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Marsano, Flavio. "Chemical kinetic modelling of hydrocarbon combustion." Thesis, Cardiff University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402067.
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Martins, Ivana. "Redução sistemática de mecanismos cinéticos de combustão." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/35625.
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Mecanismos de cinética química detalhada são rotineiramente usados para descrever, a nível molecular, a transformação de reagentes em produtos de combustão, que ocorre através de muitas etapas elementares. Seu uso em modelos computacionais para simular processos de combustão pode gerar informações para melhorar o processo de uso do combustível e o desempenho do processo de combustão, e para quantificar as emissões a partir deste processo. Assim, para descrever um processo de oxidação, o esforço computacional se torna muito grande, exigindo simplificações do mecanismo. O desenvolvimento de mecanismos de cinética química reduzida para processos de combustão visa reduzir a esforço computacional na análise numérica de chamas. Os modelos cinéticos reduzidos podem substituir as equações diferenciais das espécies intermediárias, que são consideradas estarem em estado estacionário, através de relações algébricas. Desta forma, este trabalho desenvolve um método para reduzir a cinética química para a combustão do hidrogênio, monóxido de carbono, e hidrocarbonetos C1- C7, utilizando os pressupostos de estado estacionário. Um mecanismo cinético detalhado do processo de combustão de 439 reações elementares foi estudado e reduzido a mecanismos com, no máximo, 9 passos globais. Comparações de dados experimentais com simulações do perfil de fração de massa de CO2 e H2O, produzidos utilizando o mecanismo cinético reduzido do metano, propano e n-heptano demonstram boa concordância, validando estes mecanismos e, consequentemente, aumentando a confiabilidade dos demais mecanismos estudados.Detailed chemical kinetic mechanisms are routinely used to describe, at the molecular level, the transformation of reactants to products of combustion, which occurs via many elementary steps. Its use in computer models to simulate combustion processes can generate information to improve the fuel quality and performance of the combustion process, and to quantify the emissions from this process. Thus, to describe a process of oxidation, the computational effort becomes very large, requiring simplifications of the reaction mechanism. The development of reduced kinetic mechanisms for combustion processes aims to reduce the computational effort necessary for the numerical analysis. The reduced models can replace the differential equations of the intermediate species, which are considered to be in steady state, through algebraic relationships. In this way, this work develops a method for reducing the kinetics of combustion for hydrogen, carbon monoxide and hydrocarbons C1-C7, using assumptions of steady-state. A detailed kinetic mechanism containing 439 elementary reactions was analysed and reduced mechanisms with up to 10 steps were developed. Comparisons between experiment and simulations for the reduced kinetic mechanism of methane and propane, show good agreement, validating these mechanisms, and consequently, increasing the reliability of the others mechanisms studied.
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Honnet, Sylvie. "Detailed and reduced kinetic mechanisms in low-emission combustion processes /." Göttingen : Cuvillier, 2007. http://d-nb.info/98605528X/04.
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ZANONI, M. A. B. "Smoldering Combustion In Porous Media Kinetic Models For Numerical Simulations." Universidade Federal do Espírito Santo, 2012. http://repositorio.ufes.br/handle/10/4161.
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Previous issue date: 2012-03-05Tecnologias avançadas para a geração de energia usando combustíveis não convencionais xisto betuminoso e seu semi-coque, areias betuminosas, petróleo extra-pesado e biomassa proveniente de resíduos sólidos urbanos e de lodo de esgoto - têm em comum processos termoquímicos compostos de complexas reações químicas. Este trabalho trata da formulação e otimização de mecanismos químicos normalmente envolvidos na pirólise do xisto betuminoso e na combustão do xisto betuminoso e seu semi-coque. Problemas inversos (usando o algoritmo de Levenberg-Marquardt) foram empregados para minimizar o erro entre os valores estimados e os dados de termogravimétria para os mecanismos de reação de 3 passos para a pirólise do xisto betuminos, e mecanismos de 4 e 3 passos para o xisto betuminoso e seu semi-coque, respectivamente. Os parâmetros cinéticos, tais como ordem de reação, fator pré-exponencial, energia de ativação e os coeficientes estequiométricos que afetam a secagem, as reações de oxidação, pirólise e descarbonatação foram estimadas com sucesso. Além disso, os erros estatísticos e residuais foram avaliados, resultando em um valor razoável para todas as estimativas e o mecanismo cinético proposto e estimado para a combustão do semi-coque foi aplicado em um código em meios porosos. Um estudo paramétrico entre o perfil de temperatura e a velocidade do ar, e o perfil de temperatura e a concentração de carbono fixo foi desenvolvido. Este estudo mostra que o perfil de temperatura é extremamente influenciado por estes parâmetros, confirmando que a propagação da frente é controlada pela injeção de O2. Palavras-chave: Xisto Betuminoso, Semi-Coque, Pirólise, Combustão, Estimação de Parâmetros, Problemas Inversos, Levenberg-Marquardt, Meios Porosos.
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Leung, Kai Ming. "Kinetic modelling of hydrocarbon flames using detailed and systematically reduced chemistry." Thesis, Imperial College London, 1995. http://hdl.handle.net/10044/1/7760.
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Fürst, Magnus. "Uncertainty Quantification and Optimization of kinetic mechanisms for non-conventional combustion regimes: Turning uncertainties into possibilities." Doctoral thesis, Universite Libre de Bruxelles, 2020. https://dipot.ulb.ac.be/dspace/bitstream/2013/307514/5/contratMF.pdf.
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The usage of novel combustion technologies, such as Moderate or Intense Low-oxygen Dilution (MILD) combustion, in the future energy mix provides both a flexible and reliable energy supply, together with low emissions. The implementation though is highly situational and numerical studies can help in the assessment of said technologies. However, the existing uncertainties in numerical modeling of MILD combustion are quite significant, and as detailed kinetics should be considered while modeling MILD combustion, a major part of this uncertainty can be accredited to the kinetics. Combined with the fact that existing detailed mechanisms have been developed and validated against conventional combustion targets, there exists a gap between the performance of existing mechanism and experimental findings. To handle this discrepancy, Uncertainty Quantification (UQ) and Optimization are highly viable techniques for reducing this misfit, and have therefore been applied in this work. The strategy applied consisted of first determining the reactions which showed the largest impact towards the experimental targets, by not only considering the sensitivity, but also the uncertainty of the reactions. By using a so-called impact factor, the most influential reactions could be determined, and only the kinetic parameters with the highest impact factors were considered as uncertain in the optimization studies. The uncertainty range of the kinetic parameters were then determined using the uncertainty bounds of the rate coefficients, by finding the lines which intercepts the extreme points of these maximum and minimum rate coefficient curves. Based on this prior parameter space, the optimal combination of the uncertain parameters were determined using two different approaches. The first one utilized Surrogate Models (SMs) for predicting the behavior of changing the kinetic parameters. This is a highly efficient approach, as the computational effort is reduced drastically for each evaluation, and by comparing the physically viable parameter combinations within the pre-determined parameter space, the optimal point could be determined. However, due to limitations of the amount of uncertain parameters and experimental targets that can be used with SMs, an optimization toolbox was developed which uses a more direct optimization approach. The toolbox, called OptiSMOKE++, utilizes the optimization capabilities of DAKOTA, and the simulation of detailed kinetics in reactive systems by OpenSMOKE++. By using efficient optimization methods, the amount of evaluations needed to find the optimal combination of parameters can be drastically reduced. The tool was developed with a flexibility of choosing experimental targets, uncertain kinetic parameters, objective function and optimization method. To present these features, a series of test cases were used and the performance of OptiSMOKE++ was indeed satisfactory. As a final application, the toolbox OptiSMOKE++ was used for optimizing a kinetic mechanism with respect to a large set of experimental targets in MILD conditions. A large amount of uncertain kinetic parameters were also used in the optimization, and the optimized mechanism showed large improvements with respect to the experimental targets. It was also validated against experimental data consisting of species measurements in MILD conditions, and the optimized mechanism showed similar performance as that of the nominal mechanism. However, as the general trend of the species profiles were captured with the nominal mechanism, this was considered satisfactory. The work of this PhD has shown that the application of optimization to kinetic mechanism, can improve the performance of existing mechanism with respect to MILD combustion. Through the development of an efficient toolbox, a large set of experimental data can be used as targets for the optimization, at the same time as many uncertain kinetic parameters can be used contemporary.Doctorat en Sciences de l'ingénieur et technologie
This work has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 643134, and from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 714605.
info:eu-repo/semantics/nonPublished
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Qureshi, Nafisa. "A kinetic study of Maya crude oil for in-situ combustion." Thesis, University of Salford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484213.
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SOUZA, OBERDAN MIGUEL RODRIGUES DE. "PRESUMED PDF MODEL WITH TABULATED CHEMICAL KINETIC APPLIED FOR SPRAY COMBUSTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=30283@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Neste trabalho, foi desenvolvida uma modificação do modelo para simulação de sprays Diesel com o método de PDF presumida e cinética química tabulada. Através do acoplamento entre a parte química e a parte turbulenta, avaliou-se os efeitos do spray com a metodologia flamelet. Onde o conceito flamelet trata a chama difusiva e transiente como um conjunto de chamas unidimensionais, utilizando o modelo de PDF presumida para a avaliação dos valores turbulentos. A validação do modelo foi realizada com dados experimentais do laboratório Sandia, em uma câmara a volume constante. A validação e a aplicação do modelo foram conduzidas em diferentes tipos de ensaios experimentais: avaliação e comparação para diferentes modelos de cinética química do n-heptano, validação do método para o modelo de turbulência K-epsilon na câmara de volume constante do Sandia para o n-heptano não reativo, validação e comparação do modelo para o spray reativo e aplicação de modelo para o estudo comprimento do ancoramento de chama e para o tempo de atraso de ignição do n-heptano para diferentes temperaturas ambientes. Em geral, a modelagem proposta tem demonstrado excelente capacidade de previsão para a combustão com spray Diesel numa vasta gama de aplicações e é um candidato altamente promissor para outras aplicações em motores Diesel.
In this work, a modification of the model for the simulation of diesel sprays with the presumed PDF method and tabulated chemical kinetics was developed. Through the coupling between the chemical part and the turbulent part, the effects of the spray were evaluated for the flamelet methodology. Where the textit flamelet concept treats the diffusive and transient flame as a set of one-dimensional flames, using the presumed PDF model for the evaluation of turbulent values. The validation of the model was performed with experimental data from the Sandia laboratory, in a chamber at constant volume. The validation and application of the model were conducted in different types of experimental trials: evaluation and comparison for different chemical kinetics models of n-heptane, validation of the method for the turbulence model K-epsilon in the constant volume chamber of the Sandia for non-reactive n-heptane, validation and comparison of the model for the reactive spray and model application for the study of the flame anchoring length and for the ignition delay time of n-heptane at different ambient temperatures. In general, the proposed modeling has demonstrated excellent predictive capacity for diesel spray combustion in a wide range of applications and is a highly promising candidate for other applications in diesel engines.
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Khan, Mohammad A. "Thermochemical kinetic studies of organic peroxides relevant to the combustion of hydrocarbons." Thesis, University of Aberdeen, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290241.
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In the combustion of fuels and related organic compounds the initial step consists of a free radical forming process occurring either homogeneously or heterogeneously, such as RH + O2 → R + HO_2 (1) The radical R, reacts with oxygen to produce an alkyl or other peroxy radical: R + O_2 ↔ RO2 (2) One of the controversies involved in the mechanism for the oxidation of hydrocarbons is the route for the unimolecular decomposition of the hydroperoxy alkyl radical (R-HOOH). This would be produced as a result of the isomerisation of the alkyl peroxy radical (RO2). There are three possible unimolecular paths for R-HOOH together with the addition of oxygen to form hydroperoxy alkyl peroxy radical. This study is concerned with the generation of an alkyl peroxy alkyl radical and its decomposition to both epoxide and olefin formation and at lower temperatures predominantly follows the thermochemically more favourable route. No direct information is available about the rate constants of the two decomposition routes of alkyl peroxyalkyl/hydroperoxy alkyl radicals. There are different ways to find out the rate constants for the decomposition of alkyl peroxy alkyl/hydroperoxy alkyl radical to olefin and oxirane. One such way was a study of the gas phase, hydrogen chloride catalysed decomposition of di-t-butyl peroxide. A surrogate hydroperoxy alkyl radical was generated via this study and the most favourable route for the decomposition of dtBP-H is confirmed. Again, on thermochemical grounds, the formation of isobutene oxide predominates over the formation of isobutene. The modelling of this study assisted considerably in choosing the reaction steps for a probable mechanism and in the assessment of rate parameters for the individual steps. A bonafide hydroperoxy alkyl radical was generated via the study of the sensitized decomposition of t-butyl hydroperoxide in an uncoated, coated reaction vessel and also in the presence of oxygen. The Arrhenius parameters for the ratio of the rate of formation of isobutene to isobutene oxide was observed experimentally, and are in good agreement with the estimated values in the coated reaction vessel but in uncoated and in the presence of oxygen, this ratio is nearly doubled which suggests that isobutene is formed heterogeneously and surface played an important role. In order to observe the effect of surface: volume ratio on product formation, this system was studied in four different coated reaction vessels and it was concluded that the surface effect was negligible on a coated spherical reaction vessel. The bond dissociation energy DHo(RO-OH) in alkyl hydroperoxides, is important because the value of the rate constant is critical to cool flames production. The pyrolysis of t-butyl hydroperoxide was carried out, in a bath of isobutane in order to isolate the tBuO-OH bond breaking step. Acetone formation constituted a direct measure of the rate of decomposition of t-butyl hydroperoxide. The O-O bond dissociation energy was found experimentally, which is in good agreement with other group workers values.
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Phadungsukanan, Weerapong. "Building a computational chemistry database system for the kinetic studies in combustion." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648233.
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Uddi, Mruthunjaya. "Non-Equilibrium Kinetic Studies Of Repetitively Pulsed Nanosecond Discharge Plasma Assisted Combustion." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1220625444.
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Fry, Matthew Ryan. "Development of a generalised kinetic model for the combustion of hydrocarbon fuels." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/5333.
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Includes abstract.Includes bibliographical references (leaves 73-76).
The aim of this work is to find a generalised model for the combustion of hydrocarbons. Predicted temperature-time profiles can be obtained from detailed combustion kinetics, which can be used to derive a generalised model. If the generalised model can predict results from the detailed model it can be applied in computational fluid dynamics code where detailed kinetic mechanisms cannot.A generalised kinetic model is proposed, adapting the Schreiber model (Schreiber et al., 1994) to accurately predict the combustion behaviour of hydrocarbon fuels. The combustion behaviour is described through the characteristics of the temperature-time profiles and the ignition delay diagram, which include two stage ignition and the negative temperature co-efficient region. The Schreiber model is specifically adapted to improve the description of the very low temperature rise before and between ignitions and the auto-catalytic temperature rises during ignition. Using a Genetic Algorithm to optimise the prediction of the proposed model, the pre-exponent factor Ai and the activation energy Eai are the adjustable parameters which are optimised for each reaction in the model. These parameters have been optimised for three fuels: i-octane, n-heptane and methanol. The ignition delays of the pure fuels were accurately predicted. The temperature-time profiles in the instances of two stage ignition are relatively inaccurate. The temperature profiles are however an improvement on the temperature profiles predicted by the Schreiber model, particularly in terms of the slow temperature rise during the ignition delay andthe sharp temperature rise during ignition. The combustion of the binary blends of the three fuels have been predicted using model parameters which are found using the rate constants of each fuel, the blends composition and binary interaction rules. The binary interaction parameters were also optimised using a Genetic Algorithm. The binary interaction rules are based on the Peng-Robinson mixing rules. Overall the ignition delays of binary fuel blends were accurately predicted using binary interactions. However, when modelling the blends between methanol and n-heptane, where one fuel has extreme NTC behaviour and the other fuel has no NTC behaviour, the predictions were less accurate. These binary interaction rules are then used to model ternary mixtures. It is shown that the combustion behaviour of ternary mixtures of the three fuels can be accurately predicted without any further regression or parameter fitting. The accuracy of the ternary prediction is dependent on the accuracy of the binary predictions.
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Vidal, Vargas Janeth Alina 1983. "Cinética de combustão de óleo pesado por calorimetria de taxa acelerada." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265511.
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Orientador: Osvair Vidal TrevisanDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências
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Resumo: O processo de combustão in situ (CIS) é um método térmico de recuperação melhorada que gera calor no reservatório, diminuindo a viscosidade e aumentando a mobilidade do óleo, pela combustão de uma parte do óleo in place. A frente de combustão é mantida pela injeção continua de ar enriquecido com oxigênio. O processo CIS depende basicamente das reações químicas de combustão que acontecem quando o óleo está em contato com o ar injetado. Portanto, o sucesso do processo CIS é determinado pelo conhecimento e compreensão do comportamento cinético destas reações. O objetivo deste trabalho é determinar os parâmetros cinéticos da reação de combustão de um óleo pesado brasileiro, através da realização de ensaios experimentais usando um calorímetro de taxa acelerada (ARC) com fluxo (sistema aberto). Os testes foram feitos com 2 g de amostra de óleo de 12°API, 20,4 atm (290 psi) de pressão, injeção continua de ar com fluxo de 40-60 ml/min e as amostras foram aquecidas até 550°C. Também se realizaram testes com misturas de óleo e areia, óleo e argila e óleo/areia/argila para simular melhor o comportamento das reações no reservatório. A temperatura de autoignição foi de 290°C para o óleo. Quando areia ou argila foram misturadas ao óleo na proporção 25/75, a temperatura de autoignição se reduziu a 170°C. Identificou-se a presença das reações OBT (oxidação de baixa temperatura) num intervalo de temperatura de 170 a 300 °C, as OMT (oxidação de media temperatura) entre 300 e 420°C e as OAT (oxidação de alta temperatura) de 420°a 550°C aproximadamente. Todos os testes apresentam uma zona de transição em 320°C. Também foram realizados testes com asfalteno/argila e malteno/argila na proporção 25/75, para os quais se identificaram temperaturas de autoignição de 180 e 170 °C respectivamente. A energia de ativação para a maioria das reações é da ordem de grandeza de 105[J/mol], e a ordem da reação entre 0 e 1
Abstract: In situ combustion (ISC) is a thermal method of enhanced recovery that generates heat in the reservoir, to reduce viscosity and increase the mobility of the oil, after the combustion of a portion of the oil in place. The combustion front is maintained by the continuous injection of air enriched with oxygen. ISC depends basically on the chemical reactions of combustion that happen when the oil is in contact with the injected air. Therefore the success of ISC relies on the knowledge and understanding of the kinetic behavior of these reactions. The objective of this project is to determine the kinetic parameters of the combustion reaction of Brazilian heavy oil through accelerating rate calorimetry (ARC) with flow (open system). The tests were made with 2 g of oil samples of a 12°API oil, at 20 bar pressure, continuous air injection at 40-60 ml/min flow rate and the samples heated up to 550°C. Tests were also carried out with mixtures of oil and sand, oil and clay and oil/sand/clay to better simulate the behavior of the reactions in the reservoir. The auto ignition temperature was of 290°C for the oil. When sand or clay had been mixed to the oil at a 1/3 ratio, the auto ignition temperature is reduced to 170°C. Presence of LTO (low-temp oxidation) reactions was identified in the temperature range of 170 to 300 °C, MTO (medium temperature oxidation) reactions in 300 to 420°C and the HTO (high temperature oxidation) reactions in 420° to 550°C approximately. All tests presented a transition zone at 320°C. Additional tests were carried with mixtures of asphaltene/clay and maltene/clay at a 1/3 ratio, for which auto ignition temperatures were identified at 170 and 180°C, respectively. The energy of activation for the majority of the reactions was the order of 105 [J/mol], and the order of the reaction between 0 and 1
Mestrado
Reservatórios e Gestão
Mestre em Ciências e Engenharia de Petróleo
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Navarrete, Cereijo Germán 1988. "Modelagem simplificada e simulação da combustão de uma partícula de biomassa suspensa em escoamento unidimensional." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265868.
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Orientador: Waldir Antônio BizzoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho objetivou o desenvolvimento de um modelo simples para a simulação numérica da combustão de uma partícula pequena de bagaço numa fornalha industrial. Com este fim foi feito um estudo das principais etapas na combustão de uma partícula de biomassa: secagem, devolatili- zação, gaseificação e combustão do carvão. Destaca-se os modelos cinéticos para cada etapa e os mecanismos de transferência de calor por radiação em gases e de massa por convecção. Também foi modelada a trajetória vertical da partícula baseando-se nas forças de empuxo, peso e a força de arrasto com o objetivo de desenvolver uma ferramenta para determinar quais partículas são quei- madas em suspensão, quais são queimadas na grelha e quais são arrastradas pelo escoamento de gases. Para a simulação foi desenvolvido um programa em Fortran 90 onde a resolução numérica das equações diferenciais governantes é feita utilizando o método de Runge-Kutta de quarta ordem. As equações governantes para as taxas de consumo da biomassa são determinadas a partir da cinética das reações e do transporte de massa por convecção. A devolatilização é modelada como uma pi- rólise cujo mecanismo de reação é modelado por uma equação cinética de primeira ordem baseada nos parâmetros de Arrhenius. A taxa de consumo de carvão é determinada por duas equações ciné- ticas de primeira ordem baseadas nos parâmetros de Arrhenius que representam a oxidação direta do carbono e a gaseificação do carbono utilizando como reagente o dióxido de carbono. As equa- ções governantes para a temperatura da partícula são determinadas a partir dos balanços de energia para cada etapa. A validação do modelo foi feita em base a outros modelos apresentados na literatura para par- tículas menores a 1 mm obtendo-se resultados consistentes. Nos resultados apresentam-se gráficos de massa, raio, composição e temperatura da partícula, fração molar de oxigênio na superfície da partícula, taxa de consumo da biomassa, e raio do frente de chama em função do tempo tanto para partículas esféricas como cilíndricas. Também apresentam-se gráficas da trajetória e velocidade da partícula variando a forma e tamanho desta e a velocidade do escoamento dos gases dentro da fornalha
Abstract: The aim of this work is to develop a simple model for the numerical simulation of the com- bustion of a small particle of bagasse in an industrial furnace. To this end a study of the main stages of the biomass particle combustion was carried out. Thats stages are: drying, devolatiliza- tion, char gasification and char combustion. Kinetics models for each stage and the mechanisms of heat transfer by radiation in gases and convective mass models are presented in details. Also, the vertical trajectory of the particle was modeled based on buoyant force, weight and drag force in order to develop a tool for determine which particles are burned in suspension, which are burned on the grate and which are dragged by the gas flow. It was developed a program in Fortran 90 where the numerical solution of the governing diffe- rential equations is done using a fourth order Runge-Kutta. The governing equations for the bio- mass consumption rates are determined by kinetics equations and convection mass transport. The devolatilization is modeled as a pyrolysis which reaction mechanism is modeled by a first order kinetic equation based on the Arrhenius parameters. The rate of coal consumption is determined by two first-order kinetics equations based on the Arrhenius parameters that represent the direct char oxidation and char gasification using as reagent carbon dioxide. The governing equations for the particle temperature are determined from the energy balance for each stage. Model validation is carried out by comparing the predictions with other models taken from the literature for particles smaller than 1 mm giving consistent results. The results are presented plotting the following variables as a function of time: particle mass, raio, composition and tempe- rature, oxygen concentration on the particle surface, consumption rate of biomass and flame front raio for both spherical and cylindrical particle. Also, graphics of the particle speed and trajectory are presented, varying particle¿s shape and size and gas flow velocity of gases inside the furnace
Mestrado
Termica e Fluidos
Mestre em Engenharia Mecânica
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Håkansson, David. "Aerothermal and Kinetic Modelling of a Gas Turbine Dry Low Emission Combustion System." Thesis, KTH, Strömningsmekanik och Teknisk Akustik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298477.
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Growing environmental concerns are causing a large transformation within the energy industry. Within the gas turbine industry, there is a large drive to develop improved modern dry-low emission combustion systems. The aim is to enable gas turbines to run on green fuels like hydrogen, while still keeping emission as NOx down. To design these systems, a thorough understanding of the aerothermal and kinetic processes within the combustion system of a gas turbine is essential. The goal of the thesis was to develop a one-dimensional general network model of the combustion system of Siemens Energy SGT-700, which accurately could predict pressure losses, mass flows, key temperatures, and emissions. Three models were evaluated and a code that emulated some aspects of the control system was developed. The models and the code were evaluated and compared to each other and to test data from earlier test campaigns performed on SGT-700 and SGT-600. Simulations were also carried out with hydrogen as the fuel. In the end, a model of the SGT-700 combustion chamber was developed and delivered to Siemens Energy. The model had been verified against test data and predictions made by other Siemens Energy thermodynamic calculation software, for a range of load conditions. The preforms of the model, when hydrogen was introduced into the fuel mixture, were also tested and compared to test dataEn växande medvetenhet kring klimatfrågan, har medfört stora förändringar i energibranschen. I och med detta behöver även gasturbinindustrin förbättra de nuvarande dry-low emissions systemen och göra det möjligt för gasturbiner att förbränna gröna bränslen som väte. Samtidigt måste också utsläppen av NOx hållas nere. För att kunna utforma dessa system behövs en fullständig förståelse för de aerotermiska och kinetiska processerna i en gasturbins förbränningskammare. Målet med detta examensarbete var att utveckla en endimensionell generell nätverksmodell för förbränningssystemet i Siemens Energys SGT-700. Modellen skulle noggrant kunna förutsäga tryckförluster, massflöden, viktiga temperaturer samt utsläpp. Tre modeller utvärderades och en kod som emulerade vissa aspekter av styrsystemet utvecklades också. Modellerna och koden utvärderades och jämfördes mot varandra och även mot testdata från tidigare testserier som utfördes på SGT-700 och SGT-600. Simuleringar utfördes också med väte som bränsle. Slutligen levererades en modell av SGT-700 förbränningskammaren till Siemens Energy. Modellen har verifierats för en rad olika lastfall, mot testdata och data som genererats av andra termodynamisk beräkningsprogram som utvecklats av Siemens Energy. Hur modellen uppförde sig när väte var introducerat in i olika lastfall jämfördes också mot testdata
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Benezech, Laurent Jean-Michel Dimotakis Paul E. "Premixed hydrocarbon stagnation flames : experiments and simulations to validate combustion chemical-kinetic models /." Diss., Pasadena, Calif. : California Institute of Technology, 2008. http://resolver.caltech.edu/CaltechETD:etd-05302008-113043.
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Gonzalez, Calderon Juan David. "Molecular and Kinetic Modelling of the Ammonia Oxidation on Platinum." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17683.
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The thesis contributes to the fundamental understanding of the chemistry of ammonia oxidation on platinum. The research concentrates on determining the kinetic and reaction mechanisms for the NH3(g) oxidation with O2(g) on flat and stepped platinum surfaces using first-principles methodologies. The research finds direct applications in the modelling of the NO(g) production from NH3(g), a significant key step in the HNO¬3 manufacture through the Ostwald process. This process is industrially very significant because nearly all of the world's HNO3 is made from NH3(g), and most of the world’s HNO3 production is dedicated to the production of fertilisers. The reactions studied in this work, however, are relevant to other chemical processes of interest such as the selective catalytic oxidation for the removal of NH3(g) from industrial waste streams, and the selective catalytic reduction of NOx. The work carried out seeks fundamental analysis of three main elements of the NH3(g) oxidation, i) the effect of Pt surface morphology towards the formation of N2O(g), ii) the existence of lower activated alternative pathways for NO(g) formation and iii) the effect of the surface coverage on the energetics of selected surface reactions and the adsorption/desorption process. A new thermodynamically-consistent microkinetic model for the NH3(g) oxidation over Pt has been proposed by using the DFT-calculated kinetic parameters on the Pt(211) surface as input parameters. The simulated profiles of NH3(g) conversion and product yields reproduce qualitatively the experimental data obtained previously in our group, for the NH3(g) oxidation over Pt using a micro–tubular reactor. However, sensitivity analysis of the input data suggests small changes to a selected set of values improve the quantitative agreement with experimental observations.
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Johansson, Åsa. "Laser diagnostic and kinetic modelling of reaction intermediate in catalytic combustion : thesis for the degree of doctor of phylosophy /." Göteborg : Chalmers university of technology, Göteborg university, 2004. http://catalogue.bnf.fr/ark:/12148/cb39297274m.
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Davidson, Jeffrey E. "Combustion Modeling of RDX, HMX and GAP with Detailed Kinetics." BYU ScholarsArchive, 1996. https://scholarsarchive.byu.edu/etd/6531.
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A one-dimensional, steady-state numerical model of the combustion of homogeneous solid propellant has been developed. The combustion processes is modeled in three regions: solid, two-phase (liquid and gas) and gas. Conservation of energy and mass equations are solved in the two-phase and gas regions and the eigenvalue of the system (the mass burning rate) is converged by matching the heat flux at the interface of these two regions. The chemical reactions of the system are modeled using a global kinetic mechanism in the two-phase region and an elementary kinetic mechanism in the gas region. The model has been applied to RDX, HMX and GAP. There is very reasonable agreement between experimental data and model predictions for burning rate, temperature sensitivity, surface temperature, adiabatic flame temperature, species concentration profiles and melt-layer thickness. Many of the similarities and differences in the combustion of RDX and HMX are explained from sensitivity analysis results. The combustion characteristics of RDX and HMX are similar because of their similar chemistry. Differences in combustion characteristics arise due to differences in melting temperature, vapor pressure and initial decomposition steps. A reduced mechanism consisting of 18 species and 39 reactions was developed from the Melius-Yetter RDX mechanism (45 species, 232 reactions). This reduced mechanism reproduces most of the predictions of the full mechanism but is 7.5 times faster. Because of lack of concrete thermophysical property data for GAP, the modeling results are preliminary but indicate what type of experimental data is necessary before GAP can be modeled with more certainty.
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Kazi, Rafiq Akhtar. "A high pressure kinetic study of the in-situ combustion process for oil recovery." Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261611.
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Bongartz, Dominik. "Chemical kinetic modeling of oxy-fuel combustion of sour gas for enhanced oil recovery." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92224.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 135-147).
Oxy-fuel combustion of sour gas, a mixture of natural gas (primarily methane (CH 4 )), carbon dioxide (CO 2 ), and hydrogen sulfide (H 2 S), could enable the utilization of large natural gas resources, especially when combined with enhanced oil recovery (EOR). Chemical kinetic modeling can help to assess the potential of this approach. In this thesis, a detailed chemical reaction mechanism for oxy-fuel combustion of sour gas has been developed and applied for studying the combustion behavior of sour gas and the design of power cycles with EOR. The reaction mechanism was constructed by combining mechanisms for the oxidation of CH4 and H2S and optimizing the sulfur sub-mechanism. The optimized mechanism was validated against experimental data for oxy-fuel combustion of CH4, oxidation of H2S, and interaction between carbon and sulfur species. Improved overall performance was achieved through the optimization and all important trends were captured in the modeling results. Calculations with the optimized mechanism suggest that increasing H2 S content in the fuel tends to improve flame stability through a lower ignition delay time. Water diluted oxy-fuel combustion leads to higher burning velocities at elevated pressures than CO 2 dilution or air combustion, which also facilitates flame stabilization. In a mixed CH4 and H2S flame, H25 is oxidized completely as CH4 is converted to carbon monoxide (CO). During CO burnout, some highly corrosive sulfur trioxide (SO3 ) is formed. Quenching of SO 3 formation in the combustor can only be achieved at the expense of higher CO emissions. The modeling of a gas turbine cycle showed that oxy-fuel combustion leads to SO 3 concentrations that are one to two orders of magnitude lower than in air combustion and will thus suffer much less from the associated corrosion problems. Slightly fuel-rich operation is most promising for achieving the low CO and oxygen (02) concentrations required for EOR while further minimizing SO 3. Carbon dioxide dilution is better for achiving low 02 in the EOR stream while H20 gives the better combustion efficiency.
by Dominik Bongartz.
S.M.
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Eftekharzadeh, Nooshin 1965. "Simplified kinetic models describing the fate of coal nitrogen under fuel-rich combustion conditions." Thesis, The University of Arizona, 1994. http://hdl.handle.net/10150/278453.
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Twenty three sets of experimental data describing CO, CO₂, H₂, O₂, NO, NH₃, and HCN concentration profiles for fuel-rich pulverized coal combustion in plug flow configurations were correlated by a simple kinetic mechanism. A comprehensive mechanism covering the entire fuel-rich zone was formulated by combining models describing short and long time scale combustion. Short time scale phenomena (up to 0.6 seconds) including coal devolatilization were handled by developing global semi-empirical models based on fundamental concepts. Kinetic parameters for the proposed mechanism were estimated by using a non-linear regression technique. This model then allowed the prediction of major and nitrogenous species evolved in the early stages of combustion and yielded reasonable predictions of all these species concentrations. For the long time scale phenomena (up to 3 seconds) an existing model was used. Under most experimental conditions the extended model yielded good predictions of nitrogenous species from known process variables.
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Zimmer, Leonardo. "Modelagem da combustão de carvão em um forno de queda livre." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/61397.
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O estudo de parâmetros cinéticos para a queima de carvão se dá através de utilização de equipamentos laboratoriais como o forno de queda livre (DTF). O presente trabalho trata do desenvolvimento e análise de um modelo numérico unidimensional de um DTF. A modelagem é realizada a partir de dados da literatura, e as equações discretizadas que caracterizam os fenômenos do escoamento, da transferência de calor e da combustão do carvão foram programadas na linguagem FORTRAN 90. Os resultados são comparados com um modelo de referência e com dados experimentais, e apresentaram boa concordância. Um estudo de sensibilidade é realizado para entender o comportamento da queima de carvão frente a mudanças de alguns parâmetros de operação do DTF. A análise de sensibilidade mostrou a versatilidade do modelo e, consequentemente, do experimento. A partir da variação da concentração de O2, da temperatura de operação e das vazões de entrada pode-se obter uma gama de resultados. O uso do modelo aqui apresentado concomitante com resultados experimentais resulta em um estudo aprofundado dos parâmetros cinéticos de combustão de carvão.The study of kinetic parameters for coal combustion occurs through use of laboratory equipment such as drop tube furnace (DTF). The present work shows the development and analysis of a one-dimensional numerical model of a DTF. The modeling is developed from literature works, and the discrete equations that characterize the flow, heat transfer and coal combustion are programmed in FORTRAN 90 language. The results are compared with a reference model and experimental data, and showed good agreement. A sensitivity study is performed to understand the behavior of coal combustion due to changes of some working parameters of the DTF. The sensitivity analysis showed the versatility of the model and thereby the experiment. From the variation of the O2 concentration, operating temperature and input flow rates a range of results can be obtained. Using the model presented here together with experimental results leads to a detailed study of the kinetic parameters of coal combustion.
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Liu, Zhouyang. "Heterogeneous Catalytic Elemental Mercury Oxidation in Coal Combustion Flue Gas." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045805884364.
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Zhang, Xiaoxiang. "Numerical Study on Combustion Features of Gasified Biomass Gas." Licentiate thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166252.
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There is a great interest to develop biomass combustion systems for industrial and utility applications. Improved biomass energy conversion systems are designed to provide better combustion efficiencies and environmental friendly conditions, as well as the fuel flexibility options in various applications. The gas derived from the gasification process of biomass is considered as one of the potential candidates to substitute traditional fuels in a combustion process. However, the gascomposition from the gasification process may have a wide range of variation depending on the methods and fuel sources. The better understanding of the combustion features for the Gasified Biomass Gas(GBG) is essential for the development of combustion devices to be operated efficiently and safely at the user-end. The objective of the current study is therefore aiming to achieve data associated with the combustion features of GBG fuel for improving the efficiency and stability of combustion process. The numerical result is achieved from the kinetic models of premixed combustion with a wide range of operating ranges and variety of gas compositions. The numerical result is compared with experimental data to provide a better understanding of the combustion process for GBG fuel. In this thesis the laminar flame speed and ignition delay time of the GBG fuel are analyzed, using 1-D premixed flame model and constant volume model respectively. The result from different kinetics are evaluated and compared with experimental data. The influences of initial temperature, pressure and equivalence ratio are considered, as well as the variation of gas compositions. While the general agreement is reached between the numerical result and experimental data for laminarflame speed prediction, deviations are discovered at fuel-rich region and increased initial temperature. For the ignition delay time, deviations are found in the low-temperature and low pressure regime. The empirical equations considering the influence of initial temperature,pressure and equivalence ratio are developed for laminar flame speed and ignition delay times. The influence of major compositions such as CO, H2 and hydrocarbons are discussed in details in the thesis. Furthermore, a simplified kinetic model is developed and optimized based on the evaluation of existing kinetics for GBG fuel combustion. The simplified kinetic model is expected to be used for simulating the complexc ombustion process of GBG fuel in future studies.QC 20150511
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Balme, Quentin. "Etude paramétrique et optimisation d'un processus de combustion de charges organiques." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI091/document.
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Le LPTI/CEA (Laboratoire des Procédés Thermiques Innovants) développe un procédé d’incinération-vitrification de déchets radioactifs. La première étape du dispositif consiste en l’élimination de la charge organique (polymère) par incinération du déchet suspendu dans un four. L’objectif du travail présenté dans ce document est d’étudier les paramètres opératoires susceptibles de modifier la vitesse de dégradation des polymères, pour pouvoir optimiser l’étape d’incinération.Dans cette étude, le taux de dégradation est mesuré par la perte de masse des composés. Une macro-thermobalance permettant de travailler avec des masses de polymère (polyéthylène et néoprène) allant de 5g à 65g a été développée et mise au point afin de mener les études paramétriques (masse d’échantillon, température du four, pourcentage d’oxygène dans le gaz, type de contenant) nécessaires à l’évaluation des vitesses de dégradation du polyéthylène et du néoprène. Ces études seront par la suite étendues à l’évaluation des cinétiques de combustion de systèmes organiques complexes confinés dans différents vecteurs.Parallèlement, deux modèles, l’un décrivant la phase gazeuse par CFD et le polymère par un modèle « 0D » considérant la température homogène dans l’échantillon, et l’autre décrivant les deux phases par CFD (Computational Fluid Dynamic) ont été développés. L’objectif de ces modèles, résolus en mode transitoire, est de calculer la vitesse de dégradation du polyéthylène lors de sa combustion dans la macro-thermobalance afin de décrire le comportement observé expérimentalement.Les résultats expérimentaux et de modélisation montrent l’importance de la position de la flamme et des transferts thermique dans le polymère sur sa vitesse de dégradation. Pour le néoprène dont la dégradation produit du char, il est montré expérimentalement que l’étape d’oxydation du char est, aux températures de l’étude (>600°C), limitée par le transfert d’oxygène dans les résidus solidesThe LPTI / CEA (Innovative Thermal Processes Laboratory) is developing a process for the incineration-vitrification of radioactive waste. The first step consists in the elimination of the organic charge (polymer) by incineration of the waste suspended in an oven. The objective of the work presented in this document is to study the operating parameters likely to modify the rate of degradation of the polymers, in order to optimize the incineration step.In this study, the degradation rate is measured by the mass loss of the compounds. A macro-thermobalance allowing to work with masses of polymer (polyethylene and neoprene) going from 5g to 65g was developed in order to carry out the parametric studies (mass of sample, temperature of the furnace, percentage of oxygen in gas, type of container) needed to evaluate the degradation rates of polyethylene and neoprene. These studies will then be extended to evaluate the kinetics of combustion of complex organic systems confined in different vectors.In parallel, two models were developped. The first describes the gas phase by CFD and the polymer by a "0D" model considering the homogeneous temperature in the sample, and the second is describing the two phases by CFD (Computational Fluid Dynamic). The objective of these models, solved in transient mode, is to calculate the rate of degradation of the polyethylene during its combustion in the macro-thermobalance to describe the behavior observed experimentally.Experimental and modeling results show the importance of flame position and heat transfer in the polymer on its rate of degradation. For the neoprene whose degradation produces carboneous residues (char), it is shown experimentally that the stage of oxidation of the char is, at the study temperatures (> 600 ° C), limited by the transfer of oxygen in the solid residues
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Nicol, David Gardner. "A chemical kinetic and numerical study of NOx and pollutant formation in low-emission combustion /." Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/7033.
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Zizin, Anton [Verfasser], and Uwe [Akademischer Betreuer] Riedel. "Development of a reduced chemical-kinetic combustion model for practical fuels / Anton Zizin. Betreuer: Uwe Riedel." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://d-nb.info/104804789X/34.
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Lockett, R. D. "C.A.R.S. temperature measurements and chemical kinetic modelling of autoignition in a methanol-fuelled internal combustion engine." Doctoral thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/17388.
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Bibliography: p. 258-268.The temperature inside the cylinder of a methanol-fuelled single-cylinder Ricardo E6 research engine running under knocking conditions, is measured by means of Coherent Anti-Stokes Raman Spectroscopy (CARS), and the pressure is measured with a pressure transducer. In order to obviate any errors arising from deficiencies in the spectral scaling laws which are commonly used to represent nitrogen Q-branch spectra at high pressure, a purely experimental technique is employed to derive temperatures from CARS spectra by cross-correlation with a reference library of spectra recorded in an accurately calibrated high-pressure high-temperature optical cell. The temperature and pressure profiles obtained from the engine running under knocking conditions, are then used as input data for chemical kinetic modelling of end-gas autoignition. Five published mechanisms (Grotheer et al 1992, Grotheer and Kelm 1989, Norton and Dryer 1989, Dove and Warnatz 1983, .and Esser and Warnatz 1987) are used in the autoignition study, and the results for the different mechanisms are compared. A good qualitative understanding of the mechanism underlying end-gas autoignition in the engine is obtained, although the calculated autoignition points occur slightly earlier than the observed point. A sensitivity analysis of the methanol autoignition system is undertaken, and the importance of the decomposition of hydrogen peroxide and the hydroperoxyl chemistry is demonstrated. The discrepancies between the predicted results of the different mechanisms is shown to be caused by a small number of sensitive reactions for which there are conflicting data. Finally, a linear mode analysis from the geometric qualitative theory of differential equations is performed on the non-linear chemical rate equations. The equilibrium points in the generalised phase space of the non-linear chemical system are shown to be defined in terms of three regions. The equilibrium points are unstable improper nodes in the first region (T < ll00K), unstable focii in the second region ( 1100K
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Rana, Shazadi. "Pressurized Chemical Looping Combustion of Natural Gas with Ilmenite for SAGD Application: An Oxidation Kinetic Study and Preliminary Air Reactor Model." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37653.
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To prevent the global surface temperature from increasing past the 2 oC target, it is necessary to address CO2 emissions from small point sources. Within Canada’s heavy oil industry, SAGD facilities use natural gas combustion to produce the large amounts of steam required for the process, which produces approximately 0.5-2 Mtonnes of CO2 per annum. A suitable technology for CO2 mitigation from a SAGD facility is Pressurized Chemical Looping Combustion. PCLC is an oxy-combustion, carbon capture technology with a relatively low predicted energy penalty of 3-4%. The process requires a dual, interconnected fluidized bed reactor system with circulating solids. Natural gas is converted in the fuel reactor via a solid metal oxide, which is then circulated to the air reactor for reoxidation with air. As the cost of air compression is significant, the economical feasibility of the process is reliant on air reactor performance. The objective of this study is to investigate the oxidation reaction and derive a kinetic model for reactor design and performance assessment purposes. Ilmenite ore was chosen as the metal oxide, as it is low cost and has desirable oxygen transport properties for PCLC. Pressurized TGA tests were conducted to study the effects of oxygen concentration, temperature and pressure on the rate of the oxidation reaction. The total pressure was varied from 1-16 bara at 900 oC with air. The oxygen concentration was varied from 2.5-21 vol%, and the temperature from 800-1000 oC at 8 bar.
Temperatures below 850 oC resulted in segregation of the Fe and Ti phase in the ilmenite ore, leading to a reduction in the overall oxygen carrying capacity. Crack formation was observed at higher oxygen partial pressures, resulting in increased surface area for reaction and a fast reaction rate. At lower oxygen partial pressures, a solid-state diffusion controlled regime was observed due to the absence of fissures. A dual mechanistic oxidation kinetic model was derived at 8 bar, with 2nd order random nucleation dominating at lower conversions, and Jander’s solid state diffusion model dominating at higher conversions. The transition from the nucleation and growth to the diffusion-controlled portion occurred at higher conversions with higher oxygen partial pressure. The activation energy was 16.6 kJ/mol and 48.7 kJ/mol while the order of reaction with respect to oxygen was 0.3 and 1.3 for respectively the nucleation and growth, and diffusion-controlled regimes. A preliminary air reactor model is constructed as a turbulent bed. The turbulent bed is modelled as an axial dispersion reactor for a basic performance assessment.
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Urban, David Raymond. "A kinetic investigation of As and Se speciation within coal combustion flue gases using ab initio methods." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-042806-133423/.
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KONOPKA, THIAGO FABRICIUS. "COMPARATIVE STUDY OF DETAILED CHEMICAL KINETIC MODELS OF SOOT PRECURSORS FOR ETHYLENE/AIR AND METHANE/AIR COMBUSTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23399@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROEssa dissertação apresenta um estudo comparativo de quatro diferentes modelos de cinética química detalhada que envolvem as principais espécies químicas responsáveis pelo processo de formação e oxidação da fuligem, i.e., o oxigênio molecular, o radical hidroxila, o acetileno, o propargil, benzeno, fenil e pireno. Para este fim, considera-se a combustão de misturas de etileno/ar e metao/ar. Para analisar os modelos cinéticos são utilizados um reator perfeitamente misturado (PSR) e um reator parcialmente misturado (PaSR). No caso do reator perfeitamente misturado, um estudo sistemático da influência do tempo de residência e a riqueza da mistura sobre estas espécies químicas é apresentado. São discutidas as importantes discrepâncias obtidas, para o acetileno, o propargil, o benzeno, o fenil e o pireno, entre os modelos cinéticos analisados. As espécies oxidantes exibem menores discrepâncias dentre todas as espécies analisadas. No caso do reator parcialmente misturado, a razão entre o tempo de residência e o tempo de mistura é o parâmetro de análise. De modo geral, os resultados obtidos permitem avaliar o comportamento dos mecanismos cinéticos em uma situação representativa de combustão em escoamentos turbulentos.
In this dissertation a comparative study is presented of four different detailed kinetics models involving the main chemical species responsible for the soot formation and oxidation, i.e., the molecular oxygen, the hydroxyl, the acetylene, the propargyl, the benzene and the pyrene. To this purpose is considered the combustion of ethylene/air and metane/air. To analyze the kinetic models are used a perfect stirred reactor (PSR) and a partial stirred reactor (PaSR). In the case of a perfect stirred reactor a systematic study of the influence of the residence time and of the equivalence ratio on these chemical species is presented. Are discussed the important discrepancies obtained for acetylene, propargyl, benzene, phenyl and pyrene, between the kinetic models analyzed. The oxidizing species exhibit minor discrepancies only. In the case of the partially mixed reactor, the ratio between the residence time and the mixing time is the analysis parameter. Overall, the results obtained allow to evaluate the behavior of the kinetic mechanisms in situations representative of combustion in turbulent flows.
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Agbro, Edirin Bruno. "Experimental and chemical kinetic modelling study on the combustion of alternative fuels in fundamental systems and practical engines." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/17980/.
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In this work, experimental data of ignition delay times of n-butanol, gasoline, toluene reference fuel (TRF), a gasoline/n-butanol blend and a TRF/n-butanol blend were obtained using the Leeds University Rapid Compression Machine (RCM) while autoignition (knock) onsets and knock intensities of gasoline, TRF, gasoline/n-butanol and TRF/n-butanol blends were measured using the Leeds University Optical Engine (LUPOE). The work showed that within the RCM, the 3-component TRF surrogate captures the trend of gasoline data well across the temperature range. However, based on results obtained in the engine, it appears that the chosen TRF may not be an excellent representation of gasoline under engine conditions as the knock boundary of TRF as well as the measured knock onsets are significantly lower than those of gasoline. The ignition delay times measured in the RCM for the blend, lay between those of gasoline and n-butanol under stoichiometric conditions across the temperature range studied and at lower temperatures, n-butanol acts as an octane enhancer over and above what might be expected from a simple linear blending law. In the engine, the measured knock onsets for the blend were higher than those of gasoline at the more retarded spark timing of 6 CA bTDC but the effect disappears at higher spark advances. Future studies exploring the blending effect of n-butanol across a range of blending ratios is required since it is difficult to conclude on the overall effect of n-butanol blending on gasoline based on the single blend that has been considered in this study. The chemical kinetic modelling of the fuels investigated has also been evaluated by comparing results from simulations employing the relevant reaction mechanisms with the experimental data sourced from either the open literature or measured in-house. Local as well as global uncertainty/sensitivity methods accounting for the impact of uncertainties in the input parameters, were also employed within the framework of ignition delay time modelling in an RCM and species concentration prediction in a JSR, for analysis of the chemical kinetic modelling of DME, n-butanol, TRF and TRF/n-butanol oxidation in order to advance the understanding of the key reactions rates that are crucial for the accurate prediction of the combustion of alternative fuels in internal combustion engines. The results showed that uncertainties in predicting key target quantities for the various fuels studied are currently large but driven by few reactions. Further studies of the key reaction channels identified in this work at the P-T conditions of relevance to combustion applications could help to improve current mechanisms. Moreover, the chemical kinetic modelling of the autoignition and species concentration of TRF, TRF/n-butanol and n-butanol fuels was carried out using the adopted TRF/n-butanol mechanism as input in the engine simulations of a recently developed commercial engine software known as LOGEengine. Similar to the results obtained in the RCM modelling work, the knock onsets predicted for TRF and TRF/n-butanol blend under engine conditions were consistently higher than the measured data. Overall, the work demonstrated that accurate representation of the low temperature chemistry in current chemical kinetic models of alternative fuels is very crucial for the accurate description of the chemical processes and autoignition of the end gas in the engine.
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Liu, Kun. "Thermodynamic and Kinetic Study of Carbon Dioxide and Mercury Removal from Flue Gas in Coal Combustion Power Plants." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352402585.
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PICCINELLI, ELSA. "Environmental impact of industrial plants combustion processes: kinetic and formation/destruction mechanisms of PolichlorinatedDibenzo-p-Dioxins and PolichlorinatedDibenzoFurans." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/10060.
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The aim of the project was to study the mechanism of formation and degradation of PolyChlorinatedDibenzo-p-Dioxins (PCDDs) and PolyChlorinatedDibenzoFurans (PCDFs) in combustion processes. Today the challenge is to demonstrate that the conclusion based on laboratory scale experiments and the models coming from the results are useful tools to estimate emissions and to prevent or reduce PCDD/F (sum of PCDDs and PCDFs) formation in the flue gas cleaning system of plants. Following this, the study was developed at two different scales:
Laboratory scale. The native carbon oxidation and PCDD/F formation were simultaneously studied at different temperatures (230-350 °C) and times (0-1440 min) in order to establish a direct correlation between the disappearance of the reagents and the formation of the products. The kinetic runs were conducted in a experimental set up where conditions were chosen to gain information on the role of fly ash deposits in cold zone of the plant in PCCD/F formation reaction
Real plant scale. An extensive experimental study of a secondary aluminium casting plant flue gas cleaning system was performed. In particular, on the strength of the knowledge obtained by laboratory studies and the results of the samplings, the best strategies to prevent PCDD/F formation were identify and Air Pollution Control Device (APCD) performance was improved.
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Hrbáček, Jan. "Proudění směsi ve spalovacím prostoru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-377465.
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The Master's thesis deals with the flow of fuel mixture in the combustion chamber and the influence of its geometry on squish generation caused by the compression lift. The thesis introduces design proposals of the geometry of the combustion chamber focusing on the shape of the squish area and their comparison based on the amount of kinetic energy and the velocity profile obtained using 2-D Squish programme calculations.
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Morin, Mathieu. "Gazéification de la biomasse en double lit fluidisé circulant : étude des réactions élémentaires de gazéification et de combustion du char et de reformage des goudrons." Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0089/document.
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La conversion thermochimique à haute température (>700°C) de la biomasse en double lit fluidisé circulant est une voie alternative aux énergies fossiles (pétrole, charbon) pour la production d’un gaz de synthèse à haute valeur énergétique, utilisable dans de nombreuses applications. L’objectif de cette thèse est de développer des méthodologies et des outils théoriques et expérimentaux permettant d’accéder aux cinétiques des transformations élémentaires (pyrolyse de la biomasse, gazéification et combustion du char, craquage et reformage des goudrons) présentes dans le procédé de gazéification de la biomasse en double lit fluidisé circulant. Dans un premier temps, un mini-réacteur à lit fluidisé fonctionnant entre 300 et 1000°C avec une alimentation en gaz parfaitement contrôlée (N2, O2, H2, H2O et goudrons) a été conçu et mis au point au Laboratoire de Génie Chimique de Toulouse. Un système d’échantillonnage et d’analyse de la phase gaz permet de quantifier en continu les fractions molaires des gaz incondensables et des goudrons produits. Une étude hydrodynamique et thermique a permis de déterminer les points de fonctionnement du réacteur pour chaque transformation élémentaire étudiée. Dans un second temps, les études de gazéification et de combustion du char ont été réalisées dans le mini-réacteur à lit fluidisé. L’influence de nombreux paramètres opératoires (température, pression partielle des différents constituants) a permis de comprendre la formation des différents produits et de modéliser les cinétiques de transformation du solide. Dans le cas de la combustion du char, un mécanisme réactionnel a également été établi et la cinétique obtenue en lit fluidisé a été comparée à celle déterminée par analyse thermogravimétrique. Enfin, une étude sur le reformage d’un goudron modèle (toluène) en lit fluidisé a mis en évidence l’effet de l’atmosphère réactionnelle sur le mécanisme de dégradation du toluène sur l’olivine et le charThe thermochemical conversion of biomass at high temperature (>700°C) in Fast Internally Circulating Fluidized Bed (FICFB) is a promising alternative route to fossil fuels (oil, coal) to produce syngas which can be used in several applications. The aim of the present work is to develop methodologies as well as theoretical and experimental tools for determining the intrinsic kinetic of biomass transformations (biomass pyrolysis, char gasification and combustion, cracking and reforming of tars). Firstly, a fluidized bed reactor has been designed and built at the Laboratory of Chemical Engineering (LGC). This reactor can operate for temperatures between 20 and 1000°C with a well-defined gas supply (N2, O2, H2, H2O and tars). A sampling and analysis gas system enables the continuous quantification of the non-condensable gases and tars molar fractions. A hydrodynamic and thermal study enabled the determination of the operating conditions for each experimental study. Secondly, the char gasification and combustion was performed in the fluidized bed reactor. The influence of the operating conditions (temperature and compounds partial pressure) led to the modelling of the different solid transformation kinetics. Besides, in the case of char combustion, a reaction scheme was proposed and the kinetic obtained in the fluidized bed was compared to that obtained in a thermogravimetric analyzer. Finally, a study on the tar reforming in a fluidized bed reactor highlighted the effect of the reactive atmosphere on the reaction scheme of toluene conversion over olivine and char
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Sirjean, Baptiste. "Étude cinétique de réactions de pyrolyse et de combustion d'hydrocarbures cycliques par les approches de chimie quantique." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL093N/document.
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Les carburants dérivés du pétrole constituent la première source mondiale énergétique et leur approvisionnement constitue un défi actuel majeur impliquant des enjeux économiques et environnementaux cruciaux. Une des voies les plus efficaces pour peser simultanément sur ces deux enjeux passe par la diminution de la consommation en carburant. La simulation numérique constitue dès lors un outil précieux pour améliorer et optimiser les moteurs et les carburants. Les modèles chimiques détaillés sont nécessaires pour comprendre les phénomènes d’auto-inflammation et caractériser la nature et les quantités de polluants émis. Ces modèles mettent en jeu un nombre très important d’espèces et de réactions élémentaires, pour une espèce donnée et pour lesquelles la détermination des données thermodynamiques et cinétiques est un problème crucial. La chimie quantique constitue un outil précieux permettant d’une part de déterminer de façon précise les données thermocinétiques pour bon nombre de systèmes chimiques et d’autre part de mieux comprendre la réactivité de ces systèmes. Dans ce travail, les réactions unimoléculaires de décomposition d’hydrocarbures monocycliques et polycycliques (amorçages, réactions moléculaires, ß-scissions, formations d’éthers cycliques) ont été étudiées à l’aide des méthodes de la chimie quantique. Un mécanisme détaillé de pyrolyse d’un alcane polycyclique a été développé à partir des données thermodynamiques et cinétiques et des corrélations entre structure et réactivité déterminées pour les cyclanes à partir des calculs quantiques. Les simulations effectuées à partir de ce modèle sont en très bon accord avec les résultats expérimentaux de la littératurePetroleum fuels are the world’s most important primary energy source and the need to maintain their supply is a major actual challenge involving both economical and environmental features. Decreasing fuels consumption is one of the more efficient ways to reconcile the goals of energy price and environmental protection. Numerical simulations become therefore a very important tool to optimize fuels and motors. Detailed chemical kinetic models are required to reproduce the reactivity of fuels and to characterize the amount of emitted pollutants. Such models imply a very large number of chemical species and elementary reactions, for a given species, and the determination of thermodynamic and kinetic data is a critical problem. Nowadays, quantum chemistry methods are able to calculate accurately thermodynamic data for a large number of chemical systems and to elucidate the reactivity of these systems. In this work we have used quantum chemistry to study the unimolecular reactions (initiation, molecular reactions, ß-scissions, cyclic ethers formations) involved in the decomposition of monocyclic and polycyclic hydrocarbons. From the results of quantum chemical calculations, a detailed chemical kinetic mechanism of the pyrolysis of a polycyclic alkane has been developed and validated against experimental data
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Michelon, Nicola. "Modelling and experimental investigation of microkinetic in heterogeneous catalysis: hydrogen combustion and production." Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424703.
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This thesis investigates both hydrogen combustion and production, focusing on fundamentals of Pt-catalysed oxidation and steam methane reforming on nickelbased catalysts.
On the first aspect, we started reporting and investigating discrepancies on the structure and predictions of detail surface kinetic models from Literature, for H2-O2 reaction on Pt. Quantitative comparisons have been carried out through a closed-vessel, well-stirred reactor model with catalytic internal surface. Discrepancies in the predictions of the microkinetic models apparently comes from disagreement in the experimental date they are based on. Differences in experimental set-ups and Pt surface structure prompted us to develop own data, using plane Pt surface in suitable reactors. A novel laboratory reactor to investigate hydrogen oxidation on Pt surfaces has been designed, based on modelling, and built.
Experimental catalytic activity test proved that Pt activity can vary dramatically. Catalyst pretreatments with H2 and O2 revealed the mechanism of competition for surface sites as well as restructuring of the surface. Significantly long transformation was measured, particularly after catalyst O2 pretreatment, that are not included in the elementary chemistry models from Literature. Reaction lightoff at H2 lean compositions have been measured and compared with Literature experimental data, providing explanations for the differences among published data.
Subsequently, transient simulation of hydrogen combustion in platinumcoated channel has been adopted to evaluate the behavior under heterogeneous and hetero-/homogeneous chemistries. Effects of catalyst support material properties, FeCr-alloy and cordierite, have been compared. Implication for the operation of various practical catalytic reactors are finally drawn.
Concerning H2 production, we investigated the catalytic reforming of natural gas, by steam, both theoretically and experimentally. We identified relevant ranges of operative variables to study the catalyst at industrially relevant conditions. We designed by scaling down from industrial plants an original set-up to investigate the reaction kinetics at high-pressure (10 bars). We compared three nickel-based catalysts at low steam-to-carbon conditions, approaching S/C = 1, to collect activity and coking data for validation and development of detailed surface chemistry model.Questa tesi investiga sia la combustion che la produzione di idrogeno, con particolare attenzione verso aspetti fondamentali della ossidazione catalizzata da platino e la reazione di steam reforming del metano su catalizzatori a base di nickel. Per quanto riguarda il primo aspetto, siamo partiti dall’osservare ed approfondire discrepanze sulla struttura e sui risultati di modelli cinetici di reazioni superficiali presenti in Letteratura, per la reazione di H2 e O2 su Pt. I confronti quantitativi sono stati fatti utilizzando un Modello di reattore chiuso ben mescolato con le superfici interne catalitiche. Le differenze nelle perizie dei diversi modelli sembrano discendere da differenze nei dati sperimentali su cui sono stati calibrati. Il fatto che se non state utilizzate diverse configurazioni sperimentali, e probabilmente strutture delle superfici di Pt , ci ha stimolato a intraprendere una campagna sperimentale per ottenere dati propri, utilizzando superfici di platino planari in opportuni reattori. Un nuovo reattore di laboratorio, a flusso stagnante, per indagare reazioni su Pt in forma di dischi e stato progettato sulla base di una` modellazione dettagliata e realizzato in laboratorio. I risultati sperimentali hanno dimostrato che l’attivita del Pt può variare enormemente. Pretrattamenti con H2 o O2 Hanno chiarito il meccanismo della competizione per siti superficiali e la possibilita di ristrutturazione la superficie. Sono state misurate trasformazioni di lunga durata, soprattutto dopo pretrattamenti con O2, che non trova una spiegazione in nessuno dei modelli cineticidettagliati di letteratura. Mediante misure in rampa di temperatura si e studiato` l’innesco di miscele povere di H2 in aria. Il confronto con dati di letteratura suggerisce una plausibile interpretazione della discrepanza dei dati riportati. Successivamente simulazioni transitorie della combustione di idrogeno in canali rivestiti di platino e stato utilizzato per valutare il comportamento della`reazione eterogenea con e senza reazione omogenea. L’effetto delle proprieta`del supporto del catalizzatore sono stati confrontati, considerando leghe Fe-Cre cordierite. Le implicazioni pratiche per l’operativita di questi reattori sono state`delineate. Per quanto riguarda la produzione di idrogeno abbiamo studiato sia dal punto di vista teorico che sperimentale la reazione di reforming di gas naturale mediante7 vapore. Abbiamo identificato intervalli significativi da un punto di vista industriale per le variabili operative, per studiare la cinetica dei catalizzatori. Abbiamo progettato un reattore di laboratorio mediante regole di scala rispetto a un impianto modello industriale di riferimento, con l’obiettivo di studiare la reazione a pressioni elevate (10bars). Abbiamo confrontato tre catalizzatori basati su Nickel con formulazioni diverse, modificando rapporto vapore/carbonio in alimentazione, per avvicinarsi alle condizioni stechiometriche. Si sono raccolti numerosi ,dati sia di attivita cataliticha che di formazione di carbone, utili per uno sviluppo di modelli` cinetici dettagliati della reazione superficiale.
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Gul, Kiymet Gizem. "Thermal Characterization And Kinetic Analyis Of Sara Fractions Of Crude Oils By Tga And Dsc Methods." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613614/index.pdf.
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In this thesis, four different crude oil samples and their saturate, aromatic and resin fractions were analyzed by two different thermoanalytical methods, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The experiments were performed at three different heating rates (5, 10 and 15 °C/min) under air atmosphere. Same gas flow rate and same pressure were applied to all samples. The aim is to determine the kinetic analysis and combustion behavior of crude oils and their fractions and also determining the effect of heating rate on all samples. For all samples two main reaction regions were observed in thermogravimetry (TG), differential thermogravimetry (DTG) and DSC curves due to the oxidative degradation of crude oil components. It was deduced that the free moisture, volatile hydrocarbons were evaporated from the crude oils, light hydrocarbons were burned and fuel was formed in the first reaction region. The second reaction region was the main combustion region where the fuel was burned. From the TGA curves, it was detected that the heavier fraction, resins, lost considerable amounts of their initial mass, approximately 35%, while saturates lost only approximately 3% of their initial mass in the second reaction region. DSC curves of the samples were also examined and observed that as the sample got heavier, the heat of the reaction increased. Saturates, lightest part of the crude oil fractions, gave minimum heat of reaction. As the heating rate increased, shift of peak temperatures to high values and higher reaction regions were observed. The kinetic analysis of crude oils and their fractions were also performed using different kinetic methods. Activation energies (E), mean activation energies (Emean) and Arrhenius constants were found for crude oils and fractions. It was deduced that the resins gave the highest activation energy and Arrhenius constant for both reaction regions. Moreover, it was encountered that heating rate has no effect on activation energies.
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Calisesi, Federico. "The analysis of the injection of hydrogen-oxygen mixtures in gasoline-powered internal combustion engines." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15553/.
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The effects on combustion derived by the blending of hydrogen with traditional fuels adopted for internal combustion engines have been studied. Results derived by emission tests of a gasoline-fed vehicle equipped with a system for the production of hydrogen on-board have been analysed. The energy balance for the engine was evaluated. It demonstrated the increase of fuel consumptions to perform electrolysis process on-board the vehicle. Afterwards, numerical simulations based on a detailed kinetic model have been performed to calculate pollutant emissions produced by methane and iso-octane (which represents gasoline) compared with a mixture composed of 10% mol/mol by hydrogen. Chemical species studied were residual hydrocarbons, nitrous oxides and carbon monoxide. Notable variations of pollutant has not been calculated for methane, wherease iso-octane showed a reduction of the aforementioned pollutants when hydrogen was introduced. In the end operating costs have been analysed. The use of stored hydrogen produced by methane steam reforming found a reduction by 7% of costs, compared to the production via electrolysis.
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Han, Jinyi. "Kinetic and Morphological Studies of Pd Oxidation in O2-CH4 mixtures." Digital WPI, 2004. https://digitalcommons.wpi.edu/etd-dissertations/219.
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The oxidation of Pd single crystals: Pd(111), Pd(100) and Pd(110) was studied using Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Low Electron Energy Diffraction (LEED) and Scanning Tunneling Microscopy (STM) as they were subjected to O2 in the pressure range between 1 and 150 Torr at temperatures 600-900 K. The oxygen species formed during oxidation, the oxygen uptake dependence on the sample history, the Pd single crystal surface morphology transformations, and the catalytic methane combustion over Pd single crystals were investigated in detail. The Pd single crystal oxidation proceeded through a three-step mechanism. Namely, (1) oxygen dissociatively adsorbed on Pd surface, forming chemisorbed oxygen and then surface oxide; (2) atomic oxygen diffused through a thin surface oxide layer into Pd metal, forming near surface and bulk oxygen; (3) bulk PdO formed when a critical oxygen concentration was reached in the near surface region. The diffusion of oxygen through thin surface oxide layer into Pd metal decreased in the order: Pd(110)>Pd(100)>Pd(111). The oxygen diffusion coefficient was estimated to be around 10-16 cm2 s-1 at 600 K, with an activation energy of 80 kJ mol-1. Once bulk PdO was formed, the diffusion of oxygen through the bulk oxide layer was the rate-determining step for the palladium oxidation. The diffusion coefficient was equal to 10-18 cm2 s-1 at 600 K and the activation energy was approximately 120 kJ mol-1. The oxygen diffusion through thin surface oxide layer and bulk PdO followed the Mott-Cabrera parabolic diffusion law. The oxygen uptake on Pd single crystals depended on the sample history. The uptake amount increased with the population of the bulk oxygen species, which was achieved by high oxygen exposure at elevated temperatures, for example in 1 Torr O2 at above 820 K. Ar+ sputtering or annealing in vacuum at 1300 K depleted the bulk oxygen. The Pd single crystal surface morphology was determined by the oxidation conditions: O2 pressure, treatment temperature and exposure time. When bulk PdO was formed, the single crystal surface was covered with semi-spherical agglomerates 2-4 nm in size, which tended to aggregate to form a“cauliflower-like" superstructure. The single crystal surface area during oxidation, determined by integrating the STM image, experienced three major expansions in consistent with a three-step oxidation mechanism. The surface area on the oxidized single crystals increased in the order: Pd(110)
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Anderlohr, Jörg-Michel. "Modélisation de la combustion et des polluants dans la ligne d'échappement d'un moteur." Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL100N/document.
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L'objectif de ce travail de thèse est le développement d'un modèle numérique prédictif pour la simulation des phénomènes de postoxydation dans la ligne d’échappement d’un moteur à combustion interne. Le modèle a été écrit pour reproduire le processus d'auto inflammation des hydrocarbures durant la postoxydation, mais également l'évolution des polluants et des produits de combustion en général. Ceci a nécessité de mettre au point un schéma cinétique détaillé qui tienne compte de la chimie à basse température des hydrocarbures et de l'influence sur cette chimie des différentes espèces majeures présentes dans les gaz brûlés à postoxyder. Ces espèces sont le CO2, le H2O et le N2, qui agissent comme diluants, mais également des polluants tels que le CO ou les NOx. Ces derniers, même en faibles concentrations, peuvent avoir un effet important sur l’oxydation des hydrocarbures qui doit aussi être prise en compte dans le modèle chimique.Afin de considérer, en plus de la chimie, et les phénomènes physiques de la postoxydation, tels que la turbulence et les effets de mélange, ce schéma cinétique a été couplé à un modèle de combustion turbulente adapté à l'utilisation dans un code CFD 3D moteur. Ce couplage a été effectué via une tabulation a priori de la chimie, méthode qui permet de réduire considérablement le temps de calcul, tout en décrivant l'ensemble des phénomènes liés à la chimie détaillée. Une technique de tabulation de la cinétique chimique a donc été développée et implantée dans un code CFD. Une configuration permettant de représenter les phénomènes caractéristiques de la postoxydation dans la ligne d'échappement d'un moteur à combustion interne a été simulée. Les résultats permettent de mieux appréhender ces phénomènes et de proposer des solutions technologiques visant à leur optimisationThe aim of this PhD thesis is the development of a predictive numerical model capable of simulating hydrocarbon postoxidation in an IC engine exhaust line. The model should reproduce the auto-ignition of hydrocarbons, as well as the evolution of pollutants and combustion products under postoxidation conditions. For this purpose, a detailed kinetic reaction model was developed. It should be valid at low temperatures and under highly diluted conditions. The model should also take into account the effects of the major components of engine exhaust gas on hydrocarbon postoxidation. These are CO2, H2O, and N2, acting as diluting species, but also CO and NOx, which even in small amounts, may strongly impact hydrocarbon oxidation kinetics. These species must hence be considered for postoxidation modelling.In order to gather chemical and physical effects such as turbulence and mixing, the chemical kinetic mechanism was coupled with a turbulent combustion model designed for CFD 3D engine computations. An a priori tabulation methodology was developed, minimizing computational effort and the developed tabulation technique was validated under postoxidation conditions in an IC-engine exhaust line. The coupled chemical kinetics tabulation and turbulent mixing model was implemented in the CFD code IFP-C3D. Simulations were performed on a configuration representative of the physical phenomena characteristic of hydrocarbon postoxidation in exhaust lines. Results improved the understanding of postoxidation phenomena in an IC-engine exhaust line and propose technical solutions for an enhanced postoxidation control
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Zouaoui, Nabila. "Etude expérimentale et théorique des paramètres régissant la combustion du noir de carbone au cours d'une analyse thermogravimétrique." Electronic Thesis or Diss., Mulhouse, 2009. https://www.learning-center.uha.fr/.
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La combustion du noir de carbone (NC) dans le creuset d'une thermobalance est contrôlée à la fois par la réaction et par le transport de l'oxygène jusqu'à la surface du lit et à l'intérieur du lit poreux de NC.Les expériences menées en modifiant la masse de NC ont montré que la concentration en oxygène peut tomber à zéro avant d'atteindre le fond du lit. Ainsi, à un instant donné, seule une partie du lit est en combustion. Cette masse, appelée masse critique (mc) dépend de la température. Elle passe de 35 mg à 570°C à 17,5 mg à 650°C.Un gradient d'oxygène s'établi donc dans le lit. La modélisation du transport interne de l'oxygène a montré que la diffusion de Fick constitue une bonne approximation pour représenter ce transport.Des conseils pour extraire correctement une constante cinétique à partir d'expériences thermogravimétrique sont donnés. La procédure est adaptée en fonction de la précision souhaitée.Ainsi, l'utilisation de faibles masses afin de réduire au mieux l'effet de la masse et l'exothermicité de la réaction est fortement conseillée. L'influence de la diffusion externe du gaz peut être réduite en utilisant des creusets de très faibles hauteurs, ou en mettant l'échantillon le plus proche de la bouche du creuset en remplissant le fond du creuset avec un matériau inerteCombustion of carbon black (CB) in the crucible of a thermobalance is controlled by both carbon reactivity and oxygen transport from the oxidizing flux to the surface of the bed and within the porous bed.The experiments conducted by changing the mass of CB showed that the oxygen concentration can fall to zero before the bottom of the bed. Thus, at a given time, only a part of the bed is burning. This mass, called critical mass (mc), depends to temperature. It went from 35 mg at 570°C to 17.5 mg at 650°C.An oxygen gradient is thus established in the bed. The Modelling of the internal transport of oxygen showed that the Fick diffusion is a good approximation to represent the transport.Advices to correctly extract a kinetic constant using thermogravimetric experiments are given. The procedure is adjusted depending to the precision desired.Thus, the use of low masses to best reduce the mass and exothermic reaction effects is strongly recommended. The influence of stagnant gas can be reduced by using crucibles with very low height, or by placing the sample closest to the mouth of the crucible by filling the bottom of the crucible with an inert material
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Njapha, Delani. "Determination of the kinetic models and associated parameters for the low temperature combustion and gasification of high-ash coal chars / D. Njapha." Thesis, North-West University, 2003. http://hdl.handle.net/10394/170.
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Jans, Elijah R. "Laser Diagnostics for Kinetic Studies of Nonequilibrium Molecular Plasmas and High-Speed Flows." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618850427972453.
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May-Carle, Jean-Baptiste. "Ethanol et moteur Diesel : mécanismes de combustion et formation des polluants." Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00843644.
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Les mélanges GtL/EMHC/éthanol ont un potentiel important comme carburant alternatif pour moteur Diesel.Néanmoins, l'utilisation de ce type de biocarburant en moteur Diesel nécessite une connaissance précise de la cinétiqued'oxydation de ses différents constituants.Une étude bibliographique approfondie a permis de sélectionner quatre espèces modèles représentatives des mélangesGtL/EMHC/éthanol : le n-décane, l'iso-octane, l'octanoate de méthyle et l'éthanol. L'oxydation de mélanges de cesespèces modèles a ensuite été étudiée en réacteur auto-agité à haute pression (10 atm), pour trois richesses (0,5 ; 1 et 2) etsur un large domaine de température (550-1150 K). L'analyse des échantillons par chromatographie en phase gazeuse apermis de quantifier les principaux produits issus de l'oxydation des mélanges étudiés. Un mécanisme cinétique détaillécapable de reproduire l'oxydation des mélanges n-décane/iso-octane/octanoate de méthyle/éthanol a ensuite été mis aupoint. Les prédictions du modèle reproduisent de manière satisfaisante les résultats expérimentaux sur toute la gamme derichesse et de température testée en réacteur auto-agité. L'analyse du modèle a également permis de déterminer les voiesréactionnelles prépondérantes en fonction de la composition des mélanges.Enfin, la combustion de mélanges GtL/EMAG/éthanol a été étudiée en moteur monocylindre Diesel. Cette phased'essais, incluant une analyse approfondie des émissions non réglementées, a permis d'observer l'influence de laformulation des carburants sur l'initiation de la combustion et sur la composition des gaz d'échappements.
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Zellagui, Sami. "Pyrolyse et combustion de solides pulvérisés sous forts gradients thermiques : Caractérisation de la dévolatilisation, des matières particulaires générées et modélisation." Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH9599/document.
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Le charbon est l’une des ressources fossiles les plus économiques pour la production d’énergie. Cependant, il présente des inconvénients liés à l’impact environnemental lors de sa combustion qui produit CO2, principal gaz à effet de serre, ainsi que d’autres gaz et particules polluants et nocifs pour la santé. Afin de lutter contre ces effets, plusieurs procédés sont envisagés dont l’oxycombustion (possibilité de séquestrer CO2 en sortie du système de combustion) et la co-combustion charbon/biomasse sachant que le bilan carbone est neutre pour la biomasse. Pour caractériser ces procédés, un dispositif expérimental a été développé. Il s’agit d’un four à chute qui permet de reproduire en laboratoire les conditions expérimentales prévalant dans les chaudières industrielles dont une vitesse de chauffe des particules de l’ordre de 104 K s-1. Ce dispositif a permis d’étudier la réaction de dévolatilisation de différents solides pulvérisés (charbons, biomasse) à différentes températures (de 600 à 1400 °C). Pour comparer les procédés de combustion et d’oxycombustion, la dévolatilisation sous N2 (étape préliminaire à la combustion sous air) et sous CO2 (étape préliminaire à l’oxycombustion) a été étudiée pour différents charbons à différentes températures. Les résultats obtenus montrent que l’influence de l’atmosphère gazeuse sur la dévolatilisation du charbon n’est significative que pour des températures supérieures à 1200 °C. L’influence des différentes conditions opératoires sur les émissions de particules (PM2.5) issues de la combustion du charbon et de la biomasse a été évaluée et des corrélations sont mises en évidence entre l’intensité d’émission des particules et la nature du combustible, la température et l’atmosphère gazeuse. Une étude cinétique de la pyrolyse a été effectuée et les paramètres cinétiques correspondants déterminés par modélisation à partir de plusieurs schémas cinétiques réactionnelsCoal is the most economically attractive fossil fuel and the main resource used for electricity production. However, the main issue with coal combustion is the greenhouse gas as well as other gases and particulates matter leading to environmental and human concerns. In order to reduce the environmental impact of coal utilization, researches are conducted to improve the combustion process and to use other carbon-based fuels. The first approach includes the oxy-fuel combustion that can be coupled with Carbon Capture and Storage process (CCS). The second approach promotes the partial substitution of coal by carbon-neutral fuels, such as biomasses, which are promising fuels.For the evaluation of the application of these technologies, an experimental device was developed. This device is a drop tube furnace (DTF) in which high particle heating rate (approximately 104–105 K s−1) has to be achieved in order to characterize solid fuels under conditions similar to those taking place in power plant furnaces. DTF allowed to investigate pyrolysis reaction involving coal and/or biomass particles at different temperatures (600-1400 °C). The comparison between the oxy-combustion and the conventional air combustion process starts with the investigation of the pyrolysis step. The impact of N2 (for conventional air combustion) and CO2 (for oxy-fuel combustion) atmospheres during pyrolysis of different coals at different temperatures was investigated. Results showed that the coal devolatilization is influenced by the gas under which the fuel devolatilization is carried out (N2 or CO2) only at high temperatures (>1200 °C). The influence of different operating conditions on PM2.5 emission were experimented for coals or biomass, including combustion atmosphere (air or oxy-fuel conditions), particle residence time and temperature. A kinetic study of the pyrolysis was carried out and the corresponding kinetic parameters were determined by modeling from several kinetic reaction schemes
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Li, Can. "Simultaneous Removal of Elemental Mercury and NO over Modified SCR Catalyst in Coal Combustion Flue Gas." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin161374169547422.
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Taddeo, Lucio. "Énergie recyclée par conversion chimique pour application à la combustion dans le domaine aérospatial (ERC3)." Thesis, Bourges, INSA Centre Val de Loire, 2017. http://www.theses.fr/2017ISAB0002/document.
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Le refroidissement actif par endocarburant permet d’assurer la tenue thermique d’un superstatoréacteur pour le vol hypersonique. Néanmoins, l’utilisation de cette technologie de refroidissement passe par la maitrise du couplage combustion – pyrolyse, qui fait de la définition d’une stratégie de contrôle du moteur un véritable défi. Une étude expérimentale a été réalisée afin d’analyser l’effet du paramètre de commande principal, le débit de combustible, sur des paramètres de sorties pertinents, à l’aide d’un dispositif de test spécifiquement conçu pour appréhender le couplage combustion – pyrolyse. Ceci a permis d’étudier la dynamique d’un circuit régénératif par rapport à ce paramètre de commande. Une étude cinétique paramétrique sur la pyrolyse du carburant a été conduite en parallèle de celle expérimentale afin d’affiner l’analyse et améliorer l’interprétation des expériences. La décomposition du carburant utilisé pour les tests (éthylène) a été prise en compte grâce à un mécanisme cinétique détaillé (153 espèces, 1185 réactions chimiques)Regenerative cooling is a well-known cooling technique, suitable to ensure scramjets thermal protection. The development of regeneratively cooled engines using an endothermic propellant is a challenging task, especially because of the strong coupling between fuel decomposition and combustion, which makes the definition of an engine regulation strategy very hard. An experimental study, aiming at identifying the effect of fuel mass flow rate variations on a fuel cooled-combustor in terms of system dynamics has been carried out. A remotely controlled fuel-cooled combustor, designed by means of CDF calculations and suitable for the experimental analysis of combustion-pyrolysis coupling, has been used. In order to improve tests results analysis, a parametric study to characterize fuel decomposition has also been realized. The pyrolysis has been modeled by using a detailed kinetic mechanism (153 species, 1185 chemical reactions)