Abstract:
An ultrasonic signal coupler includes a pipe having a first ultrasonic waveguide and a second ultrasonic waveguide penetrating the pipe so that ultrasonic transducers attached to ends of the ultrasonic waveguides communicate ultrasonic signals through the ultrasonic waveguides directly through a fluid traveling through the pipe.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to ultrasonic flow measurement, and more particularly to an ultrasonic waveguide assembly applied in the flow measurement. 
         [0002]    Ultrasonic flow meters are used to determine the flow rate of a variety of fluids (e.g., liquids, gases, etc.) and combinations of different fluids flowing through pipes of different sizes and shapes. One type of an ultrasonic flow meter employs a transit time method. This technique uses one or more pairs of ultrasonic transducers attached to the exterior of the pipe wall and located upstream and downstream from each other. Each of the transducers, when energized, transmits an ultrasonic signal through the flowing fluid that is detected by the other ultrasonic transducer of the pair. The velocity of the fluid flowing in the pipe can be calculated as a function of the differential transit time of ultrasonic signals as between (1) the ultrasonic signal traveling upward against the fluid flow direction from the downstream ultrasonic transducer to the upstream ultrasonic transducer, and (2) the ultrasonic signal traveling downward with the fluid flow direction from the upstream ultrasonic transducer to the downstream ultrasonic transducer. 
         [0003]    The pair(s) of transducers can be mounted on the pipe at different relative locations, for example, the pairs of transducers can be located on opposite sides of the pipe, i.e. diametrically opposed, such that a straight line connecting the transducers passes through the pipe axis or they can be located adjacently on the same side of the pipe. In the diametric example, the ultrasonic signal transmitted by one of the transducers in the pair of transducers is not reflected off of an interior pipe surface before it is detected by the other transducer in the pair. In the latter example of adjacent transducers, the ultrasonic signal transmitted by one of the transducers in the pair of transducers is reflected by an interior surface of the pipe before it is detected by the other transducer in the pair. 
         [0004]    In some applications, the pipes to which the ultrasonic flow meters are attached carry fluids that cause the pipe walls to reach relatively high temperatures, or the pipes may carry fluids that cause the pipe wall to reach relatively low temperatures. Consistent exposure to extreme temperatures introduces thermal stresses that diminish the useful life of the transducer. A waveguide coupled between the ultrasonic transducer and the pipe helps to prevent the extreme temperatures from damaging the piezoelectric material. However, the signal quality can decline due to poor acoustic coupling between the waveguide and the pipe wall caused by, for example, use of manual temporary attachment methods, or by poor acoustic coupling between the launch point of the ultrasonic signals into the fluid traveling through the pipe caused by accumulation of contaminants at the launch point, or by deterioration of the piezoelectric material in the transducer caused by exposure to harsh environments such as temperature extremes. 
         [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]    An ultrasonic signal coupler is disclosed that includes first and second ultrasonic waveguides that penetrate a pipe so that ultrasonic transducers attached to ends of the ultrasonic waveguides communicate ultrasonic signals directly to a fluid traveling through the pipe. In such a configuration, the ultrasonic transducers are not in direct contact with the pipe or the fluid and so are not directly exposed to the extreme temperatures of the fluid and the pipe. One side of the ultrasonic waveguide experiences the direct temperature transfer from the pipe and fluid while the other side of the waveguide is acoustically coupled to the ultrasonic transducer. The waveguide acts as a thermal isolation buffer and helps to protect the piezoelectric material in the ultrasonic transducer from the temperature extremes of fluid traveling through the pipe. The ultrasonic waveguide is typically made from a metal and is acoustically coupled directly to the fluid by penetrating the pipe. An advantage that may be realized in the practice of some disclosed embodiments of the ultrasonic signal coupler is improved accuracy in measuring fluid flow speeds and, therefore, a volume of fluid flowing through a pipe. 
         [0007]    In one embodiment, an ultrasonic waveguide assembly comprises a pipe having an exterior surface, an interior surface, and a pipe axis. The interior surface defines an inside diameter of the pipe which may include a fluid traveling therethrough. An ultrasonic waveguide penetrates the pipe at a first location such that the ultrasonic waveguide is in direct contact with the fluid. An ultrasonic transducer is adapted to be acoustically coupled to the ultrasonic waveguide. Another ultrasonic waveguide penetrates the pipe at another location such that it is also in direct contact with the fluid. Another ultrasonic transducer is adapted to be acoustically coupled to that ultrasonic waveguide. 
         [0008]    In another embodiment, an ultrasonic waveguide assembly comprises a pipe having an exterior surface, an interior surface, and a pipe axis. The interior surface defines an inside diameter of the pipe which may comprise a fluid traveling therethrough. An ultrasonic waveguide penetrates the pipe at a first location such that the ultrasonic waveguide is in direct contact with the fluid. The ultrasonic waveguide comprises a length, a width, and a waveguide axis. The ultrasonic waveguide penetrates the pipe such that its axis forms an acute angle with respect to the pipe axis. The length of the waveguide is greater than its width, and an ultrasonic transducer is adapted to be acoustically coupled to the ultrasonic waveguide. Another ultrasonic waveguide penetrates the pipe at another location such that it is also in direct contact with the fluid. The other ultrasonic waveguide also comprises a length, a width, and a waveguide axis, such that its waveguide axis forms an acute angle with respect to the pipe axis. Its length is also greater than its width. Another ultrasonic transducer is adapted to be acoustically coupled to this ultrasonic waveguide, and the axes of the waveguides are collinear. 
         [0009]    In another embodiment, an ultrasonic waveguide assembly comprises a pipe having an exterior surface, an interior surface, and a pipe axis. The interior surface defines an inside diameter of the pipe which may comprise a fluid traveling therethrough. An ultrasonic waveguide penetrates the pipe and protrudes into the fluid. The ultrasonic waveguide comprises a length, a thickness, and a waveguide axis. The ultrasonic waveguide penetrates the pipe such that its axis forms an acute angle with respect to the pipe axis. Its length is greater than its thickness, and an ultrasonic transducer is adapted to be acoustically coupled to the ultrasonic waveguide. Another ultrasonic waveguide penetrates the pipe and protrudes into the fluid. It also comprises a length, a thickness, a waveguide axis, and it penetrates the pipe such that its axis forms an acute angle with respect to the pipe axis. Its length is greater than its thickness, and another ultrasonic transducer is adapted to be acoustically coupled to it. 
         [0010]    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 
         [0011]    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: 
           [0012]      FIG. 1  is a front view of an exemplary diametric ultrasonic waveguide assembly; 
           [0013]      FIG. 2  is a side view of the exemplary diametric ultrasonic waveguide assembly shown in  FIG. 1 ; 
           [0014]      FIG. 3  is a front view of an exemplary chordal ultrasonic waveguide assembly; 
           [0015]      FIG. 4  is a side view of the exemplary chordal ultrasonic waveguide assembly of  FIG. 3 ; 
           [0016]      FIG. 5  is a side view of an exemplary diametric protruding ultrasonic waveguide assembly; and 
           [0017]      FIG. 6  is a side view of an exemplary chordal protruding ultrasonic waveguide assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 1  and  FIG. 2  illustrate a front view and side view, respectively, of one embodiment of an ultrasonic waveguide assembly  100 , wherein ultrasonic transducers  101 ,  103 , are attached to ultrasonic waveguides  102 ,  104 , respectively, which, in turn, penetrate and are attached to a pipe  120  carrying a fluid traveling in direction  121  therethrough, shown as traveling from left to right in the front view of  FIG. 1 , in which direction  121  is substantially parallel with an axis  122  of the pipe  120 . The ultrasonic transducers  101 ,  103  each are capable of transmitting ultrasonic signals to each other that travel along representative ultrasonic signal path segments  151 ,  152 ,  153 . Each of the ultrasonic transducers is capable of emitting ultrasonic signals and detecting ultrasonic signals. For example, when ultrasonic transducer  101  emits an ultrasonic signal it travels along representative ultrasonic signal path segment  151  through the ultrasonic waveguide  102 , then is refracted along representative ultrasonic signal path segment  152  by fluid traveling through the pipe  120 , then is refracted by ultrasonic waveguide  104  along representative ultrasonic signal path segment  153  through ultrasonic waveguide  104  whereby the ultrasonic signal emitted by ultrasonic transducer  101  is detected by ultrasonic transducer  103 . 
         [0019]    Similarly, when ultrasonic transducer  103  emits an ultrasonic signal it travels along representative ultrasonic signal path segment  153  through the ultrasonic waveguide  104 , then is refracted along representative ultrasonic signal path segment  152  by a fluid traveling through the pipe  120 , then is refracted by ultrasonic waveguide  102  along representative ultrasonic signal path segment  151  through ultrasonic waveguide  102  whereby the ultrasonic signal emitted by ultrasonic transducer  103  is detected by ultrasonic transducer  101 . In one embodiment, ultrasonic waveguides  102 ,  104  are placed into openings through the pipe  120  and are welded in place for providing high quality acoustic coupling between the ultrasonic waveguides  102 ,  104  and the fluid traveling through the pipe  120 . The ultrasonic waveguides  202 ,  204  can also be placed in pipe  120  using clamps. In either of these embodiments, the ultrasonic waveguides  102 ,  104  can be made of the same or different material as the pipe  120 . The ultrasonic waveguides  102 ,  104  can be integrally formed with pipe  120  using the same material as the pipe  120  in an extrusion based fabrication process, or they can be molded into pipe  120  using the same material as the pipe in a casting fabrication process. 
         [0020]    In the embodiment shown in  FIG. 1  and  FIG. 2 , the parallelogram shaped ultrasonic waveguides  102 ,  104 , each comprise a top end  142 , a bottom end  144 , and an ultrasonic waveguide length  116  as measured from end to end of the waveguides  102 ,  104  as shown in  FIG. 1 . Ultrasonic transducers  101 ,  103 , are attached to top ends  142  of the waveguides  102 ,  104 , respectively, opposite the waveguide bottom ends  144  that penetrate the pipe  120 . The ultrasonic waveguides  102 ,  104 , each also comprise an ultrasonic waveguide width  115  and thickness  117  that are each less than the ultrasonic waveguide length  116 . The ultrasonic waveguides  102 ,  104  are not limited to a parallelogram shape or the same size, as depicted in  FIGS. 1-2 , and can also comprise a rhomboid or trapezoid shape. In one embodiment, described herein, the top end  142  and the bottom end  144  are parallel. The ultrasonic waveguides  102 ,  104 , each also penetrate pipe  120  through exterior surface  140  of the pipe  120  and through interior surface  141  of the pipe  120  such that ultrasonic waveguides  102 ,  104 , directly contact fluid flowing through inside diameter  130  of pipe  120 . 
         [0021]    As illustrated in  FIG. 1  and  FIG. 2 , the bottom end  144  of each of ultrasonic waveguides  102 ,  104 , terminates flush with interior surface  141  of pipe  120 . In one embodiment, the bottom ends  144  of the ultrasonic waveguides  102 ,  104  are shaped to match the curvature of the interior surface  141  of pipe  120  when the ultrasonic waveguides  102 ,  104  are used in a non-protruding embodiment. It should be noted that ultrasonic waveguides  102 ,  104 , can alternatively protrude into the interior of pipe  120  ( FIG. 5 ). This can be advantageous in some applications wherein deposits form on interior surface  141  of pipe  120  caused by fluid flowing therethrough so that the sides of ultrasonic waveguides  102 ,  104  that penetrate pipe  120  do not accumulate such deposits. The signal-to-noise ratio of the ultrasonic signals may also be improved by moving the end of the ultrasonic waveguides  102 ,  104  further into the fluid flowing through pipe  120 . The ultrasonic waveguides  102 ,  104 , each penetrate pipe  120  at an acute angle  161  formed between pipe axis  122  and the axes of ultrasonic waveguides  102 ,  104 , which are collinear with each other and with representative ultrasonic signal path segment  152 . The representative ultrasonic signal path segment  152  is used herein to also represent the axes of ultrasonic waveguides  102 ,  104 . 
         [0022]    In the embodiment shown in  FIG. 1  and  FIG. 2 , the ultrasonic waveguides  102 ,  104 , are disposed in a diametric configuration. Therefore, the ultrasonic waveguides  102 ,  104 , are separated by 180° as measured by the angle  160  formed by a midpoint of the position where waveguide  102  penetrates the pipe  120 , the central pipe axis  122 , and a midpoint of the position where waveguide  104  penetrates the pipe  120 . In one embodiment the ultrasonic waveguides  102 ,  104  are made from the same material as the pipe  120 , such as carbon steel, stainless steel, or titanium. The ultrasonic transducers  101 ,  103  can comprise longitudinal ultrasonic transducers and shear wave ultrasonic transducers. Thus, the ultrasonic transducers  101 ,  103  can include ultrasonic transducers mounted on a wedge for inducing shear wave refraction between the wedge material and the ultrasonic waveguides  102 ,  104 , respectively. In either case, representative ultrasonic signal path segments  151 ,  153  illustrate the ultrasonic signals emitted thereby. 
         [0023]    A thickness of pipe  120  typically ranges from about 3 mm to 10 mm and a thickness  117  of the ultrasonic waveguides  102 ,  104  can vary from about 6 mm to 13 mm. Each of the ultrasonic transducers  101 ,  103  are electronically connected to an ultrasonic processing system (not shown) which controls the ultrasonic signals emitted by the ultrasonic transducers  101 ,  103  and processes the ultrasonic signals received by the ultrasonic transducers  101 ,  103 . The time duration between ultrasonic transducer  101  emitting the ultrasonic signal and ultrasonic transducer  103  detecting the ultrasonic signal, and vice versa, is measured by the ultrasonic processing system and is referred to as a time-of-flight measurement herein. 
         [0024]    As described above, the time-of-flight measurement for an ultrasonic signal traveling from ultrasonic transducer  101  to ultrasonic transducer  103  will be shorter than the time-of-flight measurement for an ultrasonic signal traveling from ultrasonic transducer  103  to ultrasonic transducer  101  so long as fluid is traveling through the pipe  120  in direction  121  during the time-of-flight measurement. This is because the fluid traveling through the pipe  120  is an ultrasonic sound carrying medium. Therefore, ultrasonic signals passing through the fluid in a downstream direction, e.g. from ultrasonic transducer  101  to ultrasonic transducer  103 , travel faster than ultrasonic signals passing through the fluid in an upstream direction, e.g. from ultrasonic transducer  103  to ultrasonic transducer  101 . The ultrasonic processing system detects this differential time-of-flight measurement to determine a speed of fluid flow through the pipe  120  in direction  121 . The faster that the fluid flows through pipe  120  the greater the detected time difference. A precise correspondence is determined between the flow rate and a magnitude of the differential time-of-flight measurement and is used by the ultrasonic processing system for flow rate determination. Some of the variables that affect time-of-flight measurement include materials used for the pipe  120  and ultrasonic waveguide  102 ,  104 , the physical dimensions of the pipe  120  and ultrasonic waveguide,  102 ,  104 , and the type of fluid traveling through the pipe  120 . In a configuration such as illustrated in  FIG. 1  and  FIG. 2  the transducers could be replaced without requiring a shutdown of fluid flow systems that utilize pipe  120 . 
         [0025]      FIG. 3  and  FIG. 4  illustrate a front view and side view, respectively, of one embodiment of an ultrasonic waveguide assembly  200 , wherein ultrasonic transducers  201 ,  203 , are attached to ultrasonic waveguides  202 ,  204 , respectively, which, in turn, penetrate and are attached to a pipe  220  carrying a fluid traveling in direction  221  therethrough, shown as traveling from left to right in the front view of  FIG. 3 , in which direction  221  is substantially parallel with an axis  222  of the pipe  220 . The ultrasonic transducers  201 ,  203  each are capable of transmitting ultrasonic signals to each other that travel along representative ultrasonic signal path segments  251 ,  252 ,  253 . Each of the ultrasonic transducers is capable of emitting ultrasonic signals and detecting ultrasonic signals. For example, when ultrasonic transducer  201  emits an ultrasonic signal, it travels along representative ultrasonic signal path segment  251  through the ultrasonic waveguide  202 . The ultrasonic signal is then refracted along representative ultrasonic signal path segment  252  by fluid traveling through the pipe  220 . The ultrasonic signal is then refracted by ultrasonic waveguide  204  along representative ultrasonic signal path segment  253  through ultrasonic waveguide  204  whereby the ultrasonic signal emitted by ultrasonic transducer  201  is detected by ultrasonic transducer  203 . 
         [0026]    Similarly, when ultrasonic transducer  203  emits an ultrasonic signal it travels along representative ultrasonic signal path segment  253  through the ultrasonic waveguide  204 . The ultrasonic signal is then refracted along representative ultrasonic signal path segment  252  by a fluid traveling through the pipe  220 . The ultrasonic signal is then refracted by ultrasonic waveguide  202  along representative ultrasonic signal path segment  251  through ultrasonic waveguide  202  whereby the ultrasonic signal emitted by ultrasonic transducer  203  is detected by ultrasonic transducer  201 . In one embodiment, ultrasonic waveguides  202 ,  204  are placed into openings through the pipe  220  and are welded in place for providing high quality acoustic coupling between the ultrasonic waveguides  202 ,  204  and the fluid traveling through the pipe  220 . The ultrasonic waveguides  202 ,  204  can also be placed in pipe  120  using clamps. In either of these embodiments, the ultrasonic waveguides  202 ,  204  can be made of the same or different material as the pipe  220 . The ultrasonic waveguides  202 ,  204  can be integrally formed with pipe  220  using the same material as the pipe  220  in an extrusion based fabrication process, or they can be molded into pipe  220  using the same material as the pipe in a casting fabrication process. 
         [0027]    In the embodiment shown in  FIG. 3  and  FIG. 4 , the parallelogram shaped ultrasonic waveguides  202 ,  204 , each comprise a top end  242 , a bottom end  244 , and an ultrasonic waveguide length  216  as measured from end to end of the waveguides  202 ,  204 , respectively, opposite the waveguide bottom ends  244  that penetrate the pipe  220 . The ultrasonic waveguides  202 ,  204 , each also comprise an ultrasonic waveguide width  215  and thickness  217  that are each less than the ultrasonic waveguide length  216 . The ultrasonic waveguides  202 ,  204  are not limited to a parallelogram shape or the same size, as depicted in  FIGS. 3-4 , and can also comprise a rhomboid or trapezoid shape and each have a different size. In one embodiment, described herein, the top end  242  and the bottom end  244  are parallel. The ultrasonic waveguides  202 ,  204 , each also penetrate pipe  220  through exterior surface  240  and through interior surface  241  such that ultrasonic waveguides  202 ,  204 , directly contact fluid flowing through inside diameter  230  of pipe  220 . 
         [0028]    As illustrated in the side view of  FIG. 4 , a side of each of ultrasonic waveguides  202 ,  204 , terminates flush with inside surface  241  of pipe  220 . In one embodiment, the bottom ends  244  of the ultrasonic waveguides  202 ,  204  are shaped to match the curvature of the interior surface  241  of pipe  220  when the ultrasonic waveguides  202 ,  204  are used in a non-protruding embodiment. Ultrasonic waveguides  202 ,  204  can alternatively protrude into the interior of pipe  220  ( FIG. 6 ). This can be advantageous in some applications wherein deposits form on inside surface  241  of pipe  220  caused by fluid flowing therethrough so that the sides of ultrasonic waveguides  202 ,  204 , that penetrate pipe  220  do not accumulate such deposits. Signal-to-noise ratio of the ultrasonic signals may also be improved by moving the end of the ultrasonic waveguides  202 ,  204  further into the fluid flowing through pipe  220 . The ultrasonic waveguides  202 ,  204 , each penetrate pipe  220  at an acute angle  261  formed between pipe axis  222  and the axes of ultrasonic waveguides  202 ,  204 , which are collinear with each other and with representative ultrasonic signal path segment  252 . The representative ultrasonic signal path segment  252  is used herein to also represent the axes of ultrasonic waveguides  202 ,  204 . 
         [0029]    In the embodiment shown in  FIG. 3  and  FIG. 4 , the ultrasonic waveguides  202 ,  204 , are disposed in a chordal configuration. Therefore, the ultrasonic waveguides  202 ,  204 , are separated by less than 180° as measured by the angle formed by the midpoint of the location where waveguide  202  penetrates the pipe  220 , the central pipe axis  222 , and the position where waveguide  204  penetrates the pipe  220 . Thus, the difference between the diametric configuration of  FIG. 1  and  FIG. 2 , described above, and the chordal configuration illustrated in  FIG. 3  and  FIG. 4  is easily distinguished. In one embodiment the ultrasonic waveguides  202 ,  204  are made from the same material as the pipe  220 , such as carbon steel, stainless steel, or titanium. The ultrasonic transducers  201 ,  203  can comprise longitudinal ultrasonic transducers and shear wave ultrasonic transducers. Thus, the ultrasonic transducers  201 ,  203  can include ultrasonic transducers mounted on a wedge for inducing shear wave refraction between the wedge material and the ultrasonic waveguides  202 ,  204 , respectively. In either case, representative ultrasonic signal path segments  251 ,  253  illustrate the ultrasonic signals emitted thereby. 
         [0030]    A thickness of pipe  220  typically ranges from about 3 mm to 10 mm and a thickness  117  of the ultrasonic waveguides  202 ,  204  can vary from about 6 mm to 13 mm. Each of the ultrasonic transducers  201 ,  203  are electronically connected to an ultrasonic processing system (not shown) which controls the ultrasonic signals emitted by the ultrasonic transducers  201 ,  203  and processes the ultrasonic signals received by the ultrasonic transducers  201 ,  203 . The time-of-flight measurement between ultrasonic transducer  201  emitting the ultrasonic signal and ultrasonic transducer  203  detecting the ultrasonic signal, and vice versa, is measured by the ultrasonic processing system. 
         [0031]    As described above, the time-of-flight measurement for an ultrasonic signal traveling from ultrasonic transducer  201  to ultrasonic transducer  203  will be shorter than the time-of-flight measurement for an ultrasonic signal traveling from ultrasonic transducer  203  to  201  so long as fluid is traveling through the pipe  220  in direction  221  during the time-of-flight measurement. This is because the fluid traveling through the pipe  220  is an ultrasonic sound carrying medium. Therefore, ultrasonic signals passing through the fluid in a downstream direction, e.g. from ultrasonic transducer  201  to ultrasonic transducer  203 , travel faster than ultrasonic signals passing through the fluid in an upstream direction, e.g. from ultrasonic transducer  203  to ultrasonic transducer  201 . The ultrasonic processing system detects this differential time-of-flight measurement to determine a speed of fluid flow through the pipe  220  in direction  221 . The faster that the fluid flows through pipe  220  the greater the detected time difference. A precise correspondence is determined between the flow rate and a magnitude of the differential time-of-flight measurement and is used by the ultrasonic processing system for flow rate determination. Some of the variables that affect time-of-flight measurement include materials used for the pipe  220  and ultrasonic waveguide,  202 ,  204 , the physical dimensions of the pipe  220  and ultrasonic waveguide,  202 ,  204 , and the type of fluid traveling through the pipe  220 . In a configuration such as illustrated in  FIG. 3  and  FIG. 4  the transducers could be replaced without requiring a shutdown of fluid flow systems that utilize pipe  220 . 
         [0032]      FIG. 5  illustrates an alternative embodiment of an ultrasonic waveguide assembly  300 , wherein ultrasonic transducers  301 ,  303 , are attached to ultrasonic waveguides  302 ,  304  that penetrate exterior surface  340  and interior surface  341  of the pipe  320  and, in addition, protrude into the interior of the pipe  320  in a diametric configuration of ultrasonic waveguides  302 ,  304 .  FIG. 6  illustrates another alternative embodiment of an ultrasonic waveguide assembly  400 , wherein ultrasonic transducers  401 ,  403 , are attached to ultrasonic waveguides  402 ,  404  that penetrate exterior surface  440  and interior surface  441  of the pipe  420  and, in addition, protrude into the interior of the pipe  420  in a chordal configuration of ultrasonic waveguides  402 ,  404 . The alternative embodiment of  FIG. 5  operates as described above with reference to  FIG. 1  and  FIG. 2 , and the alternative embodiment of  FIG. 6  operates as described above with reference to  FIG. 3  and  FIG. 4 . These embodiments can be advantageous in some applications, as described above, for avoiding deposits forming on the ends of ultrasonic waveguides  302 ,  304 ,  402 ,  404  caused by fluid flowing through pipe  320 ,  420 , and for improving signal-to-noise ratio of the ultrasonic signals. 
         [0033]    In view of the foregoing, embodiments of the invention provide direct communication of ultrasonic transducer signals with fluids traveling through pipes for high quality measurement of fluid flow rates. A technical effect is to accurately detect and measure physical flow speed of a fluid through pipes. 
         [0034]    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.