Torsional mode ultrasonic helical waveguide sensor for re-configurable temperature measurement

Abstract

This paper introduces an ultrasonic torsional mode based technique, configured in the form of a helical “spring-like” waveguide, for multi-level temperature measurement. The multiple sensing levels can be repositioned by stretching or collapsing the spring to provide simultaneous measurements at different desired spacing in a given area/volume. The transduction is performed using piezo-electric crystals that generate and receive T(0,1) mode in a pulse echo mode. The gage lengths and positions of measurements are based on machining multiple reflector notches in the waveguide at required positions. The time of fight (TOF) measurements between the reflected signals from the notches provide local temperatures that compare well with co-located thermocouples.

Distributed temperature sensors development using an stepped-helical ultrasonic waveguide

“…In this work, an operational frequency range (150 -500 kHz) was chosen for experiments. Here, to ensure low dispersion, an appropriate thickness of the wire and suitable mean -helical and conical configurations due to curvature effect were considered for selection of waveguide dimensions using our earlier approaches [17][18][21][22][23] . Studies of waves in helical waveguides are reported in literature [25][26] with applications in civil structures.…”

“…Different ultrasonic waveguide configurations have been reported by Periyannan and Balasubramaniam [16][17][18][19][20][21][22][23] for distributed temperature sensing. An ultrasonic system was developed for measuring the air temperature based on the phase shift records.…”

“…Multiple notches were machined along the length of the waveguide, each notch acting as a reflector that can be used to measure the local temperature. The configuration of the waveguide can be used straight 9 or can be made into shapes such as helical, [17][18][19] spiral, [21][22] or bend [14][15]23 for designing the distributed ultrasonic sensor and tested in a high temperature laboratory furnace. In this paper, our aim to develop a conical waveguide (using Chromel (d)=1.2 mm) with notch-type sensors for measuring the temperature inside the furnace.…”

“…Periodically spaced notches in the waveguide are used to reflect signals from these locations. The earlier reported measurement technique [17][18][19] (relative time of flight (TOF) between two notches) can be used to obtain the temperature between the two notches. In Fig.…”

“…A straight waveguide sensor system was reported 9 for measuring the vitrification melter temperature. The guided wave behaviour was studied in different curvature structures of helical and spiral ultrasonic waveguide configurations [17][18][19][20][21][25][26] for designing the distributed temperature measurement sensor. Here, the stepped and conical waveguides are designed based on this approach for measuring the distributed temperature measurements in a high-temperature furnace.…”