An EMAT Guided Wave Tomography System for Gas–Liquid Two-Phase Flow Imaging

The gas-liquid two-phase flow tomography technique has significant value for industrial process monitoring. However, the harsh environment and metal pipes present a challenge that limits the applicability of existing techniques. To address the challenge of gas-liquid two-phase flow tomography in metal pipes, an ultrasonic tomography (UT) system based on electromagnetic acoustic transducer (EMAT) technology was designed and developed to effectively realize process tomography. By considering the installation distance, guided wave mode, and transducer coil proportion of the EMAT array, the optimal overall scheme of the EMAT array can be obtained through finite element (FE) simulation. Through experimental tests, the consistency of each channel of the EMAT array is evaluated and normalized in order to reduce the artefacts that are caused by channel inconsistency. In order to achieve tomography in metal pipes in static experiments, a revised total focusing method (TFM) algorithm has been developed within the UT system, utilising the EMAT guided wave. The analysis of the imaging effect and the sensitivity distribution in the imaging region has led to the formulation of proposals regarding the limitations of the system and potential improvement methods.