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. © 2016 Author(s).

Prabhu Rajagopal

Department of Mechanical Engineering

Krishnan Balasubramaniam

Suresh Periyannan

Thermocouples

Ultrasonic applications

Waveguides

GAGE LENGTH

Local temperature

PIEZOELECTRIC CRYSTALS

PULSE-ECHO MODE

REFLECTED SIGNAL

Simultaneous measurement

TIME OF FIGHTS

Torsional modes

temperature measurement

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

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

AIP Advances

This paper reports on an ultrasonic waveguide sensor for liquid level measurements using three guided wave modes simultaneously. The fundamental wave modes longitudinal L(0,1), torsional T(0,1), and flexural F(1,1) were simultaneously transmitted/received in a thin stainless steel wire-like waveguide using a standard shear wave transducer when oriented at an angle of 45° to the axis of the waveguide. Experiments were conducted in non-viscous fluid (water) and viscous fluid (castor oil). It was observed that the flexural F(1,1) wave mode showed a change in both time of flight (due to the change in velocity and dispersion effects) and amplitude (due to leakage) for different levels (0-9 cm) of immersion of the waveguide in a fluid medium. For the same level of immersion in the fluid, the L(0,1) and the T(0,1) modes show only a relatively smaller change in amplitude and no change in time of flight. The experimental results were validated using finite element model studies. The measured change in time of flight and/or the shift in central frequency of F(1,1) was related to the liquid level measurements. Multiple trials show repeatability with a maximum error of 2.5% in level measurement. Also, by monitoring all three wave modes simultaneously, a more versatile and redundancy in measurements of the fluid level inside critical enclosures of processing industries can be achieved by compensating for changes in the fluid temperature using one mode, while the level is measured using another. This ultrasonic waveguide technique will be helpful for remote measurements in physically inaccessible areas in hostile environments. © 2019 Author(s).

Review of Scientific Instruments

Ultrasonic waveguide based level measurement using flexural mode F(1,1) in addition to the fundamental modes

This paper reports the feasibility of using an ultrasonic waveguide sensor for distributed temperature measurement in two different case studies, that is: 1) skin temperature of a solid structure (pipe) and 2) fluid (water). This technique improves upon the conventional multiple thermocouples approach for multi-level temperature measurements. The range of temperatures is from room temperature to maximum utility temperature for the two case studies (85 °C for water and 200 °C for pipe). Using the interaction of the propagating ultrasonic waves in a thin rodlike waveguide with intentionally designed geometric discontinuities (bends, axisymmetric, non-axisymmetric notches, and so on), the localized information on the temperature is extracted. An ultrasonic technique for accurate temperature measurement by tracking the time-of-flight of reflected guided wave modes from appropriately spaced notch reflectors is therefore proposed here, while using the reflection from a bend is used as a reference. Using a finite element model approach, the notch size and/or the bend radius were selected in order to reduce mode conversion effects as well as to obtain uniform amplitudes of the reflected signals from these designed discontinuities. The numerical results were experimentally validated for the L(0,1) wave mode using a stainless steel waveguide sensor. This paper is of interest to industrial applications including mould cooling jacket temperature monitoring during the steel manufacturing process as well as for furnace wall temperature measurements in petrochemical industries. © 2001-2012 IEEE.

IEEE Sensors Journal

Ultrasonic waveguide-based multi-level temperature sensor for confined space measurements

Ultrasonic waveguide-based sensing, that permit robust measurements and sensing, is discussed in this paper. The use of ultrasonic guided waves has several advantages including remote measurements, multi-modal nature allowing for measurement of different parameters, small footprint, low cost, multi-point measurements on the same waveguide and most importantly robustness. These inherent qualities of ultrasonic waveguide-based sensing are particularly useful in industrial applications. One of the key applications that will be described will be the measurement of E and G moduli of materials as a function of temperature over a wide range of materials will be demonstrated. Knowing the moduli as a function of temperature, the measurement of physical properties such as temperature, rheology, fluid level, etc. of the surrounding fluid material can be accomplished using several embodiments of the waveguides using the fundamental wave modes such as L(0,1), T(0,1) and F(1.1). In addition, it will be shown that under sodium imaging in large plant conditions can be performed using ultrasonic waveguides using the A0 modes. © 2018 IEEE.

Proceedings of IEEE Sensors

Ultrasonic Waveguide Sensors for Measurements in Process Industries

This paper studies the propagation of ultrasound in spiral waveguides, towards distributed temperature measurements on a plane. Finite Element (FE) approach was used for understanding the velocity behaviour and consequently designing the spiral waveguide. Temperature measurements were experimentally carried out on planar surface inside a hot chamber. Transduction was performed using a piezo-electric crystal that is attached to one end of the waveguide. Lower order axisymmetric guided ultrasonic modes L(0,1) and T(0,1) were employed. Notches were introduced along the waveguide to obtain ultrasonic wave reflections. Time of fight (TOF) differences between the pre-defined reflectors (notches) located on the waveguides were used to infer local temperatures. The ultrasonic temperature measurements were compared with commercially available thermocouples. © 2017 Author(s).

Multiple temperature sensors embedded in an ultrasonic “spiral-like” waveguide

This paper describes novel techniques for simultaneous measurement of temperatures at multiple locations using two configurations (a) a single transducer attached to multiple waveguides of different lengths (each with a single bend) and (b) single waveguide with multiple bends connected to single transducer. These techniques improve upon the earlier reported studies using straight waveguides, where the non-consideration of the effect of temperature gradients was found to be a major limitation. The range of temperature measurement is from room temperature to maximum utility temperature of the waveguide material. The time of flight difference of reflected ultrasonic longitudinal guided wave modes (L(0, 1)) from the bend, which is the reference signal, and another signal from the end of the waveguide, is utilized to measure the local temperature of the surrounding media. Finite element simulations were employed to obtain the appropriate dimensions and other design features of the multiple bent waveguide. This work is of interest to several industrial applications involving melters and furnaces. © 2016

Ultrasonics

Ultrasonic bent waveguides approach for distributed temperature measurement

A novel ultrasonic waveguide based technique for measuring the moduli of elastic isotropic material as a function of temperature using ultrasonic guided wave modes is presented here. This technique can be utilized for measuring Young’s modulus (E) and Shear Modulus (G) of multiple material using the guided ultrasonic L(0, 1) and T(0, 1) wave modes respectively over a wide range of temperatures (demonstrated here from room temperature to 1200 °C). The specimens used in the experiments here have special embodiments (for instance, a bend) at one end of the waveguide and an ultrasonic guided wave generator (transducer) at the other end for obtaining reflected signals in a pulse-echo mode. The far end of the waveguides with the embodiment is kept inside a heating device such as a temperature-controlled furnace. The time of flight difference (δTOF) were used to measure the moduli at different temperatures. Several materials were tested and the comparison between literature values and measured values were found to be in agreement, for both elastic moduli (E and G) measurements, as a function of temperature. This technique provides significant reduction in time, effort and cost over conventional means of measurement of temperature dependence of elastic moduli. © 2016, Society for Experimental Mechanics.

Experimental Mechanics

Moduli Determination at Different Temperatures by an Ultrasonic Waveguide Method

This paper introduces a novel technique for multi-level temperature measurement using a single reconfigurable ultrasonic wire waveguide that is configured in the form of a helical spring. In this embodiment, the multiple sensing levels located along the length of the helical waveguide wire can be repositioned by stretching or collapsing the spring to provide measurements at different desired spacing in a given area/volume. This method can measure over a wide range of temperatures. The transduction is performed using Piezo-electric crystals that are attached to one end of the waveguide which act as transmitter as well as receiver. The wire will have multiple reflector embodiments (notches was used here) that allow reflections of input L(0,1) mode guided ultrasonic wave, in pulse echo mode, back to the crystal. Using the time of fight measurement at multiple predefined reflector locations, the local average temperatures are measured and compared with co-located thermocouples. The finite element modeling simulation was used to study the effect of excitation frequency and the mean coil diameter of the "spring-like" waveguide. This technique improves on the limitations of a straight waveguide technique earlier reported. © 2016 AIP Publishing LLC.

Journal of Applied Physics

Re-configurable multi-level temperature sensing by ultrasonic "spring-like" helical waveguide

A novel technique for simultaneously measuring the moduli of elastic isotropic material, as a function of temperature, using two ultrasonic guided wave modes that are co-generated using a single probe is presented here. This technique can be used for simultaneously measuring Young's modulus (E) and shear modulus (G) of different materials over a wide range of temperatures (35°C-1200°C). The specimens used in the experiments have special embodiments (for instance, a bend) at one end of the waveguide and an ultrasonic guided wave generator/detector (transducer) at the other end for obtaining reflected signals in a pulse-echo mode. The orientation of the transducer can be used for simultaneously generating/receiving the L(0,1) and/or T(0,1) using a single transducer in a waveguide on one end. The far end of the waveguides with the embodiment is kept inside a heating device such as a temperature-controlled furnace. The time of flight difference, as a function of uniform temperature distribution region (horizontal portion) of bend waveguides was measured and used to determine the material properties. Several materials were tested and the comparison between values reported in the literature and measured values were found to be in agreement, for both elastic moduli (E and G) measurements, as a function of temperature. This technique provides significant reduction in time and effort over conventional means of measurement of temperature dependence of elastic moduli. © 2015 AIP Publishing LLC.

Simultaneous moduli measurement of elastic materials at elevated temperatures using an ultrasonic waveguide method

This is a novel technique for distributed temperature measurements, using single robust ultrasonic wire or strip-like waveguides, special embodiments in the form of Helical or Spiral configurations that can cover large area/volume in enclosed regions. Such distributed temperature sensing has low cost applications in the long term monitoring critical enclosures such as containment vessels, flue gas stacks, furnaces, underground storage tanks, buildings for fire, etc. The range of temperatures that can be measured are from very low to elevated temperatures. The transduction is performed using Piezo-electric crystals that are bonded to one end of the waveguide which acts as both transmitter and receivers. The wires will have periodic reflector embodiments (bends, gratings, etc.) that allow reflections of an input ultrasonic wave, in a pulse echo mode, back to the crystal. Using the time of fight (TOF) variations at the multiple predefined reflector locations, the measured temperatures are mapped with multiple thermocouples. Using either the L(0,1) or the T(0,1)modes, or simultaneously, measurements other than temperature may also be included. This paper will describe the demonstration of this technology using a 0.5 MHz longitudinal piezo-crystal for transmitting and receiving the L (0, 1) mode through the special form of waveguide at various temperatures zones. © 2015 The Authors.

Physics Procedia

Robust ultrasonic waveguide based distributed temperature sensing

This paper reports on a robust technique for the measurement of temperature at multiple heights (levels). This technique uses a bank of straight ultrasonic waveguide temperature sensors attached to a single ultrasonic pulser-receiver instrument. Since the ultrasonic waveguide does not use a junction, the robustness of the sensor is expected to be more for field applications. The measurements have been made by using the L(0,1) ultrasonic guided wave mode end reflection as the signal of interest. The changes in the time-of-flight (DTOF) of this signal as the measurement were related to the local changes temperature of the surrounding medium. Several waveguide configurations were studied and the thickness of the waveguide was optimized to provide a reliable calibration curve. Data was collected and analyzed in a laboratory furnace from 45°C to 1100°C, and the multi-level temperature measurement was demonstrated both in the laboratory as well as in a waste treatment vitrification facility. © 2014 Elsevier Ltd. All rights reserved.

Journal	Data powered by TypesetAIP Advances
Publisher	Data powered by TypesetAmerican Institute of Physics Inc.
ISSN	21583226
Open Access	Yes