Improved shear wave hockey stick transducer measures liquid flow and liquid level

Abstract

A solid waveguide of simple construction, and resembling a thin hockey stick, has been developed as a high-temperature clamp-on buffer to convey shear waves to hot pipes without dispersion, multipath or mode conversion problems. Buffer length of /spl sim/250 mm is generally adequate to isolate the piezoelectric shear wave element, whose frequency is typically 0.5, 1 or 2 MHz, from the high temperature. The buffer, passively cooled by ambient air convection, keeps the crystal cool, below 100/spl deg/C. This shear waveguide is typically clamped (but sometimes can be welded) to hot pipes (200 to 400/spl deg/C) to measure the flow of superheated water or hydrocarbon liquids. The present report covers (a) improved waveguide, yoke, and clamping means; (b) test results for prototype waveguides on 3" pipe; (c) measuring the decay rate of swirl in a plane /spl perp/ axis; (d) evaluating by means of clamp-on transducers, the transmission characteristics of narrow internal and external cavities in off-diameter planes that might be used for midradius or Gauss-Chebyshev quadrature integration of now profiles; (e) measuring liquid level in pipes whose axis is vertical, horizontal or tilted.