Abstract:
Acoustic waveguides are disclosed for mounting to a conduit. The acoustic waveguides provide a mounting area that minimizes the effect of the mount on the acoustic wave traveling through the waveguide while providing an effective seal, even under high pressure conditions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 13/314,963, filed Dec. 8, 2011 and entitled Acoustic Waveguide Assemblies, now U.S. Pat. No. 8,511,424, the entirety of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The subject matter disclosed herein relates to acoustic waveguide assemblies for mounting an acoustic waveguide to a conduit. 
         [0003]    Acoustic waveguides can be used to measure the characteristics (e.g., density, viscosity, level, temperature, etc.) of a fluid traveling in a conduit using acoustic waves. In a typical acoustic waveguide, a transducer assembly launches an acoustic wave into a waveguide that is mounted and sealed to the conduit and inserted into the fluid. The time of flight of the acoustic wave in the section of the waveguide inserted into the fluid is a function of the characteristics of the fluid and therefore can be used to determine those characteristics. 
         [0004]    Some acoustic wave types require that the waveguide be a thin elongated rod. One of the limitations of these thin elongated rods that prevent use in most commercial and industrial applications, especially in high pressure installations, is the difficulty of mounting and sealing the waveguide to the conduit in a way that will not significantly affect the acoustic wave as it passes through the waveguide in the area of the seal. Sealing with an o-ring around the thin elongated rod of the waveguide is also difficult, especially in high pressure installations. While seals made of polytetrafluoroethylene (PTFE) have been used in laboratory settings, those seals are not sufficient for long term use under high pressure as the seals can deform over time and fail. 
         [0005]    The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    Acoustic waveguide assemblies are disclosed for mounting an acoustic waveguide to a conduit. The acoustic waveguide assemblies provide a mounting area that minimizes the effect of the mount on the acoustic wave traveling through the acoustic waveguide while providing an effective seal, even under high pressure conditions. An advantage that may be realized in the practice of some disclosed embodiments of the acoustic waveguides is allowing the use of thin elongated waveguides for more accurate density measurements that can provide more accurate flow measurements. 
         [0007]    In one exemplary embodiment, an acoustic waveguide assembly for mounting to a conduit is disclosed. The acoustic waveguide comprises a waveguide rod having a proximal end and a distal end, a waveguide sensor connected to the distal end of the waveguide rod, and a disk coupler circumferentially surrounding a portion of the waveguide rod, wherein the disk coupler provides a surface to mount the waveguide rod to the conduit. 
         [0008]    In another exemplary embodiment, the acoustic waveguide comprises a waveguide rod having a proximal end and a distal end, a waveguide sensor connected to the distal end of the waveguide rod, and a disk coupler circumferentially surrounding a portion of the waveguide rod, wherein the disk coupler provides a surface to mount the waveguide rod to the conduit. A transducer assembly comprising at least two portions is coupled to the waveguide rod at the proximal end. 
         [0009]    This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which: 
           [0011]      FIG. 1  is perspective view of an exemplary acoustic waveguide; 
           [0012]      FIG. 2  is a cross-section of another exemplary acoustic waveguide with a tube coupler for mounting the acoustic waveguide to a conduit; 
           [0013]      FIG. 3  is a cross-section of the portion of the exemplary acoustic waveguide of  FIG. 2  showing the tube coupler; 
           [0014]      FIG. 4  is a cross-section of an exemplary acoustic waveguide assembly for mounting the acoustic waveguide of  FIG. 2  to a conduit through a nozzle; 
           [0015]      FIG. 5  is a cross-section of another exemplary acoustic waveguide assembly for mounting the acoustic waveguide of  FIG. 2  to a conduit in a middle flange; 
           [0016]      FIG. 6  is a cross-section of yet another exemplary acoustic waveguide assembly for mounting the acoustic waveguide of  FIG. 2  to a conduit using a compression fitting in a flange; 
           [0017]      FIG. 7  is a perspective view of yet another exemplary acoustic waveguide with a disk coupler for mounting the acoustic waveguide to a conduit; 
           [0018]      FIG. 8  is a cross-section of an exemplary acoustic waveguide assembly for mounting the acoustic waveguide of  FIG. 7  to a conduit through a nozzle; 
           [0019]      FIG. 9  is a perspective view of still another exemplary acoustic waveguide with a disk coupler for mounting the acoustic waveguide to a conduit; 
           [0020]      FIG. 10  is a cross-section of an exemplary acoustic waveguide assembly for mounting the acoustic waveguide of  FIG. 9  to a conduit through a nozzle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]      FIG. 1  is a perspective view of an exemplary acoustic waveguide  10 . In one embodiment, a transducer assembly  2  is coupled to the proximal end of a waveguide rod  4 . The distal end of the waveguide rod  4  can connect to a waveguide sensor  6 , which is the portion of the acoustic waveguide  10  that will be submerged in the fluid. The transducer assembly  2  can comprise two transducers on opposite sides of the waveguide rod  4  and be configured to launch an acoustic wave into the acoustic waveguide  10 . Each of the transducers can comprise a piezoelectric crystal encapsulated by packaging, or in another embodiment, only comprise the piezoelectric crystal. 
         [0022]    In different embodiments, the mounting locations of the transducers on the waveguide rod  4 , mounting angles of the transducers with respect to the longitudinal axis of the waveguide rod  4 , polarity of the transducers, and the excitation pulse received by the transducers can be modified to launch particular acoustic waves (e.g., ultrasonic torsional, extensional, flexural waves) into the waveguide rod  4 . Although the exemplary acoustic waveguides disclosed herein will be described with respect to use with torsional waves, it will be understood that the waveguides can be used for different acoustic waves. 
         [0023]    An ultrasonic torsional wave is a wave motion in which the vibrations of the medium are periodic twisting motions around the direction of propagation along the azimuthal direction of the torsional waveguide. For use with torsional waves, the waveguide rod  4  can be a thin (e.g., 0.25 in. diameter (6.35 mm) for a 100 kHz wave, 0.375 in. diameter (9.53 mm) for a 75 kHz wave, 0.50 in. diameter (12.70 mm) for a 50 kHz wave), elongated rod having a circular cross-section into which the transducer assembly  2  launches the ultrasonic torsional wave. The waveguide sensor  6  can be a thin, elongated non-circular cross-section (e.g., diamond shaped), which is submerged in the fluid. When the ultrasonic torsional wave traveling down the waveguide rod  4  hits the interface between the waveguide rod  4  and the waveguide sensor  6 , the ultrasonic torsional wave is partially reflected at the interface back to the transducer assembly  2  providing a first time of flight measurement, while the remainder of the ultrasonic torsional wave will transmit through the waveguide sensor  6 . When the remainder of the ultrasonic torsional wave hits the end of the waveguide sensor  6 , the ultrasonic torsional wave will reflect back to the transducer assembly  2 , providing a second time of flight measurement. The time of flight in the waveguide sensor  6  depends, in part, upon the density of the fluid, with a slower time of flight for more dense fluids and a faster time of flight for less dense fluids. The slow speed of the ultrasonic torsional wave in the waveguide sensor  6  provides high sensitivity to changes in the density of the fluid surrounding that section of the acoustic waveguide  10 . Knowledge of the actual density of a fluid, along with traditional transit time or Doppler measurements that can only provide flow velocity, can provide more accurate mass flow measurements than measurements using a calculated density based on temperature and pressure of the fluid. 
         [0024]      FIG. 2  is another exemplary acoustic waveguide  100  with a tube coupler  110  for mounting the acoustic waveguide  100  to a conduit  50  (see  FIGS. 4 ,  5 , and  6 ). Although the figures show the exemplary acoustic waveguides mounted to a pipe, it will be understood that the acoustic waveguides can be mounted to a variety of conduits in which fluid travels (e.g., a pipe, tube, vessel, tank, etc.).  FIG. 3  is a cross-section of a portion of the exemplary acoustic waveguide  100  of  FIG. 2  showing the tube coupler  110 . In one embodiment, a transducer assembly  102  is coupled to the proximal end of the waveguide rod  104 , which can have a circular cross-section. The distal end of the waveguide rod  104  can connect to a waveguide sensor  106 , which is the portion of the acoustic waveguide  100  that will be submerged in the fluid and can have a non-circular cross-section. 
         [0025]    The tube coupler  110  circumferentially surrounds a portion of the waveguide rod  104  to provide a surface for mounting the acoustic waveguide  100  to a conduit  50 . The exemplary tube coupler  110  comprises a first end  114  (e.g., a flat or curved disk) circumferentially surrounding the waveguide rod  104  at a first location and a second end  115  (e.g., a flat or curved disk) circumferentially surrounding the waveguide rod  104  at a second location. The tube coupler  110  also comprises an inner sleeve  112  circumferentially surrounding the waveguide rod  104  and extending from the first end  114  to the second end  115  proximate the waveguide rod  104 . In one embodiment, the inner sleeve  112  is not fixedly attached to the waveguide rod  104  to minimize contact between the tube coupler  110  and the waveguide rod  104  to avoid dampening of the acoustic waves traveling through the waveguide rod  104 . For example, the inner sleeve  112  can form a close sliding fit with the waveguide rod  104  without applying pressure on the waveguide rod  104 . The inner sleeve  112  can be made of a material different than the waveguide rod  104  that has a different acoustic impedance than the waveguide rod  104  to provide acoustic isolation between the waveguide rod  104  and the tube coupler  110 . 
         [0026]    The tube coupler  110  can further comprise an outer tube  116  circumferentially surrounding the inner sleeve  112  and extending from the first end  114  to the second end  115 , forming a cavity  118  between the inner sleeve  112  and the outer tube  116 . The tube coupler  110  can have varying lengths to provide the desired acoustic performance of the acoustic waveguide  110 . The cavity  118  can be filled with filler (e.g., a liquid or a non-metallic solid (e.g., epoxy)) that can provide mechanical support for the second end  115 , which provides a boundary against the pressure in the conduit  50  (see  FIGS. 4 ,  5 , and  6 ). In addition to providing mechanical support, the filler can be chosen to provide acoustic isolation between the waveguide rod  104  and the tube coupler  110 . 
         [0027]    The first end  114  and the second end  115  of the tube coupler  110  can be relatively thin (e.g., 0.007 in. (0.178 mm) to 0.010 in. (0.254 mm). The first end  114  and second end  115  can be welded to the waveguide rod  104 , while the inner sleeve  112  and the outer tube  116  can be welded to the first end  114  and the second end  115 . The components of the tube coupler  110  may be made of corrosion resistant materials (e.g., stainless steel  316 , titanium, graphite) and welded together using different welding techniques, including, e.g., groove welding, fillet welding, resistance welding, e-beam welding, friction welding, or brazing. 
         [0028]      FIG. 4  is a cross-section of an exemplary acoustic waveguide assembly  120  for mounting the acoustic waveguide  100  of  FIG. 2  to a conduit  50  through a nozzle  122 . The transducer assembly  102  can be mounted to the waveguide rod  104  using a clamp  124  (e.g., a T-clamp). The clamp  124  can be spring loaded to provide the necessary contact pressure between the transducer assembly  102  and the waveguide rod  104  to ensure proper transmission of the acoustic wave into the waveguide rod  104 . A nozzle  122  provides a port  123  for accessing the fluid inside of the conduit  50 . Although the nozzle  122  and the port  123  are shown to be oriented perpendicular to the conduit  50  and the direction of flow  60  of the fluid in  FIG. 4 , it will be understood that the orientation can be at different angles or locations on the conduit  50  (e.g., horizontal, vertical, elbow, angled). The tube coupler  110  can be inserted into the port  123  of the nozzle  122  such that the waveguide sensor  106  extends into the fluid flowing in the conduit  50 . The length of the waveguide sensor  106  can be the same as the inner diameter of the conduit  50 , recessed in the port  123  of the nozzle  122 , or mounted flush with the inner diameter of the conduit  50 . As shown in  FIG. 4 , the tube coupler  110  forms a seal of the port  123  of the nozzle  122  and therefore must withstand the pressure in the conduit  50 . The second end  115  and the filler in the cavity  118  (see  FIG. 3 ) of the tube coupler  110  provide the mechanical support to withstand the pressure in the conduit  50 . In addition, an o-ring (not shown) can be installed in the port  123  of the nozzle  122  proximate the outer tube  116  of the tube coupler  110  (see  FIG. 3 ) to further seal the port  123 . The tube coupler  110  can be fixedly attached to the port  123  of the nozzle  122  by, e.g., welding or threading. 
         [0029]      FIG. 5  is a cross-section of another exemplary acoustic waveguide assembly  130  for mounting the acoustic waveguide  100  of  FIG. 2  to a conduit  50  in a flange. A first section of the conduit  50  terminating in a first flange  52  is coupled to a second section of the conduit  50  terminating in a second flange  54  through a middle flange  56  by a plurality of bolts  53  extending through the first flange  52 , the second flange  54 , and the middle flange  56 . The middle flange  56  provides a port  57  for accessing the fluid inside of the conduit  50 . The tube coupler  110  can be inserted into the port  57  of the middle flange  56  such that the waveguide sensor  106  extends into the fluid flowing in the conduit  50 . As shown in  FIG. 5 , the tube coupler  110  forms a seal of the port  57  of the middle flange  56  and therefore must withstand the pressure in the conduit  50 . In addition, an o-ring (not shown) can be installed in the port  57  of the middle flange  56  proximate the outer tube  116  of the tube coupler  110  (see  FIG. 3 ) to further seal the port  57 . 
         [0030]      FIG. 6  is a cross-section of yet another exemplary acoustic waveguide assembly  140  for mounting the acoustic waveguide  100  of  FIG. 2  to a conduit  50  using a compression fitting  142  in a flange. A first section of the conduit  50  terminating in a first flange  52  is coupled to a second section of the conduit  50  terminating in a second flange  54  through a middle flange  58  by a plurality of bolts  53  extending through the first flange  52 , the second flange  54 , and the middle flange  58 . The middle flange  58  provides a port  59  for accessing the fluid inside of the conduit  50 . The tube coupler  110  can be inserted into a compression fitting  142 , which is then inserted into the port  59  of the middle flange  58  such that the waveguide sensor  106  extends into the fluid flowing in the conduit  50 . The port  59  of the middle flange  58  can be shaped to receive the compression fitting  142  (e.g., threaded to receive the threads of the compression fitting  142 ). As shown in  FIG. 6 , the tube coupler  110  forms a seal of the port  59  of the middle flange  58  and therefore must withstand the pressure in the conduit  50 . 
         [0031]      FIG. 7  is a perspective view of yet another exemplary acoustic waveguide  200  with a disk coupler  210  for mounting the acoustic waveguide  200  to a conduit  50  (see  FIG. 8 ). In one embodiment, a transducer assembly  202  is coupled to the proximal end of the waveguide rod  204 , which can have a circular cross-section. The distal end of the waveguide rod  204  can connect to a waveguide sensor  206 , which is the portion of the acoustic waveguide  200  that will be submerged in the fluid and can have a non-circular cross-section. The disk coupler  210  circumferentially surrounds a portion of the waveguide rod  204  to provide a surface for mounting the acoustic waveguide  200  to a conduit  50 . In one embodiment, the disk coupler  210  can be welded to the waveguide rod  204 , while in another embodiment, the disk coupler  210  can be integral with the waveguide rod  204  if both are made by machining the same block of material. 
         [0032]      FIG. 8  is a cross-section of an exemplary acoustic waveguide assembly  220  for mounting the acoustic waveguide  200  of  FIG. 7  to a conduit  50  through a nozzle  222 . The transducer assembly  202  can be mounted to the waveguide rod  204  using a clamp  124  (e.g., a T-clamp). The clamp  124  can be spring loaded to provide the necessary contact pressure between the transducer assembly  202  and the waveguide rod  204  to ensure proper transmission of the acoustic wave into the waveguide rod  204 . A nozzle  222  provides a port  223  for accessing the fluid inside of the conduit  50 . Although the nozzle  222  and the port  223  are shown to be oriented perpendicular to the conduit  50  and the direction of flow  60  of the fluid in  FIG. 8 , it will be understood that the orientation can beat different angles or locations on the conduit  50  (e.g., horizontal, vertical, elbow, angled). The bottom side of disk coupler  210  can be mounted on the outlet  225  of the port  223  of the nozzle  222  such that the waveguide sensor  206  extends through the port  223  into the fluid flowing in the conduit  50 . The disk coupler  210  is mounted between a top flange  224  on the top side of the disk coupler  210  and the nozzle  222  with a plurality of bolts  228  extending through the top flange  224  and the nozzle  222 . As shown in  FIG. 8 , the disk coupler  210  forms a seal of the port  223  of the nozzle  222 . In addition, a first gasket  226  can be installed between the top surface of the disk coupler  210  and the top flange  224 . A second gasket  227  can be installed between the bottom surface of the disk coupler  210  and the outlet  225  of the port  223  of the nozzle  222  to further seal the port  223 . 
         [0033]      FIG. 9  is a perspective view of still another exemplary acoustic waveguide  300  with a disk coupler  310  for mounting the acoustic waveguide  300  to a conduit  50  (see  FIG. 10 ). The distal end of the waveguide rod  304  can connect to a waveguide sensor  306 , which is the portion of the acoustic waveguide  300  that will be submerged in the fluid and can have a non-circular cross-section. The disk coupler  310  circumferentially surrounds a portion of the waveguide rod  304  to provide a surface for mounting the acoustic waveguide  300  to a conduit  50 . In one embodiment, the disk coupler  310  can be welded to the waveguide rod  304 , while in another embodiment, the disk coupler  310  can be integral with the waveguide rod  304  if both are made by machining the same block of material. In still another embodiment, the disk coupler  310  can be coupled to the waveguide rod  304  using mating threads on each part. 
         [0034]    As shown in  FIG. 9 , the transducer assembly  302  is coupled to the circumference of the disk coupler  310 . The transducer assembly  302  can be coupled to the disk coupler  310  using, e.g., an adhesive (epoxy) or a circumferential clamp. The transducer assembly  302  can comprise two transducers on opposite sides of the disk coupler  310  and be configured to launch an acoustic wave into the acoustic waveguide  300 . Each of the transducers can comprise a piezoelectric crystal encapsulated by packaging, or in another embodiment, only comprise the piezoelectric crystal. 
         [0035]      FIG. 10  is a cross-section of an exemplary acoustic waveguide assembly  320  for mounting the acoustic waveguide  300  of  FIG. 9  to a conduit  50  through a nozzle  322 . The transducer assembly  302  can be coupled to the disk coupler  310  to ensure proper transmission of the acoustic wave into the waveguide rod  304 . Coupling the transducer assembly  302  to the disk coupler  310  eliminates the need for a transducer clamp and can minimize the amount of acoustic signal lost through the disk coupler  310 . A nozzle  322  provides a port  323  for accessing the fluid inside of the conduit  50 . Although the nozzle  322  and the port  323  are shown to be oriented perpendicular to the conduit  50  and the direction of flow  60  of the fluid in  FIG. 10 , it will be understood that the orientation can beat different angles or locations on the conduit  50  (e.g., horizontal, vertical, elbow, angled). The disk coupler  310  can be mounted on the outlet  325  of the port  323  of the nozzle  322  such that the waveguide sensor  306  extends through the port  323  into the fluid flowing in the conduit  50 . The disk coupler  310  is mounted between a top flange  324  resting on top of the disk coupler  310  and the nozzle  322  with a plurality of bolts  328  extending through the top flange  324  and the nozzle  322 . As shown in  FIG. 10 , the disk coupler  210  forms a seal of the port  323  of the nozzle  322 . In addition, a first gasket  326  can be installed between the top surface of the disk coupler  310  and the top flange  324 . A second gasket  327  can be installed between the bottom surface of the disk coupler  310  and the outlet  325  of the port  323  of the nozzle  322  to further seal the port  323 . 
         [0036]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.