The positive column of the oxygen and argon-oxygen direct current glow discharge was investigated using a fluid plasma model at pressures around hundreds of pascals and discharge currents from ten to forty miliampers. The model describes the infinitely long positive column in cylindrical discharge tube. It is based on the continuity equation for particle concentration with the collisional right hand side. The model utilises the drift-diffusion approximation of particle flux and the mean-electron-energy approximation for the description of the electron interaction. The radial profile of particle concentration and interaction with the glass wall of the discharge tube is taken into account. The model predicts the electric field and the particle concentration in the positive column. The simulation results were compared with the measured intensity of electric field strength in the oxygen and argon-oxygen mixture. The impact of discharge conditions, like the pressure and gas composition, on the properties of the positive column was investigated. The model confirmed that the strength of longitudinal electric field at medium pressures is about 40 V/cm in oxygen, molecular gas, and it is about 3 V/cm in argon, noble gas.

[pt] O sequestro de dióxido de carbono (CO2) em campos de petróleo já desenvolvidos é considerado uma das opções para mitigar o CO2 antropogênico expelido na atmosfera. O CO2 tem sido utilizado como fluido de injeção em operações de recuperação avançada de petróleo com CO2 (CO2-EOR). Como parte deste processo, o CO2 reage com o óleo que expande seu volume, reduz sua viscosidade e a tensão interfacial CO2/óleo, tornando mais fácil sua recuperação. Enquanto, quantidades significativas de CO2 ficam retidas no reservatório. O objetivo desses projetos é maximizar a produção de óleo, minimizando a injeção de CO2. No entanto, em projetos de sequestro para maximizar a produção de óleo com a maior quantidade de armazenamento de CO2, o gás injetado requer ser maximizado. O objetivo desta pesquisa é entender melhor o potencial tanto para a recuperação avançada de óleo e armazenamento de CO2, por meio da simulação da CO2-EOR. Para atingi-lo propõe-se os seguintes objetivos específicos: (1) caracterização dos fluidos, modelagem do comportamento de fases dos fluidos usando a equação de estado (EOS) para aplicação confiável na simulação composicional; (2) investigar diferentes processos EOR, injeção contínua de gás (CGI) e injeção alternada de água e gás (WAG); e, (3) otimização do desempenho do processo CO2-EOR e a avaliação da capacidade de armazenamento de CO2 durante a produção de óleo. Os seguintes parâmetros foram considerados no estudo da otimização: i) miscibilidade; ii) a injeção cíclica; iii) a taxa de injeção e produção; iv) segregação gravitacional; v) tipo, número e locação dos poços de injeção e produção; e, vi) razão de WAG e tamanhos dos slugs. São necessárias um grande número de simulações para alcançar uma compreensão abrangente e avaliar as diferentes estratégias de injeção e tempo de injeção, em otimização de recuperação de óleo e capacidade de armazenamento de CO2. / [en] Sequestration of carbon dioxide (CO2) into already developed oil fields is considered as one of the option for mitigating anthropogenic CO2 discharge into the atmosphere. In Carbon dioxide Enhance Oil Recovery (CO2-EOR) operations the CO2 has been used as the injection fluid. As part of this process, the CO2 reacts with the oil that increases its volume, reduces its viscosity and interfacial tension CO2/oil, making easier oil recovery. While, significant quantities of CO2 remain sequestered in the reservoir. The goal of such projects is maximizing the oil production and minimizing the CO2 injection. However, in sequestration projects, for maximum oil production with the highest amount of CO2 storage, the injected CO2 requires to be maximized. The goal of this research is to better understand the potential for both enhanced oil recovery and storage of CO2, through the CO2-EOR simulation. To achieve it propose the following specific objectives: (1) the characterization fluids, modeling of fluid phase behavior using equation of state (EOS) for reliable application on the compositional simulation; (2) investigate different EOR processes, continuous gas injection (CGI) and water alternating gas (WAG) injection; and, (3) optimization the CO2-EOR process performance and evaluation of the CO2 storage capacity during oil production. The following parameters were considered in the optimization study: i) miscibility; ii) cyclic injection; iii) injection and production rate; iv) gravity override; v) type, number and location of injection and production wells; and, vi) WAG ratios and WAG slug sizes. A number of simulations are required to achieve comprehensive understanding and evaluate the different injection strategies and injection timing, on optimization of oil recovery and CO2 storage capacity.

Das thermische Verhalten von Werkzeugmaschinen verursacht geometrische Abweichungen an Werkstücken. In vielen Forschungsarbeiten wurden wertvolle Beiträge zu deren Verbesserung veröffentlicht. Dabei kommt die Finite-Elemente (FE)- Simulation zum Einsatz. Für diese ist unter anderem der Wärmeübergangskoeffizient als Randparameter notwendig. Insbesondere für Hohlräume, beispielsweise unter der Maschinenverkleidung, gibt es keine Methode diesen schnell zu berechnen. Die vorliegende Arbeit liefert umfangreiche Untersuchungen zu den thermischen Vorgängen in Hohlräumen und deren Auswirkungen auf die thermischen Verlagerungen an Werkzeugmaschinen. Dafür erarbeitet diese Arbeit eine Methode, um Metamodelle für die schnelle Berechnung des Wärmeübergangskoeffizienten in Hohlräumen zu erstellen. Mögliche Hohlraumkonfigurationen werden dafür kategorisiert und für messtechnische Untersuchungen ein Versuchsstand konzipiert. Der Einfluss des Mikroklimas auf die thermischen Verlagerungen wird analysiert. Dabei wird der Einfluss von Konvektion und Strahlung, der Maschinenverkleidung und des Öffnens der Arbeitsraumtüre untersucht. In dieser Arbeit werden zwei Metamodelle erstellt, für einen Hohlraum mit einer Seitenwand als Wärmequelle und für einen Hohlraum mit mittig platzierter Wärmequelle. Die Anwendung der Metamodelle wird mit der thermischen FE-Simulation einer Werkzeugmaschine erläutert und eine Hilfestellung für die Übertragung auf weitere Werkzeugmaschinen gegeben. / The thermal behavior of machine tools causes most of the geometric errors on workpieces. In recent years, many authors published valuable contributions to the analysis, correction and compensation of the thermal behavior of machine tools. One way is the finite element simulation, where the heat transfer coefficient is needed as an input parameter. In particular, for enclosures, for example under the machine housing, there is no method to calculate this coefficient quickly. As state of the art the heat transfer coefficient is received from a computation-intensive fluid simulation of the enclosure. The present work provides investigations of enclosures, the microclimate in enclosures, its effect on the thermal errors of machine tools and finally a method to develop metamodels for the fast calculation of the heat transfer coefficient in enclosures and to use them in the finite element simulation. Possible enclosure configurations are categorized and a test stand is designed for metrological investigations. In basic investigations the thermal processes in different enclosures are analyzed. The influence of the microclimate on thermal errors of machine tools is analyzed in experiments. The influence of convection and radiation, the machine housing and the opening of the working room door are examined. In this work two metamodels are developed. One for an enclosure with a side wall as a heat source and one for an enclosure with a centrally placed heat source. The application of the metamodels is explained in the thermal finite element simulation of a machine tool.