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(2009)Conference PaperThe non-intrusive measurement of the condition of blades within a gas turbine would be a significant aid in the maintenance and continued operation of these engines. Online condition monitoring of the blade health by non-contact measurement methods is the ambition of most techniques. The current dominant method uses proximity probes to measure blade arrival time for subsequent monitoring. It has recently been proposed however, that measurement of the turbine casing vibration response could provide a means of blade condition monitoring, and even give the prospect of providing an estimation of the blade modal parameters. The casing vibration is believed to be excited pre-dominantly by (i) the moving pressure waveform around each blade throughout its motion and (ii) the moments applied by the stationary stator blades. Any changes to the pressure profile around the rotating blades, due to their vibration, will in turn affect these two dominant excitation forces, such that there will be some correlation between the casing response and blade vibrations. Previous work has introduced an analytical model of a gas turbine casing, and simulated pressure signal, associated with the rotating blades. The effect of individual rotor blade vibrations has been developed in order to understand the complex relationship between these excitation forces. A simplified turbine test rig has been constructed. Various aspects of the previous analytical modelling are presented, and then investigated and verified using results from the experimental program with this simplified test rig.
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(2008)Conference PaperA model to describe the low frequency dynamic and acoustic responses of a submarine hull subject to an eccentric harmonic propeller shaft excitation is presented. The submarine is modelled as a fluid-loaded, ring stiffened cylindri-cal shell with internal bulkheads and conical end caps. The stiffeners are introduced using a smeared approach. A harmonic axial force is introduced by the propeller and is transmitted to the hull through the shaft. It results in excita-tion of the accordion modes only if the force is symmetrically distributed to the structure. Otherwise the excitation can be modelled as the sum of a distributed load and a moment applied to the edge of the hull. This leads to excitation of the higher order circumferential modes that can result in high noise signature. Structural and acoustic responses are presented in terms of deformation shapes and directivity patterns for the radiated sound pressure. Results for the case of purely axisymmetric excitation and the case in which an eccentricity is introduced are compared.
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(2001)Journal ArticleThe March 2001 issue of MARENSA’s newsletter, Seaspace, carried the following report: ‘It is understood that HMAS Brisbane and HMAS Anzac competed recently in a sharp sprint over a three-mile course. Anzac had hoped that a quick engagement of gas turbine power would get them first to the finish line, but Brisbane’s 35-year-old boilers and steam turbines responded promptly to full throttle and the old girl showed she still had an unequalled turn of speed. It has been reported that she reached 32 knots on one minute from a standing start.’ Having no experience with the acceleration of naval vessels, reaching 32 knots in one minute from a standing start sounded very quick to me. With interest aroused, I pulled out my copy of Lackenby’s (1952) paper and did the following calculations to check whether the claim was reasonable:
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(1998)Journal ArticleA recent publication says that the primary spelling of the word for the depth of water required to float a ship is draught, with draft as the secondary spelling. A survey of thirty practising naval architects was made to check the claim, and found that a large majority of Australian-educated naval architects spell it draft. The overall results are interesting and are given here.
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(1998)Journal ArticleThe two types of marine hydrometer commonly used by naval architects and surveyors measure two distinct, but related, properties. The properties have different units and are used for different purposes. Some users may not be aware of the two types of hydrometer, the properties measured, or the errors which can significantly affect the end result. The relationships between the measured properties are discussed, together with the specific applications of the two types of hydrometer. The conversion of measurements made on one type of hydrometer to the other type is given, with examples of the conversions. Application of the principles presented here will prevent confusion and ensure the use, rather than abuse, of the two types of marine hydrometer.
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(2001)Journal ArticleThe influence of fore-and-aft asymmetry of a ship is known to be ignored in the classic thin-ship theory for resistance. In the current work, a more sophisticated approach is utilized in which the sinkage and trim are accounted for within the framework of the same theory. It is shown that the enhanced computer program correctly predicts that vessels with the centre of buoyancy forward of midships suffer a greater sinkage. In addition, the trim is relatively more by the bow. Finally, it is demonstrated that the inclusion of the effects of sinkage and trim in the analysis results in a slightly increased resistance for vessels with the centre of buoyancy forward of midships, in keeping with the experimental evidence.
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(2009)Conference PaperThe non-intrusive measurement of blade condition within a gas turbine would be a significant aid in the maintenance and continued operation of these engines. Online condition monitoring of the blade health by non-contact measurement methods is obviously the ambition of most techniques, with a number of methods proposed, investigated and employed for such measurement. The current dominant method uses proximity probes to measure blade arrival time for subsequent processing. It has been recently proposed however, that measurement of the turbine casing vibration response could provide a means of blade condition monitoring. The casing vibration is believed to be excited pre-dominantly by (i) the moving pressure waveform around each blade throughout its motion and (ii) the moments applied by the stationary stator blades. Any changes to the pressure profile around the rotating blades, due to their vibration, will therefore in turn affect these excitation forces. Previous work has introduced an analytical model of a gas turbine casing, and simulated pressure signal associated with the rotating blades. The model has been extended in this paper to more closely represent a commercial gas turbine with experimental verification being presented for various aspects of the analytical modelling procedure.
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(2007)Conference PaperThis paper presents the hypothesis that learning occurs during a design activity carried out within a multidisciplinary team more effectively than in a design activity carried out by a mono-disciplinary team. The “Learning in Design” framework is demonstrated within the existing literature [1], and extended through a model of “Collective Learning in Design” [2]. Indications are that “Collective learning” is more effective compared to Individual Learning due to specific learning mechanisms inherent in Collective Learning [3]. An experimental analysis of “multidisciplinary team design” composed of an industrial designer and a mechanical engineer was conducted using protocol analysis [4]. The research focuses on this form of team typology due to the increase in industry demands for improved innovation and more rapid product design cycle times [5,6]. This phenomenon comes from the traditional link between these two disciplines and the trend for industrial design organisations to incorporate greater technological functions. In the first step the authors discuss the distinctive elements of the two professional roles, their academic educations, typical domain knowledge, product development methods, areas of expertise within the design process, as well as thinking styles [5, 7, 8, 9, 10]. Then, the authors show the characteristic elements of Collective Learning, and present those linked with the professional role of team members [2,3]. The authors argue that these elements within the Collective Learning model may have a strong influence on the future design education strategies for designers and engineers.
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(2002)Conference PaperThe recent history of the Naval Architecture program at The University of New South Wales is described in this paper. The challenges faced by the University are presented and the way that the academics have successfully met this challenge are detailed. Specific aspects of the Naval Architecture program and how they affect graduates are covered.
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(2003)Conference PaperConcurrent Engineering (CE) attempts to process as many product development tasks in parallel as possible while at the same time maximising the use of downstream life-cycle knowledge at early stages of the design process. An effective implementation of this strategy can reduce the duration of design projects, save development costs, and provide better quality products. The successful management and execution of CE projects within such a highly distributed, knowledge intensive environment requires an appropriate selection of Knowledge Based Engineering (KBE) software as well as Computer Aided Engineering (CAE) tools for product and process modelling and analysis, and includes tools for such functions as data management, decision-making and communications between stakeholders. Because such tools and technology play a significant role in the successful implementation of CE, an important challenge to modern industry is the ability to quickly and accurately assess and acquire the most appropriate software tools to support product development. A framework that utilises the Analytic Hierarchy Process (AHP) technique and incorporates the unique requirements of the CE product development domain is proposed.