El procesamiento del gas natural para la extracción del etano e hidrocarburos superiores es una actividad de gran impor-tancia dentro del sistema gasífero de un país. El etano constituye la materia prima fundamental de la denominada petroquímica base gas, mientras que propano, butanos, pen-tanos y superiores, se comercializan fundamentalmente como combustibles. En el caso de Argentina, la actividad de proce-samiento forma parte del sistema de transporte y distribución de gas natural, el cual se encuentra regulado para asegurar una adecuada provisión de este insumo a los consumidores industriales y domiciliarios. Por este motivo suelen existir res-tricciones sobre la cantidad de hidrocarburo que puede extraerse del gas disponible. Por otra parte, el negocio de ex-tracción se encuentra sujeto a la incertidumbre inherente a los mercados en lo que respecta a demanda y precios de los productos del procesamiento así como a la variabilidad de los gasoductos en cuanto a calidad y cantidad de gas a proce-sar. Como consecuencia, esta actividad se encuentra sometida a una gran variabilidad a lo largo del año, lo que dic-ta la necesidad de ajustar en forma permanente la operación de los complejos de extracción para optimizar el negocio.Dada la complejidad estructural de las plantas de extracción moder-nas, esta tarea puede verse beneficiada por la disponibilidad de herramientas de asistencia en la toma de decisiones basa-das en modelos matemáticos de optimización. En esta tesis se presenta un modelo matemático para optimizar la operación del complejo de extracción de hidrocarburos instalado en la localidad de Gral. Daniel Cerri próxima a la ciudad de Bahía Blanca. El modelo no-lineal mixto-entero propuesto contempla las múltiples opciones de mezclado disponibles en el complejo así como la posibilidad de operar o pasar a reserva sus cinco plantas de extracción de hidrocarburos. Dichas plantas po-seen diferentes tecnologías de extracción y por lo tanto rendi-mientos distintos en función de sus respectivas variables ope-rativas. Los resultados del modelo se comparan contra datos históricos del proceso para cinco escenarios operativos fre-cuentes a lo largo del año, con el objeto de cuantificar los potenciales beneficios de su aplicación sistemática. Se presen-tan además diversas aplicaciones con el objeto de ilustrar su uso para asistir en la toma de decisiones tanto a escala ope-rativa, como táctica y estratégica. / The processing of the natural gas for the extraction of ethane and heavier hydrocarbons is of fundamental importance within the gas system of a country. Ethane is the basic raw material of the gas based petrochemical industry, while propane, buta-nes, pentanes and heavier compounds are mainly commer-cialized as fuels. In the case of Argentina, the processing ac-tivity is a part of the natural gas transport and distribution system, which is regulated by law in order to ensure an adequate provision for home and industrial use. For this rea-son, constraints on the amount of hydrocarbons that can be extracted from the available gas frequently arise. On the other hand, the extraction business is subject to market inhe-rent uncertainty regarding demands and prices of the pro-ducts, as well as to the variability of the pipelines regarding quality and availability of raw material. As a consequence,this activity faces a high variability along the year, which dictates the necessity of tuning the operation of the extraction complexes almost permanently in order to optimize the busi-ness. Due to the structural complexity of the modern extrac-tion plants, this task could benefit from the availability of deci-sion making support tools based on mathematical optimization models. In this thesis a mathematical model is presented aimed to optimize the operation of the hydrocarbon extraction complex located in Gral. Daniel Cerri close to Bahía Blanca city. The proposed mixed-integer-nonlinear model considers all the available gas mixing options in the process as well as the possibility of turning-on and shutting-down its five hydrocar-bon extraction plants. Such plants possess different technolo-gies and therefore different extraction efficiencies as func-tions of their respective operative variables. Model results are compared against historical process data for five frequent operating scenarios along the year in order to quantify the potential benefits of its systematic application. Several appli-cations are also proposed in order to illustrate its use in decision making at operational, tactical and strategic levels.

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In gas turbine development, the direction has been toward higher turbine inlet temperatures to increase the work output and thermal efficiency. This extreme environment can significantly impact component life. One means of preventing component burnout in the turbine is to effectively use film-cooling whereby coolant is extracted from the compressor and injected through component surfaces. One such surface is the endwall of the first stage nozzle guide vane. This thesis details the design, prediction, and testing of two endwall film-cooling hole patterns provided by leading gas turbine engine companies. In addition a flush, two-dimensional slot was included to simulate leakage flow from the combustor-turbine interface. The slot coolant was found to exit in a non-uniform manner leaving a large, uncooled ring around the vane. Film-cooling holes were effective at distributing coolant throughout much of the passage, but at low blowing rates were unable to provide any benefit to the critical vane-endwall junction both at the leading edge and along the pressure side. At high blowing ratios, the increased momentum of the jets induced separation at the leading edge and in the upstream portion of the passage along the pressure side, while the jets near the passage exit remained attached and penetrated completely to the vane surface. Computational fluid dynamics (CFD) was successful at predicting coolant trajectory, but tended to under-predict thermal spreading and jet separation. Superposition was shown to be inaccurate, over-predicting effectiveness levels and thus component life, because the flow field was altered by the coolant injection. / Master of Science

Ventilation in underground mines is vital to creating a safe working environment. Though there have been numerous improvements in mine ventilation, it is still difficult to ascertain data on the state of the ventilation system following a disaster in which ventilation controls have been potentially damaged. This information is important when making the decision to send rescue personnel into the mine. By utilizing tracer gas techniques, which are powerful techniques for monitoring ventilation systems, especially in remote or inaccessible areas, analysis of the ventilation system immediately following a mine emergency can be more rapidly ascertained. However, the success of this technique is largely dependent on the accuracy of release and sampling methods. Therefore, an analysis of sampling methods is crucial for rapid response and dependable results during emergencies. This research project involves evaluating and comparing four well-accepted sampling techniques currently utilized in the mining industry using sulfur hexafluoride, an industry standard, as the tracer gas. Additionally, Solid Phase Microextraction (SPME) fibers are introduced and evaluated as an alternative sampling means. Current sampling methods include plastic syringes, glass syringes, Tedlar bags, and vacutainers. SPME fibers have been successfully used in a variety of industries from forensics to environmental sampling and are a solvent-less method of sampling analytes. To analyze these sampling methods, samples were taken from a 0.01% standard mixture of SF6 in nitrogen and analyzed using electron capture gas chromatography (GC). The technical and practical issues surrounding each sampling method were also observed and discussed. Furthermore, the use of multiple tracer gases could allow for rapid assessment of the functionality of ventilation controls. This paper describes experimentation related to the determination of a novel mine tracer gas. Multiple tracer gases greatly increase the level of flexibility when conducting ventilation surveys to establish and monitor controls. A second tracer would substantially reduce the time it takes to administer multiple surveys since it is not necessary to wait for the first tracer to flush out of the mine which can take up to a few days. Additionally, it is possible to release different tracers at different points and follow their respective airflow paths, analyzing multiple or complex circuits. This would be impossible to do simultaneously with only one tracer. Three different tracer gases, carbon tetrafluoride, octofluoropropane, and perfluoromethlycyclohexane, were selected and evaluated on various GC columns through utilizing different gas chromatographic protocols. Perfluoromethylcyclohexane was selected as the novel tracer, and a final protocol was established that ensured adequate separation of a mixture of SF6 and perfluoromethylcyclohexane. Since there is limited literature comparing sampling techniques in the mining industry, the findings and conclusions gained from the sampling comparison study provide a benchmark for establishing optimal sampling practices for tracer gas techniques. Additionally, the determination of a novel tracer gas that can be used with and separated from SF6 using the same analytical method increases the practicality and robustness of multiple mine tracer gas techniques. This initial work will contribute to the larger project scope of determining a methodology for the remote characterization of mine ventilation systems through utilizing multiple mine tracer gases and computational fluid dynamics (CFD). This will be completed through several phases including initial laboratory testing of novel tracer gases in a model mine apparatus to develop a methodology for releasing, sampling, and modeling a mine ventilation plan and tracer gas dispersion in CFD and eventually completing field trials to validate and enhance the multiple tracer gas methodology. / Master of Science

Call number: LD2668 .T4 1932 H63

Call number: LD2668 .T4 1934 V41

A modern gas turbine must be designed quicker, be more reliable, produce less emissions than its predecessors and yet the engine manufacturer must still make a profit. In order to sell their engines to the airlines, the manufacturer must show that their engines meet strict safety and reliability requirements. The creation of finite element models used for predicting temperatures and displacements of the engine component's is part of this design cycle. This thesis addresses the use of computational fluid dynamics (CFD) as a tool that can help in the prediction of iiietal temperatures for use with "industrial" problems and the associated requirements of accuracy and time-scales. The definition of 'industrial" accuracy and time-scales in this thesis is the accuracy required to enhance the modelling capability of a thermal engineer in design time-scales. A method is developed for using a commercial CFD code. FLUENT, for predicting flow and heat transfer. The code has been validated against several benchmark test cases and has shown good predictive capability and mesh independence for flow and heat transfer in the cavity between a rotating and stationary disc with and without through-flow. For cavities between co-rotating discs with radial througliflow, the predictions are acceptable, but some sensitivity of the heat transfer results to mesh spacing has been identified. The code has also been validated against some "industrial" test cases where experimental data has been available. The effects of buoyancy in the centrifugal force field are discussed and are related to a buoyancy number. The next part of the thesis develops a method of solving the heat transfer problem by coupling a finite element code, SC03, with FLUENT. The ideas are developed on two simple test cases and the problems of what information is to be passed across the coupling boundary and convergence issues are discussed. The results show that passing heat transfer coefficients and local air temperatures achieves the best convergence. The coupled method is their tested against two 'industrial problems. It is concluded that the method has considerable potential for use in design although some difficulties in applying the method are identified. Although not demonstrated, the method developed is not specific to SC03 or FLUENT and ally heat traiisfer/ CFD codes could be used.

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