The need was identified to develop an analytical performance prediction code for subsonic multistage axial compressors that can be included in network analysis software. It was found that performance calculations based on an elementary one-dimensional meanline prediction method could achieve remarkable accuracy, provided that sound models are used for the losses, deviation and the onset of rotating stall. Consequently, this study focuses on gaining more expertise on the modelling of losses in such compressors through investigating the mechanisms responsible, the methods of predicting them, their implementation and possible usage. Internal losses are seen as mechanisms that increase the entropy of the working fluid through the compressor and it was found that, at a fundamental level, all internal losses are a direct result of viscous shearing that occurs wherever there are velocity gradients. Usually the methodology employed to predict the magnitudes of these mechanisms uses theoretically separable loss components, ignoring the mechanisms with negligible velocity gradients. For this study these components were presented as: Blade profile losses, endwall losses including tip leakage and secondary losses, part span shroud losses, other losses, losses due to high subsonic Mach numbers and incidence loss. A preliminary performance prediction code, with the capability of interchanging of the different loss models, is presented. Verification was done by comparing the results with those predicted by a commercial software package and the loss models were evaluated according to their ease of implementation and deviation from the predictions of the commercial package. Conclusions were made about the sensitivity of performance prediction to using the different loss models. Furthermore, the combination of loss models that include the most parameters and gave the best comparison to the commercial software predictions was selected in the code to perform parametric studies of the loss parameters on stage efficiency. This was done to illustrate the ability of the code for performing such studies to be used as an aid in understanding compressor design and performance or for basic optimization problems. It can therefore be recommended that the preliminary code can be implemented in an engineering tool or network analysis software. This may however require further verification, with a broader spectrum of test cases, for increased confidence as well as further study regarding aspects like multi-stage annulus blockage and deviation / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.

<p>One of the grand challenges faced by industry is the accurate prediction of unsteady aerodynamics events, including frequency lock-in and forced response. These aeromechanical incidents occurring in airplane engines and gas turbines can cause high-amplitude blade vibration and potential failure of the engine or turbine. During the last decades, the development of computational fluid dynamics has allowed the design and optimization of complex components while reducing the need for expensive engine testing. However, the validation of frequency lock-in and forced response numerical results with experimental data is very incomplete. Despite tremendous advances in computational capabilities, industry is still looking to validate design tools and guidelines to avoid these potentially costly aeroelastic events early in the design process. </p><p>The research efforts presented in this dissertation investigate the aeroelastic phenomena of frequency lock-in and forced response in turbomachinery. First, frequency lock-in is predicted for two structures, namely a two-dimensional cylinder and a single three-dimensional airfoil, and the results are compared to experimental data so that the methods can be extended to more complex structures. For these two simpler structures, a frequency domain harmonic balance code is used to estimate the natural shedding frequency and the corresponding lock-in region. Both the shedding frequencies and the lock-in regions obtained by an enforced motion method agree with experimental data from previous literature and wind tunnel tests. Moreover, the aerodynamic model of the vibrating cylinder is coupled with the structural equations of motion to form a fluid-structure interaction model and to compute the limit-cycle oscillation amplitude of the cylinder. The extent of the lock-in region matches the experimental data very well, yet the peak amplitude is underestimated in the numerical model. We demonstrate that the inclusion of the cylinder second degree of freedom has a significant impact on the cylinder first degree of freedom amplitude. Moreover, it is observed that two harmonics need to be kept in the equations of motion for accurate prediction of the unsteady forces on the cylinder. </p><p>The second important topic covered is a comprehensive forced response analysis conducted on a multi-stage axial compressor and compared with the initial data of the largest forced response experimental data set ever obtained in the field. Both a frequency domain and a time domain codes are used. The steady-state and time-averaged aerodynamic performance results compare well with experimental data, although losses are underestimated due to the lack of secondary flow paths and fillets in the model. The use of mixing planes in the steady simulations underpredicts the wakes by neglecting the important interactions between rows. Therefore, for similar cases with significant flow separation, the use of a decoupled method for forced response predictions cannot yield accurate results. A full multi-row transient analysis must be conducted for accurate prediction of the wakes and surface unsteady pressures. Finally, for the first time, predicted mistuned blade amplitudes are compared to mistuned experimental data. The downstream stator is found to be necessary for the accurate prediction of the modal forces and vibration amplitudes. The mistuned rotor is shown to be extremely sensitive to perturbations in blade frequency mistuning, aerodynamic asymmetry, and excitation traveling wave content. Since this dissertation presents the initial results of a five-year research program, more research will be conducted on this compressor to draw guidelines that can be used by aeromechanical engineers to safely avoid forced response events in the design of jet engines and gas turbines.</p> / Dissertation

The need was identified to develop an analytical performance prediction code for subsonic multistage axial compressors that can be included in network analysis software. It was found that performance calculations based on an elementary one-dimensional meanline prediction method could achieve remarkable accuracy, provided that sound models are used for the losses, deviation and the onset of rotating stall. Consequently, this study focuses on gaining more expertise on the modelling of losses in such compressors through investigating the mechanisms responsible, the methods of predicting them, their implementation and possible usage. Internal losses are seen as mechanisms that increase the entropy of the working fluid through the compressor and it was found that, at a fundamental level, all internal losses are a direct result of viscous shearing that occurs wherever there are velocity gradients. Usually the methodology employed to predict the magnitudes of these mechanisms uses theoretically separable loss components, ignoring the mechanisms with negligible velocity gradients. For this study these components were presented as: Blade profile losses, endwall losses including tip leakage and secondary losses, part span shroud losses, other losses, losses due to high subsonic Mach numbers and incidence loss. A preliminary performance prediction code, with the capability of interchanging of the different loss models, is presented. Verification was done by comparing the results with those predicted by a commercial software package and the loss models were evaluated according to their ease of implementation and deviation from the predictions of the commercial package. Conclusions were made about the sensitivity of performance prediction to using the different loss models. Furthermore, the combination of loss models that include the most parameters and gave the best comparison to the commercial software predictions was selected in the code to perform parametric studies of the loss parameters on stage efficiency. This was done to illustrate the ability of the code for performing such studies to be used as an aid in understanding compressor design and performance or for basic optimization problems. It can therefore be recommended that the preliminary code can be implemented in an engineering tool or network analysis software. This may however require further verification, with a broader spectrum of test cases, for increased confidence as well as further study regarding aspects like multi-stage annulus blockage and deviation / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.

South Africa experienced a severe shortfall in electricity supply during 2008. Eskom, the national electricity supplier, implemented several strategies to alleviate the situation. The Power Conservation Programme set the mining sector a mandatory target to reduce its annual power consumption by 10%. The quickest way to achieve these savings is by optimising the largest power consumers on the mines. Compressed air is one of these, constituting approximately 40% of total electricity consumption on platinum mines. Several methods to reduce power consumption on compressed air systems were investigated. The investigation revealed that centrifugal air compressors on the mines are typically manually operated at a fixed delivery output. Attempts to reduce electricity consumption by reducing air demand will therefore not necessarily lead to savings. A control system that will enable the compressor to automatically match the supply with system demand is required. An optimised control strategy was then developed and implemented on three compressed air systems. Measurements demonstrated savings between 13% and 49%. With the Eskom tariffs proposed for 2010, this implies a total saving of R 46 million per year for these three case studies. This will achieve, and may even exceed, the mandatory reduction in electricity consumption of the mines. These results demonstrate that one of the quickest ways to reduce energy consumption on South African mines is by implementing optimised compressor controls. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2010

South Africa experienced a severe shortfall in electricity supply during 2008. Eskom, the national electricity supplier, implemented several strategies to alleviate the situation. The Power Conservation Programme set the mining sector a mandatory target to reduce its annual power consumption by 10%. The quickest way to achieve these savings is by optimising the largest power consumers on the mines. Compressed air is one of these, constituting approximately 40% of total electricity consumption on platinum mines. Several methods to reduce power consumption on compressed air systems were investigated. The investigation revealed that centrifugal air compressors on the mines are typically manually operated at a fixed delivery output. Attempts to reduce electricity consumption by reducing air demand will therefore not necessarily lead to savings. A control system that will enable the compressor to automatically match the supply with system demand is required. An optimised control strategy was then developed and implemented on three compressed air systems. Measurements demonstrated savings between 13% and 49%. With the Eskom tariffs proposed for 2010, this implies a total saving of R 46 million per year for these three case studies. This will achieve, and may even exceed, the mandatory reduction in electricity consumption of the mines. These results demonstrate that one of the quickest ways to reduce energy consumption on South African mines is by implementing optimised compressor controls. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2010

O crescimento do potencial energético a partir da biomassa estimula o desenvolvimento e a criação de novas tecnologias neste setor. Neste trabalho realizou-se uma ampla pesquisa da produção, compressão e acondicionamento do biogás. Constatou-se durante essa pesquisa a necessidade da busca por alternativas que possibilitem a utilização eficiente deste biocombustível. Analisou-se a possibilidade da fabricação de um compressor alternativo para biogás que possa ser aplicado em pequenas unidades de produção por meio da modelagem das partes componentes. Primeiro efetuou-se a escolha do material considerando-se as características adequadas para construção do sistema de compressão. Depois disto dimensionou-se a camisa de compressão e a sua modelagem tridimensional com software Inventor 2010 (versão Student), além de válvulas e matrizes para fabricação. Complementarmente foi simulado o funcionamento do compressor (gráfico do deslocamento, velocidade e força com o software FluidSim da Festo Didatic). Por último executou-se o projeto eletropneumático, energização e lista de dispositivos necessários para montagem do compressor. Observou-se que essa tecnologia pode ser aplicada em pequenas plantas de produção de biogás. A comparação com outros sistemas de compressão revelou vantagens como a não haver contaminantes na compressão e acionamento, além da compressão poder se dar em ambiente separado do seu acionamento. / The growth of the energy potential from the biomass stimulates development and creation of new technologies in this sector. In this work is carried out extensive research in production, compression and biogas bottling. The need to search for alternatives has been evidenced during the research to make possible the efficient use of biofuel. After it analyzed the possibility of manufacturing of an alternative compressor for biogas which can be applied in small production units through the modeling of the contracting parties. At first it was effected the material choice considering the characteristics for the construction of the compression system. After this, was dimensioned a compression jacket, valves and matrices with the Student software Inventor 2010. Moreover the functioning of the compressor was simulated (its graphical of the displacement, speed and force with a FluidSim software from Festo Didatic). Finally was made a pneumatic project and was executed a list of necessary devices for the compressor assembly. It was observed to that this technology can be applied in small plants of production of biogas. The comparison with other systems of compression demonstrates that tis compressor haven’t contaminants, beyond the compression to be able to give itself in separate environment of its drive.

Submitted by Diogo Barreiros (diogo.barreiros@ufba.br) on 2017-02-06T16:36:13Z No. of bitstreams: 1 Alexandre_Araripe.pdf: 1792868 bytes, checksum: 1adaa02d41a8ac826a6a455f5299d8ed (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2017-02-07T11:00:19Z (GMT) No. of bitstreams: 1 Alexandre_Araripe.pdf: 1792868 bytes, checksum: 1adaa02d41a8ac826a6a455f5299d8ed (MD5) / Made available in DSpace on 2017-02-07T11:00:19Z (GMT). No. of bitstreams: 1 Alexandre_Araripe.pdf: 1792868 bytes, checksum: 1adaa02d41a8ac826a6a455f5299d8ed (MD5) / A necessidade de garantir a disponibilidade do fornecimento de energia na malha elétrica no Brasil nos períodos de seca dos reservatórios das hidrelétricas para evitar apagões como o ocorrido em meados de 2001 promoveu a disseminação de formas alternativas de geração de energia, entre elas as unidades termelétricas, com a implantação de vários parques geradores no território nacional. Devido à crescente disponibilidade de gás natural no país houve uma maior tendência a instalação de usinas termelétricas que utiliza turbinas movidas a gás natural. Durante o ciclo de operação da turbina a gás, partículas de fumaça, sal, poeira e óleo aderem à superfície dos aerofólios do compressor alterando a rugosidade e forma dos mesmos. Esse processo é chamado de fouling (incrustantes) e produz uma queda de desempenho total da turbina ao longo to tempo. O desempenho inicíal de geração é restaurado pela lavagem periódica do compressor da turbina a gás. A interrupção da operação da turbina para a lavagem implica em interrupção da produção e é realizada periodicamente. Entretanto, as condições ambientais podem ifluir na formação do fouling resultando em uma equação de degradação que varia no tempo. Este trabalho visou obter equações que representem a degradação da eficiência energética da turbina devido ao fouling de forma a prever o melhor momento para parada e lavagem do compressor. A análise de algumas variáveis operacionais que relacionam potência energética produzida versus vazão de gás natural na turbina termelétrica sugerem uma tendência linear decrescente o que foi verificado experimentalmente utilizando-se séries temporais obtidas na operação das turbinas termelétricas escolhidas como campo de pesquisa. Também foi observada uma forte correlação entre a potência energética produzida e a temperatura do ar atmosférico. As séries de dados foram condicionadas quanto à outliers, lacunas e ruídos de alta frequência e corrigidas dos efeitos sazonais da temperaura ambiente. Valores de previsão para períodos de operação foram então calculados para as turbinas de teste. Os resultados conduzem à conclusão de que as turbinas estudadas poderiam ter seus ciclos de operação estendidos, o que resultaria em maior produção de energia e menor custo com lavagens. Além disso, conclui-se que as turbinas possuem eficiências diferentes conduzindo a ciclos de operações diferentes. Finalmente, foi calculada a energia total gerada considerando os novos ciclos previstos, obtendo-se ganhos de até 5% no ano.

O crescimento do potencial energético a partir da biomassa estimula o desenvolvimento e a criação de novas tecnologias neste setor. Neste trabalho realizou-se uma ampla pesquisa da produção, compressão e acondicionamento do biogás. Constatou-se durante essa pesquisa a necessidade da busca por alternativas que possibilitem a utilização eficiente deste biocombustível. Analisou-se a possibilidade da fabricação de um compressor alternativo para biogás que possa ser aplicado em pequenas unidades de produção por meio da modelagem das partes componentes. Primeiro efetuou-se a escolha do material considerando-se as características adequadas para construção do sistema de compressão. Depois disto dimensionou-se a camisa de compressão e a sua modelagem tridimensional com software Inventor 2010 (versão Student), além de válvulas e matrizes para fabricação. Complementarmente foi simulado o funcionamento do compressor (gráfico do deslocamento, velocidade e força com o software FluidSim da Festo Didatic). Por último executou-se o projeto eletropneumático, energização e lista de dispositivos necessários para montagem do compressor. Observou-se que essa tecnologia pode ser aplicada em pequenas plantas de produção de biogás. A comparação com outros sistemas de compressão revelou vantagens como a não haver contaminantes na compressão e acionamento, além da compressão poder se dar em ambiente separado do seu acionamento. / The growth of the energy potential from the biomass stimulates development and creation of new technologies in this sector. In this work is carried out extensive research in production, compression and biogas bottling. The need to search for alternatives has been evidenced during the research to make possible the efficient use of biofuel. After it analyzed the possibility of manufacturing of an alternative compressor for biogas which can be applied in small production units through the modeling of the contracting parties. At first it was effected the material choice considering the characteristics for the construction of the compression system. After this, was dimensioned a compression jacket, valves and matrices with the Student software Inventor 2010. Moreover the functioning of the compressor was simulated (its graphical of the displacement, speed and force with a FluidSim software from Festo Didatic). Finally was made a pneumatic project and was executed a list of necessary devices for the compressor assembly. It was observed to that this technology can be applied in small plants of production of biogas. The comparison with other systems of compression demonstrates that tis compressor haven’t contaminants, beyond the compression to be able to give itself in separate environment of its drive.

O crescimento do potencial energético a partir da biomassa estimula o desenvolvimento e a criação de novas tecnologias neste setor. Neste trabalho realizou-se uma ampla pesquisa da produção, compressão e acondicionamento do biogás. Constatou-se durante essa pesquisa a necessidade da busca por alternativas que possibilitem a utilização eficiente deste biocombustível. Analisou-se a possibilidade da fabricação de um compressor alternativo para biogás que possa ser aplicado em pequenas unidades de produção por meio da modelagem das partes componentes. Primeiro efetuou-se a escolha do material considerando-se as características adequadas para construção do sistema de compressão. Depois disto dimensionou-se a camisa de compressão e a sua modelagem tridimensional com software Inventor 2010 (versão Student), além de válvulas e matrizes para fabricação. Complementarmente foi simulado o funcionamento do compressor (gráfico do deslocamento, velocidade e força com o software FluidSim da Festo Didatic). Por último executou-se o projeto eletropneumático, energização e lista de dispositivos necessários para montagem do compressor. Observou-se que essa tecnologia pode ser aplicada em pequenas plantas de produção de biogás. A comparação com outros sistemas de compressão revelou vantagens como a não haver contaminantes na compressão e acionamento, além da compressão poder se dar em ambiente separado do seu acionamento. / The growth of the energy potential from the biomass stimulates development and creation of new technologies in this sector. In this work is carried out extensive research in production, compression and biogas bottling. The need to search for alternatives has been evidenced during the research to make possible the efficient use of biofuel. After it analyzed the possibility of manufacturing of an alternative compressor for biogas which can be applied in small production units through the modeling of the contracting parties. At first it was effected the material choice considering the characteristics for the construction of the compression system. After this, was dimensioned a compression jacket, valves and matrices with the Student software Inventor 2010. Moreover the functioning of the compressor was simulated (its graphical of the displacement, speed and force with a FluidSim software from Festo Didatic). Finally was made a pneumatic project and was executed a list of necessary devices for the compressor assembly. It was observed to that this technology can be applied in small plants of production of biogas. The comparison with other systems of compression demonstrates that tis compressor haven’t contaminants, beyond the compression to be able to give itself in separate environment of its drive.

Master of Science / Department of Mechanical and Nuclear Engineering / Kirby S. Chapman / This thesis outlines the development of a centrifugal compressor model for the Turbocharger Component Matching System (TuCMS) software package that can be used to inexpensively analyze turbocharger performance. The TuCMS can also be used to match turbocharger components to integrate and optimize turbocharger-engine performance. The software system is being developed with the intent to reduce the time taken to experimentally match a turbocharger with an engine, a task that is key to engine emission reductions. The TuCMS uses one-dimensional thermo-fluid equations to analyze the compressor side of a turbocharger. For each compressor component, the program calculates the velocities, pressures, temperatures, pressure losses, work consumption, and efficiencies for a specified set of turbocharger geometry, atmospheric conditions, rotational speed, and fluid mass flow rate. The compressor includes established loss models found in the open literature. The TuCMS utilizes a component-based architecture to simplify model enhancements. The TuCMS can be used as a cost effective engineering tool for preliminary turbocharger testing during engine upgrades and modifications. In this thesis, the TuCMS compressor model was used as an analysis tool to further understand the Variable Geometry Turbocharger (VGT) experimental results. The VGT is a unique turbocharger that can change the diffuser vane angle over a wide range of positions. The change in diffuser vane angle results in optimal turbocharger performance at various operating conditions, and potentially increases the operating range. The purpose for the use of the TuCMS compressor model analysis is to identify the change in performance as the diffuser vane angles are adjusted. The TuCMS can ideally be used as a control program for the VGT to adjust the diffuser vane angles as the compressor load changes and insure the compressor is operating at the highest efficiency.