Mechanical Engineering - Theses
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ItemModelling heat pump grain drying systems( 1990)Drying is a common process in a number of industries. Products such as furs, wools, textiles, clay, timber, grains, fruits, and vegetables, at some stage, require drying. Review of the literature reveals that commercial dryers are highly inefficient due to various factors. One such factor is that commercial dryers are generally not equipped with heat recovery facilities. Heat pumps can provide a very efficient means of recovering both sensible and latent heat, hence energy loss can be substantially reduced. Furthermore, a heat pump always delivers more heat than the work input to the compressor. These two salient features render heat pump drying a premium alternative for efficient use and conservation of energy in drying industries.
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ItemComputer simulation and practical evaluation of heavy vehicle performance and fuel economy( 1986)This thesis develops and presents optimisation methodology for heavy vehicle performance and fuel economy. The nature of research undertaken involves both computer simulation and practical evaluation. It is believed that these research components will enable the formulation of proposals supportive to the implementation of a heavy vehicle fuel conservation programme. The research commences with a review of heavy vehicle travel and fuel usage statistics relative to those of other road users. Heavy vehicles are then categorised according to their configuration and area of operation. This categorisation, which is based on the Australian Bureau of Statistics 1982 motor vehicle survey, serves as the principle criterion for the development of driving cycles representative of heavy vehicle driving patterns in urban and non-urban areas. Traffic data collection methods and various means for the translation of data into a representative speed-time trace (driving cycle) are reviewed and evaluated. Four comprehensive field surveys conducted over selected routes using an instrumented car to follow and record the driving patterns of targetted heavy vehicles are detailed. Synthesis of four driving cycles follows. These cycles provide means for the study of vehicle performance and fuel economy by giving instructions to a driver or computer on how to operate a vehicle over a given distance or period of time. The application of TARCYC, a comprehensive software package, developed to support data acquisition and reduction, and to implement an enhanced microtrip accumulation technique, is described. It is shown that application of this package leads to the development of very realistic driving cycles with a minimal statistical similarity of 94% to the target data. Vehicle proving ground and highway tests are described. The tests allowed the collection of a large data base for a vehicle with varying configurations. A test procedure providing fuel economy information for a baseline vehicle and for a modified configuration is developed and demonstrated. It is also shown that a repeatability band within 1% is achievable. The equipment and instrumentation used and the computer programs developed for data reduction and processing and for the derivation of such vehicle component characteristics as aerodynamic drag and rolling resistance coefficients are described. An account is given of a novel approach which applies a simulation model in conjunction with curve fitting in coastdown analysis. The procedure and format used in archiving the collected data for future research work is also detailed. Modelling of vehicle performance and fuel consumption, using computer programs, commences with a review of HEVSIM, the US Department of Transport model translated to Fortran 77 and adapted by the author for operation on the University of Melbourne VAX/VMS main-frame computer. The simulation capabilities and limitations of this model are assessed and a critical review of 10 other models is also undertaken. Subsequently, the development of TABESAM, a multi -purpose simulation model which incorporates varying levels of complexity and requires only simple input to provide detailed output, is traced. This model can be used for driving cycle analysis, driver training and motivation, vehicle tests, engine mapping and vehicle component optimisation and has been subjected to experimental validation. When compared with transient and steady state test results, the model shows a prediction accuracy in excess of 95%. The model has been adopted by the Society of Automotive Engineers (SAE-A) for deployment in showroom, point of sale decision making contexts and in the Society’s fuel conservation programme. Finally, and as a result of the practical evaluation and computer simulation of heavy vehicle performance and fuel economy, it is concluded that driver training and motivation, vehicle configuration matching to duty cycle and vehicle component optimisation are essential to fuel conservation. It is also maintained that a heavy vehicle fuel conservation programme depends for its success on the involvement and contributions of government bodies, vehicle designers, city and urban planners and owner/operators.
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ItemInduction and exhaust system optimisation for the Scotch-Yoke engine( 1996)A mathematical model for flow and combustion has been modified, including basic revision, and applied for the power output optimisation of valve timing and intake pipe length of the Scotch-Yoke engine which has a sinusoidal. piston motion. Comparison of the predicted engine brake torque and power in agreement with the experimental results for a normal 4 cylinder Subaru boxer engine yields helpful information for the engine design and further experiment. First, the adaptation of the simulation models for spark ignition engines is introduced to enable the further application to engine simulations. Secondly, a 2.2 litre conventional S.I. engine was tested to obtain some basic engine input data and demonstrate its behaviour under the normal range of speed. Then the computer program was modified to enhance the correlation of prediction with the experiment, and the performance at four different intake pipe lengths was predicted. Next the computer program was modified to take into account the special configuration of the Scotch-Yoke engine, and optimisation has been done for the parameters of intake pipe lengths and the valve timing. It was concluded that longer inlet manifold pipes could be employed increasing the engine torque over most of the speed range.
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ItemScheduling of distributed autonomous manufacturing systems( 1995)This thesis addresses the scheduling and control of shop-floor production units that operate in a highly autonomous and distributed environment. The distinct feature of this environment is the heterarchical nature of the control where the scheduling function is quite independently carried out by the units. The units solve only part of the overall problem while resolving conflicts to maintain consistent global schedules. The need for communication and coordination, in such circumstances, introduces many complexities that affects the quality of the schedules produced. These include lapses of open-loop control due to uncertainty of up-to-date status information, asynchronous behaviour, and uncontrollable propagation of conflicts. A behaviour-based approach is introduced to solve these problems. Using this approach, the organisation of the shop-floor is viewed as similar to a colony of ants or an eco-system. The units operate quite independently but continue to adapt their schedules to changes in their environment. While they may not directly negotiate to resolve conflicts, their cooperation is innate or in-built through their local adaptive actions. This individual cooperative action of the units brings about a collective behaviour that produces the desired emergent global schedules. The major focus of this research is in examining the link between the individual and collective behaviours and developing a model that realises the desired scheduling functionality at the shop level. In order to achieve high scheduling performance (both locally and globally) a model of a unit incorporating dynamic problem decomposition, allocation algorithms and adaptation mechanisms is developed. For the latter, a reinforcement learning model is used to adapt the scheduling horizon. In fact, an important contribution if this research is the novel view we take of the problem and the manner of adaptation. In addition, a communication model for simulating the scheduling behaviours is designed using concepts of Holonic and other emerging concepts of manufacturing systems. The model is tested for a number of scheduling problems representing a variety of production situations. Preliminary results indicate an impressive scheduling performance comparable to well-known heuristics. Further examination indicates the types of dynamic behaviour that can be expected of such a model, including the levels of unresolved conflicts, the adaptability in the face of uncertainty, consequence of alternative communication policies and the sensitivities to adaptation. This thesis has also a strong qualitative theme in reviewing and consolidating the concepts underlying the design and operational attributes of autonomous distributed organisations of the shop-floor.