Shuh-Haw Sheen

An in-line ultrasonic viscometer

An in-line viscometer is valuable to the control of a flow process, particularly a non-Newtonian flow because its viscosity is shear-rate dependent and thus requires continuous monitoring. Currently available in-line viscometers are mostly of the probe design [1] and may obstruct the flow pattern, causing plugging problem in flows with suspended particles. A probe-type viscometer generally measures a response of fluid density-viscosity product. To separate mass loading and viscous effects, Kim and Bau [2] used a dual-probe design based on torsional wave speed and attenuation measurements. However, no commercial system has been developed from their concept. Another limitation of existing probe-type viscometers is the range of application, primarily in the low-viscosity range.

Measurement of shear impedances of viscoelastic fluids

Shear-wave reflection coefficients from a solid/fluid interface are derived for non-Newtonian fluids that can be described by Maxwell, Voigt, and power-law fluid models. Based on model calculations, we have identified the measurable effects on the reflection coefficients due to fluid non-Newtonian behavior. The models are used to interpret the viscosity data obtained by a technique based on shear impedance measurement.

Cavitation-controlled ultrasonic agitator

An ultrasonic agitator has been designed for application in a confined area with a high-temperature, high-pressure, and corrosive environment. Control of this agitator is based on the detection of noise levels and subharmonics produced during cavitation and streaming. Noise signatures of agitation in different liquids and in liquids with particles are determined and discussed. The potential applications of this agitator are in a fluid-mixing device, a homogenizer during crystallization, a cavitation sensor, an acoustic streaming indicator, a fluid-characterization device, and a local liquid-solid heat-transfer enhancer.<<ETX>>

Method and apparatus for sizing and separating warp yarns using acoustical energy

A slashing process for preparing warp yarns for weaving operations including the steps of sizing and/or desizing the yarns in an acoustic resonance box and separating the yarns with a leasing apparatus comprised of a set of acoustically agitated lease rods. The sizing step includes immersing the yarns in a size solution contained in an acoustic resonance box. Acoustic transducers are positioned against the exterior of the box for generating an acoustic pressure field within the size solution. Ultrasonic waves that result from the acoustic pressure field continuously agitate the size solution to effect greater mixing and more uniform application and penetration of the size onto the yarns. The sized yarns are then separated by passing the warp yarns over and under lease rods. Electroacoustic transducers generate acoustic waves along the longitudinal axis of the lease rods, creating a shearing motion on the surface of the rods for splitting the yarns.

Critical issues in catalytic diesel reforming for solid oxide fuel cells

Developing low-cost diesel-reforming catalysts and improving fuel mixing prior to catalytic reforming were addressed as two critical issues under the current study. Ruthenium-doped lanthanum chromite and aluminite were explored as catalysts for the autothermal reforming of diesel fuel. Dodecane was used as a surrogate fuel. Both catalysts yielded nearly 20 moles of hydrogen per mole of dodecane at oxygen-to-carbon ratios of 0.5 and steam-to-carbon ratios of 2 at space velocities near 100,000/h−1. Both catalysts were shown to have good S tolerance when tested with a fuel mixture containing 50 parts per million S in the form of dibenzothiophene. Parallel to catalyst development, the impact of fuel mixing and vaporization through improved liquid injection also is under investigation.

An alternative approach of acousto-ultrasonic technique for monitoring material anisotropy of fiber-reinforced composites

An alternative acousto-ultrasonic (AU) technique has been developed for nondestructive evaluation (NDE) of fiber-reinforced composites. The technique measures the time of flight (TOF) of AU waves, instead of the stress wave factor, by two low-frequency (0.5 MHz) transducers and relates TOF to material properties and fiber orientation. As the transducer separation increases, the measured time-domain AU signals clearly separate into two groups, since the excitation is under the first critical frequency, which correspond to the first two fundamental modes of the Lamb waves. One is an antisymmetric mode with slower propagation velocity and is highly dispersive, while the other is a symmetric mode with faster propagation velocity, which is very close to that of the longitudinal bulk wave, and is nearly nondispersive. The phase velocity in the composites can be accurately determined from the slopes of the TOF curves, and depends strongly on the azimuthal angle, frequency, and plate thickness. If the wave propagates away from the fiber direction, a slower but more attenuated wave is observed. Phase-velocity curves in azimuthal angles were obtained for E-glass/polyester, S-2-glass/epoxy, and Kevlar 49 composites. The theoretical solutions, for the longitudinal bulk wave and Lamb wave, are obtained by solving an eigenproblem once the material mechanical properties are defined. Good agreement is obtained between the measurements and the theoretical calculations.<<ETX>>

Photoacoustic spectroscopy (PAS) system for remote detection of explosives, chemicals, and special nuclear materials

This paper describes a practical photoacoustic spectroscopy technique applied to remote sensing of chemicals in an open environment. A laboratory system that consists of a high-power CO2 laser and an open-field acoustic resonator is described. The acoustic resonator is a combination of a parabolic reflector and a narrow-band cylindrical acoustic resonator that resonates at the laser modulation frequency. The performance of the resonator is theoretically analyzed and experimentally verified. Significant improvement in signal-to-noise ratio has been achieved. Detection of gas-phase photoacoustic signals was demonstrated at a remote distance of several meters from the target. Potential applications to the detection of condensed-phase chemicals are discussed; the detection of the photoacoustic spectrum of trinitrotoluene (TNT) in an open environment is presented.

Ultrasonic techniques for measurement of coal slurry viscosity

The authors present a technical evaluation of ultrasonic methods as applied to the measurement of slurry viscosity. The four ultrasonic techniques examined were measurement of attenuation, acoustic impedance, relaxation, and acoustic streaming and cavitation. Acoustic impedance measurements are more sensitive to slurry viscosity than to any other fluid parameter. The three other techniques measure acoustic attenuation, but in different frequency ranges. The direct attenuation measurement technique suffers from the difficulty of extracting the viscous contribution from other effects, especially the thermal effect. The relaxation method requires an operating frequency near 10/sup 9/ Hz, which is difficult to achieve at present. Finally, the streaming and cavitation method has not been carefully examined because the technique is based on nonlinear acoustic effects which are not well understood. Results from this study indicate that it is feasible to develop an online ultrasonic viscometer based on the measurement of either acoustic impedance or acoustic streaming and cavitation. The authors describe the design and performance of an ultrasonic shear-wave wedge for acoustic impedance measurement.<<ETX>>

Standoff detection of ozone in an open environment using photoacoustic spectroscopy technique

The current work reports a practical photoacoustic spectroscopy (PAS) technique that can be applied for the standoff detection of ozone in an open environment. The developed PAS detection system consists of a laser, a parabolic acoustic reflector, and an acoustic resonator that acts as a lock-in amplifier to extract only the signals resonating with the laser chopping frequency. The design of the acoustic resonator is described, and a detection capability of 700 ppb ozone at 2 m distance in the ambient air is demonstrated. The system would have broad applications for open-air detection of chemicals in various forms.

DEVELOPMENT OF A NOVEL ULTRASONIC WAVEGUIDE TRANSDUCER FOR UNDER‐SODIUM VIEWING

A novel ultrasonic waveguide transducer (UWT) has been developed for under‐sodium inspection of sodium‐cooled fast reactor (SFR). Its performance was evaluated and compared with other four types of waveguide designs. The signal transmission efficiency and detection sensitivity has been greatly improved. The preliminary results in molten sodium demonstrate that our novel ultrasonic waveguide transducer is able to achieve 1 mm lateral resolution and 0.5 mm vertical resolution in molten sodium with temperature ranged from 300 °F to 650 °F.