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Title: Ultrasonic technique for chemical process control
Author: Wang, Chuangnan
ISNI:       0000 0004 5357 0621
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2014
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Ultrasound has found application in chemical processing control using both low power, high frequency monitoring techniques and high power, low frequency process enhancement approaches. In many cases, standard ultrasonic systems are retrofitted to a process and while these produce efficiency improvements, the design of bespoke systems may offer more potential. In particular, this Thesis has considered two techniques used in the biomedical field; harmonic imaging and high intensity focused ultrasound (HIFU) and has translated these into ultrasonic transducers for use in an industrial process control system. Traditional ultrasound monitoring techniques are based on operation in the linear domain and are used to monitor chemical processes by measurement of material acoustic velocity, attenuation or based on spectral analysis. Both active and passive methods have been reported for application in this industrial sector. One issue is the presence of multiple reflections in the received ultrasonic signal which can mask the signals of interest from the load medium. This Thesis has considered a new ultrasonic monitoring approach using a combination of both linear and nonlinear spectral components. This was applied to high-throughput products and a dual frequency transducer designed and fabricated to acquire the ultrasonic backscattered signals in both the fundamental and second harmonic frequency regimes. The additional information provided by the harmonic device enabled discrimination between shampoo and conditioner products with the same density, but different molecular weights. HIFU transducer array designs are then considered for high power, low frequency chemical process enhancement applications. Typical applications of high power ultrasound use single or multiple discrete transducers to insonify a process. These are effective, but inflexible in the delivery of the ultrasonic field. The application of a HIFU array would provide control of the high power focal region in the load medium, which offer advantages to industry. Two transducer array approaches have been considered in this Thesis based on piezoelectric composite configurations. Three HIFU arrays based on the 1-3 piezocomposite have been fabricated to operate between 200-400kHz and fully characterised to evaluate their high power performance. A second transducer configuration was based on a novel 2-2 piezocomposite with a 2 layer stacked configuration. Simulation of this transducer design illustrated its potential for high power applications, although a number of fabrication issues resulted in the manufactured array not operating at full capacity. Importantly, the transducer configurations developed in this Thesis are shown to induce cavitation through the standard aluminium foil test.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available