Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.462892
Title: A non-intrusive ultrasonic cross correlation flowmeter for liquids
Author: Leach, Kevin Graham
Awarding Body: Bradford University
Current Institution: University of Bradford
Date of Award: 1977
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Abstract:
This thesis presents the results of an investigation into the design parameters of an externally mounted ultrasonic cross correlation flowmeter. A set of operational requirements are presented for the acoustical system and from these requirements a theoretical design is formulated for the ultrasonic transducer. The selection of an operating frequency is shown to depend on the operational requirements and both the transducer design and operating frequency are shown to be interdependent. Construction of the transducer is shown to affect the mode of operation and the governing relationship is presented. Transducers built to the theoretical design are tested in practice and shown to meet the operational requirements. A study of transducer mountings to pipe sections is also presented and in the light of experimental evidence an improved method of transducer mounting is outlined. Efficient methods of coupling the electrical energy into the transducer and the acoustical energy into the pipe section are investigated. Also, two methods of assessing a given transducer's characteristics are explained and their shortcomings highlighted. Further, it is shown that the selection of a high operating frequency overcomes the problems of acoustical cross-talk between the two transmitted ultrasonic beams. The determination of a suitable method of demodulating the received signal is investigated, both theoretically and practically. The theoretical results show that in a closed conduit, amplitude modulation of an ultrasonic beam will predominate. Practical observations confirm this and the expected modulation levels are achieved. The practical results also show that an amplitude demodulated signal is less susceptible to interference by extraneous noise such as that produced by plant vibrations. These results are confirmed for all the flowmeter configurations tested. A closed loop control scheme using a phase locked loop system is developed, whereby the flowmeter will be able to compensate for environmental changes. Three combinations of this system are presented and their poor performance and inability to control the flowmeter, investigated and explained. The analysis used to explain the above is extended to develop a further control scheme using a phase shift network in one channel of the flowmeter. This system is shown to be more stable and controllable than previous systems and is less susceptible to extraneous noise. A closed loop control scheme incorporating a system of this type is presented. Suggestions are made to further investigate the selection of operating frequency, transducer mounting and to determine the most suitable strategy for implementing a phase shift type closed loop control scheme.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis - Bradford University. Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.462892  DOI: Not available
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