The Generation of Cavitation for the Removal of Fouling on Submerged Structures Using High Power Ultrasonic Transducers

污垢的积累是工业中一个众所周知的问题，它可能发生在各种不同的结构上，这取决于周围的环境条件。清除这种结垢的成本非常高，因此人们试图以经济有效的方式减轻、监测和清除结垢。由于缓解技术不能保证100%去除结构中的污垢，另一种方法是检测和监测污垢积聚，以协助进行去除污垢的程序。目前的检测方法，如清管，也可能需要停产来进行监测。近年来，应用超声引导波（UGW）进行污垢检测已被认为是一种有前途的非侵入性技术；然而，它的研究仍处于早期阶段。作为一种无创污垢检测技术的补充，超声波在原位污垢去除方面的应用受到了业界的广泛关注。人们已经进行了大量的研究，以提高超声波在不同污染应用中的潜在用途，主要是在反渗透膜和热交换器中。然而，原位超声去除污垢的优化尚未进行研究，也处于起步阶段。本文阐述了大功率超声换能器（HPUT）的基本原理，该换能器用于产生声空化气泡以实现超声波清洗。这些知识用于开发有限元（FE）模型，该模型使用阻抗的实验特性进行验证。HPUT有限元模型用于进一步了解超声电极附着物的设计和开发，为未来超声清洗技术的改进提供依据。扩展了有限元模型以预测空化产生以确定清洗模式，并在实验室条件下进行了验证。通过利用可控制的污垢产生能力，研究了使用UGW进行污垢检测，并使用FE模型进一步表征变量，这些变量可以量化污垢积累的检测，并具有监测污垢去除的潜在应用。用于污垢去除预测的FE方法用于优化HPUT配置，以实现在6.2米长、6英寸的40级碳钢管上长距离清除污垢。确认的4-HPUT配置是为实验室验证而开发的，并演示了从单个HPUT位置到3米的波传播

The accumulation of fouling is a well-known problem in industry which can occur on various different structures depending on the surrounding environmental conditions.The removal of this fouling can be very costly and has resulted in many attempts to mitigate, monitor and remove fouling accumulation in a cost-effective manner. As mitigating techniques cannot guarantee 100% fouling removal of a structure, another approach is to detect and monitor the fouling accumulation to assist in carrying out de-fouling procedures. Current detection methods such as PIGging can also require halts in production to carry out monitoring. In recent years, the application of Ultrasonic Guided Waves (UGW) for fouling detection has been recognised as a promising and non-invasive technique; however, its research is still in its early stages. To complement a non-invasive fouling detection technique, the application of ultrasounds has gained much attention from the industry for in-situ fouling removal. Much research has been conducted to advance the knowledge on the potential uses of ultrasonics across different fouling applications, primarily in reverse osmosis membranes and heat exchangers. However, the optimisation of in-situ ultrasonic fouling removal has not yet been investigated and is also in its infancy. This thesis elaborates on the fundamentals of High Power Ultrasonic Transducers (HPUT) used for generating acoustic cavitation bubbles for achieving ultrasonic cleaning. This knowledge is used in the development of a Finite Element (FE) model which is validated using experimental characterisation of the impedance. The HPUT FE model is used to further understand the design and development of sonotrode attachments for future improvements of the ultrasonic cleaning technique. The FE model is expanded for the prediction of cavitation generation to determine cleaning patterns and is validated in laboratory conditions. By utilising controlled fouling generation capabilities, fouling detection using UGW is investigated and an FE model is used to further characterise variables that can quantify the detection of fouling accumulation with potential applications of monitoring fouling removal. The FE method for fouling removal predictions is used to optimise a HPUT configuration for achieving long-distance fouling removal coverage on a 6.2 meter long, 6 inch schedule 40 carbon steel pipe. The confirmed 4-HPUT configuration is developed for laboratory validation and demonstrates wave propagation up to 3 meters from a single HPUT location