A combined cycle is one of the thermal cycles used in thermal power plants. It consists of a combination of a gas and a steam turbine, where the waste heat from the gas turbine is used for steam generation in the heat recovery steam generator. The aim of the diploma thesis was the conceptual design of a combined cycle electricity source and the balance calculation of the cycle. The calculation is based on the thermodynamic properties of the substances and the basic knowledge of the Brayton and Rankin-Clausius cycle. The result is the amount and parameters of air, flue gases, and steam/water in individual places and the technological scheme of the source, in which these parameters are listed.

The current demands for higher performance in gas turbine engines can be reached by raising combustion temperatures to increase thermal efficiency. Hot combustion temperatures create a harsh environment which leads to the consideration of the durability of the combustor and turbine sections. Improvements in durability can be achieved through understanding the interactions between the combustor and turbine. The flow field at a combustor exit shows non-uniformities in pressure, temperature, and velocity in the pitch and radial directions. This inlet profile to the turbine can have a considerable effect on the development of the secondary flows through the vane passage. This thesis presents a computational study of the flow field generated in a non-reacting gas turbine combustor and how that flow field convects through the downstream stator vane. Specifically, the effect that the combustor flow field had on the secondary flow pattern in the turbine was studied. Data from a modern gas turbine engine manufacturer was used to design a realistic, low speed, large scale combustor test section. This thesis presents the results of computational simulations done in parallel with experimental simulations of the combustor flow field. In comparisons of computational predictions with experimental data, reasonable agreement of the mean flow and general trends were found for the case without dilution jets. The computational predictions of the combustor flow with dilution jets indicated that the turbulence models under-predicted jet mixing. The combustor exit profiles showed non-uniformities both radially and circumferentially, which were strongly dependent on dilution and cooling slot injection. The development of the secondary flow field in the turbine was highly dependent on the incoming total pressure profile. For a case with a uniform inlet pressure in the near-wall region no leading edge vortex was formed. The endwall heat transfer was found to also depend strongly on the secondary flow field, and therefore on the incoming pressure profile from the combustor. / Master of Science

Le projet présenté ici consiste en la conception et l’étude de faisabilité d’une microturbopompe de type Rankine destinée à être opérée à haute température. Une étude préliminaire est d’abord effectuée pour déterminer la configuration globale ainsi que les matériaux possibles pour l’isolation thermique du dispositif. Il en découle la nécessité d’utiliser des matériaux isolants pour le rotor et la structure statique. Les matériaux retenus sont le quartz et le Pyrex et la surface de la structure statique doit être réduite tout en s’assurant de la solidité du dispositif. Le domaine d’application retenu est la récupération de la chaleur de gaz d’échappements automobiles pour la génération d’énergie électrique. Dans cette application, l’utilisation de panneaux de microturbines pourrait permettre d’économiser jusqu’à 2.7% du carburant consommé. Après que la configuration globale soit définie, les composants rotodynamiques sont conçus en utilisant les modèles physiques les plus actuels. La conception finale comporte la pompe centripète, la turbine à un étage, deux paliers axiaux, un palier radial anisotropique comportant quatre réservoirs ainsi que trois joints d’étanchéité (un joint d’étanchéité spiral à viscosité et deux joints d’étanchéité annulaires) permettant de découpler les écoulements des différents composants. Par la suite, une séquence de procédés est définie ainsi que le concept détaillé incluant les aménagements permettant l’instrumentation et l’opération dans un banc d’essai de la microturbopompe de démonstration. La conception des dix-huit photomasques de fabrication découle de cet exercice. Finalement, des tests de microfabrication sont effectués pour évaluer la faisabilité des principales étapes définies dans la séquence de procédés de fabrication. Les étapes de photolithographie, de gravure du silicium, de collage anodique et par fusion sont démontrées tandis que les défis inhérents à la gravure du Pyrex et du quartz sont explorés. Une approche pour compléter la fabrication d’un dispositif de démonstration est proposée à la fin de ces travaux. Cette étude définit pour la première fois la configuration détaillée d’une microturbopompe à vapeur opérant à haute température, confirmant la faisabilité de ce concept. Les jalons sont posés pour la fabrication d’un prototype de démonstration et la validation des modèles présentés ici.

Many people around the world still lack access to a reliable electricity grid. Supplying electricity to remote off grid areas like villages around Leticia, Colombia is often interrelated with high costs and geographical limitations. Today most of the electricity demand is met through the usage of diesel generators. The generators are easy to use and have a relatively reliable functionality. However, fuel is expensive and there are other negative aspects as fumes and sound pollution. In order to provide a cleaner, more reliable and cost efficient alternative the company Jabe Energy AB has in cooperation with the volunteer organization Ankarstiftelsen developed a new type of hydrokinetic turbine (slow moving none damming turbine). Previous studies have shown that there is potential for hydrokinetic turbines to increase their power output simply by their relative placement (coupling potential). That is, it might be possible to extrude more power from a system where two hydrokinetic turbines are placed in a close relation rather than being completely separated. Since the turbine investigated is newly developed there have been no previous studies regarding its specific coupling potential. To investigate this potential given the conditions in the Amazon basin, a field study is conducted where measurements on water velocity at different heights in the water column is collected. The data is later used as input conditions for a turbine model developed in the program COMSOL. The aim is to use simulations in order to determine whether a turbine is sensitive for its relative placement to a former (coupling potential) and furthermore to investigate a possible optimal turbine coupling position. The results will show that the turbine is coupling sensitive and that there exists more advantageous placements. Comparing the best and worst case of the coupling study displays an 11.87% difference in possible energy output. The conclusion is that further empirical studies are necessary in order to validate the results. Finally a suggestion on how these studies should be conducted is presented and discussed.

Wind energy is one of the fastest growing sources of renewable energy in the world. There has been a lot of research, development, and investment in wind energy in recent years. Offshore sites offer stronger winds and low turbulence, along with fewer noise and visual impacts. Establishing large turbines at deepwater sites offers promising opportunities for generating high power output while utilizing the favorable environmental conditions. Researchers at Sandia National Laboratories (SNL) have developed a very large wind turbine model with a 13.2 MW rating that has 100-meter long blades; this turbine is designated as the SNL100 13.2 MW wind turbine. With a hub height of 146 meters and a rotor diameter of 205 meters, such a large turbine is best suited for offshore sites. Developing a wind turbine model for an offshore site requires that a platform model be developed first. Of the various kinds of floating platforms, a moored semi-submersible platform supporting the wind turbine, which offers stability by virtue of the intercepted water-plane area, is an appropriate choice. The goal of this study is to develop a semi-submersible platform model to support the 13.2 MW wind turbine, while keeping loads and deflections within safe limits. The platform is developed based on work completed as part of the Offshore Code Comparison Collaboration Continuation (OC4) Phase II project, which involved a 5 MW wind turbine supported by a semi-submersible platform. The present study focuses on three important topics: (i) development of the combined offshore wind turbine system model with the 13.2 MW wind turbine, a floating semi-submersible platform, and a mooring system; (ii) the entire procedure involved in modeling and analyzing first-order hydrodynamics using two codes, MultiSurf and WAMIT; and (iii) assembling of the integrated aero-hydro-servo-elastic model considering hydrodynamics in order to verify the steady-state and stochastic response of the integrated wind turbine system. / text

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In-service performance deterioration of gas turbine engines can be identified, at the engine module level, in terms of reductions in the component mass flow and the efficiency. Continued operation of a deteriorated gas turbine is (i) uneconomical and (ii) unsafe. Timely identification of the faults and ensuing maintenance could prevent both. Gas Path Analysis is a technique to establish the current performance level of the gas turbines and identify the faulty modules. Computer models can predict the off_design performance of gas turbines by aero-thermo-dynamically matching the engine components. This thesis describes the development of DETEM (DEeteriorated Turbine Engine Model), a generalised computer program, developed to model degraded gas turbine engines and analyse faults. The program has an integrated graphics module and creates windows on the VDU terminal,for displaying the program output and accepting the user input. This enables the user to compare the results of two different types of runs at the same time. The program incorporates sensor models that modify the output, with noise and in bias, based on the sensor characteristics, thus simulating a real engine. It is possible to simulate the engine performance at design point, off-design and under transient conditions. The runs could be for a "clean" and a deteriorated engine. Three techniques, iterative, fault coefficient matrix, and a statistical best-estimation technique, have been used to analyse the engine performance and identify the fault. Analysis of two and three shaft turbo-shaft engines and two spool turbo-fan and turbo-jet engines have been worked out in the thesis. Effects of reducing the number of measurements and measuring different engine parameters, on the accuracy of the fault identification, have been studied. The program is considered to have a potential for the generation of fault trees for rule-based expert system applied to gas turbine diagnostics. Because of the controlled output to the screen, a direct comparison of two different runs side by side, on the same screen, makes the program a good teaching aid for gas turbine diagnostics.

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