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.
Highlights
Ultrasonic temperature sensors have the potential for providing robust measurements for many applications including determination of local temperature and temperature profiles of industrial processes in glass and metal melting plants, process industries, nuclear power plants, etc., where temperature control is critical
This paper introduces an ultrasonic torsional mode based technique, configured in the form of a helical “spring-like” waveguide, for multi-level temperature measurement
We explore the feasibility of using multiple “notch” embodiments as reflectors that are positioned along the length of the waveguide and their ability in making multiple measurements using a single ultrasonic probe that is generating a torsional guided wave mode
Summary
Ultrasonic temperature sensors have the potential for providing robust measurements for many applications including determination of local temperature and temperature profiles of industrial processes in glass and metal melting plants, process industries, nuclear power plants, etc., where temperature control is critical. The use of ultrasonic waveguides for measuring elevated temperatures and temperature profiles have been reported earlier by the authors.[1,21,22] The ultrasonic waveguide-based temperature sensing approaches have several advantages over the conventional thermocouples; the advantages include the inherent property of higher reliability, as there is no junction that can fail, as well as the ability to program several zones of measurements in one waveguide. We explore the feasibility of using multiple “notch” embodiments as reflectors that are positioned along the length of the waveguide and their ability in making multiple measurements using a single ultrasonic probe that is generating a torsional guided wave mode. The temperature measurement at multi-levels in a furnace using such a reconfigurable waveguide that supports a torsional wave T(0,1) is discussed and compared with thermocouple measurements. The T(0,1) results are compared with the results from using the L(0,1) mode that has been reported elsewhere.[21]
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