Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request

Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-16Bitstream added on 2014-06-13T20:16:15Z : No. of bitstreams: 1 beneduzzi_ah_me_ilha.pdf: 873775 bytes, checksum: 569e9acbb6c8f6e1ac86e5b1913d3b8f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A cada ano que passa a necessidade de desenvolver novas técnicas de prevenção de falhas em equipamentos vem crescendo continuamente, devido à grande necessidade de obtenção de lucros com o menor custo de manutenção possível. Atualmente, turbinas à gás, são equipamentos de extrema importância para industrias de petróleo e gás, devido sua grande capacidade de geração de energia cinética para acionamento de compressores e geradores de energia. Os custos de manutenção, formação de verniz no sistema de óleo e disponibilidade são algumas das preocupações mais importantes que se deve ter com uma turbina a gás. Um bom planejamento de manutenção otimizará os custos e maximizará a disponibilidade destes equipamentos. Os programas de manutenção devem ser eficazes, todas as recomendações do fabricante do equipamento devem ser seguidas, como o número e tipos de inspeção realizadas, peças sobressalentes, e outros fatores importantes que afetam a vida útil dos componentes e o funcionamento do equipamento. Dentre as inspeções realizadas pode-se encontrar a análise de vibração, boroscopia, termografia e a análise de óleo lubrificante. Neste trabalho são apresentadas as técnicas utilizadas na análise preditiva de óleo lubrificantes e um histórico das análises de óleo de um caso real de turbina a gás em que são observados e discutidos o procedimento ideal da realização de coletas das amostras de óleo de turbinas a gás desde o planejamento até o envio aos laboratórios para análise, verificação e diagnóstico / Each passing year the necessity to develop new techniques to prevent equipment failures increases continuously due to the great need of financial gain at the lowest possible maintenance costs. Currently, gas turbines are extremely important equipment for oil and gas industries, because to its great capacity to generate kinetic energy to drive compressors and generators. Maintenance costs, formation of varnish in the oil system and availability are some of the most important concerns that must be taken with a gas turbine. Good planning will optimize maintenance costs and maximize the availability of this equipment. Maintenance programs must be effective, all the equipment manufacturer's recommendations should be followed, as the number and types of inspections performed, spare parts, and other important factors that affect the life of the components and operation of equipment. Among the inspections it can be performed to find the vibration analysis, endoscopy, thermography and analysis of lubricating oil. This work will present the techniques used in predictive analysis of oil lubricants and oil analysis history of a real case of a gas turbine that will be seen and discussed the ideal procedure of carrying out collections of samples of oil from gas turbines planning to send to laboratories for analysis, verification and diagnosis

abstract: Efficient performance of gas turbines depends, among several parameters, on the mainstream gas entry temperature. At the same time, transport of this high temperature gas into the rotor-stator cavities of turbine stages affects the durability of rotor disks. This transport is usually countered by installing seals on the rotor and stator disk rims and by pressurizing the cavities by injecting air (purge gas) bled from the compressor discharge. The configuration of the rim seals influences the magnitude of main gas ingestion as well as the interaction of the purge gas with the main gas. The latter has aerodynamic and hub endwall heat transfer implications in the main gas path. In the present work, experiments were performed on model single-stage and 1.5-stage axial-flow turbines. The turbines featured vanes, blades, and rim seals on both the rotor and stator disks. Three different rim seal geometries, viz., axially overlapping radial clearance rim seals for the single-stage turbine cavity and the 1.5-stage turbine aft cavity, and a rim seal with angular clearance for the single-stage turbine cavity were studied. In the single-stage turbine, an inner seal radially inboard in the cavity was also provided; this effectively divided the disk cavity into a rim cavity and an inner cavity. For the aft rotor-stator cavity of the 1.5-stage turbine, a labyrinth seal was provided radially inboard, again creating a rim cavity and an inner cavity. Measurement results of time-average main gas ingestion into the cavities using tracer gas (CO2), and ensemble-averaged trajectories of the purge gas flowing out through the rim seal gap into the main gas path using particle image velocimetry are presented. For both turbines, significant ingestion occurred only in the rim cavity. The inner cavity was almost completely sealed by the inner seal, at all purge gas flow rates for the single-stage turbine and at the higher purge gas flow rates for 1.5-stage turbine. Purge gas egress trajectory was found to depend on main gas and purge gas flow rates, the rim seal configuration, and the azimuthal location of the trajectory mapping plane with respect to the vanes. / Dissertation/Thesis / M.S. Mechanical Engineering 2010

No description available.

This research programme has studied the possibilities and difficulties of using 50 kg microsatellites to perform remote imaging of the Earth. The design constraints of these missions are quite different to those encountered in larger, conventional spacecraft. While the main attractions of microsatellites are low cost and fast response times, they present the following key limitations: Payload mass under 5 kg, Continuous payload power under 5 Watts, peak power up to 15 Watts, Narrow communications bandwidths (9.6 / 38.4 kbps), Attitude control to within 5°, No moving mechanics. The most significant factor is the limited attitude stability. Without sub-degree attitude control, conventional scanning imaging systems cannot preserve scene geometry, and are therefore poorly suited to current microsatellite capabilities. The foremost conclusion of this thesis is that electronic cameras, which capture entire scenes in a single operation, must be used to overcome the effects of the satellite's motion. The potential applications of electronic cameras, including microsatellite remote sensing, have erupted with the recent availability of high sensitivity field-array CCD (charge-coupled device) image sensors. The research programme has established suitable techniques and architectures necessary for CCD sensors, cameras and entire imaging systems to fulfil scientific/commercial remote sensing despite the difficult conditions on microsatellites. The author has refined these theories by designing, building and exploiting in-orbit five generations of electronic cameras. The major objective of meteorological scale imaging was conclusively demonstrated by the Earth imaging camera flown on the UoSAT-5 spacecraft in 1991. Improved cameras have since been carried by the KITSAT-1 (1992) and PoSAT-1 (1993) microsatellites. PoSAT-1 also flies a medium resolution camera (200 metres) which (despite complete success) has highlighted certain limitations of microsatellites for high resolution remote sensing. A reworked, and extensively modularised, design has been developed for the four camera systems deployed on the FASat-Alfa mission (1995). Based on the success of these missions, this thesis presents many recommendations for the design of microsatellite imaging systems. The novelty of this research programme has been the principle of designing practical camera systems to fit on an existing, highly restrictive, satellite platform, rather than conceiving a fictitious small satellite to support a high performance scanning imager. This pragmatic approach has resulted in the first incontestable demonstrations of the feasibility of remote sensing of the Earth from inexpensive microsatellites.

Made available in DSpace on 2014-06-11T19:35:41Z (GMT). No. of bitstreams: 0 Previous issue date: 1998Bitstream added on 2014-06-13T18:07:37Z : No. of bitstreams: 1 antunes_js_dr_guara.pdf: 1990112 bytes, checksum: fec1ab4e133a1f22bdc262ef1e750b70 (MD5) / Este trabalho apresenta as fases do desenvolvimento de um programa computacional elaborado com a finalidade de selecionar, dimensionar e especificar sistemas de cogeração com turbinas a gás, buscando satisfazer as demandas térmicas do processo (operação em paridade térmica). As configurações utilizadas são: turbina a gás associada à caldeira de recuperação, turbina a gás associada ao sistema de refrigeração por absorção e turbina a gás associada à caldeira de recuperação e turbina a vapor (ciclo combinado). O programa computacional seleciona sistemas de turbinas a gás comercialmente disponíveis no mercado (condições ISO) e faz correções de performance para as condições ambientais do local da instalação. O código computacional efetua análises energéticas, exergéticas, energoeconômicas e exergoeconômicas, sempre buscando escolher os melhores sistemas de turbinas a gás dentre os previamente selecionados. / This work presents the steps to structure a computer program for selecting, dimension and specifying gas turbine cogeneration systems, satifying the termical condition of the process. The following configurations are used: gas turbine associated to the heat recovering, gas turbine associated to the absorption cooling system, gas turbine associated to the recovering and vapor turbine (combined cycles). The computational program selects gas turbine systems commercially available and performs corrections due to the local environment of the gas turbine system. The computational code develops: energetic, exergetic, economic and exergoeconomic analysis, always searching to choose the best gas turbine systems.

This thesis discusses several methods that can be used to analyse gas turbines, based on an optimal estimation algorithm called the Kalman Filter. These techniques overcome the difficulties of more 'traditional' analysis methods, which can give misleading results because they do not explicitly consider the possibility of measurement error. An enhancement to the Kalman Filter (the 'Concentrator') is presented, which overcomes the Kalman Filter's tendency to 'smear' the effects of genuine changes in a small number of component changes and/or sensor biasses over the whole set of changes and biasses being considered. To complement this, methods of optimising some of the statistical inputs to the Kalman Filter in order to improve the ability of the 'Concentrator' to carry out the required analysis are discussed. These are based on analytical methods developed to determine the sensitivity of the Kalman Filter to its inputs. Techniques are also presented for determining the gas-path measurements in a gas turbine that are needed to enable the required analysis of component changes and/or sensor biasses to be performed, including determination of both possible measurement redundancy and the ability of a set of measurements to successfully differentiate between all the component changes and sensor biasses being sought. A recursive algorithm for time series analysis (the Smoothing/Trending Algorithm) is also presented. This produces, for each point in a time series, best estimates of the underlying levels and trends (rates of change of level) of the process generating the observations. A method of combining the 'Concentrator' and the Smoothing/Trending Algorithm is also presented, which reduces the effects of sensor noise on the analysis of component changes and sensor biasses from time series data. Many types of prime movers and process plant could be effectively analysed using the methods described in this thesis.

This Thesis reports the design, build and test of two sets of blading for the Cranfield University low speed research compressor. The first of these was a datum low speed design based on the fourth stage of the DERA high speed research compressor C 147. The emphasis of this datum design was on the high-to-low speed transformation process and the evaluation of such a process through comparing detailed flow measurements from both compressors. Area traverse measurements in both the stationary and rotating frame of reference were taken at Cranfield along with overall performance, blade surface static pressure and flow visualisation measurements. These compare favourably with traverse and performance measurements taken on C147 before commencement of the PhD work. They show that despite the compromises made during the transformation process, due to both geometric and aerodynamic considerations, both the primary and secondary flow features can be successfully reproduced in the low speed environment. The aim of the second design was to improve on the performance of the datum blading through the use of advanced '3D' design concepts such as lean and sweep. The blading used nominally the same blade sections as the datum, and parametric studies were conducted into various lean/sweep configurations to try to optimise the blade performance. The final blade geometry also incorporated leading edge recambering towards the fixed endwalls of both the rotor and stator. The '3D' blading demonstrated a 1.5% increase in efficiency (over the datum blading) at design flow rising to around 3% at near stall along with an improvement in stall margin and pressure rise characteristic. The design work was completed using the TRANSCode flow solver for both the blade-to-blade solutions (used in the SI-S2 datum design calculation) and the fully 3D solutions (for the advanced design and post datum design appraisal). The 3D solutions gave a reasonable representation of the mid-span and main 3D flow features but failed to model the corner and tip clearance flow accurately. An interesting feature of the low speed flowfield was the circumferential variation in total pressure observed at exit from all rotors for both designs. This was not present at high speed and represents one of the main differences between the high and low speed flow. Unsteady modelling of mid- height sections from the first stage indicate that part of this variation is due to the potential interaction of the rotor with the downstream stator while the remainder is due to the wake structure from the upstream stator convecting through the rotor passage. Finally, the implications for a high speed design based on the success of the 3D low speed design are considered.

Gas turbine combustor design represents an ambitious task in numerical and experimental analysis. A significant number of competing criteria must be optimised within specified constraints in order to satisfy legislative and performance requirements. Currently, preliminary combustor flow and heat transfer design procedures, which by necessity involve semi-empirical models, are often restricted in their range of application. The objective of this work is the development of a versatile design tool able to model all conceivable gas turbine combustor types. A network approach provides the foundation for a complete flow and heat transfer analysis to meet this goal. The network method divides the combustor into a number of independent interconnected sub-flows. A pressure-correction methodology solves the continuity equation and a pressure-drop/flow-rate relationship. A constrained equilibrium calculation, incorporating mixing and recirculation models, simulates the combustion process. The new procedures are validated against numerical and experimental data within three annular combustors and one reverse flow combustor. A full conjugate heat transfer model is developed to allow the calculation of liner wall temperature characteristics. The effects of conduction, convection and radiation are included in the model. Film cooling and liner heat pick-up effects are included in the convection calculation. Radiation represents the most difficult mode of heat transfer to simulate in the combustion environment. A discrete transfer radiation model is developed and validated for use within the network solver. The effects of soot concentration on radiation is evaluated with the introduction of radial properties profiles. The accuracy of the heat transfer models are evaluated with comparisons to experimental thermal paint temperature data on a reverse flow and annular combustors. The resulting network analysis code represents a powerful design tool for the combustion engineer incoporating a novel and unique strategy.