Abstract: A steerable acoustic waveguide apparatus includes plural plates arranged in one or more linear arrays. Steering of an acoustic beam radiated from the waveguide apparatus may be achieved through differential delays of acoustic signals resulting from differences in timing, frequency, or mode or resulting from differences in physical attributes of the plates. In one aspect, where the apparatus is used with a target that is confined by a conduit such as a pipe, a longitudinal plane for the conduit intersects the linear array, an array plane for the linear array has a conduit orientation relative to the longitudinal plane, and the conduit orientation is substantially perpendicular or substantially parallel. The waveguide apparatus may serve as a thermal buffer and may simplify access to an acoustic path in a device such as an ultrasonic flowmeter.

Abstract: An apparatus for determining a characteristic for a fluid in a tube, the apparatus including a force applying system to cause a change in a transverse dimension of a segment of the tube, wherein the change in the transverse dimension is reversible, and an ultrasonic system that comprises a single transducer for launching and receiving ultrasonic signals. Ultrasonic signals propagate through the tube along colinear paths of different lengths that are orthogonal to the tube wall. At least one of the paths is located entirely within the segment. Each of the ultrasonic signals propagates through the tube wall in a first wall region and reflects from an inner surface of a second wall region. Path length differences between the paths are determined, and transit times are determined for each of the ultrasonic signals. The characteristic is determined based on information including the path length differences and the transit times.

Abstract: A steerable acoustic waveguide apparatus includes plural plates arranged in one or more linear arrays. Steering of an acoustic beam radiated from the waveguide apparatus may be achieved through differential delays of acoustic signals resulting from differences in timing, frequency, or mode or resulting from differences in physical attributes of the plates. In one aspect, where the apparatus is used with a target that is confined by a conduit such as a pipe, a longitudinal plane for the conduit intersects the linear array, an array plane for the linear array has a conduit orientation relative to the longitudinal plane, and the conduit orientation is substantially perpendicular or substantially parallel. The waveguide apparatus may serve as a thermal buffer and may simplify access to an acoustic path in a device such as an ultrasonic flowmeter.

Abstract: An apparatus for determining a characteristic such as sound speed for a fluid in a tube comprises means for applying a force to cause a change in a transverse dimension of a segment of the tube, wherein the change in the transverse dimension is reversible, and means for launching and receiving ultrasonic signals. Ultrasonic signals propagate through the tube along paths of different lengths. At least one of the paths is located entirely within the segment having the changed transverse dimension. The applied force may cause the transverse dimension to change continuously or in discrete steps. Path length differences between the paths are determined, and transit times are determined for each of the ultrasonic signals. The characteristic is determined based on information comprising the path length differences and the transit times.

Abstract: The mass flow rate sensor includes a waveguide disposed in a flow passage having a bluff body facing in an upstream direction. Waves are pulsed along the waveguide for interaction with the fluid. A receiver is coupled to the waveguide to detect a propagated wave and provides a first output signal proportional to the transit time of the propagated wave for determining fluid density. The receiver also provides a second output signal proportional to the shedding frequency of vortices from the waveguide to determine velocity. An electronics module calculates mass flow rate from the velocity times density times area of the flow passage and a constant. In other forms, the velocity is ascertained by transmitting an ultrasonic beam through the shedding vortices to determine vortex frequency which is proportional to velocity.

Abstract: An acoustic waveguide system including a waveguide, a housing with a port in one side of the housing for receiving the proximal end of the waveguide, the port opening into a channel in the housing. A first shear transducer is located in the channel of the housing and disposed on the waveguide, and a second shear transducer is located in the channel and disposed on the opposite side of the waveguide. The first and second transducers are configured to launch a torsional or an extensional wave in the waveguide depending on the orientation and polarity of the transducers.

Abstract: A damping material for an ultrasonic transducer system includes a spreadable matrix and a plurality of particles is suspended in the spreadable matrix, forming a coating that dissipates ultrasonic energy to dampen noise and reduce crosstalk allowing ultrasonic measurement of gas using clamp-on transducers.

Abstract: A method of and system for analyzing the mass flow rate of a fluid flowing in a conduit wherein ultrasonic energy is transmitted along multiple v paths in multiple parallel quadrature planes through the fluid, the transit time of the ultrasonic energy through the fluid with and against the flow direction of the fluid is measured, and the flow velocity of the fluid in each quadrature plane is calculated based on the transit time in each quadrature plane. The density of the fluid in each quadrature plane is then determined and quadrature integration of the product of the fluid density and fluid velocity in each quadrature plane is performed to calculate the total mass flow rate of the fluid more accurately by eliminating errors associated with assuming that the density of the fluid in the conduit is uniform.

Abstract: An acoustic waveguide system including a waveguide, a housing with a port in one side of the housing for receiving the proximal end of the waveguide, the port opening into a channel in the housing. A first shear transducer is located in the channel of the housing and disposed on the waveguide, and a second shear transducer is located in the channel and disposed on the opposite side of the waveguide. The first and second transducers are configured to launch a torsional or an extensional wave in the waveguide depending on the orientation and polarity of the transducers.

Abstract: A method of and system for analyzing the mass flow rate of a fluid flowing in a conduit wherein ultrasonic energy is transmitted along multiple v paths in multiple parallel quadrature planes through the fluid, the transit time of the ultrasonic energy through the fluid with and against the flow direction of the fluid is measured, and the flow velocity of the fluid in each quadrature plane is calculated based on the transit time in each quadrature plane. The density of the fluid in each quadrature plane is then determined and quadrature integration of the product of the fluid density and fluid velocity in each quadrature plane is performed to calculate the total mass flow rate of the fluid more accurately by eliminating errors associated with assuming that the density of the fluid in the conduit is uniform.

Abstract: A tag flow measurement system wherein a first and a second measurement path are provided across a flowing fluid, and a receiver in each path receives signals modulated by scatterers in the fluid. The direction of signal propagation in one path faces in an opposite sense to, e.g., is anti-parallel to, the direction of propagation in the other path, and the two receiver outputs are correlated to determine a time interval representative of flow velocity. In one embodiment each path is defined by a transmitter on one side of the conduit and a receiver on the other side of the conduit, and the positions or orientations of transmitter and receiver are reversed in the second pair. Thus, the first transmitter may lie on the same side of the conduit as the first receiver. Diametral or chordal paths may be used. A prototype clamp-on system detects flowing air at atmospheric pressure in a schedule 40 one inch steel pipe over an extended range, at flow rates as low as several meters per second.

Abstract: An ultrasonic coupling assembly includes a barrier layer that contacts the wall, and a generally thicker layer formed of a compliant material such as zinc foil that extends over the first layer. A third layer may cover and enclose the compliant layer, e.g., by folding the first layer over and on top of the second layer to cover the edge faces thereof. An exemplary embodiment is implemented using gold foil approximately one mil thick for the first layer, and zinc sheeting approximately four mils thick for the second layer. Use of inert top and bottom, or outside, layers prevents the inadvertent installation of the coupling element with the compliant layer directly contacting the wall. Disk embodiments may employ a stack of separate disks formed of foils or sheets of the respective materials. For cryogenic applications, a material such as indium may be used for the second layer without risk of its alloying or migration through the first layer.

Abstract: An encapsulated or rigid bundle of rods forms a substantially non-dispersive buffer usable in extreme environments, operable over wide bandwidth, and repairable in the field. The rigid assembly extends through a nozzle or flanged pipe penetration to launch its signals directly in the fluid at a defined angle. The bundles are non-degrading wave guides to carry signals through degrading environments. This is useful for numerous stack, freestream and chordal path configurations, as well as clamp-on systems and special mode-converting configurations. Beam shaping and steering may be passively effected with patterned bundle constructions, and plural faces, which may be stepped or angled, may define multiple oblique, reflective or different length paths while mounted in spoolpieces at normal incidence.

Abstract: An ultrasonic system employs a path through a fluid to determine fluid density by a differential reflection coefficient measurement of fluid impedance Z and a fluid sound speed c. Preferred configurations use clamp-on (external) transducers and combine ultrasonic measurements of flow velocity V over one or more paths, to obtain the mass flow rate. Z is determined by comparing reflections from a reference target, which may be totally reflective, with reflections from a sensor target having an effectively lower Z, which may be close to that of the fluid. Both targets are preferably located to be cleaned by the natural flow of the fluid. The low-Z target is interrogated at least once. Vee blocks provide a compact combination of reference and sensor targets that can be integrated with a velocity-sensing flowcell. Folded-path flow cells compactly measure V alone or in combination with density.

Abstract: A waveguide couples ultrasonic energy from a source on one side of a fluid-bounding wall, such as a conduit, into fluid on the other side of the wall. The waveguide has a buffer that couples to the source, and a seat with an exit face, while an intermediate portion contains a redirecting surface for internally redirecting energy propagated along the buffer toward the exit face 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 has a length effective to thermally isolate or protect the source from the conduit. The waveguide attaches easily, either as a clamp-on 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 may be positioned in an array to cover interrogation paths for an extended range of sound speeds or flow rates.

Abstract: An encapsulated or rigid bundle of rods forms a substantially non-dispersive buffer usable in extreme environments, operable over wide bandwidth, and in some implementations, easily repairable in the field. In one preferred configuration, suitable for measuring the flow of low-molecular-weight gases over a wide range of pressure, temperature and flow rates, the bundle is made of about one thousand stainless steel welding rods tightly packed inside a 1-inch diameter tube. The rigid encapsulated assembly is sealed at the end that is in contact with the gas and may be sealed into a high-pressure flange in a manner that yields broadband transmission characteristics. A second buffer bundle, aligned with the first bundle, may be pressure-coupled on the other side of the flange.

Abstract: Transducers are mounted in a housing or vessel to propagate signals along a fluid measurement path, and a plurality of massive elements are placed between transmitting and receiving transducers in the acoustic propagation path through the solid body of the housing or vessel to remove crosstalk. In a preferred embodiment, the elements are rings, or sleeves which are attached to, or are machined from a thicker cylinder to leave a thin-walled cylinder with alternating masses. An isolation structure lightly sandwiches a flange between O-rings. This structure may be formed with flanged transducer casings, allowing the transducers to be closely spaced in solid conduits or on rigid frames without ringing. Alternatively, it may be formed in a separate framework or holder, providing precise positioning for interrogating gases in unconfined or loosely confined regions. Closed path sensor configurations measure circulation or swirl.

Abstract: A sensing system detects elastic waves propagated along a sensing path in a sheet to detect a characteristic of material contacting the other side of the sheet. An acoustic load applied between transducers discriminates characteristics in diverse environments. Different systems detect density, stiffness, presence, degree of coupling, thickness, or fill height of the material, with applications to areas as diverse as aircraft wing ice measurement, storage tank fill height detection, and mass flow detection. In one preferred embodiment a protective housing covers and protects the first side of the sheet over a region of the sheet encompassing the sensing path, and may secure transducers in defined positions. The housing preferably defines a closed reservoir that is temporarily filled to determine a normative measurement such as transit time or change in phase velocity.

Abstract: An apparatus and method for measuring gas flow velocity through a high stack employs ultrasonic transducers. The transducers are placed on opposite ends of a diameter several hundred feet up, with a small vertical separation L between the transducers. Apparatus for measuring acoustic velocity in the stack gas over short path lengths is also included.

Abstract: Transducers are mounted in a housing or vessel to propagate signals along a fluid measurement path, and received signals are temporally separated to remove crosstalk in the acoustic propagation paths of interest, which may be paths through the solid body of the housing or vessel or may be separate paths. These may be segments in a closed path circulation or swirl measurement, or different paths carrying combinations of possibly unrelated measurement signals. In a preferred embodiment, a single channel instrument processes signals from plural transducers which are connected in parallel to its processing input, greatly enhancing the effective system bandwidth and reducing equipment costs. Clamp-on circulation measurement or detection systems are described that allow easy evalution and set-up of flow conditioning loops.