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A computational study has been performed to investigate the effects of blade row interaction on the performance of radial turbomachines, which was motivated by the need to improve our understanding of the blade row interaction phenomena for further improvement in the performance. High-speed centrifugal compressor stages with three settings of radial gap are configured and simulated using a three-dimensional Navier-Stokes flow method in order to investigate the impact of blade row interaction on stage efficiency. The performance predictions show that the efficiency deteriorates if the gap between blade rows is reduced to intensify blade row interaction, which is in contradiction to the general trend for stage axial compressors, hi the compressors tested, the wake chopping by diffuser vanes, which usually benefits efficiency in axial compressor stages, causes unfavourable wake compression through the diffuser passages to deteriorate the efficiency. Similarly, hydraulic turbine stages with three settings of radial gap are simulated numerically. A new three-dimensional Navier-Stokes flow method based upon the dual-time stepping technique combined with the pseudo-compressibility method has been developed for hydraulic flow simulations. This method is validated extensively with several test cases where analytical and experimental data are available, including a centrifugal pump case with blade row interaction. Some numerical tests are conducted to examine the dependency of the flow solutions on several numerical parameters, which serve to justify the sensitivity of the solutions. Then, the method is applied to performance predictions of the hydraulic turbine stages. The numerical performance predictions for the turbines show that, by reducing the radial gap, the loss generation in the nozzle increases, which has a decisive influence on stage efficiency. The blade surface boundary layer loss and wake flow mixing loss, enhanced with a higher level of flow velocity around blading and the potential flow disturbances, are responsible for the observed trend.

Orientador: Milton Dias Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T04:13:23Z (GMT). No. of bitstreams: 1 Siqueira_CristianoRoque_M.pdf: 6928797 bytes, checksum: ac276f05e511e74f07cdcb3e64193c84 (MD5) Previous issue date: 2012 / Resumo: Neste trabalho procurou-se avaliar o comportamento vibracional de uma bomba vertical centrífuga durante operação em campo, ou seja, nas instalações do cliente, e comparar os dados obtidos em relação ao critério de aceitação utilizado pelo fabricante através de normas vigentes. Para isto, foi necessário conhecer como é realizado o ensaio de desempenho da bomba, quais os pontos de medições determinados pelas normas, para uma melhor análise foram necessários incluir novos pontos em estudo nesta dissertação. Utilizou-se a análise de vibração em tempo, freqüência, deslocamento e velocidade. Os resultados obtidos através dos ensaios foram processados através da técnica de processamento de sinais, que melhor se adapta a análise investigada. Foram ensaiados, analisados e comentados os resultados experimentais deste trabalho. É da maior importância o estudo na formação de um critério de aceitação amplo da análise de vibração aplicado as bombas verticais centrífugas / Abstract: In this study sought to evaluate the vibrational behavior of a vertical centrifugal pump during operation in the field, that is, the customer premises, and compare the data obtained regarding the acceptance criteria used by the manufacturer using standards norms. For this, it was necessary to know how the test is performed pump performance, which points determined by measurement standards norms, for a better analysis was necessary to include new points studied in this dissertation.We used the analysis of vibration time, frequency, displacement and velocity. The results obtained from the tests were processed through the signal processing technique that best fits the analysis investigated. Were tested, analyzed and commented on the results of this experimental work. It is of utmost importance to study the formation of a broad acceptance criterion of vibration analysis applied vertical centrifugal pumps / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

An experimental study of the flow behavior inside the channels of an 8-blade backswept low specific speed impeller at design and off-design conditions is presented. The measurements took place at both the inlet and the outlet of the impeller channel at the mid height of the channel passage. The particle image velocimetry (PIV) technique was used to measure the velocity components in the inlet and outlet frames of the impeller channel. The flow behavior inside the channel, the mean normalized primary and secondary velocity components at six radial locations inside the channels, and turbulence intensity in terms of the variation in the relative velocity components were investigated at the design condition, 75%, 50%, 40%, 30% and 25% of the design flow rate. The results demonstrated a well behaved flow with no evidence of flow separation at the design condition. The fluid flow inside the impeller channel started experiencing a flow separation, when the flow rate is reduced, which propagated throughout the channel passage and caused the channel to stall with a large recirculation zone at severe off-design flow rates.

An experimental study of the flow behavior inside the channels of an 8-blade backswept low specific speed impeller at design and off-design conditions is presented. The measurements took place at both the inlet and the outlet of the impeller channel at the mid height of the channel passage. The particle image velocimetry (PIV) technique was used to measure the velocity components in the inlet and outlet frames of the impeller channel. The flow behavior inside the channel, the mean normalized primary and secondary velocity components at six radial locations inside the channels, and turbulence intensity in terms of the variation in the relative velocity components were investigated at the design condition, 75%, 50%, 40%, 30% and 25% of the design flow rate. The results demonstrated a well behaved flow with no evidence of flow separation at the design condition. The fluid flow inside the impeller channel started experiencing a flow separation, when the flow rate is reduced, which propagated throughout the channel passage and caused the channel to stall with a large recirculation zone at severe off-design flow rates.

Thesis (M.S.)--Ohio State University, 1966. / Includes bibliographical references. Available online via OhioLINK's ETD Center

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The mass transfer and the pressure drop characteristics for countercurrent rotating packed bed (RPB) with a continuous gas phase for the removal of ethylene dichloride (EDC) from water using air stripping have been investigated. The aim of this research was to understand the behaviour of the mass transfer performance and the pressure drop behaviour in a centrifugal environment. The mass transfer results showed that the height of a transfer unit (HTU) in a liquid film limited system can be in the range between 30 to 70mm at moderate centrifugal acceleration between 44 to 280g. Three packings of different packing densities ranging from 870 to 2300 m2/m3 were tested. The HTU values were found to vary with the centrifugal acceleration as HTU a g-0.11 to -0.28. It has been shown that the packing density may not have a notable effect on the separation performance of the bed. The pressure drop results indicated that in RPB the pressure drop is relatively higher than its equivalent packed beds operate at 1g. The usual flooding restrictions were relaxed thus high hydraulic capacities can be achieved per unit size of equipment. At the flooding point, experimental findings indicated that a part of the liquid is not accelerated by the bed. A model to predict the pressure drop was developed. The model was verified against experimental data and good agreement was obtained.

No description available.