Dissertations / Theses on the topic 'Oxidation of Soot'
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1
Meredith, Owain. "Passive catalytic soot oxidation." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/110463/.
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Increasingly stringent legislation limiting the emissions of particulate matter (commonly referred to as soot particulates) has led to the adoption of particulate filters in the exhausts of both diesel and gasoline passenger vehicles. While filters are highly effective at reducing these emissions, it is necessary to periodically remove trapped particulates in order to avoid their accumulation and the resulting loss of vehicle performance associated with backpressure build-up. An effective method of removing soot particulates is through combustion (oxidation) with the oxygen-containing species present in the atmosphere of the exhaust, however this is unattainable at the temperatures experienced under normal driving conditions. A catalyst able to lower the temperature of soot oxidation is therefore desirable in order to achieve passive regeneration of the filter. Previous studies have identified ceria, CeO2 as a promising soot oxidation catalyst due to its outstanding redox properties, and have shown that it can be enhanced by doping with various other metals. In this work, ceria-based catalysts have been prepared by the co-precipitation method. Ceria was doped with zirconium, lanthanum, praseodymium and neodymium in various ratios in order to enhance its catalytic properties. Each of these materials also contained alumina in order to improve their thermal stability. Of these materials, the most active for soot oxidation was found to be a CeO2-Nd2O3-Al2O3 catalyst prepared in a 7:3:10 molar ratio of Ce:Nd:Al and calcined at 750ºC under flowing air. This catalyst lowered the temperature at which soot oxidation reached its peak rate by over 100ºC. It was also demonstrated that the catalytic activity of these materials benefited considerably from the presence of alkali metals within their structure. The use of the ceria-based materials as supports by impregnating them with other species previously identified as active soot oxidation catalysts was also investigated, which resulted in a further lowering of the soot oxidation temperature. Structural characterisation of the materials was carried out by X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and surface area analysis (BET), while their redox properties were analysed by temperature-programmed reduction (TPR). The catalytic activity of the materials towards soot oxidation was investigated using thermogravimetric analysis (TGA).
2
Song, Haiwen. "Diesel soot oxidation under controlled conditions." Thesis, Brunel University, 2003. http://bura.brunel.ac.uk/handle/2438/4814.
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In order to improve understanding of diesel soot oxidation, an experimental rig was designed and set up, in which the soot oxidation conditions, such as temperature, oxygen partial pressure, and CO2 partial pressure, could be varied independently of each other. The oxidizing gas flow in the oxidizer was under laminar condition. This test rig comprised a naturally-aspirated single cylinder engine which acted as the soot generator, and a separate premixed oxidation burner system in which soot extracted from the engine was oxidized under controlled conditions. Diesel soot was extracted from the engine exhaust pipe and from the engine pre-combustion chamber, and the soot-laden gas was then conveyed to the burner where it was oxidized. The burner was positioned vertically and it had a flat flame whose thickness was only a few millimetres. The hot gases from the flame flew upwards through a quartz transparent tube which acted as the soot oxidation duct. The soot-laden gas from the engine was premixed with the feedgas (itself a premixed mixture of methane, air, oxygen, and nitrogen) to the burner. The soot particles passed vertically through the flame front and continued burning in the post-flame gas flowing through the quartz tube oxidation duct. The oxygen concentration and temperature of the post-flame soot oxidation gas were controllable by adjusting the flowrate and composition of the burner feedgas. Diesel soot particles were sampled at different heights along the centreline of the quartz tube above the burner. Profiles of oxygen concentration, temperature, and soot particle velocity in the oxidation zone were thus measured. Morphology and size distributions of the sampled diesel soot particles were analyzed by means of Transmission Electron Microscopy (TEM) and a computer software called ImagePro Plus. Subsequently, the specific surface oxidation rates of the soot particles were worked out based on soot particle size distributions. The TEM micrographs obtained in this study showed that the diesel soot agglomerates existed in forms of clusters and chains, each containing between a small number and thousands of individual, mostly spherical tiny particles. Of order 97% of the individual spherical particles (spherules) had a size range from 10 to 80 nm. Occasionally, individual spherules of about 150 nm in diameter could be observed. The diesel soot particles sampled from the pre-chamber of the engine had different size distributions from those sampled from the exhaust of the engine, indicating that the soot underwent an oxidation process in the combustion chamber. Soot oxidation experiments were performed in the burner post-flame gas under oxygen partial pressures ranging from 0.010 to 0.050 atm and temperatures from 1520 to 1820 K. The test results showed that the oxidation rates of the diesel soot extracted from the diesel engine were generally lower than those predicted by the well-known Nagle and Strickland-Constable formula; however, the measured oxidation rates were higher than the predictions made with another well-known formula - the Lee formula. The soot extracted from the engine pre-chamber appeared not to oxidize as fast as the soot extracted from the exhaust of the engine. CO2 gas injection to the post-flame oxidation gas at constant oxygen partial pressure and oxidation temperature seemed to have accelerated the diesel soot oxidation rate. Based on the experimental results of this study and the results of other researchers, modifications to the Nagle and Strickland-Constable formula and to the Lee formula were accomplished. Also, an empirical expression, as an alternative to semi-empirical formulae, was worked out and presented in the thesis.
3
Genc, Volkan Eyup. "Diesel Soot Oxidation Catalyst Filter System Design." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606189/index.pdf.
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The objective of this study was onboard testing of a mixed metal oxide diesel soot oxidation catalyst composing of oxides of lead and cobalt previously developed in our lab, by mounting a diesel particulate filter (DPF), which is coated with this catalyst, to the exhaust stream of a diesel vehicle.
Commercial wall flow type DPF&rsquos (Corning EX-80) were coated with the catalyst by a slurry wash-coating procedure and then mounted on the exhaust stream of a diesel light duty vehicle (LDV) provided by TOFAS (FIAT Doblo 1.9 JTD). These vehicles were driven on the rollers of the chassis dynamometer at constant speed and gear for two different loading conditions and on a standard driving cycle (NEDC) in the Test and Emission Laboratory of TOFAS-FIAT. The exhaust gases were analyzed for NOx, CO, CO2, THC and PM. The pressure drop caused by the filter was monitored during these tests as an indication of soot accumulation on the filter with the help of pressure sensors placed before and after the filter. Also temperatures before, inside and after the filter were monitored by means of thermocouples. Three different filters were tested in this manner: (1) Monocoated (CoOx), (2) Sequential PbOx coated over CoOx (PbOx/CoOx), (3) Simultaneously coated (PbCoOx). Also tests with the uncoated filter were performed to determine the pressure drops as a result of non-catalytic soot oxidation. The performances of the catalytic filters were evaluated by determining the temperature at which the soot oxidation rate on the filter equals the soot production rate in the engine (balance point temperature-Tbal). This temperature was used for comparing the catalytic activity of the supported catalyst with that of the powder form tested in the laboratory, i. e. Tpeak. The results of the onboard test were in parallel with the previous laboratory studies with similar catalytic activity temperatures. The continuous regeneration temperatures (Tbal) obtained in onboard tests with PbOx/CoOx and PbCoOx filters of about 370oC, which was close to the values attained in the lab study with the same mixed metal oxide catalyst having a Tpeak value of 385oC. Also the PM emissions during the tests were complying with the current EURO-IV emission limits.
4
Lau, Aaron. "Oxidation of soot with modified silver catalysts." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:138e06c2-ce59-4754-a71a-d2dc0c52ecbe.
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As the demand for motor vehicles has soared dramatically with the emergence of rapidly developing countries, the need for regulating vehicle emissions and pollutants is increasingly more important. With the newest regulations for diesel particulate emissions soon to be enforced, there is a great need to catalytically convert soot particles from the exhaust into relatively less polluting carbon dioxide. Here a supported silver catalyst is reported for the soot oxidation reaction. The silver catalyst is protected and supported using various capping agents and metal oxides, and modified using various synthetic methods. The catalysts are then tested with soot using thermogravimetric analysis (TGA) at a reaction temperature up to 700oC. In order for a better design and modification of the silver catalyst, an improved understanding of the interaction between silver nanoclusters and the metal oxide support must be established. XPS and UV/VIS spectroscopy are amongst the techniques used to probe the metal/metal oxide interaction. It is shown that the surface plasmon resonance of silver can be perturbed by the metal oxide support, modifying its band structure. It is also extremely important for the catalyst to be thermally stable up to 600°C for it to be employable in an exhaust system. In-situ XRD can be used to investigate the thermal stability of both the silver and metal oxide species in an oxidising environment. The phase changes, if any, of either species under heating can also provide a better understanding of the metal/metal oxide interaction and ultimately the soot combustion mechanism. It has been demonstrated that different catalyst surfaces can have different catalytic performances. By altering the morphology of the support, preferential growth of one surface can be achieved, thereby modifying the catalytic performance for soot combustion.
5
Raj, Abhijeet. "Formation, growth and oxidation of soot : a numerical study." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608718.
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6
Woods, Ian Thomas. "Hydrocarbon reactions and soot growth in fuel-rich flames." Thesis, The University of Sydney, 1988. https://hdl.handle.net/2123/26236.
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Laminar, premixed ethylene—air flames stabilized at atmospheric pressure on a water-cooled Maker-type flat-flame burner are used to study hydrocarbon chemistry under fuel-rich conditions in the post-flame region of both sooting and non—sooting flames. Profiles of temperature hydrogen radicals and major combustion products are measured on non-sooting flames with flame temperature, 1870 < Tf < 1940K and C/O ratio, 0.52 < C/O < 0.58. Similar measurements are made on sooting ethylene/air/oxygen flame with flame temperatures 1780 < Tf < 1920 and c/o ratio 0.749 < C/O < 0.869.
7
Hinot, Karelle. "Catalytic soot oxidation by platinum on sintered metal filters influence of the platinum quantity, particle size and location, and investigation of the platinum soot contact /." Karlsruhe : Univ.-Verl. Karlsruhe, 2007. http://www.uvka.de/univerlag/volltexte/2007/201/.
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8
Hinot, Karelle. "Catalytic soot oxidation by platinum on sintered metal filters influence of the platinum quantity, particle size and location, and investigation of the platinum soot contact." Karlsruhe Univ.-Verl. Karlsruhe, 2006. http://www.uvka.de/univerlag/volltexte/2007/201/.
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9
Kleiveland, Rune Natten. "Modelling of Soot Formation and Oxidation in Turbulent Diffusion Flames." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-702.
Full textAbstract:
Soot and radiation play an important role when designing practical combustion devices, and great efforts have been put into developing models which describe soot formation and oxidation. The Eddy Dissipation Concept (EDC) has proven to describe turbulent combustion well, and has the flexibility to describe chemical kinetics in a detailed manner. The aim of this work is to study how the EDC handles soot models based on a detailed representation of the gas-phase chemical kinetics.
Two versions of a semi-empirical soot model is used in conjunction with the EDC. Concentrations of various intermediate species are used as input to the soot models.
The implementation of the new soot models is discussed in relation to the previous implementation of a less detailed soot model. To assure that the interaction between soot and the gas-phase species is represented correctly, the soot models are implemented with a two-way coupling of soot and gas-phase kinetics.
Soot is a good radiator. In a sooting flame a substantial amount of energy will be transferred to the surroundings by thermal radiation. This transfer of energy will alter the temperature field of the flame and the change in temperature will affect the kinetics of soot and gas-phase chemistry. To simulate sooting flames correctly, it was therefore necessary to include a radiation model.
To validate the coupled models of turbulence, combustion, soot, and radiation two different turbulent flames were simulated. One turbulent jet flame of methane and one turbulent jet flame of ethylene. For both flames the computed results were compared with measured values.
Several aspects of the simulations are studied and discussed, such as the effect of the two-way coupling of soot and gas-phase kinetics on both soot yield and gas-phase composition, and the importance of a suitable radiation model.
The two-way coupling of soot and gas phase kinetics is shown to have a positive effect on the computed soot volume fractions, and the results are considered to be encouraging. The work has demonstrated that the EDC has the capacity to handle different types of chemical reaction mechanisms, such as mechanisms for gas-phase combustion and soot kinetics, without modification.
10
Demosthenous, Alexis. "Soot formation and oxidation in a high-pressure spray flame." Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424461.
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11
Salenbauch, Steffen [Verfasser]. "Modeling of Soot Formation and Oxidation in Reacting Flows / Steffen Salenbauch." München : Verlag Dr. Hut, 2018. http://d-nb.info/1174426152/34.
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12
Akbari, Kalhor F. "The effect of additives on the oxidation and structure of soot." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38216.
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13
Rankin, Bret A. "Design and development of a microwave enhanced diesel soot oxidation system." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=1058.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xiv, 347 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 272-276).
14
Pettersson, Henrik. "Chemical analysis for mapping of soot reactivity." Thesis, KTH, Skolan för kemivetenskap (CHE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153489.
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In order to increase the efficiency of diesel particulate filter regeneration more knowledge about diesel soot and its reactivity is required. This thesis compares soot created during accelerated filter loading by lowered rail pressure, with soot from normal filter loading. Soot properties and their correlations to oxidation reactivity are also examined through thermogravimetric analysis, scanning electron microscopy, energy dispersive x-ray spectroscopy, BET nitrogen sorption, and FTIR spectroscopy. The usefulness of these analysis methods was also evaluated. The soot samples consisted of two carbon blacks for reference (Printex U and Vulcan XC 72), four accelerated soot samples and two non-accelerated samples. The results showed that the accelerated samples contained less volatile organic compounds than the non-accelerated soot and required slightly higher temperatures to oxidize in air. Soot with a high oxygen/carbon ratio and high levels of volatile organic compounds was found to be the most reactive. The most useful method for analyzing the soot was the thermogravimetric analysis. The scanning electron microscopy and energy dispersive x-ray spectroscopy were useful additions but the FTIR spectroscopy provided very little useful information. The usefulness of BET nitrogen sorption was not decisively concluded.För att kunna förbättra regenereringen av dieselpartikelfilter krävs en ökad kunskap om dieselsot och dess reaktivitet. I detta examensarbete jämförs sot som skapas vid accelererad sotinlagring genom sänkt railtryck, med sot från normal sotinlagring. Hur sotets egenskaper påverkar dess reaktivitet undersöks också genom termogravimetrisk analys, svepelektronmikroskopi, energidispersiv röntgenspektroskopi, BET-kväveadsorption och FTIR-spektroskopi. Hur väl dessa analysmetoder lämpar sig för analys av sot utvärderades också. Sotproverna utgjordes av två så kallade ”carbon black” för referens (Printex U och Vulcan XC 72), fyra accelererade sotprov och två icke-accelererade prov. Resultaten visade att de accelererade proverna innehöll mindre flyktiga organiska föreningar än icke-accelererade sot och krävde något högre temperaturer för att oxideras i luft. Sot med ett högt syre/kol-förhållande och höga nivåer av flyktiga organiska föreningar visade sig vara mest reaktivt. Den mest användbara metoden för att analysera sot var den termogravimetriska analysen. Svepelektronmikroskopi och energidispersiv röntgenspektroskopi var användbara som komplementerande metoder men FTIR-spektroskopi gav väldigt lite användbar information. Ingen konkret slutsats drogs gällande nyttan av BET-kväveadsorption.
15
Waglöhner, Steffen [Verfasser], and H. [Akademischer Betreuer] Bockhorn. "Oxidation of soot on iron oxide catalysts / Steffen Waglöhner. Betreuer: H. Bockhorn." Karlsruhe : KIT-Bibliothek, 2012. http://d-nb.info/1021178713/34.
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16
Loukou, Alexandra [Verfasser]. "Thermal Partial Oxidation and Soot Formation in Porous Inert Media / Alexandra Loukou." Aachen : Shaker, 2014. http://d-nb.info/1050342259/34.
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17
YAMAMOTO, Kazuhiro, Shingo SATAKE, Hiroshi YAMASHITA, Akira OBUCHI, and Junko UCHISAWA. "Simulation on Soot Oxidation with NO2 and O2 in a Diesel Particulate Filter." The Japan Society of Mechanical Engineers, 2007. http://hdl.handle.net/2237/9385.
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18
Hanaki, Yasunari, and Kazuhiro Yamamoto. "Microfluidic Simulation of Diesel Exhaust Gas and Soot Oxidation in Diesel Particulate Filter." SAE International, 2013. http://hdl.handle.net/2237/20341.
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19
MARTINOVITY, FERENC. "Coupling of soot oxidation and ammonia-mediated selective catalytic reduction of nitrogen oxides." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2907024.
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20
Ahmadinejad, Mehrdad. "Modelling soot oxidation in DPF and modelling of PGM loading effect in a DOC." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7062/.
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The aim of this PhD thesis is to develop a one-dimensional (1D) mathematical model to study in designing and improving emission control systems such as those in Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). This was achieved by capturing the fundamental reaction kinetics from the microreactor data within the careful choice of concentrations/ temperatures domain; together with good understanding of the physical phenomena’s occurring in these systems. When considering a DOC, it is important to have a good description of the catalyst activity as a function of Platinum Group Metal (PGM) loading, which in this case is Pt, this enables mathematical models to be used in the optimization of the PGM loading. The work presented here looks at the design of a DOC based aftertreatment system through development of kinetics from data obtained from the microreactor for a wide range of PGM loadings (2.5-75g ft-3). The variation in catalyst activity with different PGM loadings for the key reactions was determined. The model developed in this study predicts well all the experimental data for the various loadings. DPF is another important aftertreatment technology that is used for the control of Particulate Matter (PM) emission from diesel engines. Under favourable conditions, the soot collected on the filter can be removed by oxidation with NO2 from temperatures as low as 200°C. The work presented in this thesis shows the fundamental modelling approach to develop kinetics for soot oxidation by NO2. The selectivity to CO was found to differ only marginally with temperature, and is independent of NO2 concentrations. By modelling these data using a 1D model, the rate equations for the soot-NO2 reaction were determined, and experimental data were predicted.
21
Ramdas, Ragini. "Targeting the complete range of soot components through the catalytic oxidation of diesel particulates." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/59466/.
Full textAbstract:
While total exhaust emissions from individual road vehicles continue to be reduced, it is becoming increasingly important to identify and quantify the residual chemical compounds in tail-pipe emissions that are potential hazards to the environment and to human health. Diesel particulate matter (DPM) is known to consist mostly of carbonaceous soot together with minor components, such as volatile organic fractions (from unburned fuel), lubricating oil, and inorganic compounds that include ash and sulphur compounds. Polycyclic aromatic hydrocarbons (PAHs) are invoked as the key intermediates in diesel soot formation. These are mutagenic air pollutants formed as by-products of combustion. PAH-precursors identified in soot include single ring structures such as benzene and toluene. Soot nucleation and growth gradually leads to the formation of five to six membered ring structures, such as benzopyrene, dibenzopyrene and coronene. Several methods have been devised to reduce the emissions of DPM, which include the use of a diesel particulate filter, or a technology which combines selective catalytic reduction of NOx with a regenerating particulate trap in a single unit. These oxidise the combustible content of the particulate matter collected on the filter through a non-catalytic reaction with NO2. As an alternative, the more difficult catalysed oxidation of soot by direct reaction with O2 has been gaining a lot of attention. Several studies have shown that the oxidation of soot requires a redox catalyst, such as CeO2, CeO2-ZrO2 and CeO2-ZrO2-Al2O3, or other reducible metal oxides including perovskites and spinels. In the past, proposed mechanisms have assumed that exhaust soot is simply graphitic carbon, and so have not taken into account the other organic components. In this work, we have carried out a speciation of soot that has been sourced from a diesel particulate trap. The soluble components have been identified by GC-MS, following extraction by Soxhlet and ultrasonication techniques. The speciation has been repeated as a function of temperature during the non-catalysed and catalysed combustion of the soot, allowing the conversion of individual components to be tracked. The results provide important catalyst design information, which should allow the formulation of materials that will be catalytically active in the combustion both of graphitic carbon and the complete range of retained organic species.
22
Wick, Achim [Verfasser]. "Population Balance Modeling and Large-Eddy Simulation of Soot Formation and Oxidation / Achim Wick." Düren : Shaker, 2020. http://d-nb.info/1206855894/34.
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23
Villalta, Lara David. "RADIATION HEAT TRANSFER IN DIRECT-INJECTION DIESEL ENGINES." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/114793.
Full textAbstract:
En las últimas décadas, la investigación en motores de combustión ha estado enfocada fundamentalmente en la reducción de las emisiones contaminantes y la eficiencia de los mismos. Estos hechos junto con un aumento de la concienciación sobre el cambio climático han llevado a un aumento en la importancia de la eficiencia térmica respecto a otros criterios en el diseño de motores de combustión interna (MCIA). Para alcanzar este objetivo, existen diferentes estrategias a aplicar. En concreto, la transferencia de calor a las paredes de la cámara de combustión puede ser considerada como una de las principales fuentes de disminución de la eficiencia indicada. En particular, en los modernos motores diésel de inyección directa, la emisión de radiación de las partículas de hollín puede constituir un componente importante de las pérdidas de eficiencia. En este contexto se enmarca el objetivo principal de la tesis: contribuir a la comprensión de la transferencia de calor por radiación en la combustión diésel de inyección directa junto con la mejora del conocimiento en el proceso de formación-oxidación de hollín. El trabajo se ha basado tanto en resultados experimentales mediante la aplicación de técnicas ópticas en diversas tipologías de motor como en resultados simulados a partir de modelos unidimensionales validados.
En la primera parte de resultados experimentales, se ha evaluado la cantidad de energía por radiación respecto a la energía química del combustible mediante la aplicación de una sonda optoelectrónica (basada en la técnica del 2-Colores) tanto en un motor óptico DI como en motor poli-cilíndrico DI de producción. En este estudio se han obtenido valores de intensidad espectral emitida por el hollín y posteriormente, la radiación total emitida por las partículas de hollín en todo el espectro.
Como se ha citado anteriormente, las partículas de hollín son las principales responsables de la transferencia de calor por radiación, además de uno de los principales agentes contaminantes emitidos por los motores diésel. Las emisiones de hollín son el resultado de dos procesos antagonistas: la formación y oxidación del hollín. Los mecanismos de formación de hollín se discuten extensamente en la literatura. Sin embargo, existen deficiencias en cuanto al conocimiento de la oxidación de hollín. Por lo tanto, el objetivo de esta sección ha sido evaluar el impacto del proceso de mezcla y la temperatura del gas sobre el proceso de oxidación de hollín durante la última parte de la combustión bajo condiciones reales de operación.
Finalmente, y en base a los resultados y conocimientos adquiridos hasta el momento, se ha desarrollado un modelo capaz de predecir las pérdidas de calor por radiación para un chorro diésel. El modelo está basado en tres sub-modelos: modelo de chorro, el cual analiza y caracteriza la estructura interna del chorro en términos de mezcla y combustión en un proceso de inyección con resolución temporal y espacial. Un modelo de hollín, en el que los resultados se justifican en función de procesos de formación y oxidación del hollín. La cohesión de estos dos sub-modelos se utiliza para obtener los valores de entrada al modelo de radiación, con el que se obtiene los valores de transferencia de calor por radiación para una llama diésel.En els últims anys, la recerca en motors de combustió ha estat focalitzada principalment en la reducció de les emissions contaminants i la millora de la eficiència. Aquests fets afegits al fet del augment de la conscienciació del canvi climàtic han impulsat el interés per incrementar la eficiència tèrmica per damunt de altres criteris en el disseny de motors de combustió interna alternatius (MCIA). Per aconseguir aquest objectiu, existixen diferents estratègies a aplicar. Concretament, la transferència de calor a les parets de la càmera de combustió pot ser considerada un dels principals focs de reducció de eficiència indicada. En particular, en els moderns motors dièsel de injecció directa, la emissió de radiació de les partícules de sutja pot constituir un component important de les pèrdues de eficiència. En aquest context s'emmarca el objectiu principal de la tesis: contribuir a la comprensió de la transferència de calor per radiació en la combustió dièsel de injecció directa i la millora del coneixement del procés de formació-oxidació de la sutja. El treball esta basat tant en resultats experimentals mediant l'aplicació de tècniques òptiques en diverses tipologies de motor com en resultants simulats a partir de models unidimensionals validats. En la primera part dels resultats experimentals, s'ha avaluat la quantitat de energia per radiació respecte a la energia química del combustible mediant la aplicació de una sonda optoelectrònica (basada en la tècnica del 2-Colors) tant en un motor òptic DI com en un motor poli-cilíndric DI de producció en serie. En aquest estudi s'han obtingut valors de intensitat espectral emesa per la sutja i posteriorment, la radiació total emesa per les partícules de sutja en tot el espectre. Com s'ha citat amb anterioritat, les partícules de sutja son les principals responsables de la transferència de calor per radiació, a més de un del principals agents contaminants emès per els motors dièsel. Les emissions de sutja son el resultat de dos processos antagonistes: la formació i la oxidació de sutja. Els mecanismes de formació de sutja es discuteixen àmpliament en la literatura. No obstant això, existeixen deficiències pel que fa al coneixement de l'oxidació de sutja. Per tant, l'objectiu d'aquesta secció ha sigut avaluar l'impacte del procés de mescla i la temperatura del gas sobre el procés d'oxidació de sutja durant l'última part de la combustió sota condicions reals d'operació. Finalment, i en base als resultats i coneixements adquirits fins aquest moment, s'ha desenvolupat un model que permet predir les perdudes de calor però radiació per a un raig dièsel. El model esta basat en tres sub-models: model de raig, el qual analitza i caracteritza la estructura interna del raig en termes de mescla i combustió en un procés de injecció amb resolució temporal i espacial. Un model de sutja, en el qual els resultats es justifiquen en funció del procés de formació i oxidació de la sutja. La cohesió d'aquests dos sub-models s'utilitza per obtindre els valors d'entrada al model de radiació, amb el que s'obté els valors de transferència de calor per radiació per a una flama dièsel.
In the last two decades engine research has been mainly focused on reducing pollutant emissions and increasing efficiency. These facts together with growing awareness about the impacts of climate change are leading to an increase in the importance of thermal efficiency over other criteria in the design of internal combustion engines (ICE). To achieve the objective, there are different strategies to apply. The heat transfer to the combustion chamber walls can be considered as one of the main sources of indicated efficiency diminution. In particular, in modern direct-injection diesel engines, the radiation emission from soot particles can constitute a significant component of the efficiency losses. In this context, the main objective of the thesis is framed: to contribute to the understanding of the radiation heat transfer in DI diesel combustion together with the improvement of the knowledge in the soot formation-oxidation processes. The work has been based on experimental results through the optical technique application in different types of engine and on simulated results from validated one-dimensional models. In the first part of experimental results, the amount of energy lost to soot radiation relative to the input fuel chemical energy has been evaluated by means of the optoelectronic probe application (based on the 2-Color technique) in both an optical engine DI and a production 4-cylinder DI engine. In this study, the values of soot spectral intensity emitted have been obtained and later, the total radiation emitted by the soot particles in the whole spectrum. As mentioned above, soot particles are the main responsible for the radiation heat transfer, in addition to one of the important concern in meeting emissions regulations. Soot emissions are the result of two competing processes: soot formation and soot oxidation. Mechanisms of soot formation are discussed extensively in the literature. However, there are deficiencies in the knowledge of soot oxidation. Therefore, the objective of this section has been to evaluate the impact of mixing process and bulk gas temperature on late-cycle soot oxidation process under real operating conditions. Finally, based on the results and knowledge acquired, a model able to predict heat losses by radiation for a spray diesel has been developed. The model is based on three sub-models: spray model, which analyzes and characterizes the internal spray structure in terms of mixing and combustion process with temporal and spatial resolution. A soot model, in which the results have been justified according to soot formation and oxidation processes. The link of these two sub-models has been used to obtain the input values to the radiation model, which the radiation heat transfer values for a diesel flame are obtained.
Villalta Lara, D. (2018). RADIATION HEAT TRANSFER IN DIRECT-INJECTION DIESEL ENGINES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114793
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GÓMEZ, AGUILERA Miguel. "Metaloxid katalysatorer för oxidering av kolmonoxid och förbränning av sot." Thesis, KTH, Skolan för kemivetenskap (CHE), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173384.
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The aim of this work was to manufacture and test non noble metal catalysts for CO oxidation and soot combustion. The feeding gases consist in the products of the combustion diesel in a Reformtech heater. These gases contain CO, CO2, H2O as well as small amounts of NOx and hydrocarbons. Two different catalysts were prepared for CO oxidation, based on cobalt oxide supported on ceria. 12Co/CeO2 with 12% weight of cobalt and 15CoOx/CeO2 with 15%. The first one was prepared by impregnation of cobalt nitrates in cerium oxide support; the second one was prepared by co-precipitation of cobalt and cerium nitrates. Another catalyst called 12Co4.5K/CeO2, with 12% cobalt and 4.5% potassium, was made for the simultaneous combustion of soot and oxidation of CO. The base also consisted in cobalt oxide supported on ceria, but with the addition of potassium which could stabilize the cobalt oxide particles. Both co-precipitation and impregnation methods gave the desired catalyst structure in the CO oxidation catalysts and both catalysts (12Co/CeO2 and 15CoOx/CeO2) showed activity. Nevertheless, the activity was lower than desired due to low surface area and mass transfer limitations. The catalysts also deactivated in less than three hours on stream, probably due to poisoning. The co-precipitation method for the 12Co4.5K/CeO2 catalyst gave the desired cobalt and cerium oxides, but no conclusion can be drawn regarding potassium since it was not shown in the XRD tests. The catalyst for both CO oxidation and soot combustion (12Co4.5K/CeO2) showed no activity for any of the reactions. Nevertheless, the tests performed to test the soot combustion ability were not conclusive and should be improved in future studies.
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Yamamoto, Kazuhiro, and Koji Tsuneyoshi. "Experimental study of hexagonal and square diesel particulate filters under controlled and uncontrolled catalyzed regeneration." Elsevier, 2013. http://hdl.handle.net/2237/20050.
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Roth, Kolja [Verfasser]. "Soot Formation during the Production of Syngas from the Partial Oxidation of Diesel Fuel / Kolja Roth." Aachen : Shaker, 2007. http://d-nb.info/1170526829/34.
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Yamauchi, Kazuki, and Kazuhiro Yamamoto. "Numerical simulation of continuously regenerating diesel particulate filter." Elsevier, 2013. http://hdl.handle.net/2237/20043.
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Lautenberger, Christopher W. "CFD simulation of soot formation and flame radiation." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-0115102-002543.
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Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: soot formation; FDS; flame radiation; soot oxidation; field modeling; diffusion flames; soot. Includes bibliographical references (p. 14-15).
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Cerit, Ersen Recep. "Investigation Of The Effect Of Oxidation Filters On The Particulate Emissions Of Diesel Engines." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607561/index.pdf.
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Oxidation filters are used to decrease particulate emissions commonly. In this study, design of a particulate trap to produce an alternative, low cost filter has been aimed. An experimental setup has been installed according to standards to carry out tests of these designed filters. Electronic measurement and control systems have been attached to this setup to increase efficiency of experiments.
Two filter designs have been used in the experiments. First design consists of aluminum wire cloth. Second design is sheet metal structure, which includes three longitudinal cells. Metal chip is used as filter material. Empty filter tests have been performed firstly, and then experiments have been repeated with aluminum, iron, and copper chip addition in filter.
Copper chip test results are better than other metal chip for first experiments. Afterwards, experiments have been repeated with varying copper chip amount. Suitable copper chip amount was determined based on fuel consumption rate of the engine.
As a result, designed filter reduce the particulate emissions with high efficiency. Although, carbon monoxide, and carbon dioxide gaseous emissions increase with designed filter, hydro carbon emissions decrease.
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Guo, Yi. "The effect of biodiesel soot structure on diesel particulate filter (DPF) performance." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/204305/1/Yi_Guo_Thesis.pdf.
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The research within this PhD thesis was concerned with understanding the role biodiesel soot structure has on the performance of diesel particle filters (DPF), their filtration efficiency, pressure drop and their ability to regenerate through the oxidation of accumulated soot. All DPF's have been designed for petrol-diesel particles and therefore the impact of changing fuel properties and emitted soot particles needed investigation. The research went beyond in exploration of diesel soot structure role, especially the attached oxygen functional groups at a molecular level, on the general mechanism of diesel soot and graphene-like material's oxidation, processes that have farfetched relevance.
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Contreras, Rodriguez Jorge Omar. "Numerical study of soot formation / oxidation mechanisms and radiative heat transfer in closed-and open - tip laminar diffusion flames." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4757/document.
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Microgravité éthylène laminaires couche limite flammes de diffusion générés par un brûleur poreux plat et caractérisées par les vitesses d'injection de carburant de 3 et 4 mm / s et une vitesse d'oxydation de 250 mm / s ont été simulées en utilisant un modèle de rayonnement précis, un mécanisme cinétique complète et un modèle de suie constitué de lancement par suite de la collision de deux molécules de pyrène, l'évolution de la surface hétérogène et oxydation suivant l'abstraction d'un atome d'hydrogène addition d'acétylène (HACA) mécanisme, la coagulation à particules de suie, et la condensation de la surface de l'HTAP. La distance d'écartement et la production de suie sont améliorées lorsque la vitesse du carburant augmente. H et des radicaux OH, responsables de la de-hydrogénation des sites dans le processus HACA, et le pyrène, de l'espèce pour la création de la suie et des processus de condensation HAP, se trouvent à être situé dans une région qui suit la distance stand-off. La suie est ensuite produite dans cette région et est transporté à l'intérieur de la couche limite par convection et thermophorèse. Perte radiatif est sensiblement plus élevé dans ces flammes que dans flammes de diffusion de gravité normales dues à beaucoup plus longues durées de séjour. Calculs effectués par négliger le rayonnement de la suie et en utilisant l'approximation optiquement mince (OTA) a révélé que la suie domine le transfert de chaleur par rayonnement dans ces flammes et que l'utilisation de l'OTA donne lieu à des écarts significatifs dans la fraction du volume température et la suieMicrogravity ethylene laminar boundary layer diffusion flames generated by a flat porous burner and characterized by the fuel injection velocities of 3 and 4 mm/s and an oxidizer velocity of 250 mm/s have been simulated by using an accurate radiation model, a comprehensive kinetic mechanism, and a soot model consisting of inception as a result of the collision of two pyrene molecules, heterogeneous surface growth and oxidation following the hydrogen abstraction acetylene addition (HACA) mechanism, soot particle coagulation, and PAH surface condensation. Model predictions are in reasonable agreement with the experimental data in terms of the stand-off distance and soot volume fraction. The stand-off distance and soot production are enhanced as the fuel velocity increases. H and OH radicals, responsible of the de-hydrogenation of sites in the HACA process, and pyrene, of the species for soot inception and PAH condensation processes, are found to be located in a region that follows the stand-off distance. Soot is then produced in this region and is transported inside the boundary layer by convection and thermophoresis. Radiative loss is substantially higher in these flames than in normal gravity diffusion flames owing to much longer residence times. Calculations carried out by neglecting soot radiation and by using the optically-thin approximation (OTA) revealed that soot dominates the radiative heat transfer in these flames and that the use of OTA gives rise to significant discrepancies in temperature and soot volume fraction
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Emmerich, Thomas [Verfasser], Martin [Akademischer Betreuer] Muhler, and Wolfgang [Akademischer Betreuer] Grünert. "Ceria- and zirconia-based materials for the catalytic oxidation of CO and soot / Thomas Emmerich. Gutachter: Martin Muhler ; Wolfgang Grünert." Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1099703549/34.
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Keller, Michel. "Development of a multi-scale approach using chemical kinetics and reactive force field molecular dynamics to model soot formation and oxidation." Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAE005.
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La présente étude décrit la mise au point d'une approche multi-échelles pour la modélisation des processus pendant la formation et l'oxydation précoce de la suie. Pour ce faire, des calculs cinétiques détaillés et macroscopiques en phase gazeuse sont utilisés, à l'aide de Chemkin, pour modéliser la combustion dans un réacteur fermé hétérogène dans des conditions diverses. Afin d'étudier l'impact de la température, du mélange de carburant et du rapport d'équivalence, une gamme de ces trois paramètres a été analysée. A partir des résultats des calculs de cinétique de réaction, des molécules pertinentes pour la formation de suie, appelées précurseurs de suie, ont été extraites et selon certains critères introduits dans des boîtes de simulation pour modéliser la formation de liaisons entre les molécules de précurseurs de suie par modélisation de la dynamique moléculaire du champ de force réactif. Afin d'obtenir la meilleure description de ces processus, trois champs de forces réactives sont évalués et comparés aux calculs ab initio. L'effet des paramètres de simulation utilisés dans l'approche de modélisation moléculaire du champ de force réactive, comme la température et le pas de temps, sur la précision des calculs est étudié et analysé pour confirmer les conditions optimales de modélisation. Les impacts de la température, du mélange de combustible et du rapport d'équivalence des calculs de Chemkin se traduisent par les compositions des précurseurs de suie et l'influence des différentes compositions a été étudiée sur le taux et la structure des molécules nouvellement formées. Les structures qui en résultent se comparent bien aux résultats expérimentaux précédemment rapportés. En outre, le taux de formation de liaison entre les précurseurs de suie est en corrélation linéaire avec la température à laquelle les précurseurs de suie sont produits, tandis que le combustible et le rapport d'équivalence n'ont pas d'incidence directe sur le taux de réaction. Les structures de croissance générées sont regroupées : 1) hydrocarbures polycycliques directement liés, 2) aliphatiquement liés et 3) hydrocarbures polycycliques péricondensés. On constate que la quantité de molecules aliphatiquement liés augmente avec la quantité de contenu aliphatique du mélange de carburant. De plus, un schéma de réaction est présenté montrant les voies de réaction les plus représentatives pour former des structures de croissance dans chaque classe de grumeaux et leur interconversion éventuelle. L'impact des différences structurelles dans les structures générées par la formation de liaisons entre les précurseurs de suie, sur leur cinétique d'oxydation est testé. Pour ces quatre oxydants différents, ce sont des radicaux oxygène, des radicaux hydroxyle, des radicaux hydroperoxyle et des radicaux méthoxy, qui sont introduits et les réactions modélisées. On constate que deux des oxydants introduits se décomposent et interagissent largement et ne réagissent donc pas avec les structures de suie naissantes formées. Pour les deux autres oxydants, la cinétique des réactions d'oxydation avec les structures de suie naissantes est étudiée. On peut montrer que la cinétique est différente pour les espèces qui possèdent une chaîne latérale aliphatique par rapport à celles qui n'en possèdent pas. Enfin, les énergies d'activation des réactions d'oxydation sont estimées, en traçant la constante de vitesse sur la température inverse. Les énergies d'activation trouvées se comparent bien aux expériences et autres études de modélisation de la littérature. Le présent travail - qui applique une approche combinée de calculs cinétiques macroscopiques en phase gazeuse et de simulations de champ de force atomique réactive - offre une bonne alternative pour obtenir des différences structurelles de suie naissante pour une large gamme de conditions thermodynamiques et des mécanismes de réaction détaillés pour les processus de formation et d'oxydation des suiesIn the present study bond formation reactions between soot precursors and their role in the soot inception process is investigated. The soot precursors were generated in macroscopic detailed gas-phase kinetic calculations and according to certain criteria introduced in simulation boxes to model bond formation between soot precursor molecules with reactive force field molecular dynam-ics modeling. The impacts of temperature, fuel mixture and equivalence ratio have been investigated on the rate and structure of the newly formed molecules. The resulting structures compare well to previously reported experimental results. Furthermore, the bond formation rate between PAH is found to be linearly correlated with the temperature at which the PAH precursors are generated, while fuel and equivalence ratio do not have a direct impact on the reaction rate. The generated growth structures are lumped in: 1) directly linked, 2) aliphatically linked and 3) pericondensed polycyclic hydrocarbons. It is found that the amount of aliphatically linked PAH increases with the amount of aliphatic content of fuel mixture. Finally, a reaction scheme is presented displaying the most representative reaction pathways to form growth structures in each lumping class and their eventual intercon-version. The present work – that applies a combined approach of macroscopic gas-phase kinetic calculations and atomistic reactive force field simulations – offers a good alternative to obtain structural differences of nascent soot for a broad range of thermodynamic conditions and detailed reaction mechanisms for soot inception process
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DOSA, MELODJ. "Nanostructured ceria-based catalysts for automotive application - Formulation of nanostructured systems for diesel and gasoline-type engines." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2903500.
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Hinot, Karelle [Verfasser]. "Catalytic soot oxidation by platinum on sintered metal filters : influence of the platinum quantity, particle size and location, and investigation of the platinum soot contact / Universität Karlsruhe (TH), Institut für Mechanische Verfahrenstechnik und Mechanik (IMVM) ... Von Karelle Hinot." Karlsruhe : Univ.-Verl. Karlsruhe, 2007. http://d-nb.info/983649804/34.
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SARTORETTI, ENRICO. "Doped ceria nanostructures for the oxidation of pollutants: investigations into the role of defect sites." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2910076.
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ANDANA, TAHRIZI. "Roles of morphology and foreign metals of ceria-based catalysts in improving oxidations of Diesel vehicle pollutants." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2669105.
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The present work highlights well-defined nanostructured ceria; a morphology that bestows exceptional catalytic activity on ceria towards soot oxidation. The work includes also introduction of promoting foreign metals, such as praseodymium and zirconium, to well-defined nanostructured ceria as a means of improving reducibility, thermal stability and oxygen storage capacity of the catalyst. Temperature-programmed oxidation (TPO) has been used for analyzing catalytic activity. At the first stage of the research, nanostructured equimolar ceria-praseodymia (denoted as Ce50Pr50-NP) was found to have the highest amount of surface oxygen, the highest reducibility and the highest catalytic activity towards soot oxidation. The nanostructured morphology has been proven to raise the functionality of praseodymia as the foreign metal in ceria. The work also introduces small, silane-stabilized Pt nanoparticles. Upon calcination, silyl ligands are transformed into siliceous patches that prevent the particle from migrating/coalescing. Cu nanoparticles have been prepared the same way as Pt nanoparticles; however, they sinter even under milder thermal treatment. The small Pt-NPs are proven active towards all pollutant oxidations, including NOx-assisted soot oxidation, and they function better with nanostructured ceria as the support. Unexpectedly, Ce50Pr50-NP gives higher activity towards NOx-assisted soot oxidation than Pt catalysts. Intense NO conversion and NO2 adsorption on the surface of Ce50Pr50-NP are the reason behind its high activity.
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DE, SIMONE GIULIO. "Analisi teorica, progettazione e sperimentazione di sistemi per la produzione di idrogeno da idrocarburi." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/1093.
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Nel presente lavoro sono state approfondite le tematiche relative alla riformulazione degli idrocarburi in sistemi compatti, applicabili a bordo di autoveicoli, in particolar modo quelle inerenti la progettazione. Sono stati sviluppati numerosi modelli di calcolo al fine di approntare uno strumento di fluidodinamica computazionale in grado di simulare i fenomeni che caratterizzano le diverse fasi del processo, e guidare la progettazione di detti sistemi. I modelli predisposti, prima di essere impiegati per la progettazione, sono stati ampiamente validati sulla base dei risultati sperimentali a disposizione: per quanto al reforming del gasolio si è fatto riferimento ad un reattore sviluppato nell’ambito di un progetto finanziato dall’Unione Europea denominato “Direct”, cui hanno partecipato enti di ricerca pubblici e privati ed aziende, per quanto al reforming del metano si è fatto riferimento alla letteratura scientifica. I modelli sono stati poi impiegati con successo nella progettazione di due reattori, il primo denominato “Prometer” è in grado di operare la riformulazione di combustibili liquidi, l’altro denominato “Syngas UTV” di quelli gassosi. I due sistemi sono stati concepiti in maniera da essere in grado di gestire combustibili diversi (sistemi multifuel), la sperimentazione in laboratorio si è però focalizzata sull’utilizzo di gasolio e metano. In particolare la scelta di sperimentare il reattore “Prometer” sul gasolio è dovuta al fatto che questi presenta caratteristiche che ne rendono particolarmente difficile la riformulazione senza incappare nella formazione di particolato, cui segue l’interruzione irreversibile del funzionamento del reattore. Per questo motivo lo sviluppo di sistemi stabili ed in grado di garantire durate di funzionamento adeguate, per l’ossidazione parziale del gasolio finalizzata alla produzione di idrogeno, rappresenta ancora un obiettivo per il mondo scientifico. I risultati della sperimentazione sono stati estremamente soddisfacenti, anche per la riformulazione del gasolio, sebbene in un unico ciclo di dottorato non sia stato possibile approfondire ulteriormente la sperimentazione, per l’ingente impegno di tempo che lo sviluppo dei sistemi ha richiesto. La prosecuzione delle attività di ricerca intraprese ha eccellenti possibilità di concludere favorevolmente verso la possibilità di giungere allo sviluppo di sistemi stabili ed in grado di operare senza produzione di particolato, che non è stata riscontrata nelle prime prove effettuate sul reattore. Per scongiurare tale evenienza si ritiene, sia sulla base delle evidenze sperimentali che dalle simulazioni effettuate, che le fasi di vaporizzazione e miscelazione abbiano un ruolo fondamentale.Scope of this work is to examine design issues concerning the reforming of the hydrocarbons in compact systems, which can be used for hydrogen generation onboard vehicles. Several models have been developed in order to build a comprehensive fluid dynamics tool to simulate physical and chemical phenomena that affect reforming process. Models have been extensively validated on results from scientific literature and "Direct" project, a research program funded by the European Union which concern Diesel fuel reforming. The models were then used successfully in the design of two reactors, the first called "Prometer", the other "Syngas UTV", which are capable of operating Catalytic Partial Oxidation (CPOx) of liquid fuels and gaseous fuels respectively. The two multifuel systems have been tested with Diesel fuel and methane. In particular, the choice of run "Prometer" reactor with Diesel fuel is due to the fact that gasoil CPOx is particularly difficult due to soot formation, which often involves fast and irreversible shutdown of the reactor. For this reason, the development of stable and long-life CPOx reactors for Diesel fuel is still an objective for scientific community. The experimental result were successful, even for Diesel reforming, since no soot formation was observed during experiments. To this goal, fuel vaporization and mixing were found to have a key role.
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Andana, Tahrizi. "Roles of morphology and foreign metals of ceria-based catalysts in improving oxidations of Diesel vehicle pollutants." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1066.
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Le travail au présent surligne la cérine nanostructurée et bien-définie ; une morphologie qui promeut une haute activité catalytique de la cérine dans l’oxydation des suies. Le travail présente également l’introduction des métaux pour le dopage, tels que praséodyme et zirconium, à la surface de la cérine pour améliorer la réductibilité, la stabilité thermique, et la capacité du stockage d’oxygène. L’oxydation à température programmée a été utilisée pour analyser l’activité catalytique. Au premier étage de la recherche, on a découvert que l’oxyde en mélange équimolaire de la cérine et de l’oxyde de praséodyme en nanostructure (indiqué comme Ce50Pr50-NP) possède la quantité d’espèces oxygénées à la surface la plus haute, la réductibilité la plus haute et l’activité catalytique la plus haute dans l’oxydation normale des suies. Il a été conclu que la nanostructure soulève la fonctionnalité du praséodyme dans la cérine. Le travail introduit également des nanoparticules (NPs) de Pt stabilisée par n-octylsilane. Pendant la calcination, les ligands silyliques se transforment aux « patches » de la silice qui leur évitent le frittage. Des NPs de Cu ont été préparées avec la même façon ; néanmoins elles ont souffert de sintering. Les NPs de Pt sont très actives dans l’oxydation de tous les polluants modèles des véhicules Diesel, spécifiquement l’oxydation des suies en présence de NOx, et elles fonctionnent mieux avec la cérine nanostructurée. Comme attendu, Ce50Pr50-NP donne l’activité catalytique plus haute que les catalyseurs à base du platine. La haute conversion du NO et l’adsorption du NO2 sur la surface sont la raison majeure de l’activité marquanteThe present work highlights well-defined nanostructured ceria; a morphology that bestows exceptional catalytic activity on ceria towards soot oxidation. The work includes also introduction of promoting foreign metals, such as praseodymium and zirconium, to well-defined nanostructured ceria as a means of improving reducibility, thermal stability and oxygen storage capacity of the catalyst. Temperature-programmed oxidation (TPO) has been used for analyzing catalytic activity. At the first stage of the research, nanostructured equimolar ceria-praseodymia (denoted as Ce50Pr50-NP) was found to have the highest amount of surface oxygen, the highest reducibility and the highest catalytic activity towards soot oxidation. The nanostructured morphology has been proven to raise the functionality of praseodymia as the foreign metal in ceria. The work also introduces small, silane-stabilized Pt nanoparticles. Upon calcination, silyl ligands are transformed into siliceous patches that prevent the particle from migrating/coalescing. Cu nanoparticles have been prepared the same way as Pt nanoparticles; however, they sinter even under milder thermal treatment. The small Pt-NPs are proven active towards all pollutant oxidations, including NOx-assisted soot oxidation, and they function better with nanostructured ceria as the support. Unexpectedly, Ce50Pr50-NP gives higher activity towards NOx-assisted soot oxidation than Pt catalysts. Intense NO conversion and NO2 adsorption on the surface of Ce50Pr50-NP are the reason behind its high activity
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Chhiti, Younes. "Gazéification non catalytique des huiles de pyrolyse de bois sous vapeur d'eau." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0064/document.
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La production d'énergie à partir de biomasse ligno-cellulosique via la technologie de gazéification est une option intéressante dans le contexte énergétique actuel. La combinaison d‘une pyrolyse rapide décentralisée de la biomasse pour produire les bio-huiles, suivie par le transport et le vaporeformage dans des bio-raffineries, est apparue comme l'une des méthodes économiquement les plus viables pour la production de gaz de synthèse (H2+CO). L‘objectif de ce travail est de combler le manque de connaissances concernant les processus de transformation physicochimique de l‘huile de pyrolyse en gaz de synthèse utilisant la gazéification non catalytique dans des réacteurs à flux entrainé. Il s‘agit d‘un processus complexe, mettant en oeuvre la vaporisation, les réactions de craquage thermique avec formation de gaz, de tars et de deux résidus solides : le char et les suies, qui sont des produits indésirables. Ceci est suivi par le reformage des gaz et des tars, ainsi que la conversion du char et des suies. Pour mieux comprendre le processus, la première étape de la gazéification (la pyrolyse), et par la suite l'ensemble du processus (pyrolyse + gazéification) ont été étudiés. L‘étude de la pyrolyse est focalisée sur l‘influence de la vitesse de chauffe, de la température ainsi que de la teneur en cendres dans la bio-huile, sur les rendements en char, tars et gaz. A très grande vitesse de chauffe le rendement en char est inferieur à 1%. Les cendres semblent favoriser les réactions de polymérisation et provoquent la diminution du rendement en gaz. Concernant la gazéification, l'effet de la température sur le rendement et la composition du gaz de synthèse a été étudié. Une augmentation de la température de réaction implique une augmentation du rendement en hydrogène et une conversion très élevée du carbone solide. Un calcul d'équilibre thermodynamique a montré que l'équilibre a été atteint à 1400°C. Finalement les mécanismes de formation et d‘oxydation des suies ont été étudiés expérimentalement sous différentes atmosphères : inerte (pyrolyse), riche en vapeur d‘eau (gazéification) et en présence d‘oxygène (oxydation partielle). Un modèle semi empirique est proposé et validé. Il est fondé sur la chimie détaillée pour décrire les réactions en phase gaz, une seule réaction basée sur la concentration de C2H2 pour décrire la formation des suies et principalement une réaction hétérogène pour décrire l‘oxydation des suiesEnergy production from ligno-cellulosic biomass via gasification technology appears as an attractive option in the current energy context. The combination of decentralized fast pyrolysis of biomass to produce bio-oil, followed by transportation and gasification of bio-oil in bio-refinery has appeared as one of the most economically viable methods for syngas (H2+CO) production. The objective of this work is to bridge the lack of knowledge concerning the physicochemical transformation of bio-oil into syngas using non catalytic steam gasification in entrained flow reactors. This complex process involves vaporization, thermal cracking reactions with formation of gas, tars and two solid residues - char and soot - that are considered as undesirable products. This is followed by steam reforming of gas and tars, together with char and soot conversion. To better understand the process, the first step of gasification (pyrolysis) and thereafter the whole process (pyrolysis + gasification) were studied. The pyrolysis study focused on the influence of the heating rate, the final pyrolysis temperature and the ash content of bio-oil on char, tars and gas yields. At the higher heating rate char yield is smaller than 1%. In addition, ash seems to promote polymerization reactions and causes a decrease of gas yield. Concerning gasification, the effect of temperature on syngas yield and composition was studied. An increase in the reaction temperature implies higher hydrogen yield and higher solid carbon conversion. A thermodynamic equilibrium calculation showed that equilibrium was reached at 1400°C. Finally, the soot formation and oxidation mechanisms were investigated through experiments in three different atmospheres: inert (pyrolysis), rich in steam (gasification) and in the presence of oxygen (partial oxidation). A semi-empirical model was proposed and validated. It is based on detailed chemistry to describe gas phase reactions, a single reaction using C2H2 concentration to describe soot formation and one main heterogeneous reaction to describe soot oxidation
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MARIN, FIGUEREDO MIGUEL JOSE. "Metal Oxide Catalysts for the Abatement of Volatile Organic Compounds and Carbonaceous Particulate Matter." Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2966339.
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Obeid, Emil. "Catalyseurs conducteurs ioniques pour l'oxydation des suies." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10150/document.
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Cette étude a pour finalité le développement d'une nouvelle famille de catalyseurs pour la combustion des suies Diesel afin de produire des filtres à particules (FAP) à régénération continue basse température. En effet, les régénérations périodiques des FAP actuellement commercialisés, engendrent une surconsommation plus ou moins élevée en carburant. Les catalyseurs étudiés sont des céramiques conductrices par les ions oxygènes et exempts de métal noble. L'ensemble de ces études a permis d'aboutir à plusieurs conclusions majeures. Les oxygènes actifs pour oxyder les particules de suies à basse température sont les oxygènes contenus dans le catalyseur. L'oxydation de la suie a donc lieu à l'interface solide/solide : suie/catalyseur. Un mécanisme de type électrochimique comme dans une pile à combustible mais à l'échelle nanométrique a été proposé : l'oxydation de la suie représente la réaction anodique qui se déroule aux points de contact suie / 8-YSZ, les électrons produits diffusent à travers les particules de suie vers les point triples entre les particules de suie (conductrices électroniques), la phase gaz (présence d'oxygène) et 8-YSZ (conducteur ionique) où se déroule la réaction cathodique d'incorporation de l'oxygène gazeux dans le matériau. Les paramètres clés qui gouvernent l'activité catalytique sont la surface de contact suie/catalyseur et donc la granulométrie de la poudre de catalyseur ainsi que la pression partielle d'oxygène dans la phase gaz et la mobilité de l'oxygène dans le catalyseurThis study aims to develop a new family of catalysts for diesel soot combustion to produce and optimize self-DPFs, based on ionic conducting ceramics, able to continuously burn soot particulates at low temperatures without fuel overconsumption and without the use of noble metals. The investigated catalysts are oxygen ionically conducting ceramics. Yttria stabilized Zirconia (8-YSZ containing 8 mol% of yttria) was chosen as the reference catalyst due to its high thermal and chemical stability and good ionic conductivity. A set of experiments was implemented to vary different parameters that can influence the reactivity of the reference catalyst. All of these studies have resulted in several major conclusions. Oxygen species active to oxidize soot particles at low temperature are those contained in the catalyst. An electrochemical type mechanism as in a fuel cell but at the nanoscale was proposed: the soot oxidation represents the anodic reaction which occurs at the contact points soot / 8-YSZ/O2 (gas) electrons are diffused through soot particles to triple points between the soot particles (electronic conductor), the gas phase (presence of oxygen) and 8-YSZ (ion conductor) where the cathodic reaction takes place with the incorporation of gaseous oxygen into the ceramic. The key parameters that influence the catalytic activity of 8-YSZ are soot / catalyst contact and thus the agglomerates size of the catalyst powder, the oxygen partial pressure in the gas phase and the mobility of oxygen in the catalyst
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Talbaut, Martine. "Etude de la formation et de l'oxydation des suies dans des flammes de diffusion laminaires d'éthylène : approches expérimentale et numérique." Rouen, 1996. http://www.theses.fr/1996ROUES015.
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Le travail présenté dans ce mémoire concerne l'étude, à la fois expérimentale et numérique, des processus de formation et d'oxydation des particules de suie dans des flammes laminaires de diffusion. Les travaux expérimentaux ont été réalisés dans deux flammes de diffusion, éthylène-air et éthylène-oxygène. Afin de mieux appréhender les processus d'oxydation des suies, une analyse plus complète a été menée dans la flamme éthylène-oxygène. Les mesures ont été effectuées au moyen de différentes techniques optiques. La fraction volumique de suie, le diamètre et le nombre de particules ont été déterminés par la méthode extinction-diffusion. Les diamètres ainsi déduits ont été comparés aux valeurs obtenues par P. C. S. (spectroscopie par corrélation de photons). La température a été mesurée par pyrométrie à deux couleurs. La fluorescence induite par laser a été utilisée afin de déterminer la concentration du radical OH, ainsi que le coefficient d'extinction des suies dans l'ultraviolet. L'ensemble de ces résultats a permis une analyse des processus de formation et d'oxydation des suies ainsi que la détermination, dans la flamme suroxygénée, de l'efficacité de collision du radical OH. L'étude numérique a été menée à l'aide d'un code de calcul simulant des flammes de diffusion à contre-courant. Un mécanisme réactionnel détaillé a été utilisé pour prédire la phase gazeuse. Des modèles simplifiés de formation et d'oxydation des suies ont été implantés dans le code. Les modèles d'oxydation étudiés ont permis de mettre en évidence la prédominance du rôle du radical OH sur celui de la molécule d'oxygène lors de l'oxydation des particules de suie.
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Shehee, Thomas Charles. "The Americium/lanthanide separation conundrum selective oxidation or soft donor complexants? /." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Dissertations/Spring2010/T_Shehee_041510.pdf.
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Khan, Munirah Atique [Verfasser]. "The Study of MnOx Catalysts for Water Oxidation by Soft X-Ray Spectroscopy / Munirah Atique Khan." Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1075757657/34.
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Amoah, Enoch. "Modification of Chemical Vapor-Deposited Carbon Electrodes with Electrocatalytic Metal Nanoparticles through a Soft Nitriding Technique." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3616.
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Metal nanoparticles have been widely used for many catalytic and electrocatalytic applications due to their larger surface area-to-volume ratios and higher densities of active sites compared to bulk materials. This has resulted in much interest in understanding the electrocatalytic behavior of metal nanoparticles with respect to their structure. However, most research on this topic has employed collections of nanoparticles. Due to difficulties in controlling and characterizing particle loading and interparticle distance in nanoparticle ensembles, single nanoparticles studies have recently become a topic of great interest. In this study, a soft nitriding technique was applied to chemical vapor-deposited carbon ultramicroelectrodes (UMEs) in order to immobilize ligand-free AuNPs onto the carbon substrate. The feasibility of this method is geared toward studying the properties of single AuNPs immobilized onto carbon nanoelectrodes. The ligand-free AuNPs immobilized onto the nitrided carbon UMEs were highly electrocatalytic toward methanol oxidation.
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Zhou, Ya-Mei. "Pulmonary oxidative stress and NF-[kappa]B activation in response to inhaled iron and soot particles in rats /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Carvalho, Leila Moreira de. "Características bioquímicas e químicas em filés de peito de frango com anomalia pfn (pale, firm, non-exudative) e pse (pale, soft, exudative)." Universidade Federal da Paraíba, 2016. http://tede.biblioteca.ufpb.br:8080/handle/tede/9434.
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
In the past decades, the intense genetic selection aiming at the increase of productive efficiency of chickens resulted in changes in the meat quality. The broiler breast meat have been classified in three group of quality, Normal, PSE (Pale, Soft, Exudative) and DFD (Dark, Firm, Dry); however, recently, due to the appearance with pale color and normal firmness, another category of meat quality was suggested as PFN (Pale, Firm, Non-exudative). Considering the absence of studies about the incidence of anomalies of color in broiler breast in the Northeast of Brazil, this work aimed at verifying the incidence of these anomalies in the region and carrying out the chemical and biochemical characterization of these meats. This samples were collected in a commercial slaughterhouse and evaluated the parameters of color (L *, a *, b *), pH, water-holding capacity, cooking loss, shear force, myofibrillar fragmentation index, protein denaturation, mineral and fatty acids content, TBARS values, warmed-over flavor and total carbonyls. The broiler breast meat (n = 838) were classified in three categories: Normal (44
Nas últimas décadas, a intensa seleção genética visando o aumento da eficiência produtiva de frangos resultou em modificações na qualidade da carne. Os peitos de frango tem sido classificados em três grupos de qualidade, Normal, PSE (Pale, Soft, Exudative) e DFD (Dark, Firm, Dry); porém, recentemente, devido a aparência com cor pálida e firmeza normal, outra categoria de qualidade de carne foi sugerida a PFN (Pale, Firm, Non-exudative). Considerando-se a ausência de estudos sobre a incidência de anomalias de cor em peitos de frango no Nordeste do Brasil, objetivou-se, neste trabalho verificar a incidência dessas anomalias na região e realizar a caracterização química e bioquímicas dessas carnes. Para isso, foram coletadas amostras em um abatedouro comercial e avaliados os parâmetros de cor (L*, a*, b*), pH, capacidade de retenção de água, perda de peso por cozimento, força de cisalhamento, índice de fragmentação miofibrilar, desnaturação proteica, teor de minerais e de ácidos graxos, número de TBARS, aroma requentado e carbonilas totais. Os filés de peito de frango (n=838) foram classificados em três categorias: Normal (44
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Mawudoku, Daniel. "Immobilization of Electrocatalytically Active Gold Nanoparticles on Nitrogen-Doped Carbon Fiber Electrodes." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etd/3620.
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Studies of single, isolated nanoparticles provide better understanding of the structure-function relationship of nanoparticles since they avoid complications like interparticle distance and nanoparticle loading that are typically associated with collections of nanoparticles distributed on electrode supports. However, interpretation of results obtained from single nanoparticle immobilization studies can be difficult to interpret since the underlying nanoelectrode platform can contribute to the measured current, or the immobilization technique can adversely affect electron transfer. Here, we immobilized ligand-free gold nanoparticles on relatively electrocatalytically inert nitrogen-doped carbon ultramicroelectrodes that were prepared via a soft nitriding method. Sizes of the particles were estimated by a recently reported electrochemical method and were found to vary linearly with deposition time. The particles also exhibited electrocatalytic activity toward methanol oxidation. This immobilization strategy shows promise and may be translated to smaller nanoelectrodes in order to study electrocatalytic properties of single nanoparticles.
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Nayek, Subhayu. "Toxicological and Biochemical Changes Induced by Sub-Acute Exposure of Biological Organisms to Silver Nanoparticles Using the Soft-Landing Ion Mobility Instrument." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1752347/.
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In this study, we have developed a novel way of generating and exposing biological organisms (both prokaryotic and eukaryotic) to silver nanoparticles (AgNPs) and studying the biochemical changes induced by these particles. We analyzed the various organs of Wistar rats for localization and quantification of these particles using mass spectrometric and molecular biological techniques. Highest levels of AgNP was found in the lung tissue in addition to being present in the liver and kidneys. Analysis of the of the blood plasma from AgNP exposed rats revealed elevated levels of glutathione-disulfide, which is indicative of reactive oxygen species (ROS) generation, which was further validated using ROS specific immunofluorescence staining of liver tissue. Quantification of blood lactate levels of the AgNP exposed rats showed increased lactate levels, which is indicative of anaerobic respiration and may result from AgNP-induced oxidative stress. Further analysis of bone marrow cells from AgNP exposed rats showed a higher number of micronuclei formation in developing erythrocytes and bone marrow cytotoxicity. Finally, analysis of the genes involved in the renin-angiotensin system (RAS) and inflammatory response revealed upregulation in transcript levels of many of these important genes in the liver tissue. Taken together, our study provides an initial road map for the identification of different signaling pathways that are altered by the AgNP exposure and contributes to a comprehensive understanding of the mechanism involved in silver nanoparticle-induced toxicity.