Ultrasonic waveguide with enhanced ultrasonic reflectors for developing temperature measurement sensors

Area of Science:

• Materials Science
• Sensor Technology
• Ultrasonics

Background:

• Accurate in situ temperature monitoring is crucial for industrial processes, especially in power plants and the oil/petrochemical sectors.
• Existing methods may face challenges with insulated or coated pipes, necessitating robust and adaptable sensor solutions.
• Ultrasonic guided waves offer a promising non-destructive method for sensing physical parameters on pipe surfaces.

Purpose of the Study:

• To develop and validate an ultrasonic strip waveguide sensor for distributed pipe surface temperature measurements.
• To optimize sensor design using Finite Element Method (FEM) for efficient S0 wave propagation and reflection.
• To evaluate the sensor's performance, including accuracy, repeatability, and suitability for industrial environments.

Main Methods:

• A Finite Element Method (FEM) study was conducted to determine optimal notch reflector dimensions for uniform signal amplitude using the S0 (longitudinal) wave mode.
• A thin-strip waveguide with a flattened surface was designed for improved transducer contact and thermal absorption.
• The waveguide was fabricated in a helical configuration for secure coupling to cylindrical pipe surfaces, utilizing its self-stiffness.
• A pulse-echo approach with a single shear transducer was employed to transmit and receive S0 wave modes.
• Sensor calibration was performed by measuring the time-of-flight difference (δToF) against temperature, validated with thermocouple data.
• Repeatability was assessed through multiple heating experiments on the pipe.

Main Results:

• FEM analysis successfully identified notch dimensions for consistent S0 wave reflection from distributed sensors.
• The helical configuration ensured secure and stable sensor coupling to the pipe surface.
• The developed sensor demonstrated accurate temperature readings when calibrated against thermocouples.
• Repeatability tests confirmed consistent performance across multiple heating cycles.
• The sensor effectively measures temperature changes on cylindrical or planar surfaces.

Conclusions:

• The developed helical strip waveguide sensor provides an effective, easy-to-use, and inexpensive solution for in situ temperature monitoring.
• Its design is robust and suitable for harsh industrial environments, including insulated and coated pipes.
• This technology holds significant potential for applications in power generation, oil, and petrochemical industries.