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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.
41

Výzkum progresivních metod snižování obsahu škodlivých látek ve výfukových plynech vznětových motorů / Research of Progressive Methods for Reduction of Emissions in CI Engine Exhaust Gasses

Franz, Rudolf January 2020 (has links)
The scope of this dissertation work is a description of modern methods of reducing exhaust emission in diesel engines. The fundamental part is the application of these methods for diesel engines for off-road use that means for engines that are used in tractors and road machines. The mentioned evidence for the practical utility of the results of this dissertation thesis in practice and their verification on the actual engine are given in the conclusion.
42

Realizace montážní linky ventilů AdBlue / Realization of assembling line for AdBlue valve

Kozelský, Aleš January 2011 (has links)
This diploma thesis concerns in design and realization of assembling line of a 2/2 seat valve for commercial vehicles sector. Design is using Autodesk Inventor. Thesis describes phases and goals of project management – in this case management of technological/manufacturing transfer.
43

Středotonážní spalovna odpadů - systém čištění spalin / Incineration plant of middle treatment capacity – flue gas cleaning system

Krejčí, Tomáš January 2015 (has links)
Analysis of the regional energy supply, shows that suitable alternative may be a combination of primary energy sources with the municipal solid waste to energy plant. Starting from the fact that the regional thermal energy needs are characterized by smaller power demand, but relatively significant seasonal fluctuations in heat supply. These factors limit the processing performance of the considered waste to energy plant that could be included in the system of regional energy supply. The aim of the thesis was to propose adequate treatment capacity for regional waste to energy plant and explore alternative solutions in off-gas cleaning for exhaust gases generated during incineration of MSW. The balance sheets of two alternative solutions off gas cleaning are part of the thesis, both in terms of material and energy consumption. Presented evaluation of economic demands alternative arrangement of off gas cleaning includes operating costs and the impact on earnings from energy production.
44

Optimisation énergétique de chaînes de traction hybrides essence et Diesel sous contrainte de polluants : Étude et validation expérimentale / Energy Optimization of Gasoline and Diesel Hybrid Powertrains with Pollutant Constraints : Study and Experimental Validation

Simon, Antoine 05 July 2018 (has links)
L’hybridation électrique de la chaîne de traction automobile est l’une des solutions adoptées pour respecter les règlementations futures sur ses émissions. La stratégie de supervision de la chaîne de traction hybride répartit la puissance produite par le moteur à combustion interne et la machine électrique. Elle répond habituellement à un problème d’optimisation où l’objectif est de réduire la consommation de carburant mais nécessite à présent d’y ajouter les émissions polluantes. La chaîne de dépollution, placée à l’échappement du moteur, permet de diminuer la quantité de polluants émise dans l’atmosphère. Cependant, elle n’est efficace qu’à partir d’un seuil de température, et dépend de la chaleur apportée par les gaz d’échappement du moteur thermique. La première partie de ce travail est donc consacrée à la modélisation de la consommation énergétique et des émissions polluantes de la chaine de traction hybride. La modélisation de l’efficacité de la chaîne de dépollution est réalisée selon deux contextes. Le modèle zéro-dimensionnel est adapté aux contraintes de calcul de la commande optimale. Le modèle unidimensionnel associé à un estimateur d’état permet d’être embarqué et calculé en temps réel. À partir de ces travaux, la seconde partie de cette thèse déduit des stratégies de supervision à l’aide de la théorie de la commande optimale. Dans un premier cas, le principe de Bellman permet de calculer la commande optimale d’un véhicule hybride Diesel selon des critères de supervision ayant plus ou moins connaissance de l’efficacité de la chaîne de dépollution des émissions de NOX. Dans un second cas, une stratégie issue du Principe du Minimum de Pontryagin, embarquée sur un véhicule hybride essence, fonctionnant en temps réel et calibrée selon deux paramètres est proposée. L’ensemble de ces travaux est validé expérimentalement au banc moteur et montre une réduction significative des émissions polluantes pour une faible pénalité de carburant. / Powertrain hybridization is a solution that has been adopted in order to conform to future standards for emissions regulations. The supervisory strategy of the hybrid powertrain divides the power emitted between the internal combustion engine and the electric machine. In past studies, this strategy has typically responded to an optimization problem with the objective of reducing consumption. However, in addition to this, it is now necessary to take pollutant emissions into account as well. The after-treatment system, placed in the exhaust of the engine, is able to reduce pollutants emitted into the atmosphere. It is efficient from a certain temperature threshold, and the temperature of the system is dependent on the heat brought by the exhaust gas of the engine. The first part of this dissertation is aimed at modelling the energy consumption and pollutant emissions of the hybrid powertrain. The efficiency model of the after-treatment system is adapted for use in two different contexts. The zero-dimensional model conforms to the constraints of the optimal control calculation. The one-dimensional model associated with a state estimator can be embedded in a vehicle and calculated in real time. From this work, the second part of this dissertation deduces supervisory strategies from the optimal control theory. On the one hand, Bellman’s principle is used to calculate the optimal control of a Diesel hybrid vehicle using different supervisory criteria, each having more or less information about the after-treatment system efficiency over NOX emissions. On the other hand, a strategy from Pontryagin’s minimum principle, embedded in a gasoline hybrid vehicle, running in real time and calibrated with two parameters, is proposed. The whole of this work is validated experimentally on an engine test bed and shows a significant reduction in pollutant emissions for a slight fuel consumption penalty.
45

Synthesis and Characterization of Copper-Exchanged Zeolite Catalysts and Kinetic Studies on NOx Selective Catalytic Reduction with Ammonia

Arthur J. Shih (5930264) 16 January 2019 (has links)
<p>Although Cu-SSZ-13 zeolites are used commercially in diesel engine exhaust after-treatment for abatement of toxic NO<sub>x</sub> pollutants via selective catalytic reduction (SCR) with NH<sub>3</sub>, molecular details of its active centers and mechanistic details of the redox reactions they catalyze, specifically of the Cu(I) to Cu(II) oxidation half-reaction, are not well understood. A detailed understanding of the SCR reaction mechanism and nature of the Cu active site would provide insight into their catalytic performance and guidance on synthesizing materials with improved low temperature (< 473 K) reactivity and stability against deactivation (e.g. hydrothermal, sulfur oxides). We use computational, titration, spectroscopic, and kinetic techniques to elucidate (1) the presence of two types of Cu<sup>2+</sup> ions in Cu-SSZ-13 materials, (2) molecular details on how these Cu cations, facilitated by NH<sub>3</sub> solvation, undergo a reduction-oxidation catalytic cycle, and (3) that sulfur oxides poison the two different types of Cu<sup>2+</sup> ions to different extents at via different mechanisms. </p><p><br></p> <p> </p> <p>Copper was exchanged onto H-SSZ-13 samples with different Si:Al ratios (4.5, 15, and 25) via liquid-phase ion exchange using Cu(NO<sub>3</sub>)<sub>2</sub> as the precursor. The speciation of copper started from the most stable Cu<sup>2+</sup> coordinated to two anionic sites on the zeolite framework to [CuOH]<sup>+</sup> coordinated to only one anionic site on the zeolite framework with increasing Cu:Al ratios. The number of Cu<sup>2+</sup> and [CuOH]<sup>+</sup> sites was quantified by selective NH<sub>3</sub> titration of the number of residual Brønsted acid sites after Cu exchange, and by quantification of Brønsted acidic Si(OH)Al and CuOH stretching vibrations from IR spectra. Cu-SSZ-13 with similar Cu densities and anionic framework site densities exhibit similar standard SCR rates, apparent activation energies, and orders regardless of the fraction of Z<sub>2</sub>Cu and ZCuOH sites, indicating that both sites are equally active within measurable error for SCR. </p><p><br></p> <p> </p> <p>The standard SCR reaction uses O<sub>2</sub> as the oxidant (4NH<sub>3</sub> + 4NO + O<sub>2</sub> -> 6H<sub>2</sub>O + 4N<sub>2</sub>) and involves a Cu(I)/Cu(II) redox cycle, with Cu(II) reduction mediated by NO and NH<sub>3</sub>, and Cu(I) oxidation mediated by NO and O<sub>2</sub>. In contrast, the fast SCR reaction (4NH<sub>3</sub> + 2NO + 2NO<sub>2</sub> -> 6H<sub>2</sub>O + 4N<sub>2</sub>) uses NO<sub>2</sub> as the oxidant. Low temperature (437 K) standard SCR reaction kinetics over Cu-SSZ-13 zeolites depend on the spatial density and distribution of Cu ions, varied by changing the Cu:Al and Si:Al ratio. Facilitated by NH<sub>3</sub> solvation, mobile Cu(I) complexes can dimerize with other Cu(I) complexes within diffusion distances to activate O<sub>2</sub>, as demonstrated through X-ray absorption spectroscopy and density functional theory calculations. Monte Carlo simulations are used to define average Cu-Cu distances. In contrast with O<sub>2</sub>-assisted oxidation reactions, NO<sub>2</sub> oxidizes single Cu(I) complexes with similar kinetics among samples of varying Cu spatial density. These findings demonstrate that low temperature standard SCR is dependent on Cu spatial density and requires NH<sub>3</sub> solvation to mobilize Cu(I) sites to activate O<sub>2</sub>, while in contrast fast SCR uses NO<sub>2</sub> to oxidize single Cu(I) sites. </p><p><br></p> <p> </p> <p>We also studied the effect of sulfur oxides, a common poison in diesel exhaust, on Cu-SSZ-13 zeolites. Model Cu-SSZ-13 samples exposed to dry SO<sub>2</sub> and O<sub>2</sub> streams at 473 and 673 K. These Cu-SSZ-13 zeolites were synthesized and characterized to contain distinct Cu active site types, predominantly either divalent Cu<sup>2+</sup> ions exchanged at proximal framework Al sites (Z<sub>2</sub>Cu), or monovalent CuOH+ complexes exchanged at isolated framework Al sites (ZCuOH). On the model Z<sub>2</sub>Cu sample, SCR turnover rates (473 K, per Cu) catalyst decreased linearly with increasing S content to undetectable values at equimolar S:Cu molar ratios, while apparent activation energies remained constant at ~65 kJ mol<sup>-1</sup>, consistent with poisoning of each Z<sub>2</sub>Cu site with one SO<sub>2</sub>-derived intermediate. On the model ZCuOH sample, SCR turnover rates also decreased linearly with increasing S content, yet apparent activation energies decreased monotonically from ~50 to ~10 kJ mol<sup>-1</sup>, suggesting that multiple phenomena are responsible for the observed poisoning behavior and consistent with findings that SO<sub>2</sub> exposure led to additional storage of SO<sub>2</sub>-derived intermediates on non-Cu surface sites. Changes to Cu<sup>2+</sup> charge transfer features in UV-Visible spectra were more pronounced for SO<sub>2</sub>-poisoned ZCuOH than Z<sub>2</sub>Cu sites, while X-ray diffraction and micropore volume measurements show evidence of partial occlusion of microporous voids by SO<sub>2</sub>-derived deposits, suggesting that deactivation may not only reflect Cu site poisoning. Density functional theory calculations are used to identify the structures and binding energies of different SO<sub>2</sub>-derived intermediates at Z<sub>2</sub>Cu and ZCuOH sites. It is found that bisulfates are particularly low in energy, and residual Brønsted protons are liberated as these bisulfates are formed. These findings indicate that Z<sub>2</sub>Cu sites are more resistant to SO<sub>2</sub> poisoning than ZCuOH sites, and are easier to regenerate once poisoned. </p>
46

Catalytic Consequences of Active Site Speciation, Density, Mobility and Stability on Selective Catalytic Reduction of NO<sub>x</sub> with Ammonia over Cu-Exchanged Zeolites

Ishant Khurana (7307489) 16 October 2019 (has links)
<p>Selective catalytic reduction (SCR) of NO<sub>x </sub>using NH<sub>3 </sub>as a reductant (4NH<sub>3</sub>+ 4NO + O<sub>2</sub> 6H<sub>2</sub>O + 4N<sub>2</sub>) over Cu-SSZ-13 zeolites is a commercial technology used to meet emissions targets in lean-burn and diesel engine exhaust. Optimization of catalyst design parameters to improve catalyst reactivity and stability against deactivation (hydrothermal and sulfur poisoning) necessitates detailed molecular level understanding of structurally different active Cu sites and the reaction mechanism. With the help of synthetic, titrimetric, spectroscopic, kinetic and computational techniques, we established new molecular level details regarding 1) active Cu site speciation in monomeric and dimeric complexes in Cu-SSZ-13, 2) elementary steps in the catalytic reaction mechanism, 3) and deactivation mechanisms upon hydrothermal treatment and sulfur poisoning.</p><p>We have demonstrated that Cu in Cu-SSZ-13 speciates as two distinct isolated sites, nominally divalent Cu<sup>II </sup>and monovalent [Cu<sup>II</sup>(OH)]<sup>+ </sup>complexes exchanged at paired Al and isolated Al sites, respectively. This Cu site model accurately described a wide range of zeolite chemical composition, as evidenced by spectroscopic (Infrared and X-ray absorption) and titrimetric characterization of Cu sites under <i>ex situ </i>conditions and <i>in situ </i>and <i>operando </i>SCR reaction conditions. Monovalent [Cu<sup>II</sup>(OH)]<sup>+ </sup>complexes have been further found to condense to form multinuclear Cu-oxo complexes upon high temperature oxidative treatment, which have been characterized using UV-visible spectroscopy, CO-temperature programmed reduction and dry NO oxidation as a probe reaction. Structurally different isolated Cu sites have different susceptibilities to H<sub>2 </sub>and He reductions, but are similarly susceptible to NO+NH<sub>3 </sub>reduction and have been found to catalyze NO<sub>x </sub>SCR reaction at similar turnover rates (per Cu<sup>II</sup>; 473 K) via a Cu<sup>II</sup>/Cu<sup>I </sup>redox cycle, as their structurally different identities are masked by NH<sub>3 </sub>solvation during reaction. </p><p><br></p><p>Molecular level insights on the low temperature Cu<sup>II</sup>/Cu<sup>I </sup>redox mechanism have been obtained using experiments performed <i>in situ</i>and <i>in operando </i>coupled with<i></i>theory. Evidence has been provided to show that the Cu<sup>II</sup> to Cu<sup>I </sup>reduction half-cycle involves single-site Cu reduction of isolated Cu<sup>II </sup>sites with NO+NH<sub>3</sub>, which is independent of Cu spatial density. In contrast, the Cu<sup>I</sup> to Cu<sup>II </sup>oxidation half-cycle involves dual-site Cu oxidation with O<sub>2 </sub>to form dimeric Cu-oxo complexes, which is dependent on Cu spatial density. Such dual-site oxidation during the SCR Cu<sup>II</sup>/Cu<sup>I </sup>redox cycle requires two Cu<sup>I</sup>(NH<sub>3</sub>)<sub>2</sub>sites, which is enabled by NH<sub>3</sub>solvation that confers mobility to isolated Cu<sup>I </sup>sites and allows reactions between two Cu<sup>I</sup>(NH<sub>3</sub>)<sub>2 </sub>species and O<sub>2</sub>. As a result, standard SCR rates depend on Cu proximity in Cu-SSZ-13 zeolites when Cu<sup>I </sup>oxidation steps are kinetically relevant. Additional unresolved pieces of mechanism have been investigated, such as the reactivity of Cu dimers, the types of reaction intermediates involved, and the debated role of Brønsted acid sites in the SCR cycle, to postulate a detailed reaction mechanism. A strategy has been discussed to operate either in oxidation or reduction-limited kinetic regimes, to extract oxidation and reduction rate constants, and better interpret the kinetic differences among Cu-SSZ-13 catalysts.</p><p><br></p><p>The stability of active Cu sites upon sulfur oxide poisoning has been assessed by exposing model Cu-zeolite samples to dry SO<sub>2 </sub>and O<sub>2 </sub>streams at 473 and 673 K, and then analyzing the surface intermediates formed via spectroscopic and kinetic assessments. Model Cu-SSZ-13 zeolites were synthesized to contain distinct Cu active site types, predominantly either divalent Cu<sup>II </sup>ions exchanged at proximal framework Al (Z<sub>2</sub>Cu), or monovalent [Cu<sup>II</sup>OH]<sup>+ </sup>complexes exchanged at isolated framework Al (ZCuOH). SCR turnover rates (473 K, per Cu) decreased linearly with increasing S content to undetectable values at equimolar S:Cu ratios, consistent with poisoning of each Cu site with one SO<sub>2</sub>-derived intermediate. Cu and S K-edge X-ray absorption spectroscopy and density functional theory calculations were used to identify the structures and binding energies of different SO<sub>2</sub>-derived intermediates at Z<sub>2</sub>Cu and ZCuOH sites, revealing that bisulfates are particularly low in energy, and residual Brønsted protons are liberated at Z<sub>2</sub>Cu sites as bisulfates are formed. Molecular dynamics simulations also show that Cu sites bound to one HSO<sub>4</sub><sup>- </sup>are immobile, but become liberated from the framework and more mobile when bound to two HSO<sub>4</sub><sup>-</sup>. These findings indicate that Z<sub>2</sub>Cu sites are more resistant to SO<sub>2</sub>poisoning than ZCuOH sites, and are easier to regenerate once poisoned.</p><p><br></p><p>The stability of active Cu sites on various small-pore Cu-zeolites during hydrothermal deactivation (high temperature steaming conditions) has also been assessed by probing the structural and kinetic changes to active Cu sites. Three small-pore, eight-membered ring (8-MR) zeolites of different cage-based topology (CHA, AEI, RTH) have been investigated. With the help of UV-visible spectroscopy to probe the Cu structure, in conjunction with measuring differential reaction kinetics before and after subsequent treatments, it has been suggested that the RTH framework imposes internal transport restrictions, effectively functioning as a 1-D framework during SCR catalysis. Hydrothermal aging of Cu-RTH results in complete deactivation and undetectable SCR rates, despite no changes in long-range structure or micropore volume after hydrothermal aging treatments and subsequent SCR exposure, highlighting beneficial properties conferred by double six-membered ring (D6R) composite building units. Exposure aging conditions and SCR reactants resulted in deleterious structural changes to Cu sites, likely reflecting the formation of inactive copper-aluminate domains. Therefore, the viability of Cu-zeolites for practical low temperature NO<sub>x </sub>SCR catalysis cannot be inferred solely from assessments of framework structural integrity after aging treatments, but also require Cu active site and kinetic characterization after aged zeolites are exposed to low temperature SCR conditions.</p>
47

A window into selective catalytic reduction : a RAIRS study of NO and NH3 on Cu{311}

Sitathani, Krit January 2017 (has links)
This thesis studies the interaction between the bare Cu{311} surface with NO and NH3,individually and co-adsorbed using reflection-absorption infrared spectroscopy (RAIRS). In addition to the bare Cu{311} surface, the interaction of NO and NH3 with the various oxygen phases of the Cu{311} surface phases was also studied. Several other techniques were used in tandem to support the study, such as low energy electron diffraction (LEED) and temperature programmed desorption (TPD) experiments using mass spectrometry. The study was carried out in pursuit an understanding of the underlying mechanism of the selective catalytic reduction (SCR) of NO using NH3 in current diesel engines. The dosing of NO onto the Cu{311} surface at 100 K leads to the initial adsorption of intact NO. After an exposure threshold is reached, individual NO molecules react with another NO molecule to form (NO)2 dimers. These dimer species subsequently form N2O, leaving O(a) on the surface. Oxygen was found to be an inhibitor for the reaction, either due to the reaction in a self-poisoning process or from oxygen pre-dosing onto the Cu{311} surface. Temperature plays a minor role with regards to NO/Cu{311}, as it only affects the amount of NO on the surface along with adsorbate surface mobility. Similarly, NH3 was found to adsorb intact onto the Cu{311} surface and not to react or dissociate at 100 K. Oxygen acts as a site blocker for the adsorption, but can also stabilise NH3 to remain on the surface at higher temperatures due to electronic effects. At 300 K, it was found that both the bare and oxygen pre-covered Cu{311} surface was able to dissociate NH3 into NH2. The co-adsorption of NO and that of NH3 onto the Cu{311} surface were found to be largely independent of each other and the interaction is dominated by the displacement of NO by NH3. However, as NO adsorption on the Cu{311} surface forms O(a), it indirectly affects the adsorption of NH3 by creating an oxygen covered Cu{311} surface, which changes how NH3 adsorbs onto the surface.
48

Tlakové ztráty nosičů katalyzátorů / Pressure loss of catalyst carriers

Linda, Matúš January 2018 (has links)
The diploma thesis is divided into four main parts. The first part deals with the issue of waste management and its energy utilization in waste incineration. Processed harmful substances produced by incineration as well as emission limits. It deals with the types of catalytic carriers, their description, production and more detailed processing of ceramic foam VUKOPOR. The second part is devoted to technologies utilizing catalytic processes and a more detailed specification of the process. In the third part there is processed the calculation methods for pressure losses for individual types of carriers. Fourth, the most extensive part describes the INTEQII experimental device, its technology and construction, as well as the principle of the practical part, measuring of the pressure losses of carriers. It includes the evaluation of pressure losses in separate categories of carriers, such as the bed, HoneyComb and VUKOPOR ceramic foam. Subsequently, a comparison of the pressure losses of all carriers is made relative to the reference size of 1 m. The impact of bonding of VUKOPOR foam samples on the size of pressure losses is discussed. At the end of this section, the suitability of calculation methods for individual carriers is evaluated, depending on the experimental pressure loss data.
49

Modelling and analysis of conversion efficiency in flow-through catalysts for lean-burn combustion engines

Ruiz Lucas, María José 09 June 2023 (has links)
[ES] La preocupación mundial por el cambio climático y la calidad del aire se refleja en normativas para la regulación de emisiones en el sector del transporte cada vez más estrictas, situando el desarrollo de sistemas propulsivos sostenibles como el objetivo fundamental. En el caso de los motores de combustión interna, el uso de sistemas de postratamiento de gases de escape, necesario para cumplir con los límites impuestos a las emisiones contaminantes, ha añadido mayor complejidad a la línea de escape. Una correcta comprensión de la respuesta de estos sistemas y su interacción con el motor requiere un profundo conocimiento de los procesos termo-fluidodinámicos y químicos que tienen lugar en los mismos. Su estudio indica que las mayores contribuciones a la reducción de las emisiones consisten en conseguir una activación más rápida de los catalizadores. Sin embargo, por lo general, las estrategias empleadas para alcanzar este fin se traducen en una penalización del consumo de combustible y, por consiguiente, de las emisiones de CO2. En este contexto, el objetivo de esta tesis doctoral es contribuir a la comprensión de los fenómenos presentes en los reactores monolíticos de flujo continuo utilizados en los motores de combustión pobre. En primer lugar, se presenta el desarrollo de una herramienta computacional para el modelado de los reactores estándar, es decir, los monolitos con recubrimiento catalítico monocapa, con un coste computacional bajo que permite responder de manera oportuna a las nuevas condiciones de contorno. El modelo se construyó dentro del entorno de modelo de motor virtual VEMOD, un software de dinámica de gases desarrollado por el I.U.I. CMT-Motores Térmicos para la simulación termo-fluidodinámica de motores de combustión interna y sus componentes. Apoyada sobre experimentos específicos para su calibración y validación en catalizadores de oxidación y de reducción de NOx, la herramienta computacional permite la identificación y el estudio de los parámetros que determinan la eficiencia de conversión de los sistemas de postratamiento. De esta forma, se aplica, con un enfoque de cálculo de valor medio, al análisis, en primer lugar, del impacto de la meso-geometría y el material de catalizadores de oxidación en condiciones dinámicas en función de la forma del canal. También se aborda el estudio de la sensibilidad a la composición de los gases de escape considerando diversas estrategias de combustión comparadas con el diésel convencional, así como el empleo de combustibles alternativos. Por último, se explora experimentalmente la importancia de la ubicación en la línea de escape de un catalizador de oxidación para discutir el efecto sobre las emisiones y el rendimiento del motor de la ubicación pre-turbina, por los beneficios que a nivel térmico tiene esta localización para el postratamiento. Todo ello sirve como fuente de desarrollos tecnológicos y científicos en el área de control de emisiones para el uso y comprensión de la nueva generación de sistemas de postratamiento. / [CA] La preocupació mundial pel canvi climàtic i la qualitat de l'aire es reflecteix en normatives per a la regulació d'emissions en el sector del transport cada vegada més estrictes, situant el desenvolupament de sistemes propulsius sostenibles com l'objectiu fonamental. En el cas dels motors de combustió interna, l'ús de sistemes de posttractament de gasos de fuita, necessari per a complir amb els límits imposats a les emissions contaminants, ha afegit major complexitat a la línia de fuita. Una correcta comprensió de la resposta d'aquests sistemes i la seua interacció amb el motor requereix un profund coneixement dels processos termo-fluidodinámicos i químics que tenen lloc en aquests. El seu estudi indica que les majors contribucions a la reducció de les emissions consisteix a aconseguir una activació més ràpida dels catalitzadors. No obstant això, en general, les estratègies emprades per a aconseguir aquest objectiu es tradueixen en una penalització del consum de combustible i, per consegüent, de les emissions de CO2. En aquest context, l'objectiu d'aquesta tesi doctoral és contribuir a la comprensió dels fenòmens presents en els reactors monolítics de flux continu utilitzats en els motors de combustió pobra. En primer lloc, es presenta el desenvolupament d'una eina computacional per al modelatge dels reactors estàndard, és a dir, els monòlits amb recobriment catalític monocapa, amb un cost computacional baix que permet respondre de manera oportuna a les noves condicions de contorn. El model es va construir dins de l'entorn de model de motor virtual VEMOD, un programari de dinàmica de gasos desenvolupat per l'I.U.I. CMT-Motors Tèrmics per a la simulació termo-fluidodinámica de motors de combustió interna i els seus components. Recolzada sobre experiments específics per al seu calibratge i validació en catalitzadors d'oxidació i de reducció de NOx, l'eina computacional permet la identificació l'estudi dels paràmetres que determinen l'eficiència de conversió dels sistemes de posttractament. D'aquesta manera, s'aplica, amb un enfocament de càlcul de valor mitjà, a l'anàlisi, en primer lloc, de l'impacte de la meso-geometria i el material de catalitzadors d'oxidació en condicions dinàmiques en funció de la forma del canal. També s'aborda l'estudi de la sensibilitat a la composició dels gasos de fuita considerant diverses estratègies de combustió comparades amb el dièsel convencional, així com l'ús de combustibles alternatius. Finalment, s'explora experimentalment la importància de la ubicació en la línia de fuita d'un catalitzador d'oxidació per a discutir l'efecte sobre les emissions i el rendiment del motor de la ubicació pre-turbina, pels beneficis que a nivell tèrmic té aquesta localització per al posttractament. Tot això serveix com a font de desenvolupaments tecnològics i científics en l'àrea de control d'emissions per a l'ús i comprensió de la nova generació de sistemes de posttractament. / [EN] The global concern on climate change and air quality is reflected over increasingly strict emission regulations in the transportation sector, making the development of sustainable propulsion systems the key objective. In the case of internal combustion engines, the use of aftertreatment systems (ATS), necessary to comply with the limits imposed on pollutant emissions, has added further complexity to the exhaust line. A correct comprehension of the response of these systems and their interaction with the engine requires an in-depth knowledge of the thermo-fluid-dynamic and chemical processes taking place inside them. Their study indicates that the major contributions to emission reduction rely on driving the catalysts to a faster light-off. However, in general, the strategies employed to achieve this goal involve a fuel consumption penalty and, consequently, CO2 emissions increase. In this context, the aim of this Ph.D. thesis is to contribute to the understanding of the phenomena present in flow-through catalysts used in lean burn combustion engines. First, the development of a computational tool for modelling the standard devices, i.e. mono-layers washcoat catalysts, is presented, with flexible and low computational cost, enabling timely response to the new boundary conditions. The model was built inside the Virtual Engine Model VEMOD, an open-source gas dynamics software developed by I.U.I. CMT-Motores Térmicos for thermo-fluid-dynamic simulation of internal combustion engines and their components. Supported by specific experiments for its calibration and validation on oxidation and NOx reduction catalysts, the computational tool allows the identification and study of the parameters that determine the conversion efficiency of the ATS. In the first instance it is used to analyze the impact of meso-geometry and oxidation catalyst material under dynamic conditions as a function of the channel shape. The study of the sensitivity to exhaust gas composition is also addressed considering various combustion strategies compared to conventional diesel, as well as the use of alternative fuels. Finally, the importance of the position in the exhaust line of an oxidation catalyst is explored experimentally to discuss the effect on emissions and engine performance of the pre-turbine location, because of the thermal benefits of this location for the aftertreatment. All of this serves as a source of technological and scientific developments in the area of emissions control for the use and comprehension of the new generation of aftertreatment systems. / Ruiz Lucas, MJ. (2023). Modelling and analysis of conversion efficiency in flow-through catalysts for lean-burn combustion engines [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/194012

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