集成超声透射和反射层析成像的理论与实验研究

Theoretical and Experimental Study on Ultrasonic Transmission and Reflection Integrated Tomography

超声过程层析成像能可靠地表征颗粒两相流的空间分布。为增加有效投影数据量,提出一种融合超声波透射和反射信息的双模式超声过程层析成像方法。设计了基于聚偏氟乙烯压电薄膜的微型传感器阵列,搭建24通道超声成像系统,并提出扫描过程中识别、提取透射波和反射波的方法,实现对扫描路径上的超声透射波和反射波同步测量。对四个不同的钢珠颗粒体系进行了数值和实验研究:通过COMSOL软件仿真获得成像区的声压分布,发现颗粒尺寸的测量下限应大于换能器发射面宽度;其后分别采用透射、反射和双模式成像方法对钢珠颗粒体系进行实验研究。结果对比表明,双模式超声成像方法从图像去噪和颗粒轮廓增强方面明显改进了超声层析成像效果。

Ultrasonic process tomography can reliably characterize spatial distribution of particulate two-phase flow. In order to increase effective projection data in ultrasonic tomography, dual-mode ultrasonic tomography integrating transmission and reflection information were investigated. A 24-channel ultrasonic imaging system based on designed miniaturized polyvinylidene fluoride transducer array and a proposed method for the identification and extraction of transmission and reflection waves were applied to achieve simultaneous measurement of ultrasonic transmission and reflection waves. A particle system with four steel particles was then investigated numerically and experimentally. The sound pressure distribution in the imaging area was obtained by COMSOL software, and the results indicate that the detection limit of particle size should be larger than the width of the transducer emission surface. The reconstructed results from transmission-mode, reflection-mode and dual-mode were compared. The dual-mode ultrasonic imaging method shows obvious improvement in image blurring reduction and particle profile enhancement.