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Made available in DSpace on 2014-06-11T19:35:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-10-29Bitstream added on 2014-06-13T20:46:42Z : No. of bitstreams: 1 batista_jc_dr_guara.pdf: 2889755 bytes, checksum: 2777cd1f4225a0232c6281a5ca3d1e00 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho desenvolve um sistema para gerar energia elétrica com caldeira e turbina, para ocupar um nicho de mercado em que os sistemas a vapor existentes não são economicamente viáveis. O sistema utiliza a turbina Tesla que é compatível para essa faixa e não possui pás, podendo operar com vapor saturado fornecido por uma pequena caldeira consumindo lenha. A micro-geração proposta pode levar energia a milhões de brasileiros no campo, onde se dispõe de algum tipo de biomassa. Apesar do baixo custo da turbina Tesla, por ser de simples construção e compacta, e de suas incontáveis possibilidades de aplicação, se desconhece, até então, aplicações comerciais massivas devido ao baixo torque obtido nos protótipos feitos desde 1910 e por essa razão foi modificada. Este trabalho inova ao desenvolver um protótipo da turbina Tesla modificado para fornecer maior torque e ao comparar à turbina Tesla original. Devido à inexistência de equações que descrevem a turbina Tesla, um modelo matemático que permite projetar a turbina Tesla foi desenvolvido e validado por resultados experimentais e de simulação. Testes comparativos com duas turbinas com as mesmas dimensões mostraram que a turbina Tesla modificada apresentou eficiência superior à turbina Tesla original. Desenvolveu-se, também, um protótipo do sistema para micro-geração utilizando a turbina Tesla modificada, caldeira e gerador elétrico. Os custos do sistema e da energia gerada foram comparados com os de outros meios de geração mostrando serem competitivos economicamente para essa faixa de operação. / This work develops a system to generate electric power with boiler and turbine that aims to occupy the niche of the market for which steam systems are not economically viable. The system uses a Tesla turbine, which is compatible to the range of power. Also, it does not have blades, being able to operate with steam delivered by a small boiler fed with wood. The proposed micro-generation system can take energy to millions of Brazilians living in the country, where some type of biomass is available. In despite of the low cost of the Tesla turbine, because it is compact and simple to build, and despite of its uncountable possibilities of applications, massive commercial applications of the technology are not found due to the low torque of the prototypes built since 1910. For this reason, the Tesla turbine was modified. This work is original since it develops a modified Tesla turbine prototype to furnish a higher torque when compared to an original Tesla turbine. Due to the lack of equations that model a Tesla turbine, a mathematical model was developed to allow the design of the Tesla turbine; it was validated by means of experimental and simulating results. The comparative tests with two turbines, with same dimensions, showed that the modified Tesla turbine presents a higher efficiency than the original Tesla turbine. A micro-generation system, using the modified Tesla turbine, boiler and electric generator, was also developed. The costs of the system and of the generated energy were compared with other means of generation and showed to be commercially competitive for that range.

The low pressure (LP) exhaust system presents a promising avenue for improving the performance of large steam turbines. For this reason, LP exhaust systems have attracted the attention of the research community for decades. Nevertheless, we still lack understanding of the flow physics and loss mechanisms in the exhaust system, especially at part-load conditions. It is also unclear how the exhaust system should be designed when its required operating range widens. This thesis provides solutions to these aerodynamic issues through experimental and numerical investigations, and provides tools that could contribute to better designs of LP exhaust systems. Firstly, the Computational Fluid Dynamics (CFD) solver ANSYS CFX was validated against experiments performed on a scaled test rig under representative part-load flow conditions. This validation exposed the weakness of Reynolds-averaged Navier-Stokes (RANS) CFD when there is a highly swirling flow and large separation regions in the exhaust diffuser. To facilitate the numerical studies, a series of tools were also developed. A design suite, ExhaustGen, was used to automate the pre- and post-processing of CFD calculations. The exhaust diffuser was parametrised using "Minimum Energy Curves", which reduce the dimension of parameter space. Further, a suitable stage-hood interface treatment (Multiple Mixing Planes) was chosen to predict the circumferentially non-uniform flow in the exhaust hood at low computational cost. Numerical investigation of the baseline geometry provided insights into the key flow features and loss mechanisms in the exhaust system, over a wide range of operating conditions. In particular, the bearing cone separation was identified as a key source of loss at part-load conditions. The effect of stage-hood interaction on the performance and design of the exhaust system was studied by varying the rotor blade design, which can positively influence system performance. Finally, a global sensitivity study was performed to identify the most influential design parameters of the exhaust hood. These findings allow, for the first time, LP exhaust hood performance maps to be constructed, so that the benefits of choosing a suitable hood geometry and blade design can be revealed. The thesis also offers contribution towards formulating LP exhaust system design guidance for a wide operating range.

Resumo: Este trabalho desenvolve um sistema para gerar energia elétrica com caldeira e turbina, para ocupar um nicho de mercado em que os sistemas a vapor existentes não são economicamente viáveis. O sistema utiliza a turbina Tesla que é compatível para essa faixa e não possui pás, podendo operar com vapor saturado fornecido por uma pequena caldeira consumindo lenha. A micro-geração proposta pode levar energia a milhões de brasileiros no campo, onde se dispõe de algum tipo de biomassa. Apesar do baixo custo da turbina Tesla, por ser de simples construção e compacta, e de suas incontáveis possibilidades de aplicação, se desconhece, até então, aplicações comerciais massivas devido ao baixo torque obtido nos protótipos feitos desde 1910 e por essa razão foi modificada. Este trabalho inova ao desenvolver um protótipo da turbina Tesla modificado para fornecer maior torque e ao comparar à turbina Tesla original. Devido à inexistência de equações que descrevem a turbina Tesla, um modelo matemático que permite projetar a turbina Tesla foi desenvolvido e validado por resultados experimentais e de simulação. Testes comparativos com duas turbinas com as mesmas dimensões mostraram que a turbina Tesla modificada apresentou eficiência superior à turbina Tesla original. Desenvolveu-se, também, um protótipo do sistema para micro-geração utilizando a turbina Tesla modificada, caldeira e gerador elétrico. Os custos do sistema e da energia gerada foram comparados com os de outros meios de geração mostrando serem competitivos economicamente para essa faixa de operação. / Abstract: This work develops a system to generate electric power with boiler and turbine that aims to occupy the niche of the market for which steam systems are not economically viable. The system uses a Tesla turbine, which is compatible to the range of power. Also, it does not have blades, being able to operate with steam delivered by a small boiler fed with wood. The proposed micro-generation system can take energy to millions of Brazilians living in the country, where some type of biomass is available. In despite of the low cost of the Tesla turbine, because it is compact and simple to build, and despite of its uncountable possibilities of applications, massive commercial applications of the technology are not found due to the low torque of the prototypes built since 1910. For this reason, the Tesla turbine was modified. This work is original since it develops a modified Tesla turbine prototype to furnish a higher torque when compared to an original Tesla turbine. Due to the lack of equations that model a Tesla turbine, a mathematical model was developed to allow the design of the Tesla turbine; it was validated by means of experimental and simulating results. The comparative tests with two turbines, with same dimensions, showed that the modified Tesla turbine presents a higher efficiency than the original Tesla turbine. A micro-generation system, using the modified Tesla turbine, boiler and electric generator, was also developed. The costs of the system and of the generated energy were compared with other means of generation and showed to be commercially competitive for that range. / Orientador: João Andrade de Carvalho Junior / Coorientador: Heraldo da Silva Couto / Banca: Luiz Roberto Carrocci / Banca: Teófilo Miguel de Souza / Banca: Paulo César Razuk / Banca: Rogério José da Silva / Doutor

Research to date has highlighted a number of conditions where dropwise condensation may offer heat transfer enhancements over filmwise condensation. Previous studies have shown at pressures above or around atmospheric, dropwise condensation offers significant benefit over filmwise. However, some of this research suggests that as the system pressure is reduced below atmospheric, the benefits of dropwise condensation diminish rapidly, to the extent that, at pressures around 50mbar the benefits of dropwise over filmwise are minimal. This thesis details a series of experiments which were conducted to investigate the heat transfer and pressure drop distributions in tube bundles during both dropwise and filmwise condensation of steam. The primary objective of the work was to determine the design implications associated with switching the mode of condensation of a electricity generating steam turbine condenser from the current filmwise mode, to dropwise. Experimental data were obtained from a new purpose build apparatus containing seventy-five, 150mm long titanium tubes, arranged in an in line configuration of five columns and fifteen rows. Dropwise and filmwise data were recorded from each row at test cell inlet pressures down to 50mbar using both pure steam and steam air mixtures. Filmwise heat transfer data indicated that, under most conditions, heat transfer coefficients were generally in agreement with those obtained by previous workers. Heat transfer data obtained during dropwise condensation suggested that the benefits of dropwise condensation are not significantly diminished at low pressure, and that, unlike filmwise condensation, inundation has little or no effect in a fifteen row bundle. The data also indicated that the pressure drop characteristics and effects of air are, within experimental error, identical during both modes of condensation and in line with models and theories proposed by previous workers.

The master´s thesis concentrates on a project of condensing steam turbine for existing heating plant with back pressure turbine. The master´s thesis subject consists in the thermodynamic calculation of regulating stage and turbine stages. Design documentation is worked up according to the calculated record. From calculated power of turbine is worked a basic project of gearbox and disposal arrangement system.

An experiment was conducted to investigate the aerodynamic losses of two high-pressure steam turbine nozzles (526A, 525B) subjected to a large range of incident angle and exit Mach number. The blades were tested in a 2D transonic windtunnel. The exit Mach number ranged from 0.60 to 1.15 and the incidence was varied from -34o to 35o. Measurements included downstream Pitot probe traverses, upstream total pressure, and endwall static pressures. Flow visualization techniques such as shadowgraph photography and color oil flow visualization were performed to complement the measured data. When the exit Mach number for both nozzles increased from 0.9 to 1.1, the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses observed at subsonic condition (M2<0.9). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on shadowgraphs taken during the experiment, it's believed that the large increase in losses at transonic conditions is due to strong shock/boundary layer interaction that may lead to flow separation on the blade suction surface. From the measured total pressure coefficients, a modified loss model that accounts for higher losses at transonic conditions was developed. The new model matches the data much better than the existing Kacker-Okapuu model for transonic exit conditions. / Master of Science

This thesis presents the results of a linear cascade experiment performed on the mean-line and near-tip sections of a low-reaction steam turbine blade and compares them to CFD of the former. The purpose of these tests was the refinement of a proprietary empirical profile loss model. A review of the literature shows that experimental data on this type of blade is not openly available. The continued efficacy of empirical loss models to low-reaction steam turbine blades requires data from experiments such as the present study. Tests covered a range of incidence from -6 to +4 and exit Mach numbers from 0.4 to 0.6. Extensive static pressure taps on the blades allowed detailed examinations of blade loading. This loading was dissimilar to steam turbine blade loading in the open literature. A traversing five-hole probe measured conditions downstream of the blade row to enable the calculation of a total pressure loss coefficient. The area-averaged total pressure loss coefficient for both profiles was near 0.08 and was not sensitive to incidence or exit Mach number over the ranges tested. / Master of Science

The content of this diploma thesis is proposal of repair, reconstruction of equipment and installation of electrohydraulic regulation of steam turbine. Thesis is given for specific case. At the beginning there is a basic description of repairing turbine. The next part of thesis deals with checking of main turbine parts and recalculation of gland steam. In the following part there is revisional report with repair or exchange suggestions of demaged turbine parts, followed by description of turbine regulation reconstruction. The last part deals with economical evaluation used innovation and recommendations for repairment procedure.

A computational study aimed at improving the understanding of rotating instability in the LP steam turbine last stage working under low flow rate conditions is described in this thesis. A numerical simulation framework has been developed to investigate into the instability flow field. Two LP model turbine stages are studied under various flow rate conditions. By using the 2D simulations as reference and comparing the results to those of the 3D simulations, the basic physical mechanism of rotating instability is analysed. The pressure ratio characteristics across the rotor row tip are found to be crucial to the inception of rotating instability. The captured instability demonstrates a 2D mechanism based on the circumferential variation of unsteady separation flow in the rotor row. The 3D tip clearance flow is found not a necessary cause of the instability onset. Several influential parameters on the instability flow are also investigated by a set of detailed studies on different turbine configurations. The results show that the instability flow pattern and characteristics can be altered by the gap distance between the stator and rotor row, the rotor blading and the stator row stagger angle. Some flow control approaches are proposed based on the observations, which may also serve as design reference. The tip region 3D vortex flow upstream to the rotor row is also captured by the simulations under low flow rate conditions. Its appearance is found to be able to suppress the inception of rotating instability by disrupting the interaction between the rotor separation flow and the incoming flow. Finally, some recommendations for further work are proposed.