The purpose of this research was to determine if installing a smaller air compressor could reduce the electrical usage of a large semiconductor manufacturing plant. A 200 horsepower Atlas Copco compressor was installed with the existing 500 horsepower Ingersoll-Rand compressors. Testing was conducted during the regular manufacturing process at MEMC Southwest in Sherman, Texas. Analysis of the data found that installing the new compressor could reduce electrical consumption. The study also found there are specific operational setpoints that allow the compressor to operate more efficiently.

Approved for public release; distribution is unlimited / A computational fluid dynamic (CFD) investigation is presented that provides predictions of the aerodynamic impact of uniform and non-uniform coatings applied to the leading edge of a compressor airfoil in a cascade. Using a NACA 65(12)10 airfoil, coating profiles of varying leading edge non-uniformity were added. This non-uniformity is typical of that expected due to fluid being drawn away from the leading edge during the coating process. The CFD code, RVCQ3D, is a steady, quasi-three-dimensional Reynolds Averaged Navier-Stokes (RANS) solver. A k-omega turbulence model was used for the Reynolds' Stress closure. The code predicted that these changes in leading edge shape can lead to alternating pressure gradients in the first few percent of chord that create small separation bubbles and possibly early transition to turbulence. The change in total pressure loss and trailing edge deviation are presented as a function of the coating non-uniformity parameter. Results are presented for six leading edge profiles over a range of incidences and inlet Mach numbers from 0.6 to 0.8. Reynolds number was 600,000 and free-stream turbulence was 6%. A two-dimensional map is provided that shows the allowable degree of coating non-uniformity as a function of incidence and inlet Mach number. / Lieutenant Commander, United States Navy

This research tested to see how audio engineers navigate and use compressors differently with alternative designs. A pre-study in the form of a semi-structured interview with a focus group was held to determine a compressor considered having a “good design” and a compressor considered having a “bad design”. An active test was conducted with audio engineer students to investigate if there is any connection between time it takes for an engineer to navigate a compressor depending on its design. The test also investigated patterns in how audio engineers use compressors differently depending on their design, and what makes it easier to navigate and more satisfactory to use. 6 paired T-test were made between different compressor designs and a video and screen capture was annotated to investigate how audio engineers navigated the compressor. The results showed that 2 out of 6 T-tests gave a significant result, meaning that the time it took to navigate some of the compressors against each other were affected by the design of the compressor interface. Results showed that there are many contributing factor towards why a compressors is easier navigate and more satisfactory to use, but with a slight tendency that “parameter controls”, “visual information” and “aesthetically pleasing” are the most important factors. No findings on how engineers might use compressors differently depending on its design were found. Some additional patterns for audio engineers using compressors were found as well.

Este trabalho tem como objetivo propor e avaliar um novo método para controle antissurto de compressores dinâmicos. É sabido que compressores dinâmicos são sujeitos ao fenômeno de surto, o qual pode danificar gravemente os componentes do compressor e provocar distúrbios de produção. O surto pode surgir a partir da ocorrência de distúrbios (por exemplo, fechamento da válvula de descarga do compressor) os quais, sem ação antissurto, fariam com que o ponto de operação se deslocasse para uma região de baixas vazões delimitada por uma linha conhecida como linha de surto. Portanto, compressores dinâmicos sempre são equipados com mecanismos antissurto: tipicamente uma válvula de reciclo de ação rápida controlada por um controlador PI antissurto. Dado que o surto se desenvolve extremamente rápido, usualmente não se permite que o compressor opere muito próximo da linha de surto. Esse objetivo de controle (manter o compressor afastado da linha de surto) é conflitante com objetivos de eficiência energética, pois os pontos de maior eficiência estão localizados próximos a essa linha. Logo, é desejável operar o compressor utilizando a mínima margem de surto que ainda garanta que a ação antissurto seja efetiva. Este trabalho propõe um método para ativação da ação antissurto no compressor com o objetivo de atingir uma ação mais rápida que o controle PI tradicional. O método proposto se baseia no cálculo offline das aberturas necessárias para a válvula de reciclo para cada possível combinação das posições dos atuadores do sistema, considerando um conjunto discreto pré-definido de valores dentro da faixa de valores de cada atuador. Esse processo gera uma tabela auxiliar para uso online. Os valores da tabela auxiliar são utilizados para gerar valores de referência para um controlador por realimentação, o qual é responsável por garantir que a trajetória do sistema irá do estado inicial no momento da ativação do controle antissurto para o estado estacionário desejado. Diversos cenários de distúrbio são simulados para diferentes controladores por realimentação e comparados com o controle antissurto PI tradicional. Os resultados mostram que a estratégia proposta é um candidato para melhorias na prática atual de controle antissurto, mas um controle por realimentação adequado deve ser selecionado e avaliado também considerando o aspecto de robustez, o qual é brevemente considerado no escopo deste trabalho. / This work aims at proposing and evaluating a novel method for anti-surge control of dynamic compressors. Dynamic compressors are known to suffer from surge, which can severely damage compressor components and disturb production. Surge may arise by the occurrence of disturbances (e.g. compressor discharge valve closure) that would bring its operating point to a region at low flows delimited by the so called surge line. Therefore, dynamic compressors are always equipped with anti-surge mechanisms: typically a fast actuating recycle valve controlled by a PI anti-surge controller. Since surge develops extremely fast, the compressor is usually not allowed to operate too close from the surge line. This control objective (keep the compressor away from the surge line) is conflicting with energy efficiency requirements, since higher efficiency operating points are located close to the surge line. Therefore, it is desirable to operate the compressor using the smallest possible surge margin that still guarantees anti-surge action is effective. This work proposes a method for triggering the compressor anti-surge action, aiming at a faster action than traditional PI control. The proposed anti-surge control method relies on an offline computation of necessary recycle valve openings for each possible combination of the system actuators positions, considering a predefined discrete set of values from the actuators positioning ranges. This generates a look-up table for online use. The values from the look-up table are used to identify the necessary compressor flow set-point for a feedback controller, which is responsible for ensuring that the system trajectory goes from the state upon anti-surge activation to the desired steady state. Several disturbance scenarios are simulated for different feedback controllers and compared to the traditional PI anti-surge controller. Results show that the proposed strategy is a candidate for improvements in current anti-surge control practice but an adequate feedback control strategy must be chosen and evaluated also under the consideration of robustness, which is slightly considered in the scope of this work.

INTRODUÇÃO: O tratamento da fibrose cística (FC) envolve o uso de medicamentos fornecidos através de nebulizadores e seu funcionamento adequado é essencial. OBJETIVOS: Avaliar o desempenho de nebulizadores a jato utilizados por pacientes com FC e comparar dois manômetros para avaliação dos compressores. MÉTODOS: Estudo descritivo, transversal, de avaliação dos nebulizadores usados pelos pacientes com FC da Associação Mineira de Assistência a Mucoviscidose. Os pacientes trouxeram compressores (Proneb Ultra®) e nebulizadores (Pari LC plus®) para avaliação. O desempenho do compressor foi avaliado por medidas de pressão operacional através dos manômetros PARI PG101® (PARI GmbH, Starnberg, Alemanha) e FSA analógico (Famabras, Itaquaquecetuba, Brasil).As variáveis de eficiência do nebulizador foram: O débito de volume nebulizado (DVN), taxa de oferta da medicação (TOR) e volume residual (VR) foram calculados por diferenças de peso de cada nebulizador após 10 minutos de nebulização de solução salina (2,5ml). O diâmetro médio de massa da partícula (DMM) foi calculado através da equação proposta por Standaert et al. A análise estatística incluiu o pacote R (v.2.15) e MINITAB, com alfa=0,05. O coeficiente Kappa foi calculado para avaliar concordância de valores entre os equipamentos, e curva ROC construída para calcular o valor aferido no manômetro FSA com melhor sensibilidade/especificidade, utilizando o manômetro PARI PG101® como referência. A associação entre valores de pressão, DVN, TOR e VR foi calculada pela correlação de Spearman. RESULTADOS: Avaliados 146 sistemas com tempo mediano de uso de 32(12-60) meses±36 meses. Cinquenta e sete (39%) não funcionaram adequadamente, com valores pressóricos inferiores à metade da referência. Os sistemas com funcionamento inadequado comprometeram as variáveis de eficiência dos nebulizadores A concordância entre os diferentes métodos de avaliação de acordo com a classificação; com funcionamento adequado e inadequado através do coeficiente Kappa foi 0,81(IC95%- 0,65-0,97), p<0,001. Na avaliação da sensibilidade e especificidade foi observado o ponto de corte de 23,5 PSI no manômetro FSA mostrou sensibilidade=99% e especificidade=79% (p<0,001). Houve associação significativa entre DVN, VR e pressões aferidas. CONCLUSÕES: Uma proporção significativa dos sistemas de nebulização não funcionou adequadamente. As variáveis de eficiência da nebulização estavam comprometidas indicando que a pressão gerada no compressor é um aspecto crítico na eficiência do tratamento. O método alternativo da avaliação dos compressores se apresentou adequado para ser utilizado nos compressores utilizados no tratamento da FC. / INTRODUCTION: Cystic fibrosis (CF) treatment of involves the use of medications supplied through nebulizers and their proper functioning is essential. OBJECTIVES: To evaluate the performance of jet nebulizers used by CF patients and to compare two pressure gauges Compressors evaluation. METHODS: This was a descriptive, cross - sectional study of the nebulizers used by patients with CF of the Mucoviscidosis Care Association of Minas Gerais. The patients brought compressors (Proneb Ultra®) and nebulizers (Pari LC plus®) for evaluation. The performance of the compressor was evaluated by operating pressure measurements using PARI PG101® manometers (PARI GmbH, Starnberg, Germany) and analog FSA (Famabras, Itaquaquecetuba, Brazil). The variables of efficiency of nebulization under study were: nebulizer delivery volume (NDV), drug output rate (DOR), and residual volume (RV), which were calculated by weighing each nebulizer before nebulization and 10 minutes after nebulization using a saline solution (2.5 mL). The mass median diameter (MMD) was calculated using the equation proposed by Standaert et al. Statistical analysis included the package R (v.2.15) and MINITAB, with alpha = 0.05. The Kappa coefficient was calculated to evaluate agreement of values between the equipment\'s, and ROC curve constructed to calculate the value measured in the FSA manometer with better sensitivity / specificity, using the PARI PG101® manometer as reference. The association between pressure values, NDV, DOR and RV was calculated by the Spearman correlation. RESULTS: We evaluated 146 systems with a median time of use of 32 (12-60) months ± 36 months. Fifty-seven (39%) did not function properly, with pressure values lower than half the reference. The systems with inadequate functioning compromised the efficiency variables of the nebulizers. The agreement between the different evaluation methods according to the classification; with adequate and inadequate functioning through the Kappa coefficient was 0.81 (95% CI -0.65-0.97), p <0.001. In the evaluation of sensitivity and specificity, the cut-off point of 23.5 PSI on the FSA manometer showed sensitivity = 99% and specificity = 79% (p <0.001). There was a significant association between NDV, DOR, RV and measured pressures. CONCLUSIONS: A significant number of the nebulizer systems were ineffective. The variables of nebulization efficiency were compromised, which indicated that the pressure generated by the compressor was a critical aspect for treatment efficiency. The alternative method of compressors evaluation was suitable for use in CF treatment routine.

INTRODUÇÃO: O tratamento da fibrose cística (FC) envolve o uso de medicamentos fornecidos através de nebulizadores e seu funcionamento adequado é essencial. OBJETIVOS: Avaliar o desempenho de nebulizadores a jato utilizados por pacientes com FC e comparar dois manômetros para avaliação dos compressores. MÉTODOS: Estudo descritivo, transversal, de avaliação dos nebulizadores usados pelos pacientes com FC da Associação Mineira de Assistência a Mucoviscidose. Os pacientes trouxeram compressores (Proneb Ultra®) e nebulizadores (Pari LC plus®) para avaliação. O desempenho do compressor foi avaliado por medidas de pressão operacional através dos manômetros PARI PG101® (PARI GmbH, Starnberg, Alemanha) e FSA analógico (Famabras, Itaquaquecetuba, Brasil).As variáveis de eficiência do nebulizador foram: O débito de volume nebulizado (DVN), taxa de oferta da medicação (TOR) e volume residual (VR) foram calculados por diferenças de peso de cada nebulizador após 10 minutos de nebulização de solução salina (2,5ml). O diâmetro médio de massa da partícula (DMM) foi calculado através da equação proposta por Standaert et al. A análise estatística incluiu o pacote R (v.2.15) e MINITAB, com alfa=0,05. O coeficiente Kappa foi calculado para avaliar concordância de valores entre os equipamentos, e curva ROC construída para calcular o valor aferido no manômetro FSA com melhor sensibilidade/especificidade, utilizando o manômetro PARI PG101® como referência. A associação entre valores de pressão, DVN, TOR e VR foi calculada pela correlação de Spearman. RESULTADOS: Avaliados 146 sistemas com tempo mediano de uso de 32(12-60) meses±36 meses. Cinquenta e sete (39%) não funcionaram adequadamente, com valores pressóricos inferiores à metade da referência. Os sistemas com funcionamento inadequado comprometeram as variáveis de eficiência dos nebulizadores A concordância entre os diferentes métodos de avaliação de acordo com a classificação; com funcionamento adequado e inadequado através do coeficiente Kappa foi 0,81(IC95%- 0,65-0,97), p<0,001. Na avaliação da sensibilidade e especificidade foi observado o ponto de corte de 23,5 PSI no manômetro FSA mostrou sensibilidade=99% e especificidade=79% (p<0,001). Houve associação significativa entre DVN, VR e pressões aferidas. CONCLUSÕES: Uma proporção significativa dos sistemas de nebulização não funcionou adequadamente. As variáveis de eficiência da nebulização estavam comprometidas indicando que a pressão gerada no compressor é um aspecto crítico na eficiência do tratamento. O método alternativo da avaliação dos compressores se apresentou adequado para ser utilizado nos compressores utilizados no tratamento da FC. / INTRODUCTION: Cystic fibrosis (CF) treatment of involves the use of medications supplied through nebulizers and their proper functioning is essential. OBJECTIVES: To evaluate the performance of jet nebulizers used by CF patients and to compare two pressure gauges Compressors evaluation. METHODS: This was a descriptive, cross - sectional study of the nebulizers used by patients with CF of the Mucoviscidosis Care Association of Minas Gerais. The patients brought compressors (Proneb Ultra®) and nebulizers (Pari LC plus®) for evaluation. The performance of the compressor was evaluated by operating pressure measurements using PARI PG101® manometers (PARI GmbH, Starnberg, Germany) and analog FSA (Famabras, Itaquaquecetuba, Brazil). The variables of efficiency of nebulization under study were: nebulizer delivery volume (NDV), drug output rate (DOR), and residual volume (RV), which were calculated by weighing each nebulizer before nebulization and 10 minutes after nebulization using a saline solution (2.5 mL). The mass median diameter (MMD) was calculated using the equation proposed by Standaert et al. Statistical analysis included the package R (v.2.15) and MINITAB, with alpha = 0.05. The Kappa coefficient was calculated to evaluate agreement of values between the equipment\'s, and ROC curve constructed to calculate the value measured in the FSA manometer with better sensitivity / specificity, using the PARI PG101® manometer as reference. The association between pressure values, NDV, DOR and RV was calculated by the Spearman correlation. RESULTS: We evaluated 146 systems with a median time of use of 32 (12-60) months ± 36 months. Fifty-seven (39%) did not function properly, with pressure values lower than half the reference. The systems with inadequate functioning compromised the efficiency variables of the nebulizers. The agreement between the different evaluation methods according to the classification; with adequate and inadequate functioning through the Kappa coefficient was 0.81 (95% CI -0.65-0.97), p <0.001. In the evaluation of sensitivity and specificity, the cut-off point of 23.5 PSI on the FSA manometer showed sensitivity = 99% and specificity = 79% (p <0.001). There was a significant association between NDV, DOR, RV and measured pressures. CONCLUSIONS: A significant number of the nebulizer systems were ineffective. The variables of nebulization efficiency were compromised, which indicated that the pressure generated by the compressor was a critical aspect for treatment efficiency. The alternative method of compressors evaluation was suitable for use in CF treatment routine.

近年來微型製冷系統有許多應用。例如，電子器件的冷却是研製更快速、更小型和更可靠的芯片的重要課題, 隨著電子芯片功耗的增加，散熱量不断增長，傳統的被動式散熱方法已經過時，新的主動式散熱方法成爲必須。又例如微型個人冷卻系統可用於救火等各種惡劣環境。与其它製冷方法相比，蒸氣壓縮製冷技術是最有潜力的方法。 / 本文闡述了两种微型蒸氣壓縮製冷系統的研製工作：一是電子冷却系统，一是個人热舒适系统。研究主要包括以下幾個方面： / 1) 微型蒸氣壓縮製冷系統的熱力學分析。對系統在不同工作條件下（包括壓縮機效率、環境溫度等）的性能進行了分析。对換熱器的設計也作了详述。 / 2) 微型蒸氣壓縮製冷系統的熵分析。通過分析發現，壓縮機和系統漏熱造成的熵是產生系統不可逆性的主要因素,因此高效的壓縮機和降低系統漏熱是提高微型蒸氣壓縮製冷系統性能的關鍵所在。 / 3) 實驗系统的詳細介紹。一共做了两套微型蒸氣壓縮製冷系統，一为電子冷卻系統和一为個人冷卻系統。爲了縮小微型蒸氣壓縮製冷系統的尺寸，系統的元件必須小型化。系統的壓縮機是在市場上直接购買的，但是換熱器包括冷板蒸發器、管翅式蒸發器和微通道冷凝器都是特別設計和製造的。實驗裝置建成可以方便的改變工作條件，諸如壓縮機轉速、製冷劑充灌量、毛細管長度、換熱器面積等。 / 4) 對電子冷卻系統和個人冷卻系統分別進行了實驗。對於電子散熱系統來，當發熱管的功率為200瓦時，冷板溫度可以控制在大約60攝氏度。系統的熱力學完善度在0.23到0.31，而壓縮機的效率介乎40%至65%。對個人冷卻系統來，系統製冷量可達321瓦，其性能係數達到4.59。系統的熱力學完善度為0.21 ~ 0.27。 兩种系統的熱力學完善度都與當前家用製冷系统的熱力學完善度相似。相信不久的将来会有不少应用。 / Micro refrigeration systems are being increasingly used nowadays. One example is electronic cooling. With the rapid advancement of chips, traditional passive heat dissipation techniques are becoming obsolete and hence, new active cooling techniques become necessary. The other example is the personal thermal comfort system demanded by people working in the hazardous environment, such as fire fighting. Among various cooling methods, Vapor Compression Refrigeration (VCR) is the most promising method. According literatures, however, few miniature refrigeration systems are available. / This thesis presents two Miniature Vapor Compression Refrigeration (MVCR) systems, one for electronics cooling and the other for personal thermal comfort. In particularly, following aspects are focused: / 1) Thermodynamic analysis. The thermodynamic models of the systems are developed and the performances are studied under various working conditions including compressor efficiencies, ambient temperature and so on. / 2) Entropy analysis. It is found that entropy of the compressor and the heat leakage play crucial roles. High efficient compressor and the heat leakage minimization are very important. / 3) Prototype building. Two prototypes are built: one for electronics cooling and the other for personal thermal comfort. The miniature compressors are purchased from market. The heat exchangers, including the cold pate, tube-fin evaporator and micro channel condenser, are custom designed and made. / 4) Experiment testing. The two prototypes are tested under various working conditions such as compressor speed, refrigerant charge and capillary tube length. For the electronics cooling system, the cold plate temperature could be maintained at about 60 ºC under the 200 W heater power input. The second-law efficiency of the system varies from 0.23 to 0.31; and the compressor efficiency is between 40% ~ 65%. For the personal thermal comfort system, its capacity could reach 321 W with 100 g refrigerant charge, 1200 mm capillary tube length, and the compressor speed of 4503 rpm. The COP is 4.59 and the second-law efficiency is between 0.21 ~ 0.27. The performances of the two systems are comparable to that of the current domestic refrigeration systems. Therefore, it is expected that they will find some practical applications in the near future. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wu, Zhihui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 99-110). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.I / Acknowledgement --- p.IV / List of Tables --- p.VIII / List of Figures --- p.IX / Nomenclature --- p.XII / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Backgound --- p.1 / Chapter 1.2 --- Thesis Outline --- p.5 / Chapter Chapter 2 --- Literature Review --- p.6 / Chapter 2.1 --- History of Refrigeration --- p.6 / Chapter 2.2 --- Availabe Refrigeration Methods --- p.7 / Chapter 2.2.1 --- Heat pipe and vapor chamber --- p.9 / Chapter 2.2.2 --- Thermoelectric cooler --- p.10 / Chapter 2.2.3 --- Stirling refrigerator --- p.10 / Chapter 2.2.4 --- Pulse tube refrigerator --- p.11 / Chapter 2.2.5 --- Absorption refrigerator --- p.12 / Chapter 2.3 --- Vapor Compression Refrigeration System --- p.14 / Chapter 2.3.1 --- Development of the miniature refrigeration system --- p.15 / Chapter 2.3.2 --- Development of the miniature compressors --- p.20 / Chapter 2.3.3 --- Development of the micro heat exchangers --- p.24 / Chapter 2.3.4 --- Applications --- p.28 / Chapter Chapter 3 --- System Analsysis and Components Design --- p.29 / Chapter 3.1 --- A Brief Review of a Typical VCR System --- p.29 / Chapter 3.1.1 --- Refrigerant comparison --- p.33 / Chapter 3.1.2 --- Effect of the compressor efficiency --- p.34 / Chapter 3.1.3 --- Effect of the ambient temperature --- p.35 / Chapter 3.1.4 --- Effect of the evaporator temperature --- p.36 / Chapter 3.2 --- Analysis on Entropy Generation of a MVCR System --- p.37 / Chapter 3.2.1 --- Derivation of coefficient of performance --- p.38 / Chapter 3.2.2 --- Entropy generation calculation for a MVCR system --- p.39 / Chapter 3.3 --- System Design --- p.46 / Chapter 3.3.1 --- System Configuration --- p.46 / Chapter 3.3.2 --- Heat Exchanger Design --- p.47 / Chapter 3.3.2.1 --- Condenser design --- p.48 / Chapter 3.3.2.2 --- Cold plate design --- p.50 / Chapter 3.3.2.3 --- Tube-fin evaporator design --- p.51 / Chapter Chapter 4 --- The MVCR System for Electronics Cooling --- p.55 / Chapter 4.1 --- Experimental Setup --- p.55 / Chapter 4.1.1 --- Components --- p.55 / Chapter 4.1.2 --- Instrumentation --- p.61 / Chapter 4.1.3 --- Testing plans --- p.63 / Chapter 4.1.4 --- Data reduction --- p.64 / Chapter 4.1.5 --- Uncertainty analysis --- p.67 / Chapter 4.2 --- Results and Discussion --- p.68 / Chapter 4.2.1 --- Effect of the compressor speed --- p.68 / Chapter 4.2.2 --- Effect of the refrigerant charge --- p.70 / Chapter 4.2.3 --- Effect of the capillary tube length --- p.71 / Chapter 4.2.4 --- Cold plate temperature comparison --- p.72 / Chapter 4.2.5 --- Location of the Cartridge heater --- p.76 / Chapter 4.2.6 --- System efficiency --- p.78 / Chapter 4.2.7 --- Thermal resistance --- p.81 / Chapter 4.3 --- Summary --- p.83 / Chapter Chapter 5 --- The MVCR System for Personal Cooling --- p.85 / Chapter 5.1 --- Experimental Setup --- p.85 / Chapter 5.2 --- Results and Discussions --- p.87 / Chapter 5.2.1 --- Effect of the compressor speed --- p.87 / Chapter 5.2.2 --- Effect of the refrigerant charge --- p.88 / Chapter 5.2.3 --- Effect of the capillary tube length --- p.89 / Chapter 5.2.4 --- Effect of the evaporator area --- p.90 / Chapter 5.2.5 --- Effect of the evaporator fan speed --- p.91 / Chapter 5.2.6 --- System efficiency --- p.92 / Chapter 5.3 --- Summary --- p.94 / Chapter Chapter 6 --- Conclusions and Future Work --- p.96 / Chapter 6.1 --- Conclusions --- p.96 / Chapter 6.2 --- Future Work --- p.98 / Bibliography --- p.99

The operating range and efficiency of a centrifugal compressor is limited by the development of rotating stall and surge at low mass flow rates. To extend the operating range of a compressor, flow control in the compressor can be used to suppress secondary flow structures that lead to rotating stall. The presented work seeks to use the novel idea of placing passive vortex generators (VG) upstream of the impeller to suppress rotating stall, while also developing new concepts and optimization of microvortex generators (MVG). To accomplish this goal, a new SIMPLE-type algorithm for compressible flows was written in Code_Saturne along with a 2nd-order MUSCL scheme for convective terms and an AUSM+-up scheme for mass flux computation. The new algorithm was successfully validated against several widely-used test cases. The new algorithm was used to model the flow of the NASA CC3, a high-speed centrifugal compressor, from choke to rotating stall with a vaneless and vaned diffuser. The new algorithm predicted the performance of the compressor with a vaneless diffuser very well; satisfactory results were obtained for the compressor with a vaned diffuser. The full compressor with a vaned diffuser was used to model rotating stall. A complex stall cycle between the inlet of the impeller and diffuser was observed and studied. The fundament behavior of MVG, i.e. micro (sub-boundary layer) vortex generator, in a turbulent boundary layer was investigated in a channel flow with RANS and LES. Complementary wind tunnel testing was conducted to validate the computational predictions. The configuration of the MVG was studied to determine an optimal configuration and several conclusions were reached on the design of MVG. Most importantly triangle MVG were found to be the most efficient shape followed by NACA0012 and e423-type MVG, and a MVG angle of 18˚ to 20˚ was found to be optimal. Rectangle MVG were observed to suffer flow separation on the vanes which reduced their performance. The circulation and drag of a MVG was found to have a logarithmic relationship with the device's Reynolds number. These findings were incorporated in a LES study to control separated flow on the e387 airfoil and achieved an improvement in lift-to-drag ratio of 11.27%. Additional recommendations for MVG implementation were given. Combining the work on the NASA CC3 with the work on MVG, vortex generators were implemented near the inlet of the impeller. A detailed optimization study was conducted for the implementation vortex generators in the compressor. It was found vortex generators equal to the boundary layer thickness were the most efficient on controlling the downstream flow. The best configuration was implemented into the full compressor with a vaned diffuser to assess the ability of vortex generators to suppress rotating stall. The vortex generators were found to suppress rotating stall and extend the operating range of the compressor.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / A theoretical study is presented of the fluid mechanics of the inlet vortex (or ground vortex) phenomenon. The vorticity field associated with the vortex is investigated using a secondary flow approach. In this approach the flow is assumed to be composed of an irrotational primary flow and a weak shear flow, with the vortex filaments associated with the latter being regarded as convected by the former. The potential flow field induced by the inlet-ground plane combination is computed using the panel method developed by · Hess, Mack and Stockman. Using the analysis, material lines (which coincide with vortex lines) can be tracked between a far upstream location, where this vorticity can be taken as known, and the engine face location. The deformation of the material lines thus shows directly the generation and amplification of the streamwise component of vorticity, which is responsible for the velocity distortion at the compressor face. Two representative flow configurations are considered, one with headwind only and one with the flow at forty-five degrees to the inlet axis of symmetry. Although the results so far yield only qualitative information, they appear to provide some insight into one mechanism associated with the inlet vortex formation. / by Henri Charles Viguier. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO. / Includes bibliographical references. / by Anthony Henry James Eastland. / M.S.