Abstract:
A fluidic oscillator is disclosed, wherein the fluidic oscillator includes a fluid source and a housing coupled to the fluid source. At least one recess is formed within the housing. An insert resides within each at least one recess; the insert provides at least one substantially flat surface. A fluid flowpath in the at least one substantially flat surface generates fluid pulses from fluid received from the fluid source.

Description:
BACKGROUND 
   The present invention relates to apparatuses for creating pulsating fluid flow. Known as fluidic oscillators, these devices connect to a source of fluid flow, provide a mechanism for oscillating the fluid flow between two different locations within the device, and emit fluid pulses downstream of the source of fluid flow. Fluidic oscillators require no moving parts to generate the oscillations and have been used in various applications for which pulsating fluid flow is desired, such as massaging showerheads, flowmeters, and windshield-wiper-fluid-supply units. 
   A fluidic oscillator may include a body  10  with a nozzle  20  that attaches to a fluid source  30 , as shown in  FIG. 1 . The nozzle  20  expels the fluid as a jet into a chamber  40  toward a flow splitter  50 . This flow splitter  50  traditionally assumes a triangular or trapezoidal shape, with a narrow leading edge directly in the path of the jet. The sides of flow splitter  50  form the inner walls of two fluid pathways  60  and  60 ′ that diverge and exit the apparatus. The body  10  forms the outer walls of the two fluid pathways  60  and  60 ′, as well as at least two feedback passages  70  and  70 ′ leading from the fluid pathways back into the chamber. Each feedback passage  70  or  70 ′ will be disposed along one of the fluid pathways,  60  or  60 ′, respectively. 
   The jet will cling to one side of chamber  40  due to a phenomenon called the Coanda effect, explained in more detail later in this disclosure. Thus, the fluid will flow through one of the two fluid pathways  60  or  60 ′ at a time. Flow splitter  50  also helps guide the flow into either fluid pathway  60  or fluid pathway  60 ′. As the fluid flows through one fluid pathway such as fluid pathway  60 , feedback passage  70  will divert a portion of the fluid and return it to chamber  40 . The fluid will then disturb the fluid flow along the side of chamber  40  closest to fluid pathway  60 . This disturbance will cause the fluid flow to switch to the side of the chamber closest to fluid pathway  60 ′. Fluid will thus leave from fluid pathway  60 ′, rather than from fluid pathway  60 . As a result, the apparatus for creating pulsating fluid flow will emit pulses of fluid in succession from the two fluid pathways  60  and  60 ′, with only one fluid pathway  60  or  60 ′ ejecting fluid at a given time. 
   Fluidic oscillators may be manufactured from two rectangular blocks of a material suitable for the particular application. For example, if the fluidic oscillator will be used in a well bore, stainless steel blocks may be appropriate. A flowpath may be machined into the largest flat surface of one of the rectangular blocks. The two blocks may be joined together, and the entire apparatus may be lathed into a generally cylindrical form. This design has several flaws: it requires a time-, labor-, and material-intensive method of manufacture and does not permit on-the-fly changes to the flowpath in the field. More importantly, if the fluid-flow path erodes beyond repair, the entire fluidic oscillator must be replaced. 
   Some applications for fluidic oscillators require sharper fluid pulses than others. For example, fluidic oscillators may be used to clean fluid flowlines or well bores. The fluidic oscillator may be joined to a source of cleaning fluid and then inserted into the flowline or well bore, where the pulses of cleaning fluid can break up any buildup or debris on the inside of the flowline or well bore. Pulsating fluid flow has been found to be superior to steady fluid flow for cleaning surfaces such as the interior of a fluid flowline or well bore. Moreover, sharp fluid pulses dislodge buildup and debris from these surfaces better than less-defined fluid pulses. Many current fluidic oscillators, however, may not provide the pulse definition cleaning applications require. In addition, current fluidic oscillators often emit fluid parallel to the nozzle and thus may not effectively clean areas located alongside the apparatus. For example, a fluidic oscillator that emits pulses of fluid parallel to the fluid nozzle may not effectively remove matter caked on the well bore because it will eject fluid only down the center of the well bore, not at the sides. 
   Fluidic oscillators also often rely on atmospheric air entering the fluid pathway to boost the oscillations. As a result, these fluidic oscillators exhibit erratic, weak or even no oscillation when used in submerged environments such as fluid flowlines or well bores. These apparatuses fail to provide reliable, robust fluid pulses in environments where air is unavailable, such as in fluid flowlines or well bores. 
   SUMMARY 
   The present invention relates to apparatuses for creating pulsating fluid flow. A fluidic oscillator is disclosed, wherein an example fluidic oscillator includes a fluid source and a housing coupled to the fluid source. At least one recess is formed within the housing. An insert resides within each at least one recess; the insert provides at least one substantially flat surface. A fluid flowpath in the at least one substantially flat surface generates fluid pulses from fluid received from the fluid source. At least one port on the housing allows the fluid pulses to escape from the fluid flowpath to outside the housing. 
   An alternative example fluidic oscillator is also provided. This example fluidic oscillator includes a fluid source and a housing, wherein the housing is coupled to the fluid source. At least one tapered recess is formed within the housing. A tapered insert resides within each at least one tapered recess. The tapered insert provides at least one substantially flat surface. An inlet into which fluid flows is also provided, wherein the inlet is formed on the at least one substantially flat surface. The fluidic oscillator also includes a chamber having an upstream end and a downstream end, wherein the chamber is formed on the at least one substantially flat surface, wherein the chamber is defined by a pair of outwardly-projecting sidewalls, and wherein the inlet is disposed at the upstream end of the chamber. At least two feedback passages are formed on the at least one substantially flat surface, wherein the at least two feedback passages have opposed entrances at the downstream end of the chamber and opposed exits at the upstream end of the chamber near where the chamber joins the inlet. A feedback cavity is formed on the at least one substantially flat surface, wherein the feedback cavity is disposed at the downstream end of the chamber. At least one exit flowline leaves each of the feedback passages, wherein the at least one exit flowline is formed on the at least one substantially flat surface. At least one port in the housing allows fluid to escape from the at least one exit flowline to outside of the housing. 
   Another alternative example fluidic oscillator is provided. This example fluidic oscillator includes a fluid source and a housing coupled to the fluid source. Four recesses are formed within the housing; the four recesses are evenly spaced about a central longitudinal axis of the housing. An insert resides within each of the four recesses, wherein the insert provides at least one substantially flat surface. A fluid flowpath is provided on the at least one substantially flat surface, wherein the fluid flowpath generates fluid pulses from fluid received from the fluid source. At least one port on the housing allows the fluid pulses to escape from the fluid flowpath to outside the housing. 
   The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the detailed description that follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  illustrates a prior art fluidic oscillator; 
       FIG. 2  illustrates an example fluidic oscillator with a portion of its housing removed to expose an insert. 
       FIG. 3  illustrates an insert for an example fluidic oscillator; 
       FIG. 4  illustrates a pattern view of an insert for an example fluidic oscillator; 
       FIG. 5  illustrates a side view of an insert for an example fluidic oscillator; 
       FIG. 6  illustrates an insert for an example fluidic oscillator; 
       FIG. 7  illustrates a side view of an insert for an example fluidic oscillator; 
       FIG. 8  illustrates an insert for an example fluidic oscillator; 
       FIG. 9  illustrates a housing for an example fluidic oscillator; 
       FIG. 10  illustrates a longitudinal cross-section of a housing for an example fluidic oscillator; 
       FIG. 11  illustrates a housing for an example fluidic oscillator; 
       FIG. 12  illustrates a longitudinal cross-section of a housing for an example fluidic oscillator; and 
       FIG. 13  illustrates a housing for an example fluidic oscillator. 
   

   While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and are herein described in detail. The description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as described by the appended claims. 
   DETAILED DESCRIPTION 
     FIG. 2  illustrates an example fluidic oscillator  100 . Example fluidic oscillator  100  comprises a housing  200  that encloses at least one insert  300 . Insert  300  contains flowpath  302 , which generates the oscillation effect that drives the fluid pulses.  FIG. 2  displays a partially cutaway view of housing  200  to better display insert  300  and flowpath  302 . The example housing shown in  FIG. 2  is cylindrical, with a circular cross-section; housing  200  may alternatively take other forms, including, but not limited to, a bar-shaped form with a rectangular cross-section. Alternatively, housing  200  may include multiple inserts, as discussed in more detail later in this disclosure. A fluid flowline  400  supplies fluid to fluidic oscillator  100 . Fluid flowline  400  may fit inside housing  100  or alternatively connect to fluidic oscillator  100  via a transitional piece (not shown in  FIG. 2 ). 
   Housing  200  and insert  300  may be formed of any material capable of withstanding the environment in which fluidic oscillator  100  will be used. If, for example, fluidic oscillator  100  will be used to clean a flowline or well bore containing formation fluids, housing  200  and insert  300  may be formed of metal. Alternatively, housing  200  and insert  300  may be formed of a phenolic plastic capable of withstanding a downhole environment. Fluidic oscillator  100 &#39;s design allows the user to replace insert  300  without replacing fluidic oscillator  100  entirely. That is, if flowpath  302  erodes after heavy use, insert  300  may be replaced and housing  200  may be reused. The use of an insert  300  also permits customization of the flowpath in the field. 
     FIGS. 3 and 4  illustrate an example insert  300 . As shown in  FIG. 3 , insert  300  has flowpath  302  cut into its upper surface  301 ; flowpath  302  may be created through traditional machining processes, such as milling, casting, or molding or may be generated through an Electrical Discharge Machining (EDM) process. For ease of illustration,  FIG. 4  illustrates a plan view of flowpath  302  in upper surface  301 . Fluid supplied by fluid flowline  400  enters into flowpath  302  via interior flowline  303  and passes through inlet  304 . Interior flowline  303  may decrease in width as it approaches inlet  304  to form a focused jet as it enters inlet  304 . The fluid passes through inlet  304  into chamber  305 . Chamber  305  is defined by two outwardly projecting sidewalls  306  and  307  and has an upstream end  308  and a downstream end  309 . A feedback cavity  310  is disposed at downstream end  309 . 
   Flowpath  302  may have the configuration of the flowpath described and depicted in the application for United States Patent entitled “Apparatus and Method for Creating Pulsating Fluid Flow, and Method of Manufacture for the Apparatus,” Ser. No. 10/808,986 filed on Mar. 25, 2004, assigned to the assignee of this disclosure. The fluid forms a jet as it streams from inlet  304  into chamber  305  in example insert  300 . As the jet leaves inlet  304 , the fluid tends to cling to one of the two outwardly projecting sidewalls  306  or  307 . This tendency is a result of the well-documented phenomenon known as the “Coanda effect.” When the fluid exits inlet  304  as a jet into chamber  305 , it draws any fluid between the jet and one of the two outwardly projecting sidewalls  306  or  307  into the jet. For example, the jet may first draw fluid between the jet and outwardly projecting sidewall  306  into the jet. The temporary absence of fluid between the jet and outwardly projecting sidewall  306  creates a low-pressure region. Before the ambient pressure in chamber  305  can restore pressure to this region, the jet is drawn to outwardly projecting sidewall  306  and clings to its surface. The result of this Coanda effect is that the fluid enters chamber  305  along one of the outwardly projecting sidewalls  306  or  307 , rather than through the center of chamber  305 . 
   The pulsating action of the fluid flow generated by exemplary fluidic oscillator  100  arises from switches in the fluid flow from along outwardly projecting sidewall  306  to along outwardly projecting sidewall  307 , and vice versa. At least two feedback passages  311  and  312  are disposed on opposite sides of chamber  305  to help achieve these switches. Two opposed entrances  313  and  314  leave from downstream end  309  of chamber  305 . Two opposed exits  315  and  316  to feedback passages  311  and  312  join upstream end  308  of chamber  305 . To continue with the example of the previous paragraph, a portion of the fluid traveling alongside outwardly projecting sidewall  306  will reach opposed entrance  313  and be diverted into feedback passage  311 . Most of the fluid that enters feedback passage  311  will exit insert  300  through exit flowline  317 , as discussed later in this disclosure in more detail. The remaining fluid that enters feedback passage  311 , however, will return to chamber  305  through opposed exit  315 . The entry of this fluid into chamber  305  disturbs the path of the jet of fluid issuing from inlet  304  such that the jet no longer adheres to outwardly projecting sidewall  306 . The jet of fluid instead will adhere to outwardly projecting sidewall  307  in the same manner as it adhered to outwardly projecting sidewall  306 . 
   The jet of fluid will then travel along outwardly projecting sidewall  307 , and a portion of the fluid will enter feedback passage  312  through opposed entrance  314 . Most of the fluid will exit insert  300  through exit flowline  318 , as discussed in detail later in this disclosure. The remaining fluid in feedback passage  312  will continue to opposed exit  316  and return to chamber  305 . As with the fluid entering chamber  305  from opposed exit  315 , the fluid passing through opposed exit  316  will disturb the flow of fluid along the surface of outwardly projecting sidewall  307 . The fluid will then switch from traveling alongside outwardly projecting sidewall  307  to traveling alongside outwardly projecting sidewall  306 , and the cycle will repeat. 
   At any time when fluid flows along outwardly projecting sidewall  306  and through feedback passage  311 , no fluid flows along outwardly projecting sidewall  307  or through feedback passage  312 . The converse is also true: no fluid flows along outwardly projecting sidewall  306  or through feedback passage  311  while fluid flows along outwardly projecting sidewall  307  and through feedback passage  312 . This oscillation of fluid from one half of insert  300  to the other helps create the desired pulsating fluid flow. In particular, as fluid travels through either feedback passage  311  or  312 , exit flowline  317  or  318 , respectively, will draw off a portion of the passing fluid. Fluid entering exit flowline  317  or  318  will exit insert  300 . The effect of the oscillation of the fluid between outwardly projecting sidewall  306  and outwardly projecting sidewall  307  is that fluid will exit through only one exit flowline  317  or  318  at a time. Thus insert  300  will emit pulses of fluid from one side to the other, in succession. 
   Exit flowlines  317  and  318  in this example insert  300  are perpendicular to feedback passages  311  and  312 , respectively. Exit flowlines  317  and  318  may, however, take any number of different paths, as described in the application for United States Patent entitled “Apparatus and Method for Creating Pulsating Fluid Flow, and Method of Manufacture for the Apparatus,” Ser. No. 10/808,986 filed on Mar. 25, 2004, assigned to the assignee of this disclosure. For example, fluidic oscillator  100  might be used to clean the interior walls of a fluid flowline or a well bore. If exit flowlines  317  and  318  are perpendicular to feedback passages  311  and  312 , the pulses of fluid emitted from insert  300  could jet from the sides of fluidic oscillator  100  (as discussed below) onto the interior walls of the well bore, cleaning their surfaces of collected debris and scale. The best path for the exit flowlines will depend upon how the apparatus will be used, as will be readily apparent to a person of ordinary skill in the art having the benefit of this disclosure. 
   Feedback cavity  310 , disposed at downstream end  309  of chamber  305 , further promotes the oscillation of fluid flow in insert  300 . While a portion of the fluid traveling along outwardly projecting sidewalls  306  and  307  is directed into opposed entrances  313  and  314 , the remainder of the fluid exits chamber  305  into feedback cavity  310 . If the fluid enters feedback cavity  310  after traveling along outwardly projecting sidewall  306 , the fluid will follow a clockwise path around feedback cavity sidewall  319  and return to chamber  305  near outwardly projecting sidewall  307 . This fluid flow will destabilize the fluid flow near outwardly projecting sidewall  307 . The added instability amplifies the oscillation effect produced by feedback passage  311  by drawing fluid to outwardly projecting sidewall  307  from outwardly projecting sidewall  306 . The cycle then reverses, with fluid entering from outwardly projecting sidewall  307  and following a counterclockwise path in feedback cavity  310  to near outwardly projecting sidewall  306 . Example feedback cavity  310  has a rounded shape. Any volume that extends beyond opposed entrances  313  and  314  may serve as a feedback cavity  310 , regardless of the shape the volume assumes. At least one forward jet  320  may be present at feedback cavity sidewall  319 . Forward jet  320  may be useful for the well bore and fluid flowline cleaning applications discussed previously in this disclosure. For example, if fluidic oscillator  100  travels within a fluid flowline with forward jet  320  at the leading edge, forward jet  320  will jet fluid ahead of fluidic oscillator  100  and could thus clear debris from the path of fluidic oscillator  100 . Forward jet  320  should have a smaller cross-section than feedback passages  311  and  312 , to prevent disturbances to the pulsating action. 
   Insert  300  is wedge-shaped, as illustrated in  FIG. 3 . Upper surface  301 , a corresponding lower surface  330  (not shown in  FIG. 3 ), and two side surfaces  331  and  332  (not shown). Each side slopes such that insert  300  is narrower at its downstream end  333  than at its upstream end  334 . The angle of the slope may vary between approximately 0 degrees to approximately 15 degrees. For certain flowline cleaning jobs, a 1.5 degree downward slope from upstream end  334  to downstream end  333  may be desirable. The slope of upper surface  301  and lower surface  330  is made obvious in  FIG. 5 , which illustrates a side view of insert  300 . The tapered wedge shape of insert  300  has the benefit of allowing flowpath  302  to maintain a substantially constant depth inside insert  300  with only a gradual slope downstream in the height of the walls that form flowpath  302 . The walls maintain a substantially constant height across the width of the insert at any one location along the fluid flowpath. Rather, the height of the walls will only gradually decrease toward the downstream end of the insert. In contrast, if insert  300  assumed a cylindrical form, the height of the walls that form flowpath  302  would be much shorter near feedback outlets  317  and  318  than near chamber  305 . Moreover, the wedge shape for the insert provides a substantially flat surface for flowpath  302 . This configuration enhances the performance of fluidic oscillator  100 , as compared to, for example, a cylindrical insert which would have a curved surface for the flowpath. 
   The wedge shape is also more conducive to precision EDM processes and field customization than a cylindrical form would be. Inserts may be customized for particular jobs; a given fluidic oscillator may include multiple inserts that may be switched before use, even on site, depending on the job. The wedge shape of insert  300  also permits a tight, fluid-impermeable fit directly between housing  200  and insert  300 . That is, insert  300  may be designed to fit inside housing  200  such that all the outside surfaces of insert  300  directly contact the interior of housing  200  and create a fluid-tight seal that prevents any fluid from escaping from flowpath  302 . The direct housing-to-insert seal eliminates the need for any additional sealing structure and thus eliminates a manufacturing and operational variable. 
   The insert may also assume alternate forms. For example, the insert may be a rectangular block, rather than a wedge.  FIG. 6  illustrates a top view of a rectangular insert  340 . A tab  341  may be provided to lock insert  340  into housing  200 , which is discussed in greater detail later in this disclosure. The rectangular profile of insert  340  is evident in  FIG. 7 , which illustrates a side view of insert  340 . A second tab  342  may also be provided on lower surface  343  of insert  340 .  FIG. 8  displays another sample insert  350 . Insert  350  provides enough material to support walls  351  to surround flowpath  302 , but not very much more. Thus, rather than assuming a wedge or rectangular shape, the insert assumes a shape that models flowpath  302 . Interior flowline  353  and two exit flowlines  354  and  355  may attach to specially-adapted notches in housing  200 , which is discussed in greater detail later in this disclosure. 
   Fluidic oscillator  100  also comprises a housing  200 . Examples of housing  200  are illustrated in  FIGS. 9 ,  10 ,  11  and  12 .  FIG. 9  illustrates an outside view of a housing  200 . Port  201  is positioned to allow fluid exiting from exit flowline  317  in insert  300  to escape housing  200 . Although not visible in  FIG. 9 , a corresponding port  202  is located on the opposite side of housing  200  (180 degrees from port  201 ). Port  202  allows fluid exiting from exit flowline  318  in insert  300  to escape housing  200 . Slot  203  in end  204  of housing  200 , fits directly around downstream end  333  of insert  300 . 
     FIG. 10  illustrates longitudinal cross-sectional views of housing  200 , with ports  201  and  202  at the top and bottom, respectively. To achieve the fluid-tight seal, housing  200  may include a recess  205  that is shaped to receive and directly engage the insert. The insert fits inside recess  205 , sliding in through entrance  206  and slot  203  until the insert mates with the housing. If the insert is tapered, like insert  300 , recess  205  must be tapered to fit closely over the insert. Surfaces  301 ,  330 ,  331  and  332  of insert  300 , shown in  FIGS. 3 ,  4 , and  5 , for example, may create a fluid-tight seal with an inside surface  210  of housing  200 . This fluid-tight seal eliminates the need for any intervening sealing mechanism. Just inside entrance  206 , a series of threads  208  is provided to engage a fluid flowline  400 ; the threads may be either male or female or otherwise customized to accommodate a specific fluid flowline  400 .  FIG. 11  illustrates an additional cross-sectional view of housing  200  in which housing  200  has been rotated about a central longitudinal axis from the view in  FIG. 10 . 
   If the insert is not tapered, but instead is rectangular, the recess may also be rectangular. The recess may also be rectangular, or otherwise shaped, to accept an insert that is formed only of the walls of the flowpath, such as insert  350 . Another example housing  250  for insert  350  is shown in  FIG. 12 ; recess  251  is rectangular. Housing  200  may then have slots  252  and  253  that are specially adapted to accommodate and retain exit flowlines  354  and  355 . 
   Alternatively, a fluidic oscillator may include a housing designed to accommodate multiple inserts. Such a fluidic oscillator may allow for a higher volume of fluid to pass through this example fluidic oscillator than fluidic oscillators including only one insert, thereby increasing, for example, the potential cleaning performance of the fluidic oscillator.  FIG. 13  illustrates an example housing  260  with four recesses  261 ,  262 ,  263 , and  264  spaced substantially evenly about a central longitudinal axis of housing  260 , or approximately 60 degrees apart. Support  265  of housing  260  maintains the spacing between each insert and provides the structure for recesses  261 ,  262 ,  263 , and  264 . Each recess  261 ,  262 ,  263 , or  264  may enclose one insert, similar to the recesses described previously in this disclosure. Alternatively, housing  260  may include recesses large enough to accommodate more than one insert. As one of ordinary skill in the art having the benefit of this disclosure will realize, housing  260  may enclose any number of inserts spaced at any interval; the housing  260  shown in  FIG. 13  is merely an example. The inserts will contain flowpaths that generate fluid pulses in the manner described earlier in this disclosure. 
   Housing  260  also provides at least one port, not shown in  FIG. 13 , to allow fluid to escape from each insert, similar to ports  201  and  202 . A single high-volume port may be provided. However, multiple ports for the example fluidic oscillator may be aligned such that fluid jets from housing  260  in multiple directions at the same time. For instance, housing  260  may have multiple ports for each insert, allowing the fluidic oscillator to jet fluid in substantially 360 degrees. Such a configuration would allow, for example, the fluidic oscillator to clear debris from nearly the entire inner circumferences of a flowline and potentially reduce the need for multiple cleaning passes by the fluidic oscillator through the flowline. 
   The present invention is well-adapted to carry out the objects and attain the ends and advantages mentioned, as well as those that are inherent therein. While the invention has been depicted, described, and is defined by reference to the exemplary embodiments of the invention, such a reference does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. The depicted and described embodiments of the invention are exemplary only and are not exhaustive of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.