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Les réglementations européennes étant de plus en plus restrictives en ce qui concerne les émissions de polluants et plus particulièrement les émissions d'oxydes d'azote (NOx) et de suies, l'objectif de ce travail est de fournir des outils de modélisation permettant l'analyse des mécanismes de réduction de ces émissions à la source, c'est-à-dire au niveau de la chambre de combustion. Dans un premier temps, un modèle de tabulation pour la prédiction des oxydes d'azote a été développé. Ce modèle (appelé NORA: NO Relaxation Approach) repose sur une méthode de perturbation d'état d'équilibre et présente l'avantage d'être simple d'utilisation, robuste et totalement indépendant du modèle de combustion turbulente. L'utilisation du modèle NORA permet une amélioration significative des résultats par rapport à une résolution directe du mécanisme de Zel'dovich couplé à une cinétique réduite. Dans un second temps, le travail a porté sur la modélisation des suies avec comme objectif la prédiction des suies en terme de masse et de distribution en taille de particules (PSDF: Particle Size Distribution Function). La méthode sectionnelle a tout d'abord été implémentée dans un solveur de flamme 1-D et validée par rapport à des données expérimentales en flammes laminaires d'éthylène. La question du couplage du modèle de suies avec un modèle de combustion turbulente a ensuite été posée. Ce travail montre que le couplage entre la phase gazeuse et la phase solide n'est pas négligeable. Un premier modèle de combustion mixte (appelé MTKS) utilisant une méthode tabulée et un solveur de chimie détaillé dans les gaz brûlés a été couplé au modèle de suies. L'approche MTKS a été testée dans des réacteurs hétérogènes à volume variable et les résultats sont encourageants. / European rules are more and more restrictive concerning pollutants emissions. This work deals with the modeling of NOx and soot particles. The final aim is to provide modeling tools in order to analyse the mechanismes leading to reduce these emissions in the combustion chamber. First, a tabulated NO prediction model has been developed. This model (called NORA: NO Relaxation Approach) is based on equilibrium state perturbation method. NORA is simple to use, robust and totally independent of the turbulent combustion model. The use of the NORA allows a significative improvement of the results compared to the direct resolution of the Zel'dovich mechanism with a reduce chemistry. In a second part, this work deals with soot predictions with the final aim the prediction of the soot volume fraction and the particle size distribution function (PSDF). The sectional method approach was first implemented in a 1-D flame solver and validated against experimental flames data. The question of the coupling between the soot sectional model and a turbulent combustion model has been addressed. Studies show that the coupling between gaseous and solid phase is non-negligible. A first mixed combustion model (called MTKS) using a tabulated method and a kinetic solver in the burned gases has been coupled to the soot sectional model. The MTKS approach has been tested in heterogeneous variable volume reactors and results are promising.

Orientadores: Pedro Teixeira Lacava, Cristiane Aparecida Martins / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T15:33:30Z (GMT). No. of bitstreams: 1 Lourenco_AlvaroAugustodeMattos_M.pdf: 3468846 bytes, checksum: 9323ce32ffd4213746598242a62aa82f (MD5) Previous issue date: 2010 / Resumo: A tecnologia de motores diesel tem sido guiada por legislações cada vez mais severas. Para cumprir estas legislações, os sistemas de controle de emissões estão se desenvolvendo rapidamente. Neste contexto, o desenvolvimento de sistemas de pós tratamento de gases de escape assume um papel bastante importante, porém o controle da emissão "In Cylinder" é primordial para o cumprimento das legislações futuras. Níveis de emissões cada vez mais severos, tempo de desenvolvimento extremamente reduzido, aliados ao compromisso entre consumo de combustível, ruído e dirigibilidade obrigam os fabricantes de motores diesel a buscar soluções rápidas, práticas e eficientes que os tornem competitivos. O presente trabalho tem como objetivo analisar o comportamento de diferentes tipos de agentes redutores de óxido nitroso utilizando um sistema de pós tratamento de gases de escape do tipo catalisador seletivo e diversos agentes redutores a base de uréia e formamida. Em relação à eficiência do sistema catalítico SCR quanto a redução de NOx, pode-se dizer que as misturas à base de uréia são as mais eficientes, porém são as que apresentam maiores valores de emissão de amônia. As misturas à base de formamida não apresentaram uma eficiência tão significativa como as misturas a base de uréia, porém os níveis de amônia produzidos por estas misturas é praticamente zero. Em relação às emissões de CO e HC, as misturas à base de formamida apresentaram aumento significativo na emissão destes dois gases, enquanto que nas misturas à base de uréia os valores permaneceram praticamente inalterados / Abstract: Diesel engine technology has been driven by stringent regulation. To fulfill this demands emission control systems are constantly improving. In this context exhaust gas aftertreatment development assumes an important role however the "In Cylinder" emission control is fundamental to comply with future legislations. Severe emissions levels, reduced development timing allied to the compromise among fuel consumption, noise and driveability require diesel engines manufacturers to look for fast, practical and efficient solutions to make it competitive. The current work aims to evaluate the behavior of different types of nitrous oxide reducing agents using a selective catalytic reduction aftertreatment system using several reducing agents based on urea and formamide. Regarding NOx reduction the efficiency of the selective catalytic reduction system using mixtures of urea are the most efficient but also shows higher values of ammonia emission. Mixtures based on formamide did not show a significant efficiency as the mixtures based on urea but the ammonia levels produced by those mixtures are close to zero. Regarding CO and HC mixtures based on formamide showed a significant increase of these two gases while mixtures based on urea remained unchanged / Mestrado / Motores / Mestre em Engenharia Mecânica

Orientadores: Pedro Teixeira Lacava, Cristiane Aparecida Martins / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T17:20:07Z (GMT). No. of bitstreams: 1 Souza_AndersondeAlmeida_M.pdf: 2437052 bytes, checksum: 4d9d2474bf3d815f70a9be4908239d1a (MD5) Previous issue date: 2010 / Resumo: A cada introdução de uma nova norma de emissões de poluentes para motores diesel, modificações se fazem necessárias e um dos sistemas do motor que sofre diretamente tais modificações é o sistema de gerenciamento de ar, que é composto por: turbo-compressor,resfriador EGR e válvula EGR. Assim, todo um ciclo de desenvolvimento do motor é realizado com diversos tipos de ensaios, desde a definição dos componentes até a validação do motor. Com o intuito de reduzir a quantidade de ensaios realizados e o tempo durante a fase de definição dos componentes, uma alternativa é a utilização da simulação computacional. Com a ajuda de softwares específicos, é possível reduzir a quantidade de ensaios para a avaliação dos componentes, deixando para avaliação em dinamômetro apenas os ensaios das configurações que apresentaram os melhores resultados na simulação. Neste trabalho foi utilizado o software GTPOWER, sendo primeiramente realizada a calibração e a validação do modelo para um motor já existente, devido a gama de informações disponíveis sobre esse motor. Na seqüência, foi adicionado ao modelo outros componentes, como o sistema EGR, com o intuito de avaliar o comportamento de diferentes modelos de turbo-compressores em relação às suas características aerodinâmicas e também avaliar diferentes resfriadores EGR em relação à sua capacidade de troca térmica (efetividade) / Abstract: Every introduction of a new pollutant emissions standard for diesel engines, modifications are necessary and one of the engine systems that directly suffer such changes is the air management system, which is composed of turbocharger, EGR cooler and EGR valve. Thus an engine development cycle is carried out with several types of tests, from components definition to engine validation. Aiming at reducing the number of tests performed and the time during the definition phase of the components, an alternative is the use of computer simulation. With the help of specific software, it is possible to reduce the amount of tests for the assessment of the components, leaving only for assessment in the dynamometer testing the configurations that produced the best results in the simulation. In this work used the GT-POWER software. The model was first calibrated and validated for an existing engine, because of the range of information available for the engine. In the sequence, other components, such as the EGR system, were added to the model in order to evaluate the performance of different turbocharger models for aerodynamic characteristics and also evaluate different EGR coolers for thermal exchange capacity (effectiveness) / Mestrado / Motores / Mestre em Engenharia Automobilistica

Orientador: Celso Aparecido Bertran / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-15T06:28:19Z (GMT). No. of bitstreams: 1 Sperl_Andre_M.pdf: 9852829 bytes, checksum: eb971c769176d86c8d4dd5564c6ed768 (MD5) Previous issue date: 2009 / Resumo: Nas últimas décadas as normas de emissões de poluentes vêem tornando-se cada vez mais exigentes, assim como a competição acirrada de produtos, implicando em desenvolvimento de tecnologias para melhoria das emissões de poluentes, que atendam as rígidas normas de emissões de poluentes que estão por vir, como Euro V e Euro VI, porém, com sistemas de uma complexidade e custo que atendam a realidade de mercado. Dentro deste escopo, neste trabalho, foram ensaiados seis diferentes tipos de combustível foram estudados: Diesel Comum Metropolitano, Diesel Euro IV, Diesel Comum Metropolitano apenas com surfactante sem água, e três outras formulações de emulsões chamadas 1, A e B respectivamente, porém com o mesmo conteúdo de água em massa - 22% - no entanto com surfactantes diferentes e patenteados com o objetivo de melhorar a densidade e viscosidade para funcionamento em motor de combustão interna ciclo Diesel. Os resultados de emissões foram obtidos com uma única estratégia de calibração inalterada utilizando o ciclo estacionário de 13 pontos conforme NBR15634 (2008), em um motor de alta rotação 3.0L, o qual possui calibração que atende os requisitos Euro III Heavy Duty. As emissões de NOx e Material Particulado pesado foram reduzidas em relação ao Diesel convencional em 22% e 42%, respectivamente utilizando a emulsão B, enquanto o consumo de específico de combustível aumentou em média 8%. Baseado nestes resultados, alguns mecanismos de redução de emissões de NOx e material particulado são propostos, e estes, podem ser os responsáveis pela redução de poluentes observadas com a utilização destas emulsões de água em óleo Diesel como combustíveis. / Abstract: In the last decades the emission of pollutants are becoming more stringent, also the fierce competition of products, resulting in development of technologies to improve emissions of pollutants that meets the fore coming stringent pollutant emission standards, as Euro V and Euro VI, but with systems of complexity and cost that match market reality. In this work six different kinds of fuels were studied: Diesel Standard Metropolitano, Diesel Euro IV, Diesel Standard Metropolitano only with surfactant without water, and three other formulations of emulsions called 1, A and B respectively, but with the same water content by weight - 22% - but with different patented surfactants, these ones with the aim of improving the density and viscosity for operation in internal combustion Diesel engines. The emission results were obtained with a single dataset strategy unchanged using the stationary cycle for 13 points as NBR15634 (2008) standard requirements in a high-speed engine 3.0L, which dataset meets the requirements of Euro III Heavy Duty emission standard. The NOx and particulate matter emissions were reduced compared to conventional Diesel by 22% and 42% respectively using emulsion B, while the best specific fuel consumption increased on average 8%. Based on these results, some mechanisms for reducing emissions of NOx and particulate matter are proposed, which may be responsible for the reduction of pollutants observed with the use of these emulsions as fuels. / Mestrado / Motores / Mestre em Engenharia Automobilistica

The recognition of the negative impact of NOx resulted in increasingly tighter automotive emission regulations. Companies are under pressure to develop methods, which can meet the legislative demands. After treatment solutions, and especially Selective Catalytic Reduction, became the focus of research and have shown so far promising results. However, more in depth understanding of the SCR process under different conditions is needed. This thesis describes an investigation of the SCR performance using gas and urea injections under steady state and transient conditions undertaken on a light duty diesel engine using a 1D exhaust system designed for uniform flow across the catalyst. Under steady state conditions, the SCR performance was examined for low and high temperature conditions. Ammonia was supplied either as 5% ammonia gas or in form of urea injection. The engine was operating at 1500 rpm and 6 and 8 bar BMEP to provide an exhaust gas temperature of 210 °C and 265 °C respectively. Also, the effect of SCR brick length on the NOx conversion was investigated using SCR catalysts of length 30, 45 and 75 mm. To measure the influence of NO2:NOx ratio on the SCR performance, different sizes of standard DOC were used. NH3:NOx dosage levels included; α~0.5 - deficient ammonia, α~1.0 - stoichiometric ammonia, α~1.25 - excess ammonia. Gas emissions were measured before and after the SCR catalysts with a Horiba FTIR analyser during steady state and long transient tests. It was found that conditions such as temperature and NO2:NOx had the biggest impact on the SCR performance. During the steady state engine conditions, at α~1.0 ammonia dosing and NO2:NOx ratio of 0, only 17% of NO was converted in the first 30 mm of the SCR brick length. The conversion was improved at high temperature (263 °C) to 31%. A fast response CLD analyser was used during short transient testing to sample emissions with a high resolution. The short transient test with standard 0.5 and 1 DOC, and fixed ammonia dosing, showed that NOx conversion was reduced during the ramp event due to deficient ammonia and a drop in the supplied NO2:NOx ratio. During urea injection experiments, urea was injected either through an oblique pipe arrangement with a mixer device placed downstream or directly into a mixing can. In this case the mixer device was replaced with a straight pipe. A 75mm SCR was fitted and to ensure that supplied NO2:NOx ratio was zero, a palladium only DOC was used post a DPF. It was found that a large proportion of urea decomposition and hydrolysis was occurring on the surface of the SCR catalyst. Comparing NOx performance between urea injection and ammonia gas dosing experiment, more NO was converted for a given NH3:NOx ratio when ammonia was supplied in the form of gas. That was true for low and high temperature tests. For most studies, a long 10 degree diffuser was used in front of the SCR to provide uniform gas distribution across the catalyst. In addition SCR performance was investigated with a 180 degree sudden expansion diffuser in order to measure the influence of temperature and velocity profiles. During this study, a 45 mm SCR catalyst was used to provide a moderate amount of NO conversion and ammonia slip. The results showed that the flow and temperature distribution upstream of the SCR catalyst will have an effect on the NOx conversion, and that gas velocity has bigger impact on NOx conversion than gas temperature.

To determine the feasibility of using low thermal expansion ceramics and aluminum titanate in diesel engine applications, the mechanical and thermal properties and corrosion resistance were evaluated. NZP (Ba_1.25Zr₄P_5.5Si_.0.50₂₄ and Ca_0.5 Sr_O.5Zr₄P₆0₂₄) and aluminum titanate (AT) were exposed to a simulated diesel engine environment. The effects of thermal cycling from room temperature to 700°C, and a combination of alkali corrosion and thermal cycling on the mechanical and thermal properties of these ceramics were examined. It was found that NZP and AT materials demonstrated near zero bulk thermal expansion, good thermal up shock resistance and resistance to Na and V corrosion, because of their porous structure and low density. However, the AT materials exhibited lower flexural strength. This is a direct result of the inherent micro cracking across the AT grains upon cooling from the sintering temperature, which reduces the flexural strength and elastic modulus. / Master of Science

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