| 摘要 |
<p>A waveguide (10) couples ultrasonic energy from a source (15) on one side of a fluid-bounding wall, such as a conduit, into fluid on the other side of the wall. The waveguide (10) has a buffer (12) that couples to the source (15) and a seat (14) with an exit face (16), while an intermediate portion contains a redirecting surface (18) for internally redirecting energy propagated along the buffer (12) toward the exit face (16) to exit as a narrow directed beam. The waveguide core has a rectangular cross section which is narrow, i.e., has an aspect ratio above two and preferably above three or four, while the buffer (12) has a length effective to thermally isolate or protect the source (15) from the conduit. The waveguide (10) attaches easily, either as a clampon or welded unit, to a pipe or spoolpiece, allowing local fabrication of massive or custom flow cells, such as large spoolpieces with Gauss-Chebyshev interrogation paths. Several guides (10) may be positioned in an array to cover interrogation paths for an extended range of sound speeds or flow rates. In one embodiment, the redirecting face (18) may be curved, or stepped at different angles, to provide output beams at several or a continuum of exit angles. A low sound speed material may be added to control the refraction angle of the exit in the wall or fluid. The construction readily adapts to wetted systems. The waveguide (10) may have the overall shape of a hockey stick, with the buffer (12) and the seat (14) lying in a common plane, or one may curve into, or join at an angle, the other. Features as holes (17), notches (17b) or the like may provide reference echoes for a flow meter to automatically calculate temperature-dependent transit time corrections for the buffer (12), and additional reflective surfaces or topological features such as holes may redirect echoes or noise out of the measurement path. In one embodiment, the buffer (12) is a thin tube which couples shear waves into the seat portion (14), which has a rectangular cross section.</p> |
