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的一个众所周知的问题，根据周围环境条件的不同，可能会出现在各种不同的结构上。清除这种污垢可能非常昂贵，并导致了许多尝试以经济有效的方式减轻、监控和清除污垢积累。由于缓解技术不能保证建筑物100%清除污垢，另一种方法是检测和监测污垢堆积，以帮助执行除垢程序。目前的检测方法，如清管器，也可能需要在生产过程中暂停才能进行监测。近年来，超声导波(UGW)在污垢检测中的应用被认为是一种很有前途的非侵入性技术，但其研究还处于起步阶段。作为一种非侵入性污垢检测技术的补充，超声波在现场除垢方面的应用受到了业界的极大关注。人们已经进行了大量研究，以促进人们对超声波在不同污染应用中的潜在用途的了解，主要是在反渗透膜和热交换器中。然而，现场超声除垢的优化还没有被研究，而且还处于起步阶段。本文阐述了高功率超声换能器(HPUT)产生声空化气泡以实现超声清洗的基本原理。这一知识被用于开发有限元(FE)模型，该模型通过阻抗的实验特性进行了验证。HPUT有限元模型被用来进一步了解超声波电极附件的设计和开发，以便将来改进超声波清洗技术。扩展了有限元模型以预测汽蚀的产生，以确定清洗模式，并在实验室条件下进行了验证。通过利用可控的污垢生成能力，研究了UGW的污垢检测，并使用有限元模型进一步表征了可以量化污垢累积检测的变量，以及监测污垢清除的潜在应用。污垢清除预测的有限元方法被用于优化HPUT配置，以实现6.2米长、6英寸Schedule 40碳素钢管道的长距离污垢清除覆盖。已确认的4-HPUT配置是为实验室验证而开发的，并演示了从单个HPUT位置传播长达3米的波

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