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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
411

Numerical and Experimental Investigation of Particle Separation and Flow Behavior Inside an Induction Crucible Furnace

Asad, Amjad 15 October 2020 (has links)
Die Existenz der nichtmetallischen Einschlüsse in der Metallschmelze führt zur Verschlechterung der physikalischen Eigenschaften des gegossenen Stahls. Die im Rahmen des SFB 920 entstandene Arbeit beschäftigt sich hauptsächlich mit der Untersuchung der reaktiven Reinigung und aktiven Filtration der Metallschmelze im Induktionsofen mithilfe der numerischen Strömungsmechanik. Dazu werden im Rahmen der Arbeit neue numerische Simulationsmodelle entwickelt. Die Ergebnisse zeigen, dass die reaktive Reinigung einen ausschlaggebenden positiven Einfluss auf die Entfernung der Einschlüsse aus der Metallschmelze hat, wobei der Reinheitsgrad der Metallschmelze innerhalb einer kurzen Eintauchzeit des kohlenstoffgebundenen Filters ansteigt. Der in der reinen aktiven Filtration erzielte Reinheitsgrad ist deutlich niedriger als im Falle der reaktiven Reinigung. Des Weiteren befasst sich die Arbeit mit dem Effekt der Turbulenzmodellierung auf die Beschreibung der Schmelzeströmung und der Verteilung der Einschlüsse. Weiterhin stellt die Arbeit ein experimentelles Wassermodell zur Nachbildung der rezirkulierenden Schmelzeströmung im Induktionsofen vor.:Abstract List of figures List of Tables Nomenclature 1 Introduction 2 State of the Art 3 Numerical Model 4 Results 5 Summary and Conclusion 6 Outlook Bibliography / During the continuous casting, non-metallic inclusions such as deoxidation or reoxidation products may arise in steel melt due to different reactions. These inclusions have to be removed from the melt with the aim of improving the cleanliness of steel products. There are many approaches in continuous casting to enhance inclusion removal from the melt. However, this Phd thesis focuses particularly on inclusion removal by reactive cleaning and active filtration during the melt casting in an induction crucible furnace using ceramic foam filter developed in CRC 920. For this purpose, a numerical model is developed in OpenFOAM in order to simulate the melt flow and reactive cleaning as well as active filtration. Besides the numerical model, an experimental water model are created to validate the capability of the numerical model to predict the recirculating turbulent flow in the induction crucible furnace. The results show that reactive cleaning and the formation of carbon monoxide bubbles, which arise on the inclusions, have a positive impact on the melt cleanliness. Reactive cleaning can improve inclusion removal and enhance the melt cleanliness sufficiently. Based on the results, one can conclude that the rate of inclusion removal in case of reactive cleaning is considerably higher than that in case of active filtration. Furthermore, the results indicate the considerable influence of filter position and filter number on the flow field as well as on the cleaning efficiency in the induction crucible furnace. Moreover, the results shows that turbulence modeling has a considerable impact on the prediction of the melt flow and inclusion dispersion in the induction crucible furnace.:Abstract List of figures List of Tables Nomenclature 1 Introduction 2 State of the Art 3 Numerical Model 4 Results 5 Summary and Conclusion 6 Outlook Bibliography
412

Theoretische Betrachtung des Glasschmelzprozesses in Glasschmelzöfen

Wiltzsch, Sven 10 February 2014 (has links)
Die vorliegende Arbeit beinhaltet die theoretische Betrachtung des Glasschmelzprozesses in Glasschmelzöfen und die Darstellung von fünf Bewertungsprinzipien zur qualitativen Bewertung von Glasschmelztechnologien für die Abschmelz-, Restquarz- und Läuterzone. Es konnte gezeigt werden, dass zum verbesserten Einschmelzen des Gemenges nicht nur der Energieeintrag, sondern auch der Abtransport der neu entstehenden Schmelze intensiviert werden muss. Bei der qualitativen Bewertung und der Auswahl von Schmelztechnologien zur Beschleunigung der Restquarzlösung wurde dargestellt, dass der Einfluss der Schmelztechnologie auf das Verweilzeitverhalten und damit rückwirkend auf die Effizienz der Restquarzlösezone bei der Vorauswahl von Schmelztechnologien berücksichtigt werden muss. Für die Läuterzone wurde nachgewiesen, dass zwei teils in der Literatur diskutierte Bewertungsprinzipien zur Läuterung von Glasschmelzen abzulehnen sind bzw. zu überschätzten Aussagen zur Effizienz von Läutertechnologien führen. Weiterhin konnte gezeigt werden, dass für den theoretischen Fall einer Läuterbank ohne Konvektionsströmungen die Blasenwachstumsgeschwindigkeiten für Konstruktionen mit minimalen Kosten im Bereich von 4-12*10-7 m/s mit möglichen Ausreißern zu 5*10-6 m/s bei Massengläsern liegen sollten.
413

Gazéification de la biomasse en réacteur à flux entrainé : études expérimentales et modélisation / Biomass gasification in entrained flow reactor : experiments and modeling

Billaud, Joseph 02 December 2015 (has links)
Ce travail porte sur l'étude de la gazéification de biomasse en Réacteur à Flux Entrainé (RFE), dans le contexte du développement de procédés pour la production de biocarburants de deuxième génération. L'objectif de cette thèse est de modéliser les différents phénomènes qui régissent la conversion de la biomasse dans des conditions représentatives d'un RFE. La pyrolyse et la gazéification de particules de hêtre de taille comprise entre 315 et 415 µm ont été étudiées entre 800 et 1400°C en four à chute de laboratoire. L'influence de l'ajout de H2O, de CO2 et de O2 sur les produits de gazéification a été explorée, et les essais ont été simulés à partir d'un modèle 1D. L'ajout de H2O ou de CO2 permet de diminuer les rendements en char de manière significative. En phase gaz, l'influence principale de ces deux espèces est la modification de la composition en espèces majoritaires avec la réaction de gaz à l'eau. L'ajout de O2 a pour effet d'améliorer la conversion du carbone de la biomasse en gaz, et de réduire de manière significative la production de suies et de char. Le modèle, basé sur une chimie détaillée, permet de simuler ces essais de façon très satisfaisante sur toute la gamme de variation des conditions opératoires. La pyrolyse et la gazéification de particules de hêtre tamisées entre 1,12 et 1,25 mm a été étudiée en présence de O2. À 800, 1000 et 1200°C, la conversion de ces « grosses » particules est plus faible que celles des petites particules, mais à 1400°C la taille de particule n'a pas d'influence. Enfin, une étude expérimentale a été menée dans un RFE pilote pour étudier l'influence de la quantité de O2, de la taille de particule et de la pression sur la gazéification de particules de bois. Ces essais ont été simulés de façon satisfaisante en adaptant le modèle 1D. / The present work deals with biomass gasification in Entrained Flow Reactor (EFR) in the context of the development of new Biomass-to-Liquid processes. The objective of this study is to develop a comprehensive model to better understand the phenomena controlling biomass gasification in conditions representative of an EFR. Biomass pyrolysis and gasification of beech particles sieved between 315 and 450 µm have been studied between 800 and 1400°C in a drop tube furnace. The influence of H2O, CO2 and O2 addition on gasification products has been investigated and the tests have been simulated with a 1D model. The addition of H2O or CO2 leads to a significantly lower char yield. The main influence of these two oxidants in gas phase is the modification of major species composition with water gas shift reaction. With the addition of O2, the carbon conversion into gas is improved and the char and soot yields are significantly lower. The simulations are in very good agreement with the experimental results. Biomass pyrolysis and gasification of beech particles sieved between 1.12 and 1.25 mm have been studied in presence of O2. Between 800 and 1200°C the carbon conversion into gas is lower than with the smaller particles but at 1400°C the particle size has no influence. At last, the influence of O2 addition, particle size and pressure on biomass gasification has been studied in a pilot scale EFR. These experimental results have been satisfactorily simulated by adapting the 1D model.
414

Development of a heat treatment method to form a duplex microstructure of lower bainite and martensite in AISI 4140 stee

Claesson, Erik January 2014 (has links)
Research on bainite and martensite structures has indicated that lower bainite needles have a refining effect on the lath martensitic structure. Lower bainte needles partitions prior austenite grains and will consequently have a refining effect on the subsequent formed lath martensite. Smaller austenite grains will result in smaller lath martensitic packets and blocks and will result in enhanced mechanical properties.   In order to create a variation of lower bainte structure in a matrix of martensite, two different heat treating methods were tested. The work was focused towards the formation of lower bainite during isothermal heat treating in molten salt, above and below the MS-temperature. Both un-tempered and tempered samples were analyzed .Two different materials were tested, both were AISI 4140 but with a slightly difference in hardenability. The material provided by Ovako Steel is 326C and 326F the later had a higher hardenability. In order to better distinguish the two structures from each other when studied under a microscope, a variation of etching methods were tested.  It was possible to create a variation of lower bainite structures in a matrix of martensite.  326F shows less amount of lower bainite and provides a higher average surface hardness before tempering.
415

Increase the capacityof continuous annealing furnaces at Ovako

Dahlqvist, v January 2012 (has links)
The capacity of soft annealing of low alloyed tubes at Ovako’s continuous annealing furnaces have been evaluated by comparing how it is done today with information from published and internal articles on the subject. It was found that it is possible to reduce the cycle time by 30 % for one furnace, 55 % for one furnace and 72 % for two furnaces. Two separate fullscale tests were made to assess whether the faster soft annealing procedure was feasible. The tests were performed without any reconstruction of the furnace and were made by continuously vary the speed of the batch inside thefurnace. The temperature in the batch was measured and compared with results from computer simulations of the heating/cooling sequences. The computer simulations were performed in COMSOL. The soft annealing was evaluated according to the SEP-520 standard ,which means evaluating the microstructure and hardness. The results show that the faster heat treatment could yield lower grades than today but still meet it’s requirements. In order to achieve this increase  a reconstruction of the furnaces is needed and the reconstruction is  briefly treated in the report. Ideas to further increase the speed of the soft annealing procedure are also presented.
416

Utformning och installation av internetuppkopplad datalogger för kontinuerlig sintringsugn : Utveckling och implementation av Raspberry Pi baserad internetupkopplad datalogger, samt framtagning av lösningsförslag för viktmätning / Design and installation of internet-connected datalogger for continous sintering furnace : Development and implementation of Raspberry Pi based internet-connected datalogger, and generation of solutions for weight measuring

Nygårds, Erik, Oliw, Martin January 2021 (has links)
Höganäs AB has a customer center where they perform their cutomers production processes usingtheir own metal powder, thereby gaining knowledge of how the powder behaves and how it can be improved. The powder is usually pressed, and then sintered in a sintering furnace where temperature and atmosphere composition gives the component its desired characteristics. Höganäs AB didn’t save the parameters from these process’s in a easily accessible way, some values were not saved at all. To increase understanding of these parameters impact on the produced detail they wanted these parameters collected and stored in the cloud. They also wanted solution ideas and concepts for implementation of weight measuring on both the in- and output side of the furnace. This project used Ulrich & Eppinger’s product development method, modified by performing continous testing parallell to the design process. The project was also separated into three parts worked on simultaneously. Computer architecture, physical casing and weight measuring. To compile and upload to the cloud a Raspberry Pi 3 B+, a micro processor, was used. It connected via WiFi to upload files to OneDrive. The measured values from the furnace were gathered from the furnace’s PLC via OPCUA and a gas measuring unit via serial communication. Because of the use of metal powder there was conductive dust in the air which could lead to leakage currents and short circuiting if it were to gather on the processor unit. Hence the dust had to be keptaway. The casing was therefore designed to be relatively airtight. The casing was made with 3D-printed PETG. The seal utilized PETG’s elasticity to elastically deform an elevated seal, and thereby sealing the casing, without having to produce more components than a bottom and a lid. The cable feedthrough used the cables elastic deformation to seal. A screen was implemented to start and stop logging processes, which was also sealed using an overlapping lip around it’s rim. The logging of the furnace parameters was split in two logs, a day-log and a job-log. The daylog took measurements continously over a day in long intervals, 30 minutes. At the end of the day a log was uploaded for that day, hence the name. The job-log had to be started manually via the screen and was used to take measurements with higher frequency during a production series. Log files of both types were uploaded to a OneDrive folder. The product was tested with a number of final tests, both for the casing and the software. The casing was tested primarily for the numerical requirements set in the requirements specification. While the software was tested over a longer period of time to ensure functionality.The final product was a sealed, robust, easily disassembled and cable strain relieved 3D-printed box with a 3.5 inch touchscreen and a connected keyboard. It collected the desired data and compiled it to log files readable by programs such as Microsoft Excel. The weight measuring concept produced was a self-made solution with load cells under the loading ramp. The weight is then measured automatically during the regular loading process without disrupting it. Two backup solutions were also put forward.
417

Detecting Slag Formation with Deep Learning Methods : An experimental study of different deep learning image segmentation models

von Koch, Christian, Anzén, William January 2021 (has links)
Image segmentation through neural networks and deep learning have, in the recent decade, become a successful tool for automated decision-making. For Luossavaara-Kiirunavaara Aktiebolag (LKAB), this means identifying the amount of slag inside a furnace through computer vision.  There are many prominent convolutional neural network architectures in the literature, and this thesis explores two: a modified U-Net and the PSPNet. The architectures were combined with three loss functions and three class weighting schemes resulting in 18 model configurations that were evaluated and compared. This thesis also explores transfer learning techniques for neural networks tasked with identifying slag in images from inside a furnace. The benefit of transfer learning is that the network can learn to find features from already labeled data of another context. Finally, the thesis explored how temporal information could be utilised by adding an LSTM layer to a model taking pairs of images as input, instead of one. The results show (1) that the PSPNet outperformed the U-Net for all tested configurations in all relevant metrics, (2) that the model is able to find more complex features while converging quicker by using transfer learning, and (3) that utilising temporal information reduced the variance of the predictions, and that the modified PSPNet using an LSTM layer showed promise in handling images with outlying characteristics.
418

Cupolofen-Register 1879 bis 1893

Franke, Simone January 2011 (has links)
No description available.
419

Using internet -enabled remote instrumentation for research and training in physics: Evaluation of different diffusion barriers for silver metallization

Majiet, Siradz January 2007 (has links)
>Magister Scientiae - MSc / The growth of the Internet has led to many interesting developments for both educational and commercial purposes. In this project an attempt was made to use the Internet for a research purpose to facilitate the determination of the thermal stability of diffusion barriers. Another purpose of this thesis is to investigate the teaching and training use of the Internet through the development of online interactive tools and activities as well as materials. The training aspects are mentioned as it is hoped that this thesis can serve as a form of documentation of the use of the Internet, while the central part was the determination of thermal stability of TiN, TaN and TiW diffusion barriers on Ag. The fact that most advanced instruments are computer driven or can be interfaced with a computer was exploited to set up a virtual laboratory facility through which sophisticated and scarce instrumentation can be remotely accessed. The major piece of equipment that forms part of the laboratory is a four-point probe furnace at Arizona State University, Tempe, USA. The Internet made it possible to use the facility to perform an online experiment to determine the effectiveness of different diffusion barriers for silver metallisation. This was accomplished by measuring the resistance of the different samples remotely over the Internet through the control of the four-point probe furnace at Arizona State University. Four types of analysis were used to determine the thermal stability of the diffusion barriers, namely the Scanning Electron Microscopy, Rutherford Backscattering Spectrometry, X-Ray Diffraction and resistivity measurements. Similar facilities exist at Oak Ridge National Laboratory, Tennessee, USA, where a range of different electron microscopes can be accessed remotely via the Internet. The measurements of the diffusion barriers form the main part of this work. However, the other aspects required for the use of the Internet in such a system, such as the development of a website to receive and upload scanning electron microscopy (SEM) images, the development of the virtual scanning electron microscope and the learning of the Virtual Reality Markup Language are also included.
420

Investigation of the scale factor between full scale ladle furnace process and water models

Abelin, Mathias, Blomkvist, Håkan January 2020 (has links)
The ladle furnace process is an important process in the steel manufacturing industry. The purpose of this process is to optimize the composition of the elements in the melt as well as to homogenize the temperature in the liquid. It is common practice to model this process using smaller water models. In order to accurately scale these models a variety of criteria and scaling factors are needed. The central phenomenon which all else is derived from is the two-phase gas plume dominating the fluid flows. The plume, and its dependant parameters are difficult to define. Which ones ought to be used and how to use them has not been standardized. Concerns have been raised whether the most common method of scaling is even applicable in ladle metallurgy. This report gives an account for studies concerning these variables and their effect on the subject. The objective of this report is to highlight ways to improve these simulations with respect to debated parameters. The conclusion of this study points out the reasons for why these variables may be of importance for the modeling of the ladle furnace process. It also specifically mentions future work that should be conducted in order to provide deeper knowledge of thedifferent parameters affecting the method of modeling. / Skänkmetallurgin är en viktigt process inom stålindustrin. Syftet med denna process är att optimera den kemiska sammansättningen i smältan och att homogenisera temperaturen i vätskan. Det är vanligt att modelera denna process med hjälp av vattenmodeller. För att träffsäkert skala dessa modeller krävs en mängd kriterier och skal-faktorer. Det mest centrala fenomenet, utifrån vilket allt annat kan härledas, är två-fas gasplymen som dominerar flödena i skänken. Plymen och dess beroende parametrar är svåra att definera. Vilka som bör användas och hur de används har inte standardiserats. Oro har väckts över om den vanligaste skalningsmetoden ens går att använda i skänkmetallurgi. Denna rapport redogör för studier rörande dessa variabler och deras påverkan på ämnet. Syftet med denna rapport är att belysa olika tillvägagångssätt till att förbättra dessa simulationer med hänsyn till debaterade parametrar. Slutsatsen för denna studie lyfter fram anledningarna till varför dessa variabler är av vikt för modellering för skänkmetallurgin. Även framtida arbete som bör utföras föratt ge djupare förståelse för de olika parametrarna belyses.

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