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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.
21

A Computational Study of Diesel and Biodiesel Combustion and Nox Formation in a Light-Duty Compression Ignition Engine

Wang, Zihan 11 August 2012 (has links)
Diesel and biodiesel combustion in a light duty compression ignition engine were simulated during a closed cycle, using a commercial computational fluid dynamics (CFD) code, CONVERGE. The corresponding computational domain was constructed for the engine based on combustion chamber geometry and compression ratio measurements. Submodels were calibrated for simulation. The results were able to capture the experimental pressure and apparent heat release rate trends for both fuels over a range of engine loads and fuel injection timings. NOx emissions trends were captured for diesel, while under-predicted for biodiesel. The NOx trends were also analyzed based on the thermal NO mechanism. A new modular tool in Matlab was developed for studying the residence time. It was found that high in-cylinder temperatures and their residence time are critical in NOx formation.
22

Impact of urea injection on NOx emissions for MSU Challenge X hybrid electric vehicle using a green fuel

Crawford, Kyle Elliott 05 May 2007 (has links)
The addition of Tier 2 standards by United States Environmental Protection Agency (EPA) has increased focus on light-duty vehicle emissions. In this study, a diesel-electric hybrid vehicle was used for testing under the Challenge X program. The diesel engine was powered by a 20% soy-based biodiesel - 80% diesel blend, and the electric motor received its energy from a 330 volt Nickle Metal Hydride battery pack. The diesel engine, notorious for high emissions of nitrogen oxides (NOx) and particulate matter (PM), requires aftertreatment of these emissions to achieve Tier 2 EPA compliance. The primary focus of this thesis is use of a urea injection selective catalytic reduction (SCR) system to reduce NOx emissions. Also, a diesel particulate filter (DPF) was employed for PM reduction purposes. Significant decreases in both NOx and PM emissions were achieved.
23

NOx-Speicherkatalysatoren: Einfluss der katalytischen Bestandteile und mathematische Modellierung

Schmeisser, Volker January 2009 (has links)
Zugl.: Stuttgart, Univ., Diss., 2009
24

Ceria Based Catalysts for Low Temperature NO<sub>x</sub> Storage and Release

Jones, Samantha 01 January 2016 (has links)
Model ceria catalysts were evaluated for NOx storage and desorption performance under lean conditions. Three different storage temperatures (80 °C, 120 °C, and 160 °C) were utilized to evaluate NOx storage. Higher temperatures resulted in higher NOx storage. It was observed that storage of platinum promoted ceria resulted in higher NOx storage compared to promotion with palladium. NOx desorption behavior of platinum promoted ceria indicated that the majority of NOx is released at high temperatures (> 350 °C), comparatively palladium promotion released more of the stored NOx at lower temperatures. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) indicated that platinum promotion results in NOx storage as thermally stabile nitrates, while palladium promotion results in NOx storage as thermally labile nitrites. Doping ceria with trivalent rare earth oxides has been shown to improve NOx storage by generating lattice oxygen vacancies. Ceria doped with Pr, Y, La, Sm, and Nd at two different concentrations (5 and 20 mol%) and promoted with Pt were evaluated. Doping ceria with 5% Sm, Nd, and Pr improved the amount of NOx stored while the addition of Sm and La did not improve storage. Upon increasing dopant concentration, NOx storage decreased in all cases but Pr. However, increasing Pr concentration was found to increase NOx storage as well as low temperature NOx release. Ceria doped with Pr promoted with Pd increased the amount of NOx released at lower temperatures compared to Pt promotion, although palladium promotion resulted in lower storage. Similar DRIFTS spectra were obtained with Ce-Pr when promoted with Pt or Pd compared to model catalysts. Platinum promotion results in the storage of NOx at nitrates, which require high temperatures for removal. Comparatively, Pd promotion results in NOx stored at nitrites requiring lower temperatures for removal. Ceria doped with Pr proved to be promising, although not thermally stable when exposed to high temperatures as may be seen during a DPF clean up. Therefor, stabilizing Ce-Pr catalysts with Zr were evaluated. It was found that stabilizing Ce-Pr with Zr was not found to be beneficial to the catalyst performance.
25

Development and Validation of a NOx Emission Testing Setup for a Diesel Engine, Fueled with Bio-Diesel

Kohli, Dhruv 27 April 2009 (has links)
No description available.
26

The combustion of fossil and waste solid fuels

Ou, Jenq-Jang January 1994 (has links)
No description available.
27

Filbornaverket : En analys på ombyggnationen av pannan med avseende på kväveoxidutsläpp / Filbornaverket : An analysis of the reconstruction of the boiler regarding nitrogen oxide emissions

Hedlund, Ingemar, Ovenmark, Erik January 2019 (has links)
Studiens syfte var att studera en ombyggnation av SNCR-anläggningen i Filbornaverket, enavfallseldad rosterpanna, på uppdrag av Öresundskraft Kraft &amp; Värme AB. Anledningen var attse om en minskning av NOx-utsläpp var möjlig då det innebär en minskning av försurning avskog och mark. Naturvårdsverket har som mål att minska mängden NOx-utsläpp genom attanvända sig av ekonomiska styrmedel.Filbornaverket är en panna på cirka 60 MW fjärrvärmeeffekt och 18 MW eleffekt. Metodensom användes var en jämförande metod. Ombyggnationen ledde till en minskning av NOxutsläppunder perioden oktober till november 2018 på 5,45% jämfört med samma period2017. Detta innebar en årlig besparing på cirka 250 000 kr i minskade NOx-avgifter tillNaturvårdsverket för Öresundskraft Kraft &amp; Värme AB. Mängden insprutad ammoniak blev igenomsnitt 4,73% lägre 2018 jämfört med 2017. / This study examined the reconstruction of the SNCR equipment in Filbornaverket, a wasteburning grate boiler, on behalf of Öresundskraft Kraft &amp; Värme AB. The purpose was to see ifa reduction of NOx was possible. A reduction of NOx means a reduction in acidification offorest and land. Naturvårdsverkets goal is to reduce the amount of NOx by using economiccontrol means.Filbornaverket is a boiler of about 60 MW district heating power and 18 MW electrical power.A comparative method was used in this study. The reconstruction lead to a reduced amountof NOx during the period October to November 2018 of 5,45% compared to same period2017. This means an annual saving of around 250 000 kr in reduced NOx-fees toNaturvårdsverket for Öresundskraft Kraft &amp; Värme AB. The amount of injected ammonia wasin average 4,73% lower during 2018 compared to 2017.
28

Reducción de NOx en efluentes gaseosos mediante materiales de potasio/carbón conformados: desarrollo de un modelo cinético

Bueno López, Agustín 23 October 2002 (has links)
No description available.
29

Caractérisation numérique et expérimentale d'un brûleur à gaz à swirl variable: longueur de flamme, transferts thermiques et production de NOx

Pesenti, Barbara 10 March 2006 (has links)
Dans la chaîne de fabrication des produits plats sidérurgiques, les brames sont des produits semi-finis sortant de la coulée continue, se présentant sous la forme de parallélépipèdes d'acier de 150 à 320 mm d'épaisseur qui devront passer dans le laminoir à chaud afin de réduire leur épaisseur à quelques millimètres pour être enfin enroulées en bobines de tôle. Pour permettre les importantes déformations du laminage, les brames doivent entrer dans le laminoir à une température comprise entre 800 et 1200°C; elles sont amenées à cette température en traversant un four de réchauffage où leurs faces supérieure et inférieure sont chauffées par des brûleurs de différents types, parmi lesquels figurent des brûleurs à longueur de flamme réglable, qui doivent permettre une variation, en cours de fonctionnement, de la longueur de la flamme générée par le brûleur afin d'adapter le profil de transfert de chaleur aux caractéristiques géométriques du produit à réchauffer. Ce travail a permis de caractériser le fonctionnement et les performances d'un tel brûleur, en particulier de déterminer la réglabilité effective de la longueur de flamme en fonction des conditions opératoires, ainsi que d'établir l'utilité de la modulation de flamme pour le procédé de chauffage en mesurant les effets de cette variation sur le profil de flux de chaleur transmis à la charge. Les conséquences de ces modifications sur la stabilité de la combustion et sur les quantités de polluants émis, en l'occurrence sur les émissions d'oxydes d'azote (NOx), ont également été examinées. Les performances du brûleur à longueur de flamme variable ont été étudiées par le biais de mesures réalisées sur une unité pilote à échelle réduite, conçue et réalisée au cours de ce travail. La détermination de la longueur de flamme a été réalisée par la mesure de l'émission de chimiluminescence du radical $OH$ tandis que la mesure du profil de flux radiatif incident sur la charge a mis en évidence que les transferts de chaleur au sein du four n'étaient que faiblement modifiés par les variations de longueur de la flamme. Les résultats expérimentaux ont également montré que la forme de la flamme n'influençait pas de manière significative le niveau d'émissions de NOx à la sortie du four. Cette approche a été complétée par une démarche de simulation numérique détaillée de l'équipement à l'aide d'un code commercial de CFD (pour Computational Fluid Dynamics) permettant de résoudre les équations différentielles de l'aéro-thermochimie (écoulement, turbulence, combustion et transfert de chaleur) dans le four. La comparaison des données numériques et expérimentales a permis de valider les résultats de simulation et d'établir leur sensibilité aux hypothèses des modèles utilisés. Elle a montré que la prédiction de la forme de la flamme était principalement conditionnée par les paramètres cinétiques du modèle de combustion plutôt que par le choix des modèles de turbulence et de rayonnement; elle a en outre établi que les niveaux d'émissions d'oxydes d'azote de l'ensemble des flammes modélisées ne pouvaient être calculés correctement par des modèles simples de combustion et de production de NOx. Ce travail s'inscrit dans le contexte de recherches réalisées en collaboration avec l'Agence Internationale de l'Energie, portant sur l'étude des phénomènes liés à la combustion du gaz naturel dans des brûleurs alimentés en air préchauffé; il a bénéficié du soutien financier de la Région Wallonne pour l'acquisition des outils expérimentaux et numériques utilisés au cours de cette étude.
30

Numerical Study of NOx and Flame Shape of a DLE Burner

Hamedi, Naser January 2012 (has links)
For natural gas combustion, there is a large amount of experience in the gas turbine industry. However, much of the design work is based on costly combustion tests due to insufficient accuracy of existing prediction tools for data such as emissions and effects due to fuel composition. In the present work, Computational Fluid Dynamics (CFD) approach is used to study partially premixed combustion in the 3rd generation DLE (Dry Low Emission) burner that is used in SGT-700 and SGT-800 gas turbines. The fuels that are studied here are natural gas and enriched hydrogen fuel. The CFD models which are used in this work are an axisymmetric and a 3D model and the softwares are ANSYS CFX and ANSYS FLUENT. One of the main objectives of this thesis is the study of flame shape and NOx emission in hydrogen enriched combustion. In the first study of the present work, effect of adding hydrogen to non-preheated gas combustion was investigated and the results were compared with the available measurement data. Calculated laminar burning velocity with CANTERA showed a good agreement with the experimental and numerical references. Also, the accuracy of generated flamelet libraries in CFD tools to calculate adiabatic flame temperature was compared with different available tools. Results showed good agreement between available tools for the ranges of interest. In addition, flame shape and NOx prediction was studied in the gas turbine burner. Adding hydrogen to the fuel increased significantly turbulent burning velocity and OH distribution in the domain. The effect of hydrogen on the central stagnation point was studied and the simulation results did not show a significant effect on the stagnation point location. Beside the flame shape, this study showed that although the CFD NOx prediction tools in ANSYS CFX and ANSYS FLUENT predict the trend of NOx and the flame propagation in the right manner, in order to use as a reliable prediction tool in the gas turbine industry they need to be improved.

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