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Sensors 2018, 18(12), 4256; https://doi.org/10.3390/s18124256

Ultrasonic Transmission Tomography Sensor Design for Bubble Identification in Gas-Liquid Bubble Column Reactors

1
School of Automation, Northwestern Polytechnical University, Xi’an 710129, China
2
Agile Tomography Group, School of Engineering, University of Edinburgh, Edinburgh EH9 3FG, UK
3
School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China
4
Department of Applied Nuclear Technology, China Institute of Atomic Energy, Beijing 102413, China
*
Author to whom correspondence should be addressed.
Received: 31 October 2018 / Revised: 24 November 2018 / Accepted: 30 November 2018 / Published: 4 December 2018
(This article belongs to the Special Issue Ultrasound Transducers)
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Abstract

Scientists require methods to monitor the distribution of gas bubbles in gas-liquid bubble column reactors. One non-destructive method that can potential satisfy this requirement in industrial situations is ultrasonic transmission tomography (UTT). In this paper, an ultrasonic transmission tomography sensor is designed for measuring bubble distribution in a reactor. Factors that influence the transducer design include transmission energy loss, the resonance characteristics and vibration modes of the transducer, and diffusion angles of the transducers, which are discussed. For practical application, it was found that an excitation frequency of 300 kHz could identify the location and size of gas bubbles. The vibration mode and diffusion also directly affect the quality of the imaging. The geometric parameters of the transducer (a cylinder transducer with a 10 mm diameter and 6.7 mm thickness) are designed to achieve the performance requirements. A UTT system, based on these parameters, was built in order to verify the effectiveness of the designed ultrasonic transducer array. A Sector-diffusion-matrix based Linear Back Projection (SLBP) was used to reconstruct the gas/liquid two-phase flow from the obtained measurements. Two other image processing methods, based on SLBP algorithm named SLBP-HR (SLBP-Hybrid Reconstruction) and SLBP-ATF (SLBP-Adaptive Threshold Filtering), were introduced, and the imaging results are presented. The imaging results indicate that a gas bubble with a 3 mm radius can be identified from reconstructed images, and that three different flow patterns, namely, single gas bubble, double gas bubble with different diameters, and eccentric flow, can be identified from reconstructed images. This demonstrates that the designed UTT sensor can effectively measure bubble distribution in gas-liquid bubble column reactors. View Full-Text
Keywords: ultrasonic transmission tomography; sensor design; bubble distribution; bubble distribution; bubble column reactors ultrasonic transmission tomography; sensor design; bubble distribution; bubble distribution; bubble column reactors
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Li, N.; Cao, M.; Xu, K.; Jia, J.; Du, H. Ultrasonic Transmission Tomography Sensor Design for Bubble Identification in Gas-Liquid Bubble Column Reactors. Sensors 2018, 18, 4256.

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