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

Suresh Periyannan,Prabhu Rajagopal,Krishnan Balasubramaniam

doi:10.1063/1.4977965

Suresh Periyannan, Prabhu Rajagopal + Show 1 more

Open Access

https://doi.org/10.1063/1.4977965

Copy DOI

Journal: AIP Advances	Publication Date: Mar 1, 2017
Citations: 13	License type: CC BY 4.0

Affiliation: Indian Institute of Technology Madras

Abstract

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.

Highlights

Ultrasonic temperature sensors are of much interest for temperature profile measurement requirements in several industrial applications
The calibration was based on the time of flight difference at locations in-between the pair of notches using peak-tracking method that has been reported earlier.[19,20,34]
This paper reported on the development of an ultrasonic spiral waveguide temperature sensor for a more robust, small footprint approach to distributed measurement of temperatures over a plane when compared to thermocouples or other waveguide methods

Summary

INTRODUCTION

Ultrasonic temperature sensors are of much interest for temperature profile measurement requirements in several industrial applications (e.g., power plants). Temperature distribution in a solid was measured using phase shift of acoustic beam.[16] Most of the previous approaches described measurements limited to a single zone of interest Using these approaches, it would be necessary to have multiple sensors for multi-point distributed measurements. A novel single ultrasonic waveguide in a spiral configuration is shown to yield the possibility for multiple distributed sensing on a plane This approach has some similarities to reports in the literature on distributed fiber optic temperature sensors using Fiber Bragg Grating reflectors[17,18] using a light source along with wavelength division multiplexing. The main (and perhaps only) similarity between the spiral and the helical[19] configurations is that both propose the use of time of flight measurement from ultrasonic wave reflections from notches in a single waveguide for temperature measurement at multiple locations. Finite Element (FE) simulations were employed to better understand the physics of ultrasonic guided waves in spiral configurations and to select the appropriate spiral dimensions

Waveguide temperature sensors

Ultrasonic waves in spiral wire waveguide

Experimental apparatus description

SUMMARY AND CONCLUSION