This thesis describes the work undertaken by the author in collaboration with Wyman-Gordon Forgings, USA, to assist in the development of a cooling system,based on air assisted atomised water sprays primarily for the quenching of aerospace components from high temperatures. The mechanical properties of forgings used in aircraft engines depend on the rate of cooling from the heat treatment solution temperature. It is well known that water quenching produces high cooling rate. Although, the severity of the quench can sometimes produce unacceptable distortion and high residual stresses in the component. For this reason water quenching is only used when a high cooling rate is definitely needed and it is often replaced by a less severe oil quench. However, over the last 10 years the trend to reduce manufacturing costs has led to the forging of parts that are closer to the net shape. In these cases even oil quenching can lead to residual stresses being developed that result in difficulties during the final machining of the engine component. Forced air cooling has been adopted in problem cases where the part is thin enough to attain the desired cooling rate. In many instances, however, the component is of intermediate size or varying in cross section and fan cooling cannot provide the cooling rate which is needed to obtain the desired mechanical properties, whilst oil quenching produces an unacceptable level of residual stresses. The use of air assisted atomised water sprays can provide heat transfer coefficients whose values lie between those for air cooling and oil quenching. Another advantage is that control of the air pressure enables the spray nozzle to operate with a much wider range of water flow rates so that the cooling rate can be readily controlled over the range. This study describes the investigation of the heat transfer characteristics of air assisted atomised water sprays to quench aeroengine components from temperatures of approximately 850°C. New data were obtained at high temperatures for air assisted atomised water sprays operating over a wide range of water mass fluxes, (8.01>w 0 >0kg/m2 .s). In practice the geometry of a component can be complex in shape. Therefore an investigation was also carried out into the application of spray cooling on recessed surfaces. It was found that the surface recess contributes significantly to the reduction in the rate of heat transfer at low and high water mass fluxes, but had little effect at intermediate flow rates. Pulsed sprays were investigated and proposed as a means of controlling heat transfer coefficients for both plane and recessed surfaces. The use of a pulsed spray makes it possible to control the amount of water impacting on a surface per second. It was found that "water off periods of 5 and 10 seconds resulted in a reduction in heat transfer coefficients at low temperatures and also reduced considerably the differences in cooling previously observed between plane and recessed surfaces. A finite element code was used to predict the residual stresses produced in a forged component for a range of spray parameters, and spray arrangements. The data were compared with cooling rates and stress patterns produced by both air and oil quenching. It was found that spray cooling resulted in cooling rates which met the mechanical property specification and provided residual stresses lower than those obtained during oil quenching. Furthermore, simulations of residual stress formation using two different spray arrangements in a typical forging indicated that spray non uniformities can substantially disturb the resultant residual stress patterns which could result in less predictable distortions during final machining. The study of spray cooling presented here suggests that the use of air assisted atomised water sprays has considerable potential and could provide the required cooling rate for individual forgings.

Made available in DSpace on 2016-12-08T17:19:26Z (GMT). No. of bitstreams: 1 Franciele Cunico.pdf: 3433679 bytes, checksum: d1b2f4bdf3c2cb1319aec0d878accf90 (MD5) Previous issue date: 2015-08-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The search for different alternatives for using solid waste contributes to effective sustainable development of industries and the generation of new consumer goods. Under this scenario this paper proposes an alternative to the use of exhaust dust generated in the in the green sand molding and demolding process in the foundry industry, bringing alternative uses for this by-product in more noble applications such as ceramic coating. The ceramic industry has assumed the role of consumer-products generated by industries, especially the existence of some similarity between the composition of by-products and raw materials used in the industry. This study aimed to show the effect of exhaust dust addition in a ceramic matrix for development of ceramic coatings. A preliminary study was performed which determined the parameters for use in a Design of Experiments model. The raw materials used were characterized by Scanning Electron Microscopy, X-ray diffraction, X-Ray Fluorescence, grain size, pycnometry density, Loss Fire, Differential Scanning Calorimetry and thermal gravimetric analysis. In addition, the variables used in the statistical model and its respective upper and lower limits have been defined in the preliminary study too. In order to obtain better efficiency of the data, a factorial project with 3³ Statistic software for the analysis of the results was performed. Three factors have been selected for the project, and for each factor three levels were chosen, with residue content (0%, 20% and 40%), compacting pressure (10MPa, 30MPa and 50MPa) and sintering temperature (1000°C, 1100°C and 1200°C ). Cylindrical specimens were made to determine the technological and mechanical properties and rectangular specimens for the three-point bending test. In order to achieve reliability of the experimental data using the average values, a replica of the experiment was carried out. The results confirmed the feasibility of using the residue in the ceramic body and it show effectively in the interaction between the variables and the importance of controlling the fire temperature, the amount of waste used, and the compaction pressure. / A busca por alternativas para o uso de resíduos sólidos contribui para o efetivo desenvolvimento sustentável das indústrias e a geração de novos bens de consumo. Dentro deste cenário este trabalho propõe uma alternativa para uso do pó de exaustão gerado no processo de moldagem e desmoldagem em areia a verde na indústria de fundição, trazendo alternativas de uso deste subproduto em aplicações mais nobres como o revestimento cerâmico. A indústria cerâmica já assumiu o papel de consumidor de subprodutos gerados pelas indústrias, principalmente pela existência de alguma similaridade entre a composição dos subprodutos e das matérias-primas empregada no setor. Este estudo procurou mostrar o efeito da adição deste pó de exaustão em uma matriz cerâmica para desenvolvimento de revestimentos cerâmicos. Foi realizado um estudo preliminar que determinou parâmetros para a utilização em um modelo de Planejamento de Experimentos. As matérias-primas empregadas foram caracterizadas por Microscopia Eletrônica de Varredura, Difratometria de Raios X, Fluorescência de Raios X, Granulometria, Densidade picnométrica, Perda ao Fogo, Análise Térmica Diferencial e Termogravimétrica. As variáveis utilizadas no modelo estatístico e seus respectivos limites inferiores e superiores, foram definidos no estudo preliminar. Para obter uma melhor eficiência dos dados obtidos foi realizado o projeto fatorial 33 com software Statistic, para a análise dos resultados. Foram selecionados três fatores para o projeto, e para cada fator três níveis, sendo teor de resíduo (0%, 20% e 40%), pressão de compactação (10MPa, 30MPa e 50MPa) e temperatura de sinterização (1000ºC, 1100ºC e 1200ºC). Foram confeccionados corpos de prova cilíndricos para determinar as propriedades tecnológicas e retangulares para ensaio mecânico de resistência a flexão em três pontos. Para atender com confiabilidade os dados experimentais com o uso dos valores médios, foi realizado uma réplica do experimento. Os resultados confirmaram a viabilidade do uso do resíduo na formulação da massa cerâmica e mostraram efetivamente a interação entre as variáveis e a importância do controle da temperatura de queima, a quantidade de resíduo utilizada e a pressão de compactação.

The Nigeria economy is wholly dependent on revenue from oil. However, bitumen has been discovered in the country since 1903 and has remained untapped over the years. The need for the country to complement oil exploration with the huge bitumen deposit cannot be overemphasized. This will help to improve the country's gross domestic product (GDP) and revenue available to government. Bitumen is classifled as heavy crude with API (American petroleum Institute) number ranging between 50 and 110 and occurs in Nigeria, Canada, Saudi Arabia, Venezuela etc from which petroleum products could be derived. This dissertation looked at the Canadian experience by comparing the oil and tar sand deposit found in Canada with particular reference to Athabasca (Grosmont, Wabiskaw McMurray and Nsiku) with that in Nigeria with a view of transferring process technology from Canada to Nigeria. The Nigeria and Athabasca tar sands occur in the same type of environment. These are the deltaic, fluvial marine deposit in an incised valley with similar reservoir, chemical and physical properties. However, the Nigeria tar sand is more asphaltenic and also contains more resin and as such will yield more product volume during hydro cracking albeit more acidic. The differences in the components (viscosity, resin and asphaltenes contents, sulphur and heavy metal contents) of the tar sands is within the limit of technology adaptation. Any of the technologies used in Athabasca, Canada is adaptable to Nigeria according to the findings of this research. The techno-economics of some of the process technologies are. x-rayed using the PTAC (petroleum technology alliance Canada) technology recovery model in order to obtain their unit cost for Nigeria bitumen. The unit cost of processed bitumen adopting steam assisted gravity drainage (SAGD), in situ combustion (ISC) and cyclic steam stimulation (CSS) process technology is 40.59, 25.00 and 44.14 Canadian dollars respectively. The unit cost in Canada using the same process technology is 57.27, 25.00 and 61.33 Canadian dollars respectively. The unit cost in Nigeria is substantively lesser than in Canada. A trade off is thereafter done using life cycle costing so as to select the best process technology for the Nigeria oil/tar sands. The net present value/internal rate of return is found to be B$3,062/36.35% for steam assisted gravity drainage, B$I,570124.51 % for cyclic steam stimulation and B$3,503/39.64% for in situ combustion. Though in situ combustion returned the highest net present value and internal rate of return, it proved not to be the best option for Nigeria due to environmental concern and response time to production. The best viable option for the Nigeria tar sand was then deemed to be steam assisted gravity drainage. An integrated oil strategy coupled with cogeneration using MSAR was also seen to considerably amplify the benefits accruable from bitumen exploration; therefore, an investment in bitumen exploration in Nigeria is a wise economic decision. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2010.

The Nigeria economy is wholly dependent on revenue from oil. However, bitumen has been discovered in the country since 1903 and has remained untapped over the years. The need for the country to complement oil exploration with the huge bitumen deposit cannot be overemphasized. This will help to improve the country's gross domestic product (GDP) and revenue available to government. Bitumen is classifled as heavy crude with API (American petroleum Institute) number ranging between 50 and 110 and occurs in Nigeria, Canada, Saudi Arabia, Venezuela etc from which petroleum products could be derived. This dissertation looked at the Canadian experience by comparing the oil and tar sand deposit found in Canada with particular reference to Athabasca (Grosmont, Wabiskaw McMurray and Nsiku) with that in Nigeria with a view of transferring process technology from Canada to Nigeria. The Nigeria and Athabasca tar sands occur in the same type of environment. These are the deltaic, fluvial marine deposit in an incised valley with similar reservoir, chemical and physical properties. However, the Nigeria tar sand is more asphaltenic and also contains more resin and as such will yield more product volume during hydro cracking albeit more acidic. The differences in the components (viscosity, resin and asphaltenes contents, sulphur and heavy metal contents) of the tar sands is within the limit of technology adaptation. Any of the technologies used in Athabasca, Canada is adaptable to Nigeria according to the findings of this research. The techno-economics of some of the process technologies are. x-rayed using the PTAC (petroleum technology alliance Canada) technology recovery model in order to obtain their unit cost for Nigeria bitumen. The unit cost of processed bitumen adopting steam assisted gravity drainage (SAGD), in situ combustion (ISC) and cyclic steam stimulation (CSS) process technology is 40.59, 25.00 and 44.14 Canadian dollars respectively. The unit cost in Canada using the same process technology is 57.27, 25.00 and 61.33 Canadian dollars respectively. The unit cost in Nigeria is substantively lesser than in Canada. A trade off is thereafter done using life cycle costing so as to select the best process technology for the Nigeria oil/tar sands. The net present value/internal rate of return is found to be B$3,062/36.35% for steam assisted gravity drainage, B$I,570124.51 % for cyclic steam stimulation and B$3,503/39.64% for in situ combustion. Though in situ combustion returned the highest net present value and internal rate of return, it proved not to be the best option for Nigeria due to environmental concern and response time to production. The best viable option for the Nigeria tar sand was then deemed to be steam assisted gravity drainage. An integrated oil strategy coupled with cogeneration using MSAR was also seen to considerably amplify the benefits accruable from bitumen exploration; therefore, an investment in bitumen exploration in Nigeria is a wise economic decision. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2010.