordingly, the volume ratio of the air flow rate to the water flow rate was 0.024. The combined water and air then passed through the local constriction of flow245creating hydrodynamic cavitation to thereby effectuate the generation of micro bubbles. The resultant bubble size of the micro bubbles was between 5,000 and 7,000 microns.

The following example of a method of generating micro bubbles in liquid was carried out in a device substantially similar to the device200as shown inFIG. 2, which included two stages of hydrodynamic cavitation. Water was fed, via a high pressure pump, through the flow-through channel225, at a velocity of 46.21 m/sec and a flow rate of 8.71 l/min. Air was introduced, via a compressor, into the flow-through channel225via the port270in the first local constriction of flow245at a flow rate of 0.614 sl/min. Accordingly, the volume ratio of the air flow rate to the water flow rate is 0.070. The combined water and air then passed through the first and second local constrictions of flow245,255creating hydrodynamic cavitation to thereby effectuate the generation of micro bubbles. The resultant bubble size of the micro bubbles was between 200 and 300 microns.

The method above was repeated in the device200, except that the gas flow rate was changed. The results are illustrated in Chart 2 below.

The following example of a method of generating micro bubbles in liquid was carried out in a device substantially similar to the device200as shown inFIG. 2, except that the device included only one stage of hydrodynamic cavitation. Water was fed, via a high pressure pump, through the flow-through channel225, at a velocity of 60.48 m/sec and a flow rate of 11.4 l/min. Air was introduced, via a compressor, into the flow-through channel225via the port270in the first local constriction of flow245at a flow rate of 0.236 sl/min. Accordingly, the volume ratio of the air flow rate to the water flow rate is 0.021. The combined water and air then passed through the local constriction of flow245creating hydrodynamic cavitation to thereby effectuate the generation of micro bubbles. The resultant bubble size of the micro bubbles was between 5,000 and 8,000 microns.

The following example of a method of generating micro bubbles in liquid was carried out in a device substantially similar to the device200as shown inFIG. 2, which included two stages of hydrodynamic cavitation. Water was fed, via a high pressure pump, through the flow-through channel225, at a velocity of 60.48 m/sec and a flow rate of 11.4 l/min. Air was introduced, via a compressor, into the flow-through channel225via the port270in the first local constriction of flow245at a flow rate of 0.991 sl/min. Accordingly, the volume ratio of the air flow rate to the water flow rate is 0.087. The combined water and air then passed through the first and second local constrictions of flow245,255creating hydrodynamic cavitation to thereby effectuate the generation of micro bubbles. The resultant bubble size of the micro bubbles was between 200 and 300 microns.

The method above was repeated in the device200, except that the gas flow rate was changed. The results are illustrated in Chart 3 below.

Although the invention has been described with reference to the preferred embodiments, it will be apparent to one skilled in the art that variations and modifications are contemplated within the spirit and scope of the invention. The drawings and description of the preferred embodiments are made by way of example rather than to limit the scope of the invention, and it is intended to cover within the spirit and scope of the invention all such changes and modifications.