Tomonori Ihara

A Study of Phased Array Ultrasonic Velocity Profile Monitor for Flow Rate Measurement

A new ultrasonic velocity profile measurement system with a phased array sensor was developed for accurate flow rate measurements. This measurement system employs phased array technique to reduce noise from multiple reflections which occurs in a wedge. However, phased array technique has some difficulties — one of them is about grading lobes. Thus, the array sensor was designed to reduce the grading lobes using simple calculations. Performance of the manufactured array sensor was evaluated by experimental measurements of sound pressure distribution emitted from the array sensor, and optimal parameters to control the array sensor were obtained. Hardware and software of the ultrasonic velocity profile measurement system with a phased array sensor were also developed. The software is based on ultrasonic Doppler method. Velocity profiles of horizontal pipe flow were measured using the developed system, and the availability of the system applying a phased array sensor was confirmed.Copyright

Ultrasound Pulse-Echo Coupled with a Tracking Technique for Simultaneous Measurement of Multiple Bubbles

Bubbly flows are commonly used in various applications and their measurement is an important research topic. The ultrasound pulse-echo technique allows for the detection of each bubble and the measurement of the position of its surface. However, so far it has been used only to measure single bubbles. This paper investigates whether the pulse-echo technique can be applied for measuring multiple bubbles concurrently. The ultrasonic transducer wavelength and diameter were selected based on expected bubble diameters so that each bubble produced a strong reflection. The pulse-echo was implemented to obtain good accuracy without sacrificing the signal processing speed. A tracking technique was developed for the purpose of connecting detected reflections to trajectories. The technique was tested experimentally by measuring the horizontal position of rising air bubbles in a water tank. The results show that the pulse-echo technique can detect multiple bubbles concurrently. The pulse-echo technique detected almost the same number of bubbles as a high-speed video. For average void fractions up to around 1% (and instantaneous void fraction reaching 5.3%), the rate of bubbles missed by the pulse-echo and the rate of noise trajectories both stayed less than 5%. The error rate increased with the void fraction, limiting the technique’s application range.

Ultrasound Characteristics in High-Temperature Fluid

To investigate the ultrasound characteristics in high-temperature (over 1000 °C) viscous fluid such as molten glass, we developed an experimental apparatus. This apparatus consists of an electric furnace, a glass container and a transducer employing buffer rod with a cooling jacket to use room-temperature ultrasonic transducers. An ultrasonic velocity and its attenuation in molten glass are measured using the pulsed echo method. To derive the desired echoes, the buffer rod with grooves and cross-correlation analysis are applied.Copyright

Fundamental Study on Application of Ultrasonic Velocimetry to Molten Glass

This paper describes fundamental study intended to apply ultrasonic velocimetry to molten glass. Buffer rod is employed to transmit ultrasound into molten glass. Several ceramics are tested for capability, which regards transmission characteristic and corrosion resistance. Among tested materials, mullite provides perfect wetting with a borosilicate glass and highest transmission ratio. Trailing echo level, which is the level of spurious signal arouse inside buffer rod, is evaluated both numerically and experimentally. Trailing echo level can be improved by using higher frequency of ultrasound. Acoustic field after buffer rod is investigated. Measurement near the buffer rod surface should be avoided due to ununiformed pressure distribution as a normal planner ultrasonic transducer has. Ultrasonic beam become sharp due to absorption on the side wall when buffer rod is equipped. Sound speed in the molten glass is obtained from 1000 °C to 1200 °C. Obtained values are almost constant within this temperature range although small negative slope is observed against temperature. Attenuation coefficient of ultrasound in the molten glass is also measured. The coefficient is well modelled to temperature dependent exponential function. Finally, application of velocimetry via buffer rod is demonstrated. From velocity profiles, maximum measurable range is investigated. Experimental results suggest that velocimetry measurement can be done unless ultrasound energy is attenuated to trailing echo level.Copyright

A Study of Air-Coupled Ultrasonic Flowmeter

A new non-contact flow metering system is developed using air-coupled ultrasonic technique. The principle of the present system is based on the time-of-flight (TOF) ultrasonic flowmeter. The TOF ultrasonic flowmeter has two transducers, a transmitter and a receiver, which are strapped on the outside wall of a pipe. However, it is difficult to set the transducers on very high temperature pipe walls, since the transducers loose piezoelectricity over Curie point. Therefore, we focused on air-coupled ultrasonic waves for flow field measurement, and developed an air-coupled ultrasonic transducers and a signal processing system.Copyright