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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.
11

Optimisation des flux dans les réseaux de transport pour les systèmes dynamiques étendus : cas des systèmes hydrographiques / Dynamic network flow optimization for large scale systems : application to hydrographic systems

Tahiri, Ayoub 23 May 2019 (has links)
L’allocation de la ressource de manière optimale, dans un système dynamique étendu, consiste à la répartir et à l’acheminer aux bons endroits, aux bons moments et en bonne quantité. Les flux transportés sont caractérisés par des non-linéarités et sont soumis à des retards lors de leur transfert, mais aussi, à des déformations importantes lorsque la ressource est un fluide. Dans ce travail, nous proposons de prendre en compte, dans la modélisation de ces systèmes, l’ensemble de ces contraintes pour une gestion optimale de transport de fluide. Le système est modélisé par un réseau de transport étendu afin de représenter l’évolution de la ressource au cours du temps et d’intégrer les retards inhérents aux transferts des flux. Afin d’introduire dans le graphe la dynamique des écoulements des fluides à surface libre, nous définissons des sommets de répartition permettant la modélisation des phénomènes de propagation des flux. Les objectifs de gestion sont représentés par des coûts sur les arcs. L’allocation optimale de la ressource est obtenue par la recherche du flot de coût minimal sur le réseau de transport. A cette fin, un algorithme d’optimisation prenant en compte les contraintes additionnelles issues des sommets de répartition est proposé. Les méthodes et algorithmes développés sont appliqués au cas des systèmes hydrographiques et à la problématique de l'allocation de la ressource en eau associée. Cette dernière est devenue cruciale en raison des effets négatifs de l'anthropisation des espaces naturels, du changement climatique et de l’augmentation des besoins. Il s’agit de partager la ressource en eau entre différents usagers, conformément à un ensemble d’objectifs et de priorités. L'allocation de la ressource en eau est réalisée en trois étapes principales : le diagnostic de l'état de la ressource disponible sur le système hydrographique à l'instant initial, incluant la prévision de son évolution sur l'horizon de gestion ; la détermination des actions à réaliser sur le système hydraulique pour allouer la ressource en respectant les contraintes et les objectifs ; la surveillance des données mesurées fournissant des indicateurs reconstitués de l’état du système. Les performances de la démarche proposée sont évaluées sur divers systèmes hydrographiques soumis à de multiples régimes hydrologiques. / Optimal allocation of the resource, in a large scale system, consists in distributing it and delivering it to the right places, at the right time and in the right quantity. The transported flows are characterized by nonlinearities and are subject to delays during their transfer, but also to significant deformations when the resource is a fluid. In this work, we propose to take into account, all these constraints in the modeling of these systems, for an optimal management of fluid transport. The system is modeled by an expanded flow network in order to represent the evolution of the resource over time and to integrate the delays that are inherent in flow transfers. In order to introduce the flow dynamics of open-channel flows into the graph, we define distribution nodes allowing to model the flow propagation phenomena. The water allocation objectives are represented by costs on the network’s arcs. The optimal allocation of the resource is obtained by the search for the minimal cost flow on the network. To this end, an optimization algorithm taking into account the additional constraints resulting from the distribution nodes is proposed. The methods and algorithms developed, are applied to the case of hydrographic systems and to the water resources management problem. The latter has become crucial due to the negative effects of anthropisation of natural areas, climate change and increasing needs. Water allocation consists in sharing the water resource between different users, according to a combination of objectives and priorities. The allocation of the water resource is carried out in three main steps: the diagnosis of the state of the available resource on the hydrographic system at the initial time step, including the forecast of its evolution over the management horizon; the determination of operations to be carried out on the hydraulic system to allocate the resource according to the constraints and objectives; the monitoring of the measured data in order to provide reconstructed indicators of the system’s state. The performances of the proposed approach are evaluated on various hydrographic systems, subjected to multiple hydrological regimes.
12

Simulation des Wärme- und Stofftransports in Partialoxidationsprozessen

Richter, Andreas 27 March 2018 (has links)
Die vorliegende Habilitationsschrift stellt den erreichten Stand der CFD-basierten Modellierung ein- und mehrphasiger Hochtemperaturprozesse dar. Die hierzu vorgelegten Arbeiten umfassen die Hochdruck-Partialoxidation von Erdgas, die Vergasung fester Einsatzstoffe in einem endothermen Flugstromreaktor und in einem mehrstufigen Wirbelschichtprozess sowie die Synthesegasaufbereitung in einem neuen Quenchreaktor. Der Forschungsschwerpunkt reicht dabei von der Entwicklung neuer Korrelationen zur Beschreibung der Strömungskräfte und des Wärmeübergangs basierend auf partikelaufgelösten Rechenmodellen über die Modellierung der thermochemischen Konversion reaktiver Einzelpartikel bis hin zur Berechnung und Optimierung unterschiedlicher Hochtemperaturreaktoren. / This habilitation thesis discusses the state of the art for the CFD modeling of single-phase and multi-phase high-temperature processes. The presented publications comprise the high-pressure partial oxidation of natural gas, the gasification of solid fuels in entrained-flow gasifiers and multi-stage fluidized-bed gasifier as well as the syngas treatment in a new quench reactor. The scientific approach covers the development of new correlations for flow forces and heat transfer based on particle-resolved numerical models, the modeling of the thermochemical conversion of reactive single particles, and the calculation and optimization of different high-temperature processes.
13

Konstruktionsåtgärd för lutande bränsletank / Konstruktions åtgärder för bränsleexportering vid lutning av bränsletank

Elmashaad, Farook, Abdulmageed, Ammar January 2019 (has links)
Bränsle är en viktig substans för fordon och utan bränsle så är de flesta fordon inte funktionella. I de allra flesta instruktionsböcker för fordon så rekommenderas det att bränslet inte får nå en kritisk låg nivå av bränsle. Då man talar om den kritiska bränslenivån så handlar det om ¼ kvarliggande bränsle. Då bränslet når den kritiska nivån i bränsletanken så kan problem ske och dessa problem är direkt kopplade till bränsletanken och pumpen.     Syftet med denna kandidat examensarbete är att undersöka problemet och det befintliga bränslesystemets konstruktion för att sedan generera en eller fler lösningar till problemet. Då information för detta arbete är begränsad över nätverket så skedde en del intervjuer med verkstan och fordons företag och fabriker såsom Volvo och Scania för att få en bra mängd information som sedan användes som utgångspunkt till arbetet.   För att generera lösningar till problemet med informationen som erhållits av intervjuer och andra källor så användes vissa verktyg och metoder. Då arbetet var begränsad att utföra praktiskt så utfördes den teoretiskt med hjälp av kunskaper från materiallära, hållfasthetsberäkningar, simulations program såsom AutoCAD, NASTRAN, fysik och en mängd andra ingenjörs baserat litteratur för att åstadkomma goda resultat.   Resultat blev en enkel konstruktion som är anpassat för tillverkningen av bränsletankar och som både funkar för cylindriska och rektangulära bränsletankar.   I denna rapport så presenteras resultatet i form av några förslags modeller av ett koncept som anses vara en lämplig lösning för problemet och resultat utfört med konceptet som då visar att konceptet uppfyller en fungerande lösning för det presenterade problemet. Storlek för konstruktionen presenteras i en form av enkla beräknings steg där man utgår ifrån bränsletanks modellen man vill tillämpa konceptet i. / The fuel is an important substance for vehicles and without fuel the most vehicles are not functional. In other words, they cannot move. In all instruction manuals, it is recommended that the fuel should not attain a low level in the fuel tank itself because it could lead to many consequences and these consequences are directly linked to the fuel pump and the engine itself.   The purpose of this bachelor's thesis is to investigate the issues and the existing fuel system design, then generate concepts to solve the problem. The information about the problem is limited on the world wide web, therefore we have been in contact with various truck workshops, vehicle companies and been visiting some of them. Volvo and Scania were at the top of the list. The reason was to get good and reliable information about the fuel tanks and then use it as a starting point.   Using information from interviews and sources helped very much to generate different concepts and solutions to the problem. Also, some tools and methods were very useful to build, chose and evolve the concepts. Note that some work was not performed practically because of limitations, therefore it was theoretically done with help of knowledge from different courses like materials theory, strength of materials calculations, physics, simulation programs like AutoCAD, NASTRAN and other engineering literature to achieve good results.   The result was a simple design adapted for the production of fuel tanks for the manufacture of fuel tanks, which works for both cylindrical and rectangular fuel tanks. In this report, the results are presented in the form of some proposal models and results performed with the concept, which then shows that the concept satisfies a solution to the presented problem. / <p><strong>Presentationerna genomfördes på distans med zoom</strong></p>

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