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1
TERNER, MATHIEU. "Innovative materials for high temperature structural applications: 3rd Generation γ-TiAl fabricated by Electron Beam Melting". Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2527509.
Повний текст джерелаАнотація:
In the aeronautics industry, the propulsion systems stand among the most advanced and critical components. Over the last 50 years, gas turbine aeroengines were subjected to intensive research to increase efficiency and reduce weight, noise and harmful emissions. Together with design optimization, breakthrough in materials science for structural applications triggered the development of the most advanced gas turbine engines. For low temperatures, basically ahead of the combustion section, lightweight Ti alloys are preferred for their good mechanical properties. For high temperatures instead, Ni-based superalloys exhibit outstanding properties up to very high temperatures despite a rather high material’s density.
Research have focused on enhancing to the maximum the potential of materials in gas turbine engines. According to the application, the components experience various mechanical and environmental constraints. Special designs, manufacturing process, material compositions and protective coatings have been developed to push the limits of advanced materials. Nowadays, the attention is focused on innovative materials to replace the existing Ti and Ni based alloys leading to substantial benefits. Light weight composite materials in particular were found very attractive to replace some components’ Ti alloys. At higher temperatures, it is of great interest to replace Ni-based superalloys by materials with lower density and/or higher temperatures applications, which in turn would lead to substantial weight reduction and increase efficiency.
At the highest temperatures range, in particular in the combustion chamber and high pressure turbine sections, ceramic based materials offer promising balance of properties. Research are dedicated to overcome the drawbacks of ceramics for such structural applications, and in particular their brittle fracture behavior, by addition of reinforcing fibers. At lower temperatures range, TiAl based intermetallics emerged as very promising materials at half the density of Ni-based superalloys. Significant weight reduction could be achieved by the introduction of TiAl based alloys for rotating components of the compressor and low pressure turbine. 2nd generation γ-TiAl alloys were lately introduced in GE’s GEnx and CFM’s LEAP engines.
The present work concerns the fabrication by the additive manufacturing technique Electron Beam Melting of 3rd generation γ-TiAl alloys for high temperatures application in gas turbine aeroengines. EBM, building parts layer by layer according to CAD, offers many advantages compared to other manufacturing processes like casting and forging. Reported by Avio, 2nd generation γ-TiAl alloys have been successfully fabricated by EBM. To increase the material’s potential, the production of 3rd generation γ-TiAl alloys Ti-(45-46)Al-2Cr-8Nb was therefore studied. The optimization of the EBM parameters led to high homogeneity and very low post-processing residual porosity ≤ 1%. The fine equiaxed microstructure after EBM could be tailored towards the desired mechanical properties by simple heat treatment, from equiaxed to duplex to fully lamellar. In particular, a duplex microstructure composed by about 80 % lamellar grains pinned at grain boundaries by fine equiaxed grains was obtained after heat treatment slightly over the α transus temperature.
The study showed that addition of a higher amount of Nb significantly increased the oxidation resistance of the material, thus increasing the application temperature range of these γ-TiAl alloys.
2
Brundin, Carl. "Alternative energy concepts for Swedish wastewater treatment plants to meet demands of a sustainable society." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-146831.
Повний текст джерелаАнотація:
This report travels through multiple disciplines to seek innovative and sustainable energy solutions for wastewater treatment plants. The first subject is a report about increased global temperatures and an over-exploitation of natural resources that threatens ecosystems worldwide. The situation is urgent where the current trend is a 2°C increase of global temperatures already in 2040. Furthermore, the energy-land nexus becomes increasingly apparent where the world is going from a dependence on easily accessible fossil resources to renewables limited by land allocation. A direction of the required transition is suggested where all actors of the society must contribute to quickly construct a new carbon-neutral resource and energy system. Wastewater treatment is as required today as it is in the future, but it may move towards a more emphasized role where resource management and energy recovery will be increasingly important. This report is a master’s thesis in energy engineering with an ambition to provide some clues, with a focus on energy, to how wastewater treatment plants can be successfully integrated within the future society. A background check is conducted in the cross section between science, society, politics and wastewater treatment. Above this, a layer of technological insights is applied, from where accessible energy pathways can be identified and evaluated. A not so distant step for wastewater treatment plants would be to absorb surplus renewable electricity and store it in chemical storage mediums, since biogas is already commonly produced and many times also refined to vehicle fuel. Such extra steps could be excellent ways of improving the integration of wastewater treatment plants into the society. New and innovative electric grid-connected energy storage technologies are required when large synchronous electric generators are being replaced by ‘smaller’ wind turbines and solar cells which are intermittent (variable) by nature. A transition of the society requires energy storages, balancing of electric grids, waste-resource utilization, energy efficiency measures etcetera… This interdisciplinary approach aims to identify relevant energy technologies for wastewater treatment plants that could represent decisive steps towards sustainability.
3
Muritala, Ibrahim Kolawole. "Investigation of trace components in autothermal gas reforming processes." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2018. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-232005.
Повний текст джерелаАнотація:
Trace component analysis in gasification processes are important part of elemental component balances in order to understand the fate of these participating compounds in the feedstock. Residual traces in the raw synthesis gas after quench could bring about the poisoning of catalysts and corrosion effects on plant facilities. The objective of this work is to investigate the effects of quenching operation on the trace components during test campaigns of the autothermal non-catalytic reforming of natural gas (Gas-POX) mode in the HP POX (high pressure partial oxidation) test plant. In order to achieve this, Aspen Plus simulation model of the quench chamber of the HP POX test plant was developed to re-calculate the quench chamber input amount of different trace compounds from their output amount measured during test points of the Gas-POX campaigns.
Variation in quench water temperatures from 130 °C to 220 °C and pH value of quench water as well as the resulting variation in Henry´s and Dissociation constant of the traces (CO2, H2S, NH3 and HCN) changed the distribution of traces calculated in the quench water. The formation of traces of organic acid (formic acid and acetic acid) and traces of BTEX, PAHs and soot in the quench water effluent were discussed. The discrepancies between equilibrium constant and reaction quotient (non-equilibrium or real) for the formation of NH3 and HCN at the exit of the gasifier were discussed. The assessment of the results in this work should lead to the improvement in the understanding of trace components and concepts that could be employed to influence their formation and reduction.
4
Wu, Stanley W. M. "Hydrodynamics of gas spouting at high temperature." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26345.
Повний текст джерелаАнотація:
The spouted bed technique was developed for handling solids which were too coarse to fluidize well. In its early stages, it was primarily used for drying wheat. It was later found that spouting has potential application in high temperature operations such as coal combustion and gasification. However, literature review will show that there are very few reports on the hydrodynamics of spouted beds at high temperature and/or pressure. Most existing correlations or expressions are based upon experiments done at room conditions; they have not been tested with data from higher temperatures.
The goal of this study was to obtain experimental data at high temperatures, to examine the validity of existing equations and to modify the latter where appropriate. Spouting of sand particles (Ottawa sand) with preheated air, ranging from 20 to 420 °C, was conducted in a 156 mm stainless steel half-column, equipped with a glass panel. The transparent surface allowed one to measure spout diameter, fountain height, annulus height and other important parameters which otherwise are difficult to obtain in a full stainless steel column. In addition to air, helium and methane, at room conditions, were also used as spouting gases. With these two gases, it became possible to investigate the effect of changing gas density at constant gas viscosity and the effect of changing gas viscosity at constant gas density.
The main experimental measurements were of minimum spouting velocities, spout diameters, maximum spoutable heights and bed pressure drops. For selected runs, additional measurements, such as of flow regime maps, particle circulation rates, radial and longitudinal pressure profiles, fountain heights and annular fluid velocities, were also obtained.
In general, it was found that the range of stable spouting decreased with decreasing gas density and increasing gas viscosity, hence with increasing air temperature. Some of the existing equations were found to be inadequate. The Mathur and Gishler (1955) equation was unsatisfactory when tested against the experimental values of Ums. The expression of Epstein and Levine (1978) gave good prediction of the overall bed pressure drop for room conditions but overestimated the effect of temperature. The McNab (1972) equation for estimating spout diameter worked reasonably well for air spouting at room temperature but it underpredicted at higher temperatures. These equations were empirically modified to fit the new data obtained.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
5
Stevens, Nancy Shanan Moore. "Composite membranes for high temperature gas separations." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/10082.
Повний текст джерела
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Astbury, Christopher John. "High temperature chemistry in the gas phase." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236061.
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Plewacki, Nicholas. "Modeling High Temperature Deposition in Gas Turbines." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587714424017527.
Повний текст джерела
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Vounki, Brenda. "Adsorbants à base de phosphates pour l'abattement des métaux lourds en phase gazeuse." Electronic Thesis or Diss., Ecole nationale des Mines d'Albi-Carmaux, 2023. http://www.theses.fr/2023EMAC0015.
Повний текст джерелаАнотація:
Les normes environnementales concernant les émissions de polluants dans l'air deviennent de plus en plus restrictives avec de nouveaux seuils d'émission à obligatoirement respecter. A cet effet, il est nécessaire de développer ou d'améliorer les techniques actuelles d'abattement des émissions de métaux lourds à haute température (> 240°C). Ce travail de thèse se place dans cette problématique et a pour objectif le développement d'adsorbant à base de phosphates de calcium aux propriétés contrôlées permettant l'élimination des métaux lourds en phase gazeuse à haute température. Si les procédés d'élimination de ces métaux lourds à basse température (< 240°C) existent, ceux à haute température (> 240°C) restent rares. Dans un premier temps, différentes synthèses de phosphates de calcium ont été réalisées afin d'identifier l'influence des conditions opératoires sur les propriétés physico-chimiques et thermiques du solide. Le rapport liquide/solide et la vitesse d'agitation se sont avérés comme les paramètres les plus influents sur les propriétés finales du produit obtenu. Une hydroxyapatite avec une surface spécifique comprise entre 90 et 100 m2 /g a été obtenue. Sur la base des résultats obtenus, l'hydroxyapatite retenue pour les essais d'adsorption du cadmium ou du plomb en lit fixe à l'échelle laboratoire a été celle présentant les meilleures caractéristiques en termes de stabilité thermique, physique et chimique. Néanmoins, ce manuscrit couvre en grande partie les travaux sur l'adsorption du cadmium. Une deuxième hydroxyapatite fournie par l'industriel (surface spécifique :119 m2 /g) a également été utilisée pour les essais d'adsorption. Les différents tests d'adsorption ont été réalisés en faisant varier des paramètres tels que le débit de gaz (1-3 L/h), la température (700-1000°C), le temps de contact, la concentration initiale du métal lourd et la hauteur du lit de poudre d'adsorbant (0,5-1,5 cm). Les résultats ont montré la capacité de ces adsorbants à capter les métaux lourds sous des contraintes thermiques (T > 700°C). Les données expérimentales d'adsorption du cadmium ont ensuite été modélisées à l'aide d'un modèle mathématique basé sur la cinétique des processus d'adsorption, et les phénomènes de transfert de matière. Il a permis de prédire la dynamique d'adsorption du cadmium par l'hydroxyapatite à travers les courbes de percée décrivant le profil de concentration du cadmium en fonction du temps. Ce travail a démontré que les hydroxyapatites synthétisées présentent des propriétés de surface, d'écoulement, thermiques et thermomécaniques intéressantes permettant d'envisager leur application à haute température à l'échelle industrielle dans une unité d'incinération des déchetsEnvironmental standards for emissions of pollutants into the air are becoming increasingly restrictive, with new emission thresholds that must complied with. It is therefore necessary to develop and/or improve current techniques to remove heavy metals. This thesis aims to develop a calcium phosphate sorbent with controlled properties to remove heavy metals from the gas phase at high temperature (> 240°C). Although the process from getting the removal of heavy metals at low temperature (< 240°C), the one for high temperature conditions are still scarce. Initially, various syntheses of calcium phosphates were carried out to identify the influence of operating conditions on the physico-chemical and thermal properties. The liquid/solid ratio and the stirring speed proved to be the most influential parameters to control the final properties of the product. A hydroxyapatite with a specific surface area of between 90 and 100 m2/g was obtained. Based on the results obtained, the hydroxyapatite chosen for the laboratory-scale fixed-bed cadmium or lead adsorption tests was the one with the best characteristics in terms of thermal, physical, and chemical stability. Nevertheless, this manuscript mostly covered the work on cadmium adsorption. A second hydroxyapatite was also used for the adsorption tests. The adsorption tests were carried out by varying parameters such as the gas flow rate (1-3 L/h), the temperature (700-1000 °C), the contact time, the initial concentration of the pollutant and the height of the adsorbent powder bed (0.5-1.5 cm). The results demonstrated the ability of these sorbents to capture heavy metals under thermal stress (T > 700°C). Experimental data on cadmium adsorption were modelled using a mathematical approach based on the kinetics of adsorption processes and mass transfer phenomena. The model was used to predict the dynamic of cadmium adsorption on hydroxyapatite using breakthrough curves describing the cadmium concentration profile as a function of time. This work has shown that the synthesised hydroxyapatites have interesting surface, flow, thermal and thermomechanical properties, showing their possible application at high temperatures at industrial scale in a waste incineration unit
9
Baldwin, Thomas James. "Aerosol formation in high temperature vapour-gas mixtures." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843166/.
Повний текст джерелаАнотація:
Understanding the formation and growth of aerosols is important to a better understanding of a diverse range of problems. The identification of key parameters affecting aerosol behaviour is discussed, and a number of approaches for predicting this behaviour are developed in this thesis. Models appropriate to a wide range of industrial processes are used. Turbulent and laminar flow scenarios are considered, and an assessment is made of the likely differences in system behaviour according to whether nucleation occurs by a predominantly homogeneous, binary or ion-induced mechanism. A number of techniques for predicting aerosol behaviour are compared, ranging from the rigorous to more elementary approaches. It is shown that the simpler techniques are able to demonstrate many of the most important features of aerosol behaviour, whilst allowing the isolation of the parameters which influence this behaviour. This thesis presents methods which are capable of rapidly characterising the growth and formation behaviour of an aerosol system, and in doing so has identified many of the parameters which control this behaviour.
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Zwierlein, Martin W. "High-temperature superfluidity in an ultracold Fermi gas." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39290.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, February 2007.Includes bibliographical references (p. 258-280).
This thesis presents experiments in which a strongly interacting gas of fermions was brought into the superfluid regime. The strong interactions are induced by a Feshbach scattering resonance that allows to tune the interfermion scattering length via an external magnetic field. When a Fermi mixture was cooled on the molecular side of such a Feshbach resonance, Bose-Einstein condensation of up to 107 molecules was observed. Subsequently, the crossover region interpolating between such a Bose-Einstein condensate (BEC) of molecules and a Bardeen-Cooper-Schrieffer superfluid of long-range Cooper pairs was studied. Condensates of fermion pairs were detected in a regime where pairing is purely a many-body effect, the pairs being stabilized by the presence of the surrounding particles. Superfluidity and phase coherence in these systems was directly demonstrated throughout the crossover via the observation of long-lived, ordered vortex lattices in a rotating Fermi mixture. Finally, superfluidity in imbalanced Fermi mixtures was established, and its Clogston limit was observed for high imbalance. The gas was found to separate into a region of equal densities, surrounded by a shell at unequal densities.
by Martin W. Zwierlein.
Ph.D.
11
Forsyth, Peter. "High temperature particle deposition with gas turbine applications." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:61556237-feed-43cb-9f4a-d0aed00ca3f8.
Повний текст джерелаАнотація:
This thesis describes validated improvements in the modelling of micron-sized particle deposition within gas turbine engine secondary air systems. The initial aim of the research was to employ appropriate models of instantaneous turbulent flow behaviour to RANS CFD simulations, allowing the trajectory of solid particulates in the flow to be accurately predicted. Following critical assessment of turbophoretic models, the continuous random walk (CRW) model was chosen to predict instantaneous fluid fluctuating velocities. Particle flow, characterised by non-dimensional deposition velocity and particle relaxation time, was observed to match published experimental vertical pipe flow data. This was possible due to redefining the integration time step in terms of Kolmagorov and Lagrangian time scales, reducing the disparity between simulations and experimental data by an order of magnitude. As no high temperature validation data for the CRW model were available, an experimental rig was developed to conduct horizontal pipe flow experiments under engine realistic conditions. Both the experimental rig, and a new particulate concentration measurement technique, based on post test aqueous solution electrical conductivity, were qualified at ambient conditions. These new experimental data compare well to published data at non-dimensional particle relaxation times below 7. Above, a tail off in the deposition rate is observed, potentially caused by a bounce or shear removal mechanism at higher particle kinetic energy. At elevated temperatures and isothermal conditions, similar behaviour is observed to the ambient data. Under engine representative thermophoretic conditions, a negative gas to wall temperature gradient is seen to increase deposition by up to 4.8 times, the reverse decreasing deposition by a factor of up to 560 relative to the isothermal data. Numerical simulations using the CRW model under-predict isothermal deposition, though capturing relative thermophoretic effects well. By applying an anisotropic Lagrangian time scale, and cross trajectory effects of the external gravitational force, good agreement was observed, the first inclusion of the effect within the CRW model. A dynamic mesh morphing method was then developed, enabling the effect of large scale particle deposition to be included in simulations, without continual remeshing of the fluid domain. Simulation of an impingement jet array showed deposition of characteristic mounds up to 30% of the hole diameter in height. Simulation of a passage with film-cooling hole off-takes generated hole blockage of up to 40%. These cases confirmed that the use of the CRW generated deposition locations in line with scant available experimental data, but widespread airline fleet experience. Changing rates of deposition were observed with the evolution of the deposits in both cases, highlighting the importance of capturing changing passage geometry through dynamic mesh morphing. The level of deposition observed, was however, greater than expected in a real engine environment and identifies a need to further refine bounce-stick and erosion modelling to complement the improved prediction of impact location identified in this thesis.
12
Andrienko, Daniil. "Non-equilibrium Models for High Temperature Gas Flows." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1405505300.
Повний текст джерела
13
Abercrombie, Matthew G. "Acoustic microsensor with optical detection for high-temperature, high-pressure environments." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/19467.
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Harra, L. K. "Spectral studies of high temperature plasmas." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359071.
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15
Arvanitidis, Ioannis. "Intrinsic kinetics of some high temperature gas-solid reactions /." Stockholm : Tekniska högsk, 1998. http://www.lib.kth.se/abs98/arva0925.pdf.
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Guha, P. K. "Smart micro-hotplate platform for high temperature gas sensor." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599774.
Повний текст джерелаАнотація:
There has been an increasing demand of hand held battery operated gas monitors because of their widespread applications. However, the existing gas sensors suffer from high power consumption (> 100 mW) and most of them are not CMOS compatible, thus expensive. The aim of this research is to develop a smart micro-hotplate platform for high temperature gas sensor application. The gas sensor devices should consume low power and be fully CMOS compatible. This will enable the monolithic integration of interfacing circuitry with the sensor device on the same chip and thus will make the device performance more reliable and reproducible. The work mainly focused on two aspects: (i) design and development of low power reliable micro-hotplates and (ii) design and integration of intelligent electronic interface for the amplification and read out of the gas sensing signal. The design and simulation were carried out in Cadence and ANSYS software. The devices were fabricated in two batches in XFAB, Germany. Both aluminium and tungsten metallization were used. Tungsten was used to avoid electro migration at high temperature. The first batch was a proof of concept batch, which contains mostly discrete micro-hotplates; whereas electronic integration was the main focus on the second batch. The micro-hotplate contains MOSFETs as the heating elements. The heaters are embedded in thin SOI membrane. The membranes were realized using DRIE technique in Silex, Sweden. The electro-thermal and optical characterisation of the micro-hotplates shows that the membranes are very stable. The devices measured on different positions and wafers show excellent reproducibility. The MOSFET micro-heaters survived temperatures above 500° C. The hotplates consumed low power, operating temperature up to 550° C was achieved at a power cost of only 16 mW, which is much lower than the present gas sensors. The sensing material in the form of a CNT layer was grown on the micro-hotplates (using local growth technique) and the preliminary gas testing results showed lots of promise.
17
Wilcock, Roger. "The thermodynamics of cooling in high temperature gas turbines." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/272029.
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Zhang, P. "Development of next generation high temperature materials for high performance gas turbine." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1474017/.
Повний текст джерелаАнотація:
Thermal barrier coatings (TBCs) are advanced protective coating systems used to protect metallic substrates at high-temperature application. Currently, the state-of-the-art industrial TBC material is 6-8wt% Y2O3 stabilized ZrO2 (6-8YSZ), but it cannot be used over 1200oC for a long time due to sintering behaviour and phase transformation. The purpose of this thesis was to explore new thermal barrier materials that can be used at high temperature for a long time to replace YSZ. Micron lanthanum titanium aluminum oxide (LaTi2Al9O19, LTA) has been proven as a very promising thermal barrier material due to low thermal conductivity, and excellent phase and thermochemical stability. The main drawback of LTA is the low fracture toughness. Therefore, this thesis studied nano-structured LTA, toughened LTA, and ion doped LTA synthesized by sol- gel method, and LTA and toughened LTA coatings on steel substrate prepared by air plasma spray (APS). The experimental results indicate that compared to micron LTA, the nano-structured LTA had higher coefficients of thermal expansion (CTEs) and comparable thermochemical stability. LTA toughened by 10vol% tetragonal zirconia (LTA-4YSZ) was synthesized by a hybrid sol-gel method. The ceramic composite LTA- 4YSZ had lower thermal conductivity of approximately 1.054 W/(m·K) at room temperature, stable CTEs, better sintering resistance, and mechanical properties. Single phase ion doped LTA by gadolinium was obtained with a Gd3+ content of less than 10mol%, La0.9Gd0.1Ti2Al9O19 (L9G1) had higher CTEs around 11.7×10-6 oC-1 at 950oC, lower thermal conductivity circa. 1.404 W/(m·K) at room temperature, and better sintering resistance than LTA. The APS produced LTA-4YSZ coatings were prepared with optimized granulated powders, which were typical APS coatings with five types of defects: cracks, gaps, cavities, voids, and interspace.
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Arvanitis, Antonios. "High Temperature High Pressure Water Gas Shift Reaction in Zeolite Membrane Reactors." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563872266361549.
Повний текст джерела
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Rieger, Michael. "The alkali sorption process by solid sorbents at high temperature." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843101/.
Повний текст джерелаАнотація:
The aluminosilicate materials kaolinite, calcium montmorillonite and emathlite have been tested as solid sorbents for alkali vapour in controlled gaseous environments, in order to study their sorption characteristics. The study used pan pelletised and extruded pellets in single pellet and fixed bed reactor systems under gaseous environmental conditions containing water vapour, hydrogen chloride and nitrogen at a temperature of 850°C. The means of producing the pellets and the composition of the gaseous environment were shown to determine the sorption performance of the sorbent pellets. The physical properties of the pellet (particle size, total pore volume, surface area, crush strength) significantly affect the sorption effectiveness, while the formation of reaction products is dependent upon the sorbents' chemical composition and on the sorption conditions. Reaction products identified under the various sorption conditions indicated possible pathways for alkali capture. Hydrogen chloride mixtures were shown to cause a reverse of the sorption process for some sorbents. A leaching method for extracting sodium from treated pellets enabled the type of bonding to be determined but not necessarily the prime sorption mechanism. With the introduction of water vapour, some evidence was presented that the alkali sorption rate can change significantly. The previously reported effect of hydrogen chloride upon alkali capture by the sorbent material, calcium montmorillonite; shown by McLaughlin (1990) was confirmed and the effect was also investigated for emathlite and kaolinite. Reversibility depended upon the presence or absence of hydrogen chloride. Both water vapour and hydrogen chloride determine sorption activity and capacity. Likewise the structural characteristics of the pellet influences the sorption activity and capacity. The sorption process is not due to aluminosilicate reaction alone but also due to replacement mechanisms. Conclusions are drawn regarding mechanism and theoretical model proposed.
21
Dunne, David John. "Upgrading South Australian lignites by high-temperature pre-treatment /." Title page, summary and table of contents only, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phd9231.pdf.
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Rud, A. D., I. M. Kiryan, R. М. Nikonova, V. I. Ladyanov, N. M. Bilyi, and M. A. Merzlyakova. "Structure Transformation in Fullerenes C60 at High Temperature Treatment." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35439.
Повний текст джерелаАнотація:
The changes in the local structure of the fullerenes C60 are studied after high-temperature annealing. Based on the model of atomic configurations obtained by reverse Monte Carlo, the quantitative character-istics of the topological order are founded for the C60 in initial state and after annealing. It is shown that the critical temperature of the beginning of the destruction of the structure of molecular lattice of fuller-enes is 900° C (30 min). At this temperature, a partial breakage of the fullerene molecules occurs. At tem-perature of 1600° C, fully breakage of fullerene molecules and formation of amorphous carbon takes place.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35439
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Vilorio, Carlos R. "Gas Chromatography Micro-Chip with High Temperature Interface and Silk Screen Heaters." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8690.
Повний текст джерелаАнотація:
There has been substantial market demand for a portable Gas Chromatography (GC) system. Throughout the years, much progress has been made on fabricating a micro system that works as well as a benchtop system. Unfortunately, even though many substrates, channel types, channel widths, temperature control systems, and interface solutions have been attempted, existing versions of the micro-GC still fall short of the ideal. This thesis presents the design, fabrication, and testing of a silicon based micro-GC column that presents a solution for interfacing and heating of the chip. A polyimide resin is used to create a durable high temperature low thermal mass interface with the chip, while a silk screen method is demonstrated for easy printing of heaters. Chromatogram results are shown in both Temperature Program and Thermal Gradient runs.
24
Heath, David John. "Characterisation of waxy gas-condensates by high temperature capillary gas chromatography and oxidative degradation." Thesis, University of Plymouth, 1995. http://hdl.handle.net/10026.1/460.
Повний текст джерелаАнотація:
High molecular weight (HMW) hydrocarbons (defined herein as C35+ compounds) are difficult to characterise by conventional analytical methods. Very few studies have reported precise and reproducible quantification of such compounds in fossil fuels. Nonetheless, such components have important effects on the physical and biological fate of fossil fuels in the geosphere. For example, the phase behaviour of waxy gas condensates is significantly affected by the varying proportions of HMW compounds. Similarly HMW compounds are amongst the most resistant petroleum components to biodegradation. The current study reports the development of reproducible quantitative high temperature capillary gas chromatography (HTCGC) methods for studying both these aspects of the chemistry of HMW hydrocarbons. In addition those hydrocarbons which remain unresolved when analysed by gas chromatography (so called unresolved complex mixtures UCMs) are also studied. UCMs may account for a large portion of the hydrocarbons in many fossil fuels yet very little is known about their composition. Knowledge of these compounds may be important in enhancing the prediction of phase behaviour. Oxidative degradation and GC-MS is used to elucidate the types of structures present within the UCM. The concentrations of C3S4h. ydrocarbons in two unusually waxy gas condensates from high temperature wells in the North Sea were determined by HTCGC. The whole C, 5+ fraction comprised about 20% of the total hydrocarbons and consisted of compounds with carbon numbers extending up to and beyond Coo. By paying particular attention to sample dissolution and injection, good reproducibility and precision were obtained. For example, for authentic n-C, to n-C60 alkanes a relative standard deviation of under 5% for manual injection, linear response factors (1.01 Cm to 0.99 C6), and a linear calibration for 5 ng to 25 ng on-column were found. Limits of detection are reported for the first time for HMW n-alkanes. The limits were found to be as low as 0.8 ng for Cto to 1.87 ng for C60. Tristearin is proposed as a suitable HTCGC internal standard for quantification since the FID response factor (1.1) was close to that of the HMW n-alkanes and response was linear. Importantly, when co-injected with the two waxy North Sea condensates, tristearin was adequately separated from the closest eluting alkanes, n-C59 and n-C60 under normal operating conditions. Qualitative characterisation of the HMW compounds in the waxy gas condensates and in synthetic wax blends (polywax 1000) using HTCGC-EI MS and HTCGC-CI MS produced molecular ions or pseudo molecular ions for n-alkanes up to n- C6o. The spectra of some HMW compounds contained fragment ions characteristic of branched compounds but detailed characterisation was very limited. This study has also shown, for the first time, the significance of the unresolved complex mixture in gas condensatesU. CM hydrocarbonsa ccountedf or over 20% of the total hydrocarbons in a waxy North sea condensateT. he condensatew as first distilled and the distillate UCMs isolated. Thesew ere found to be between 64 to 97 % unresolved after molecular sieving (5A) and urea adduction. The UCMs were oxidised using CrO3/AcOHw hich produced5 -12% C02, and 55-83% dichloromethane-solublep roducts. Thus 65-94% of the original UCMs were accounted for as oxidation products. The remainder were thought to be water soluble acids which could not be determined in the presence of the AcOH reagent. Of the recovered oxidised products, 27- 81 % were resolved and these comprised mainly n-monocarboxylic acids (19-48 %). The average chain length was found to be C12 indicating the average length of alkyl groups. Branched acids, ketones, ketoacids, ndicarboxylic acids, branched dicarboxylic acids, lactones, isoprenoid acids, alkylcyclohexane carboxylic acids and toluic acids accounted for the majority of the remaining resolved products. The distillate UCMs all showed variations in amountso f productsb ut not in composition. Retro-structurala nalysis suggestedth at the UCM in the gasc ondensatew as mainly aliphatic and branched.T he numbero f isomerso f simple brancheda lkaneso ver the UCM molecular weight range (determined by cryoscopy) was calculated to be over 15000. Overall, oxidation provided structural information for about half of the UCM. HTCGC was also used to measure the biodegradability of HMW alkanes in a waxy Indonesian oil. Traditional alkane isolation techniques (TLC and CC) discriminated against HMW compounds above C40 whereas adsorption onto alumina in a warm cyclohexane slurry provided an aliphatic fraction still rich in HMW compounds and suitable as a biodegradation substrate. A waxy Indonesian oil was subjected to 136 day biodegradation by Pseudomonas fluorescens. Extraction efficiencies of over 90 % (RSD <5 %) were obtained for n-alkanes up to C6o using continuous liquid-liquid extraction. Over 80 % of the oil aliphatic fraction was degraded within 14 days. After 136 days only 14% of the original aliphatic fraction remained, yet surprisingly no decreases in the concentrations of compounds above C45 were observed. However, the use of a rapid screening biodegradation method proved conclusively that Pseudomonasfluorescens was capable of utilising n-alkanes up to C60 once the bacteria had acclimated to the HMW alkanes. This is the first report of bacterial utilisation of an n-alkane as large as C.
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Tanaka, Yasunori, Yasunobu Yokomizu, Motohiro Ishikawa, and Toshiro Matsumura. "Particle Composition of High-Pressure SF_6 Plasma with Electron Temperature Greater than Gas Temperature." IEEE, 1997. http://hdl.handle.net/2237/7280.
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Benny, S. "High temperature water gas shift catalysts : a computer modelling study." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/20444/.
Повний текст джерелаАнотація:
The high-temperature (HT) Water Gas Shift (WGS) reaction has considerable technological relevance for lowering CO content during the conversion of natural gas or liquid hydrocarbons to hydrogen. Conventional HT-WGS catalysts based on oxides of iron and chromium are well established industrially. However, it is crucial to remove any impurities present such as Cr6+, S or N during the catalytic process. In particular, Cr6+ is regarded as a Class I carcinogen and its presence is restricted by EU legislation. Even though Cr6+ is reduced during the catalytic process, caution must still be taken to eliminate any further impurities. Hence, it is desirable to identify alternative promoters and develop a Cr-free HT-WGS catalyst. This thesis presents results obtained using atomistic simulation techniques to investigate the effect of Cr3+ and possible alternative dopants in three important iron oxide materials, Hematite (α-Fe2O3), Maghemite (γ-Fe2O3) and Magnetite (Fe3O4). The starting point is to develop an understanding of the structural properties and distribution of Cr3+ on the bulk and surface material of hematite. The critical stage of understanding the role of Cr3+ provides the basis from which criteria for novel dopants can be assessed. Al3+ and Mn3+ are proposed as the promising candidates on the basis of this study. The research has been extended to other complex iron oxides, such as maghemite and magnetite. In summary, the role of chromium in the HT-WGS reaction has been investigated to establish criteria for effective, alternative promoter dopants. This investigation has provided a detailed insight into the atomic level behaviour of Cr3+, Mn3+, Al3+ impurities in three major iron oxide phases. The alternative dopants predicted in this study have been the subject of parallel experimental studies conducted by Johnson Matthey. The results of this study are already benefiting the design of more efficient iron-oxide catalysts for the HT-WGS reaction.
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Kim, Seok-Jhin. "High Temperature Water Gas Shift Reaction in Zeolite Membrane Reactors." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321888491.
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Laubscher, Ryno. "Development aspects of a high temperature heat pipe heat exchanger for high temperature gas-cooled nuclear reactor systems." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80096.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: High temperature heat sources are becoming an ever-increasing imperative in the process industry for the production of plastics, ammonia and fertilisers, hydrogen, coal-toliquid fuel and process heat. Currently, high temperature reactor (HTR) technology is capable of producing helium temperatures in excess of 950°C; however, at these temperatures, tritium, which is a radioactive contaminant found in the helium coolant stream, is able to diffuse though the steel retaining wall of the helium-to-steam heat exchanger. To circumvent this radioactivity problem, regulations require an intermediate heat exchange loop between the helium and the process heat streams. In this paper, the use of a uniquely designed sodium-charged heat pipe heat exchanger is considered, and has the distinct advantage of having almost zero exergy loss as it eliminates the intermediate heat exchange circuit. In order to investigate this novel heat pipe heat exchanger concept, a special intermediate-temperature (± 240°C) experimental heat pipe heat exchanger (HPHE) was designed. This experimental HPHE uses Dowtherm A as working fluid and has two glass windows to enable visual observation of the boiling and condensation two-phase flow processes. A high temperature air-burner supply simulates the high temperature stream, and the cold stream is provided by water from a constant-heat supply tank. This experimental apparatus can be used to evaluate the validity of steady-state and start-up transient theoretical models that have been developed. This paper will highlight the special design aspects of this HPHE, the theoretical model and the solution algorithm described. Experimental results will be compared with the theoretically calculated results. The theoretical model will then be used to predict the performance of a high temperature (sodium working fluid at 850°C) HPHE will be undertaken and conclusions and recommendation made.
AFRIKAANSE OPSOMMING: Hoë temperatuur hitte bronne is besig om ‘n toenemende noodsaaklikheid te raak in die proses industrie vir die vervaardiging van plastieke, ammoniak, kunsmis, waterstof, steenkool-tot-vloeibare brandstof en proses hitte. Huidige hoë temperatuur reaktor tegnologie is in staat om helium te verhit tot temperature hoër as 950°C, maar by sulke hoë temperature is die vorming van tritium, wat ‘n radioaktiewe produk is, in die helium verkoeling stroom wat deur die reaktor vloei, ‘n probleem. Die tritium is in staat om deur die staal wand van ‘n enkel fase warmte uitruiler te diffundeer. Om hierdie radioaktiewe probleem te uitoorlê, stel huidige regulasies voor dat ‘n oorgangs hitte uitruil lus gebruik raak tussen die helium en proses strome van die reaktor stelsel. In hierdie tesis word ‘n unieke natrium gevulde hitte pyp warmte uitruiler nagevors, hierdie ontwerp het die voordeel dat dit geen “exergy” verlies het omdat dit nie ‘n oorgangs hitte uitruil lus benodig nie. Hierdie unieke konsep was nagevors deur ‘n spesiale oorgangs temperatuur (± 230°C) eksperimentiële hitte pyp warmte uitruiler te ontwerp. Hierdie eksperimentiële hitte pyp warmte uitruiler gebruik Dowtherm A as oordrags medium tussen die warm en koue strome en het twee glas venters waardeur die kook en kondensasie van die oorgangs medium dop gehou kan word. ‘n Hoë temperatuur verbrander simuleer die warm stroom deur die reaktor en die koue stroom word gesimuleer deur koue water. Die eksperimentiële opstelling sal gebruik word om die tyd afhangklike en tyd onafhangklike teoretiese wiskundige modele te valideer. Hierdie tesis sal die spesiale ontwerp aspekte van die hitte pyp warmte uitruiler, teoretiese modelle en oplos algoritme te bespreek. Eksperimentiele resultate sal met die teoretiese resultate vergelyk word en dan sal die teoretiese modelle gebruik word om ‘n natrium gevulde warmte uitruiler te simuleer. Gevolgtrekkings en aanbevelings sal in die lig van die resultate verskaf word.
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Phillips, M. E. "Studies of high temperature laboratory and astrophysical plasmas." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252580.
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Bérubé, Pierre. "High temperature biological treatment of foul evaporator condensate for reuse." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0028/NQ48606.pdf.
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Talyzin, Alexandr. "New Fullerene Materials Obtained in Solution and by High Pressure High Temperature Treatment." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5138-1/.
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McCann, S. M. "Spectroscopic diagnostics for high temperature astrophysical and laboratory plasmas." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335434.
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Lei, Yun School of Chemical Engineering & Industrial Chemistry UNSW. "Novel Fe2O3-Cr2O3 catalyst for high temperature water gas shift reaction." Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/23321.
Повний текст джерелаАнотація:
The thesis is focused on the study of high temperature water gas shift catalysis, the identification of new improved catalysts and the study of the kinetics and mechanism of reaction over these catalysts. Rh-promoted Fe2O3-Cr2O3 was found to offer best performance which was significantly better than unpromoted catalyst over wide temperatures range. An extensive literature survey is first reported. Guidelines to develop new WGS catalysts are developed. As a result, the activities of precious metals supported on various oxides for high temperature WGS reaction have been tested. Rh(1wt%) doped Fe2O3/Cr2O3, exhibits the highest activity for WGS over a wide temperature range. 5wt%CuO/Fe2O3-Cr2O3, 1wt%Pt/Cr2O3, 1wt%Pt/Fe2O3-Cr2O3, 1wt%Pt/U3O8, 1wt%Pt/10%U3O8-Al2O3 and 1wt%Pt/5%V2O5-TiO2 fall into the second most active catalysts group, with an improved activity compared to commercial Fe2O3-Cr2O3 catalyst. It is clear that both the support/catalyst and the promoter can affect the efficiency of the WGS, leading to the obvious inference that the reaction rate is controlled at the promoter ??? support interface. Further kinetic studies and characterisation (TPR, TPD, pulse-adsorption (reaction)) on Rh/Fe3O4/Cr2O3 have been conducted. The study, conducted under conditions without inhibition from products of both forward and backward reactions, shows that the overall reaction rate expression is described as: 2 22 ??? =0.0041exp(???4042.6 ) 0.64 0.5 ???0.024 exp(???6022.9 ) 0.46 0.73 CO CO H O CO H r PP P P T T . Kinetics studies carried out under fuel reforming gas compositions shows that reaction rate expression changed when the temperature of reaction varied. The reaction rate equations at temperatures of 573K, 623K and 673K are derived as: 573K: 2 2 2 - 2.84 10-6 0.6 0.12 - 9.08 10-7 0.09 0.52 rCO = ?? PCO PH O ?? PCO PH 623K: 2 2 2 - 1.45 10-6 0.99 0.40 - 7.12 10-7 0.11 0.73 rCO = ?? PCO PH O ?? PCO PH 673K: -6 2 2 2 - = 4.37 ?? 10 0.86 0.41 -1.83 ??10-6 0.28 0.66 rCO PCO PH O PCO PH , The apparent activation energy was 61.7??2.5 kJmol-1 . TPR, TPD, TPO characterisation studies and reoxidation of catalysts by CO2 or H2O show that the active site for high temperature WGS reaction on Rh/Fe2O3/Cr2O3 is reduced magnetite Fe3O4 which dissociatively breaks down the H2O to form H* and OH* and adsorbs CO2. The deposited metal, Rh, acts as a promoter by facilitating the uptake of hydrogen (H2) and carbon monoxide (CO), desorption of H2 (at high temperature) and CO2.
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Thiele, Jeremy Allan. "High Temperature LGX Acoustic Wave Devices and Application for Gas Sensors." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/ThieleJA2005.pdf.
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Pappano, Scott William. "Environmental impacts of the modular high temperature gas-cooled reactor (MHTGR)." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13668.
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Dudek, David Robert. "Single particle, high temperature, gas-solid reactions in an electrodynamic balance." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/39089.
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Savage, Nancy Ortins. "Development and characterization of high temperature, selective, titania-based gas sensors /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488203857249405.
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Singh, Suniti. "High rate anaerobic treatment of LCFA-containing wastewater at low temperature." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2042.
Повний текст джерелаАнотація:
La hausse des prix des carburants et les incitations favorisant le marché des énergies renouvelables poussent le marché mondial de l'eau et les technologies des eaux usées vers la digestion anaérobie. Les gains financiers résultant de la réduction de l'empreinte de l'usine et du transport des boues constituent également des moteurs économiques importants. La croissance efficace des méthanogènes est la clé de la fonctionnalité AD, pour laquelle les températures mésophiles (30-35 ° C) ou thermophiles (48-55 ° C) et pH 6,8-7,2 sont optimales. Le goulot d'étranglement dans la polyvalence de la mise en œuvre de la DA est son inefficacité à des températures plus basses. Comme un énorme morceau de biosphère est en permanence à moins de 5 ° C, le développement du DLTA fournirait une meilleure efficacité énergétique pour le traitement des eaux usées dans les régions tempéréesFats, oil and grease (FOG) is a significant constituent in numerous wastewaters such as those in dairy industry. The hydrolysis of FOG results in the production of long chain fatty acids (LCFA) which destabilize the anaerobic treatment process due to their physico-chemical and microbial toxicity effects. Harnessing the high methanogenic potential of FOG necessitates effective treatment of high LCFA loads, wherein the feasibility of LCFA treatment at low temperatures has been not investigated up to now. The aim of this thesis was to study the feasibility of high-rate anaerobic treatment of LCFA-rich wastewaters at low ambient temperatures using a dairy wastewater matrix.The screening of mesophilic inocula for treatment of mixed LCFA containing synthetic dairy wastewater (SDW) in batch studies showed that granular sludge inoculum achieved faster and higher methane yields (76-82% of theoretical yield) than the two municipal digestates (1-72%) at both 20 and 10°C. The LCFA degradative capacity in the granular sludge inoculum was attributed to the presence of β-oxidizing bacteria from the family Syntrophaceae (Syntrophus and uncultured taxa), the acetotrophic activity from Methanosaeta and putative syntrophic acetate oxidizing bacteria (SAOB). Continuous high-rate treatment of SDW was found to be feasible in expanded granular sludge bed (EGSB) reactors at 20°C (hydraulic retention time (HRT) 24 h, LCFA loading rate (OLR) 670 mgCOD-LCFA/L·d, 33% COD-LCFA) with a COD removal of 84–91% and methane yield of 44–51%. SDW feeding for longer than two months resulted in LCFA accumulation, which led to granular sludge flotation (36-57%) and disintegration. To counter the LCFA induced granular sludge disintegration and flotation, a novel reactor type, dynamic sludge chamber-fixed film (DSC-FF), was designed and achieved sCOD removal of 87-98% at HRTs from 12-72 h (LCFA loading rate 220-1333 mgCOD-LCFA/L·d) at 20°C. Moreover, even at the 12 h HRT, the unsaturated LCFAs (linoleate and oleate) were treated and only part of saturated LCFAs (stearate, palmitate) remained after treatment in the DSC-FF reactors. An increased methanogenic activity was established in the reactor sludges during reactor runs; evidenced by a higher acetotrophic activity in the granular sludge (from DSC), and a higher hydrogenotrophic activity in the biofilm (from FF) indicating development of distinct metabolic capabilities in the different reactor compartments. High throughput 16S rRNA sequencing showed that the relative abundance of the acetoclastic methanogen, Methanosaeta increased in EGSB reactors when fed with increased LCFA concentrations. The relative abundance of Methanosaeta increased also in the active microbiomes of granules (from DSC) and biofilm (from FF) during the 150-d reactor operation, demonstrating acetoclastic methanogenesis as the predominant methanogenesis pathway for SDW and LCFA degradation at 20°C. Microbial communities with a high β-oxidizing along with high methanogenic activity were developed during SDW treatment in DSC-FF reactors at 20°C. In DSC-FF reactors, the biofilm microbiome (from FF) had a prominent presence of the β-oxidizing bacteria Syntrophus and the hydrogenotrophic methanogen Methanospirillum; in comparison to the presence of the acetogenic bacteria - Syntrophobacter, Desulfobulbus, and Geobacter in the granular sludge microbiome, suggesting a role of these taxa at different trophic levels during LCFA degradation. In summary, this work demonstrated successful inoculum selection at low temperatures (10 and 20°C), and high-rate anaerobic LCFA degradation at 20°C using combined approaches of inoculum mixture and novel reactor design (here, DSC-FF). The key bacterial and archaeal taxa involved in the anaerobic conversion of LCFA to methane at 20°C were also deduced
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Krsmanovic, Dalibor. "High temperature ultrasonic gas flow sensor based on lead free piezoelectric material." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/245065.
Повний текст джерелаАнотація:
The review of current technologies for measurement of gas velocity in stack flow applications is undertaken and it is shown that the ultrasonic time-of-flight method is the most suitable and offers a number of advantages over alternatives. Weakness of current piezoelectric based transducers are identified as the inability to operate at temperatures above 400 °C due to limitation of piezoelectric materials used, and a case for development of an alternative high temperature material is put forward. A novel and highly enhanced, lead free piezoelectric material, suitable for continuous operation at temperatures above 400 °C has been engineered for ultrasonic gas velocity sensor applications. Structural modification of pure bismuth titanate (Bi4Ti3O12) or BIT compound, through multi-doping at the Ti-site, has been found to enhance piezoelectric properties accompanied with a mild reduction in Curie temperature, Tc. Initially, compounds doped with tungsten and chromium were found to increase the piezoelectric coefficient (d33) from around 5 pC N¯¹ in pure bismuth titanate, to above 20 pC N¯¹ in doped compounds. This increase is attributed to lower conductivity and improved poling conditions. Further increases in d33 (up to 35 pC N¯¹) were then realised through controlled grain growth and reduction in conductivity for niobium, tantalum and antimony doped compounds. The Curie temperature of the material with best properties is found to be 667 °C, which is a slight reduction from 675 °C for pure bismuth titanate ceramic. The enhancements in modified bismuth titanate achieved in present work allow the material to be considered as suitable for high temperature ultrasonic transducer applications. Integration of bismuth titanate material into a working high temperature transducer is then considered and the investigation of suitable, high temperature bonding method is undertaken. It is shown that reactivity of bismuth titanate with the titanium based fillers makes brazing unsuitable as a bonding method between piezo-ceramics and stainless steel. A novel assembly method, using liquid gallium as an electrically conductive bond, and a mechanical restraint for the piezo actuator is then presented as an alternative with the potential to reduce the negative effects of differences in thermal expansion coefficients between constituents of the transducer assembly.
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Salama, I. M. "High temperature particle -to-metal interaction in a simulated gas turbine environment." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/4610.
Повний текст джерелаАнотація:
An experimental study of the particle-to-metal
interaction during high temperatures and velocity impact
conditions is presented. A novel continuous erosion
testing facility have been used to study the effect of
particle and metal target temperatures as well as impact
particle velocity on the erosion/deposition behaviour of
the stainless steel 321, Nimonic 75, and aluminium target
materials. The study was carried out to provide database
information on the behaviour of those metals under
simulated gas turbine conditions. The erosive particles
used were quartz sand with diameters ranging from 20-30
μm. The erosion characteristics of stainless steel 321
were recorded at target surface temperature of 285°C,
415°C, 570°C and 715°C. The tests were carried out at two
different impingement angles of 30° and 60° and at
particle impact velocities of up to 300m/s. The effects
of particle temperatures of 550°C, 750°C and 950°C on
erosion/deposition rates were examined. The Nimonic 75
target temperatures were slightly modified to give a
similar surface to melting point ratio as the stainless
steel. The Nimonic 75 was tested at 545°C, 685°C, 825°C
and 965°C surface temperatures and at the same particle
velocities and temperature used for the stainless steel
tests. The Nimonic targets were only tested at one impact
angle of 30°. The aluminium targets were only tested at an
impact angle of 60° and particle impact velocity of 100
m/s. The surface temperature was modified to give a ratio
up to 0.8 of the melting point temperature, where the
particle temperature was set to be 350°C, 550°C and 750°C.
It was found that particle and target temperatures,
impact velocity and angle have a significant effect on
the erosion/deposition characteristics. There is a
threshold target and particle temperature for which
deposition begins, and it depends on impact velocity and
angle. The Nimonic 75 targets exhibit a better resistance
to particle deposition over the stainless steel 321 at
high impact velocity and temperatures. Simple models of
the erosion/deposition were established to describe the
conditions of particle deposition on the stainless steel
and Nimonic targets. The aluminium targets show an
increase in the erosion rate as target temperature
reaches certain level, which then drops as target
temperature continues to increase beyond this point.
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Mylavarapu, Sai K. "Development of Compact Heat Exchangers for Very High-Temperature Gas-Cooled Reactors." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228150070.
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Elm, Svensson Erik. "Nanotemplated High-Temperature Materials for Catalytic Combustion." Doctoral thesis, KTH, Kemiteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4800.
Повний текст джерелаАнотація:
Catalytic combustion is a promising technology for heat and power applications, especially gas turbines. By using catalytic combustion ultra low emissions of nitrogen oxides (NOX), carbon monoxide (CO) and unburned hydrocarbons (UHC) can be reached simultaneously, which is very difficult with conventional combustion technologies. Besides achieving low emission levels, catalytic combustion can stabilize the combustion and thereby be used to obtain stable combustion with low heating-value gases. This thesis is focused on the high-temperature part of the catalytic combustor. The level of performance demanded on this part has proven hard to achieve. In order to make the catalytic combustor an alternative to the conventional flame combustor, more stable catalysts with higher activity have to be developed. The objective of this work was to develop catalysts with higher activity and stability, suitable for the high-temperature part of a catalytic combustor fueled by natural gas. Two template-based preparation methods were developed for this purpose. One method was based on soft templates (microemulsion) and the other on hard templates (carbon). Supports known for their stability, magnesia and hexaaluminate, were prepared using the developed methods. Catalytically active materials, perovskite (LaMnO3) and ceria (CeO2), were added to the supports in order to obtain catalysts with high activities and stabilities. The supports were impregnated with active materials by using a conventional technique as well as by using the microemulsion technique. It was shown that the microemulsion method can be used to prepare catalysts with higher activity compared to the conventional methods. Furthermore, by using a microemulsion to apply active materials onto the support a significantly higher activity was obtained than when using the conventional impregnation technique. Since the catalysts will operate in the catalytic combustor for extended periods of time under harsh conditions, an aging study was performed on selected catalysts prepared by the microemulsion technique. The stability of the catalysts was assessed by measuring the activity before and after aging at 1000 C in humid air for 100 h. One of the most stable catalysts reported in the literature, LMHA (manganese-substituted lanthanum hexaaluminate), was included in the study for comparative purposes. The results showed that LMHA deactivated much more strongly compared to several of the catalysts consisting of ceria supported on lanthanum hexaaluminate prepared by the developed microemulsion method. Carbon templating was shown be a very good technique for the preparation of high-surface-area hexaaluminates with excellent sintering resistance. It was found that the pore size distribution of the carbon used as template was a crucial parameter in the preparation of hexaaluminates. When a carbon with small pores was used as template, the formation of the hexaaluminate crystals was strongly inhibited. This resulted in a material with poor sintering resistance. On the other hand, if a carbon with larger pores was used as template, it was possible to prepare materials with hexaaluminate as the major phase. These materials were, after accelerated aging at 1400 C in humid air, shown to retain surface areas twice as high as reported for conventionally prepared materials.QC 20100719
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Elm, Svensson Erik. "Nanomaterials for high-temperature catalytic combustion." Licentiate thesis, Stockholm : School of Chemical Science, KTH, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4360.
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Ashraf, Syeda Nishat. "Applicability of coagulation technologies for high-turbidity coal seam gas water treatment." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/127500/1/Syeda_Ashraf_Thesis.pdf.
Повний текст джерелаАнотація:
This project developed new strategies to facilitate reuse of water from the coal seam gas (CSG) industry. Both chemical coagulation and electrocoagulation were examined for their ability to protect downstream reverse osmosis (RO) desalination systems from detrimental fouling and scaling. Electrocoagulation in particular was highly effective at removing dissolved silicates, alkaline earth ions and suspended solids; thus RO operation was expected to be improved. In addition the purification of resultant brine was demonstrated, thus potentially enabling the recovery of salt as a product. It was recommended to scale-up electrocoagulation testing to pilot plant.
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Berger, T., J. Konheiser, A. V. Anikeev, V. V. Prikhodko, P. A. Bagryansky, E. Yu Kolesnikov, E. I. Soldatkina, Yu A. Tsidulko, K. Noack, and A. A. Lizunov. "Study of high temperature and high density plasmoids in axially symmetrical magnetic fields." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-27870.
Повний текст джерелаАнотація:
Within the framework of an Institutional Partnership of the Alexander von Humboldt Foundation, the Budker Institute of Nuclear Physics Novisibirsk (BINP) and Forschungszentrum Dresden-Rossendorf worked together in a joint project devoted to the research at the coupled GDT-SHIP facility of the BINP with the focus on the study of plasma phenomena within the SHIP mirror section. The project began at July 1st, 2005 and ended on August 30th, 2008. It included work packages of significant theoretical, computational and analyzing investigations. The focus of this final report is on the presentation of results achieved whereas the work that was done is described briefly only. Chapter 2 illustrates the GDT-SHIP facility and describes shortly the planned topics of the SHIP plasma research. Chapter 3 explains the main extensions and modifications of the Integrated Transport Code System (ITCS) which were necessary for the calculations of the fast ion and neutral gas particle fields in SHIP, describes briefly the scheme of computations and presents significant results of pre-calculations from which conclusions were drawn regarding the experimental program of SHIP. In chapter 4, the theoretical and computational investigations of self-organizing processes in two-component plasmas of the GDT-SHIP device are explained and the results hitherto achieved are presented. In chapter 5, significant results of several experiments with moderate and with enhanced plasma parameters are presented and compared with computational results obtained with the ITCS. Preparing neutron measurements which are planned for neutron producing experiments with deuterium injection, Monte Carlo neutron transport calculations with the MCNP code were also carried out. The results are presented. Finally, from the results obtained within the joint research project important conclusions are drawn in chapter 6.
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Ryan, David J. "High temperature degradation of combustion CVD coated thermal barrier coatings." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/18909.
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Okano, Terumi. "High temperature mercury oxidation kinetics via bromine mechanisms." Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-012509-223212/.
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Kerrigan, Brannon Michael. "System Design of a High-Temperature Downhole Transceiver." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/85006.
Повний текст джерелаАнотація:
The oil and gas industry, aerospace, and automotive industries are constantly pushing technology beyond their current operational boundaries, spurring the need for extreme environment electronics. The oil and gas industry, in particular, is the oldest and largest market for high-temperature electronics, where the operating environment can extend up to 260 degrees Celsius. The electronics currently employed in this field are only rated to 200 degrees Celsius, but with the rise of wideband gap technologies, this could be extended to 250 degrees Celsius or more without the needed for active or passive cooling. This reduces the complexity, weight, and cost of the system while improving reliability. In addition, current downhole telemetry data rates are insufficient for supporting more sophisticated and higher resolution well-logging sensors. Increasing the data rates can also save the industry significant amount of time by decreasing the amount of well-logging excersions and by increasing the logging speed.
Previous work done by this research group saw the prototyping of a high bit rate transceiver operating at 230 MHz - 300 MHz and 230 degrees Celsius; however, at these frequencies, the system could not meet size requirements. Thus, a new high-temperature high data rate transceiver design using the 2.4 GHz - 2.5 GHz ISM band is proposed to miniaturize the design and to allow for IC implementation. The transceiver was designed to meet the minimum specifications necessary to give designers flexibility between power consumption and performance. The performance of the design is simulated using AWR design environment software, which shows the system can support a downlink data rate up to 68 Mbps and an uplink data rate up to 170 Mbps across 10 channels. The effects temperature has on the system performance is also evaluated in the simulation.Master of Science
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Yesilyurt, Gokhan. "Numerical simulation of flow distribution for pebble bed high temperature gas cooled reactors." Texas A&M University, 2004. http://hdl.handle.net/1969.1/372.
Повний текст джерелаАнотація:
The premise of the work presented here is to use a common analytical tool,
Computational Fluid dynamics (CFD), along with a difference turbulence models. Eddy
viscosity models as well as state-of-the-art Large Eddy Simulation (LES) were used to
study the flow past bluff bodies. A suitable CFD code (CFX5.6b) was selected and
implemented.
Simulation of turbulent transport for the gas through the gaps of the randomly
distributed spherical fuel elements (pebbles) was performed. Although there are a
number of numerical studies () on flows around spherical bodies, none of them use the
necessary turbulence models that are required to simulate flow where strong separation
exists. With the development of high performance computers built for applications that
require high CPU time and memory; numerical simulation becomes one of the more
effective approaches for such investigations and LES type of turbulence models can be
used more effectively.
Since there are objects that are touching each other in the present study, a special
approach was applied at the stage of building computational domain. This is supposed to
be a considerable improvement for CFD applications. Zero thickness was achieved
between the pebbles in which fission reaction takes place.
Since there is a strong pressure gradient as a result of high Reynolds Number on
the computational domain, which strongly affects the boundary layer behavior, heat
transfer in both laminar and turbulent flows varies noticeably. Therefore, noncircular
curved flows as in the pebble-bed situatio n, in detailed local sense, is interesting to be
investigated.
Since a compromise is needed between accuracy of results and time/cost of effort
in acquiring the results numerically, selection of turbulence model should be done
carefully. Resolving all the scales of a turbulent flow is too costly, while employing
highly empirical turbulence models to complex problems could give inaccurate
simulation results. The Large Eddy Simulation (LES) method would achieve the
requirements to obtain a reasonable result. In LES, the large scales in the flow are solved
and the small scales are modeled.
Eddy viscosity and Reynolds stress models were also be used to investigate the
applicability of these models for this kind of flow past bluff bodies at high Re numbers.
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Stone, Michael. "An assessment of the modular high temperature gas-cooled reactor for actinide burning." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/13369.
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