Ultrasonic path bundle and systems

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. Ultrasonic pulses transmitted into the first bundle remote from the gas are transmitted with little loss and little pulse distortion into the gas, while the transducer is thermally isolated by the second bundle and remains near ambient temperature. The high-pressure flange is thinned locally over a central area yet supports the rod safely and withstands pressures of 300 bar. This locally-thin region supports and aligns both buffers, while transmitting a broad band-width pulse in the preferred axial direction, while discouraging transmission in all other directions. This helps reduce solid-body-borne crosstalk and results in a high signal-to-noise ratio and high accuracy in the measurement of flow or other measurands. Signals may be combined to remove noise and then be processed to compute flow-related terms. The bundles are non-degrading waveguides 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.