In this study, the synergistic elfects of ethylene-propane and ethylene-dimethyl ester (DME) mirtures on soot formation were investigated experimentully using u coflow dilfusion flame burnen The soot volume fraction, soot particle diameter and number density were measured and compured to the homogenous mixture. Addition of DME and propane to the ethylene fuel increased soot volume fraction in the ethylene flames. The ethylene- propnne has more pronounced synergistic ffict in compsrison to the ethylene-DME flame* This is due to the fact that during the decomposition of propane some methyl radicals are generated, The reuctions related to these methyl radicals promote the formation of propargyl rodiculs and conseqaently the formation of benzene through propargyl self-reaction and finally to the soot formation. Althoagh DME decomposition produces methyl, the C-O bond in the DME removes some carbon from the reaction puth that produces soot, Hence the soot formation in ethylene-DME mixture is much slower than that in ethylene-propane mixtuFe,

Thesis (Ph.D.)--Boston University / The most common polagraphic electrode in use at the present time is the dropping mercury electrode (DME). There are, however, certain well-recognized disadvantages attendant on the use of the DME: (1) oxidation analysis is limited to 0.4 v.; (2) there are rather large charging currents associated with the growing drop; (3) the area of the drops, and hence the sensitivity can not be appreciably increased; (4) because of drop growth, a a spiky sort of current is obtained which introduces a reading error into the results obtained, especially at low concentrations. It can be seen that these disadvantages are largely a function either of the electrode shape and size, or of the method of electrode propagation. [TRUNCATED]

No description available.

Yes / Process simulation of a single-step synthesis of DME based on CO2-enhanced gasification of rice straw was conducted using Aspen PlusTM. The process consists of gasification unit, heat recovery unit, gas purification unit, single-step DME synthesis, and DME separation unit. In the simulation, highly pure DME was produced by the control of CO2 concentration in syngas to a very low level prior to synthesis. A gasification system efficiency of 36.7% and CO2 emission of 1.31 kg/kg of DME were achieved. Bio-DME production based on CO2-enhanced gasification of biomass was found to be more cost-effective as it required 19.6% less biomass than that of DME production based on conventional biomass gasification. The performance and environmental benefits of the proposed process could be further improved by the utilization of unreacted gases and the handling of CO2 generated via incorporating poly-generation concept or carbon storage, which could also potentially improve process economics. / Ningbo Bureau of Science and Technology; Innovation Team Scheme; Major R&D Programme; Provincial Innovation Team on the Commercialisation of SOx and NOx Removal Technologies; University of Nottingham Ningbo China

This diploma thesis concerns with creating of study which deals with the optimization of the ground network infrastructure of radio navigation aids for RNAV in FIR Praha. The thesis contains an analysis of concept of development of Czech navigation environment and introduces DEMETER software, in which the optimization analyses are realized. The thesis describes DME/DME navigation system from the perspective of individual components and parameters. The actual study deals with an optimization of the ground network infrastructure of the radio navigation aids and includes the definition of network performance requirements, creation of general methodology of optimization of navigation performance analysis and a procedure of choosing a suitable placement of radio navigation aid. The integral parts of the study are analyses of current state of navigation performance and analyses of possible improvement of radio navigation infrastructure.

No description available.

DME est un carburant propre qui contribue à diminuer les émissions de gaz à effet de serre; il est aussi une molécule plate-forme pour le stockage d'énergie. L'objectif de la thèse est le développement de matériaux catalytiques bifonctionnels pour la synthèse directe de DME à partir de CO2/H2 à partir de Cu/ZnO/ZrO2 comme le catalyseur de la synthèse de méthanol à partir de CO2/H2 et Al-TUD-1 comme le catalyseur de déshydratation du méthanol en DME. Dans cette thèse, Al-TUD-1 a été étudiée comme un catalyseur de la déshydratation du méthanol en DME pour la première fois. Son activité en déshydratation du méthanol en DME augmente avec la diminution du rapport Si/Al. Les catalyseurs bifonctionnels ont été préparés par un procédé de dépôt par co-précipitation. Le SMSI a été démontré et était bénéfique pour la dispersion de cuivre métallique, la surface de cuivre métallique augmente avec le rapport Si/Al. Dans le même temps, on a observé le blocage des sites acides d'Al-TUD-1 par le cuivre. Afin d'exposer les sites acides d'Al-TUD-1, la méthode de « core-shell » a été adoptée pour préparer le catalyseur bifonctionnel. Elle aide à libérer la fonction acide en empêchant son blocage par le cuivre. Cette méthode de synthèse a été bénéfique pour la stabilité des particules de cuivre métalliques, mais des faibles conversions de CO2/H2 ont été observées en raison de l'inaccessibilité du noyau. Un autre catalyseur bifonctionnel a été préparé par une méthode de mélange physique pour comparaison. L'optimisation du catalyseur bifonctionnel Cu/ZnO/ZrO2@Al-TUD-1 pour la synthèse directe de DME à partir de CO2/H2 a permis d'éclairer les principaux paramètres affectant le contact intime de deux fonctions catalytiques: surface et dispersion du cuivre, les propriétés acide et basic, la présence d'eau et l'accessibilité des sites actifs pour les réactifs. / DME is a clean fuel that helps to diminish the emissions of green house gases; it is as well a platform molecule for the energy storage. The objective of the thesis is the development of bifunctional catalytic materials for the direct DME synthesis from CO2/H2 based on Cu/ZnO/ZrO2 as the methanol synthesis from CO2/H2 catalyst and Al-TUD-1 as the methanol dehydration to DME catalyst. In this thesis, Al-TUD-1 was investigated as the methanol dehydration to DME catalyst for the first time. The methanol dehydration to DME performance increases with the decrease of Si/Al ratio. The bifunctional catalysts were prepared by co-precipitation deposition method. The SMSI was demonstrated and was beneficial for the metallic copper dispersion, the metallic copper surface area increases with the Si/Al ratio. In the same time the blockage of acid sites of Al-TUD-1 by copper was observed. In order to expose the acid sites of Al-TUD-1, the core shell method was adopted to prepare the bifunctional catalyst. It helps to free the acid function preventing its blockage by copper. This method of synthesis was beneficial for the stability of metallic copper particles, but performed low conversions of CO2/H2 due to the inaccessibility of the core. Another bifunctional catalyst was prepared by physically mixing method for comparison. The optimization of the bifunctional Cu/ZnO/ZrO2@Al-TUD-1 catalyst for the direct DME synthesis from CO2/H2 allowed enlightening the main parameters that affect the intimate contact of two catalytic functions: copper surface area and dispersion, acid and basic properties, water presence and the accessibility of the active sites for the reactants.

Au début des années 2000, les instances aéronautiques ont exprimé le besoin de développer un nouveau système de radiocommunication aéronautique du fait de l'augmentation du trafic aérien et de la saturation croissante des capacités de communication radio entre les aéronefs et les stations de contrôle aérien. L'une des composantes de ce système, nommée L-DACS (« L-band Digital Aeronautical Communication System »), devrait opérer dans la bande L-aéronautique (960-1164 MHz), dans laquelle fonctionnent également de nombreux autres systèmes radioélectriques. La compatibilité radioélectrique (CRE) de L-DACS avec ces systèmes est un des facteurs principaux à prendre en considération dans le développement d'un tel système.L'objectif principal de cette thèse est d'identifier les principaux problèmes reliés à la CRE et d'en étudier les cas critiques. Ces travaux sont fondamentaux en aéronautique, puisque tout dysfonctionnement dans la communication ou dans les systèmes de radionavigation peut mettre en danger la sécurité du vol. Les conclusions de cette thèse contribueront à la normalisation du système L-DACS et à la finalisation de ses spécifications.Dans une première étape, on étudie l'état de l'art dans les communications aéronautiques et en CRE. On analyse en particulier les dernières spécifications des deux systèmes candidats L-DACS. Ensuite, on propose un algorithme de calcul de brouillage dans le but d'étudier la CRE dans le domaine fréquentiel, d'en identifier et d'en traiter les cas critiques. L'analyse fréquentielle étant insuffisante dans plusieurs cas, on propose alors une approche temporelle d'étude de CRE. Après en avoir présenté les avantages, on présente un exemple d'étude de l'effet d'un système L-DACS sur un récepteur DME (« Distance Measuring Equipment ») à l'aide d'un banc de test CRE aéronautique.Cette thèse a été réalisée en collaboration avec la Direction Générale de l'Aviation Civile (DGAC), qui est un acteur principal pour la réglementation des communications et un affectataire de fréquence pour le spectre aéronautique en France. La thèse contribue aux études menées par la DGAC à l'échelle nationale et internationale.Dans les perspectives, on propose la poursuite de cette étude par une approche temporelle plus générale pour étudier la CRE entre des systèmes radioélectriques quelconques en tenant compte de paramètres supplémentaires liés à la dynamique des systèmes et aux propriétés de leurs technologies. / In the beginning of the 21th century, the aeronautical authorities expressed their need to develop a new system for aeronautical radiocommunications, because the air-traffic is increasing and that current communication systems between pilots and air-controllers are reaching their capacity limits. The L-band Digital Aeronautical Communication System (L-DACS) is the part of the future system that will be operating in a part of the aeronautical L-band (960-1164 MHz), already occupied by a large number of radio-frequency legacy systems. Consequently, it is essential to consider its radio-frequency compatibility (RFC) for the development of the future L-DACS system. This thesis aims at identifying the principal issues related to RFC and studying its critical situations. Such topics are fundamental in aeronautics, as any communication or radionavigation dysfunction may endanger flight and passengers security. Some obtained results will be used for the L-DACS standardization and its specifications finalization. We first analyze the state-of-the-art in both aeronautical communications and RFC, focalizing on updated specifications of both preselected L-DACS candidate systems. We then propose a deterministic algorithm to compute the interference level in order to study the RFC in the frequency domain under identified critical scenarios. Since the frequency-domain analysis seems to be insufficient in several cases, we develop a different methodology, called the time-frequency approach, to analyze the RFC for such situations. We apply this new approach to analyze the effect of an L-DACS interferer on a Distance Measuring Equipment (DME) receiver, using an aeronautical RFC test-bed that we implemented at SUPELEC. This work has been performed in collaboration with the French Civil Aviation Authorities (DGAC), which are an important actor in aeronautical communication regulations and aeronautical spectrum management in France. The thesis contributes to DGAC studies at national as well as international levels. For further work, we suggest to generalize the proposed time-frequency approach to analyze the RFC between any two radio-frequency systems, taking into account additional parameters related to system dynamics and their technology properties.

Today’s society is adapting to reduce the climate footprint which is why the Swedish Armed Forces is expected to revise its use of fossil fuel. The choice of fuel is not obvious, and this report aims to examine the possibilities and limitations for a few renewable fuel’simplementation in the Swedish Armed Forces. Based on Moche Kress logistics concept an analyzing tool were created. The analyzing tool is based on the category’s economy, industry/engine technology, technology/characteristics, inventory, storage facilities and transports. Methods used is a mixture of document collection and interviews with an expert in the area of alternative fuels and combustion engines. The renewable fuels analyzed are FAME, HVO, biogas and DME. Results of the analysis show that FAME has a relative low cost for production, only requires small-scale modifications in engines, the domestic production is expected to expand and is interoperable with the current supply chain. The biggest limitations are the bad qualities regarding cold temperatures and can’t be stored longer periods of time. HVO has a bit higher production cost but has good qualities even in colder temperatures, high energy density, can beused in all diesel engines after an approval from the manufacturer and can be implemented incurrent infrastructure as well as supply chain. Raw materials consist on the other hand largely from palm oil production. Biogas has a relatively high production cost, low energy density, requires extensive renovations/installations of engines/fuel systems and can neither be implemented in current infrastructure nor supply chain. Positive features are its good qualities in cold temperatures and big part domestic production. DME also has good qualities in cold temperatures but requires a new injection system and a new tank, can’t be implemented in neither current infrastructure nor supply chain and is not produced anywhere globally today. Based on the results from the analysis HVO were concluded as the most realistic alternative for the Swedish Armed Forces. Further conclusions were that FAME is not the best alternative and neither biogas nor DME were estimated as a realistic choice today. The last conclusion of the analysis is that none of the alternatives had possible self-sufficiency in Sweden as of now. / Mot bakgrund av att samhället ställer om till att bli mer klimatpolitiskt hållbart förväntas ett drivmedelsbyte vara aktuellt för Försvarsmakten. Vilket drivmedel som är aktuellt för detta är inte självklart och detta arbete syftar till att undersöka vilka förutsättningar ett antal förnybara drivmedelsalternativ har för implementering i Försvarsmakten. Utifrån Moche Kress logistikkoncept togs ett analysverktyg fram som utgår från kategorierna ekonomi, industri/motorteknik, teknologi/egenskaper, lagerhållning/tillgänglighet, infrastruktur för lagerhållning och transporter. Empiri samlades därefter in via en dokumentinsamling samt intervjuer med en expert inom alternativa drivmedel och förbränningsmotorer. Alternativen som analyserats är FAME, HVO, biogas och DME. Resultat av analysen var att FAME har en relativt låg produktionskostnad, enbart kräver mindre anpassningar i motorer, har inhemsk produktion som förväntas expandera och kan implementeras i befintlig försörjningskedja. Största begränsningarna är att det har begränsade köldegenskaper samt låg lagringsbeständighet. HVO har en något högre produktionskostnad men goda köldegenskaper, högt energiinnehåll, kan nyttjas i samtliga dieselmotorer efter tillverkarens godkännande och kan implementeras i befintlig försörjningskedja respektive infrastruktur. Råvaror kommer dock till stor del från palmoljeproduktion. Biogas har en relativt hög produktionskostnad, lågt energiinnehåll, kräver omfattande renoveringar/installationer av motorer/bränslesystem och kan inte implementeras i varken befintlig försörjningskedja eller infrastruktur. Det har dock bra köldegenskaper och hög andel inhemsk produktion. DME har bra köldegenskaper, men kräver nytt insprutningssystem och ny tank, kan inte implementeras i dagens försörjningskedja eller infrastruktur och produceras ingenstans i världen idag. Utifrån analysens resultat bedömdes HVO som det mest realistiska alternativet för Försvarsmakten. Utöver det bedöms inte FAME som mindre fördelaktigt, och biogas respektive DME som orealistiska alternativ i dagsläget. Den sista slutsatsen av analysen var att inget alternativ medger självförsörjning i Sverige idag.

Student Number : 9506932W - MSc research report - School of Mechanical Engineering - Faculty of Engineering and the Built Environment / In this research project, the performance and emissions of a conventional compression ignition engine fuelled on ethanol as main fuel and dimethyl ether as ignition promoter were investigated. Tests were first conducted on diesel fuel, then on ethanol fuel with dimethyl ether and compared. All tests for both fuelling techniques were conducted at the same engine speed and injector pressure. However, engine settings with specific reference to injection timing and injector pressure were optimised to suit diesel fuel, and were left unaltered when the engine was fuelled on ethanol and dimethyl ether. The injector nozzle configuration used for diesel fuel was a standard three-hole type nozzle, whereas for ethanol fuel with dimethyl ether a standard three-hole nozzle as well as a four-hole type nozzle was used. Also investigated was the effect a catalytic converter would have on exhaust emissions, from both fuelling techniques. The performance results of ethanol/dimethyl ether fuel compared favourably to that of diesel fuel. The brake power attained for both fuelling techniques was approximately the same, however the only penalty incurred to this desired result was the simultaneous increase in the brake specific fuel consumption of ethanol/dimethyl ether fuel. The fuel conversion efficiency of ethanol/dimethyl ether fuel was also found to be lower than that of diesel fuel, this largely attributed to the difference in energy release patterns between the two fuels. The emissions results obtained showed that ethanol/dimethyl ether fuel burns cleaner, mainly due to its chemical structure containing oxygen molecules. The NOx, THC, CO and CO2 emissions, produced before the catalytic converter, of ethanol/dimethyl ether fuel were lower than those of diesel fuel. The catalytic converter further produced lower emissions, with the four-hole type nozzle producing the most desired results. In terms of catalytic converter efficiency, THC and CO emissions were more readily removed compared to NOx. In addition, virtually no smoke emissions were detected for ethanol/dimethyl ether fuel combustion.