A fiber optic ultrasonic sensing system for 2D temperature field monitoring using optically generated acoustic waves

Abstract

In this paper, we present a novel fiber optic ultrasonic sensing system to conduct a 2D temperature field monitoring. The fiber optic ultrasonic sensing system was used as an ultrasonic pyrometer to measure the temperature field. The ultrasonic pyrometer was based on the thermal dependence of the speed of sound in air. The speed of a sound wave traveling in a medium was proportional to the medium's temperature. A fiber optic ultrasonic generator and a microphone were used as the ultrasonic signal generator and receiver, respectively. A carbon black-Polydimethylsiloxane (PDMS) material was utilized as the photoacoustic material for the fiber optic ultrasonic generator. A test was performed outside of a lab furnace, the testing area temperature range was from 26°C to 70°C. A 2D temperature field was mapped. The 2D temperature field map matched with the reference thermocouple results. This system could lead to the development of a new generation temperature sensor for temperature field monitoring in coalfired boilers or exhaust gas temperature monitoring for turbine engines.

A Fiber Optic Ultrasonic Sensing System for High Temperature Monitoring Using Optically Generated Ultrasonic Waves

“…However, the photoacoustic conversion efficiency of metals is low since their low thermal expansion. Researchers have developed composite materials with both high thermal expansion and light absorption, such as gold-nanocomposites [16,17,18], carbon black combined with PDMS (black PDMS) [19,20], CNTs [21], candle soot nanoparticles [22], and polymer-thin metal-polymer [23]. In this paper, black PDMS material was used as a photoacoustic material.…”