En propulsion solide, l'ajout de particules d'aluminium dans le propergol améliore de façon significative les performances du moteur grâce à une augmentation sensible de la température de chambre. La présence de gouttes d'aluminium et de résidus d'alumine de différentes tailles et en quantité importante a un impact notoire sur le fonctionnement du moteur. Dans cette optique, nous souhaitons obtenir une meilleure prévision de la stabilité de fonctionnement en cas de déclenchement d'instabilités d'origine aéroacoustique ou thermoacoustique. Nous visons des calculs plus précis de l'étendue de la zone de combustion, de la chaleur dégagée par la combustion distribuée des gouttes et de la distribution en taille des résidus. Nos efforts ont porté sur la modélisation des échanges entre la phase gazeuse et cette phase dispersée composée de gouttes de nature et de taille très diverses. Le paramètre taille pilotant la dynamique du spray et le couplage avec le gaz, le suivi précis des changements de taille est un enjeu majeur.Dans cette contribution, nous avons choisi une approche cinétique pour la description des sprays polydisperses. L'équation cinétique de Williams-Boltzmann utilisée pour suivre l'évolution des propriétés du spray est résolue par une approche eulérienne. Les méthodes Multi-Fluide (MF) traitent naturellement les changements de taille tels que l'évaporation et la coalescence. Ces méthodes reposent sur une intégration continue de la variable taille sur des intervalles fixes appelés sections sur lesquels nous pouvons dériver des systèmes d'équations de conservation. Chaque système est vu comme un fluide qui est en couplage fort avec la phase gazeuse via des termes sources.Nous avons travaillé sur une méthode MF à deux moments en taille basée sur une famille de fonctions de forme polynomiale pour reconstruire la distribution en taille au sein des sections. Cette approche d'ordre deux en temps et en espace s'avère performante car elle décrit avec précision l'évolution de la distribution avec un nombre modéré de sections. Un travail original a été mené afin d'étendre l'approche MF à des gouttes bicomposants. Cette méthode ouvre la voie à des modèles de combustion des gouttes d'aluminium plus représentatifs. Dans le contexte des simulations instationnaires, nous avons porté une attention particulière à l'emploi d'une stratégie numérique robuste et précise pour le couplage entre les phases modélisées par une approche Euler-Euler. Nous montrons qu'une méthode de splitting séparant le traitement du transport des phases gazeuse/dispersée de celui des termes sources est particulièrement adaptée pour la résolution d'un problème multi-échelle spatial et temporel. Dans la mesure où les conditions de réalisabilité sur les moments en taille des méthodes MF ne sont pas garanties avec des méthodes d'intégration traditionnelles, nous avons développé des schémas innovants pour l'intégration des termes sources. Les travaux proposés dans cette contribution répond à deux exigences : 1- un ratio coût/précision attractif pour des simulations industrielles 2- une facilité d'implémentation des méthodes et une modularité assurant la pérennisation des codes industriels. Ces développements ont d'abord été vérifiés à l'aide d'un code ad hoc ; des cas test d'étude d'acoustique diphasique linéaire ont notamment souligné la pertinence de la technique de splitting pour restituer avec précision les interactions spray-acoustique. Les nouvelles méthodes ont ensuite été implémentées et validées au sein du code multi-physique CEDRE développé à l'ONERA. Des calculs de propulsion solide sur des configurations moteur réalistes ont finalement mis en évidence le niveau de maturité atteint par les méthodes eulériennes pour décrire avec fidélité la dynamique des sprays polydisperses. Les résultats de ces simulations ont mis en avant la sensibilité des niveaux d'instabilités en fonction de la distribution en taille des gouttes d'aluminium et des résidus. / The addition of a significant mass fraction of aluminum particle in the propellant of Solid Rocket Motors improves performance through an increase of the temperature in the combustion chamber. The distributed combustion of aluminum droplets in a portion of the chamber yields a massive amount of disperse aluminum oxide residues with a large size spectrum, called a polydisperse spray, in the entire volume. The spray can have a significant impact on the motor behavior and in particular on the onset/damping of instability. When dealing with aeroacoustical and thermoacoustical instabilities, the faithful prediction of the interactions between the gaseous phase and the spray is a determining step for understanding the physical mechanisms and for future solid rocket motor optimization. In such a harsh environment, experimental measurements have a hard time providing detailed explanation of the physical mechanisms and one has to resort to numerical simulation. For such a purpose, the distributed combustion zone and thermal profile therein, the heat generated by the combustion of the dispersed droplets and the large size distribution of the aluminum oxide residues and its coupling with he gaseous phase hydrodynamic and acoustic fields have to be accurately reproduced through a proper level of modeling and a high fidelity simulation including a precise resolution of size polydispersity, which is a key parameter.In this contribution, we choose a kinetic approach for the description of polydisperse sprays. The Williams-Boltzmann Equation is used to model the disperse phase and we derive a fully Eulerian approach through moment methods. The Multi-Fluid (MF) methods naturally treat droplet size evolution through phenomena such as evaporation and coalescence. These methods rely on the conservation of size moments on fixed intervals called sections and yield systems of conservation laws for a set of "fluids" of droplet of various sizes, which is strongly coupled with the gas phase via source terms. We derive a new optimal and flexible Two Size Moment MF method based on a family of polynomial reconstruction functions to describe the size distribution in the sections, which is second order accurate and particularly efficient at describing accurately the evolution of the size distribution with a moderate number of sections. An original work is also conducted in order to extend this approach to two-component droplets. For size moment MF methods, realizability of the moments is a crucial issue. Thus, we have developed innovative schemes for integrating source terms in moment conservation equations describing transport in phase space. This method enables the use of more representative aluminum droplet combustion models, and leads to more advanced studies of the distributed combustion zone. Moreover, for unsteady two-phase flow simulations, we have developed a robust and accurate coupling strategy between phases that are modeled by a fully Eulerian approach based on operator splitting in order to treat such spatial and temporal very multi-scale problems with reasonable computational time. All the proposed developments have been carried out following two criteria : 1- an attractive cost/accuracy ratio for industrial simulations in the context of high fidelity simulations 2- a preservation of industrial code legacy. Verification of the models and methods have been conducted first using an in-house reseach code and then in the context of a two-phase acoustic study thus emphasizing the relevance of the splitting technique to capture accurately spray-acoustic interactions.

Le modèle multi-fluide permet de décrire par une approche Eulérienne les sprays polydispersés et apparaît donc comme une méthode indiquée pour les applications de combustion diphasique. Sa pertinence pour la simulation à l’échelle d’applications industrielles est évaluée dans ce travail, par sa mise en oeuvre dans des configurations bi-dimensionnelle et tri-dimensionnelle plus représentatives de ce type de simulations. Cette évaluation couple une étude de faisabilité en terme de coût de calcul avec une analyse de la précision obtenue, par des comparaisons avec les résultats de méthodes de références pour la description des sprays. Afin de définir une telle référence, une hiérarchisation des modèles de spray est proposée dans ce travail, soulignant les niveaux de modélisation associée aux diverses méthodes. Une première configuration d’écoulements tourbillonnaires est utilisée pour caractériser la méthode multi-fluide. L’étude de la structure mathématique du système de lois de conservation permet d’analyser la formation de singularités et de fournir les outils permettant d’évaluer leur impact sur la modélisation. Cette étude permet également de dériver un schéma numérique robuste et efficace pour des configurations bi- et tri-dimensionnelle. La description des dynamiques de gouttes conditionnées par la taille est évaluée dans ces configurations tourbillonnaires au moyen de comparaisons quantitatives, sur des champs instantanés, où le multi-fluide est confronté à une méthode Lagrangienne, ainsi qu’à des résultats expérimentaux. Afin d’évaluer le comportement de la méthode multi-fluide dans des configurations plus représentatives des problématiques industrielles, le solveur MUSES3D est développé, permettant, entre autres, une évaluation fine des méthodes de résolution des sprays. Une implémentation originale de la méthode multi-fluide, conciliant généricité et efficacité pour le calcul parallèle, est réalisée. Le couplage de ce solveur avec le code ASPHODELE, développé au CORIA, permet d’effectuer une évaluation opérationnelle des approches Euler/Lagrange et Euler/Euler pour la description des écoulements diphasiques à inclusions dispersées. Finalement, le comportement de la méthode multi-fluide dans des jets bi-dimensionnels et dans une turbulence homogène isotrope tri-dimensionnelle permet de montrer sa précision pour la description de la dynamique de sprays évaporant dans des configurations plus complexes. La résolution de la polydispersion du spray permet de décrire précisément la fraction massique de combustible en phase vapeur, un élément clé pour les applications de combustion. De plus, l’efficacité du calcul parallèle par décomposition de domaine avec la méthode multi-fluide permet d’envisager son utilisation à l’échelle d’applications industrielles. / The multi-fluid model, providing a Eulerian description of polydisperse sprays, appears as an interesting method for two-phase combustion applications. Its relevance as a numerical tool for industrial device simulations is evaluated in this work. This evaluation assesses the feasibility of multi-fluid simulations in terms of computational cost and analyzes their precision through comparisons with reference methods for spray resolution. In order to define such a reference, the link between the available methods for spray resolution is provided, highlighting their corresponding level of modeling. A first framework of 2-D vortical flows is used to assess the mathematical structure of the multi-fluid model governing system of equations. The link between the mathematical peculiarities and the physical modeling is provided, and a robust numerical scheme efficient for 2-D/3-D configurations is designed. This framework is also used to evaluate the multi-fluid description of evaporating spray sizeconditioned dynamics through quantitative, time-resolved, comparisons with a Lagrangian reference and with experimental data. In order to assess the multi-fluid efficiency in configurations more representative of industrial devices, a numerical solver is designed, providing a framework devoted to spray method evaluation. An original implementation of the multifluid method, combining genericity and efficiency in a parallel framework, is achieved. The coupling with a Eulerian/Lagrangian solver for dispersed two-phase flows, developed at CORIA, is conducted. It allows a precise evaluation of Euler/Lagrange versus Euler/Euler approaches, in terms of precision and computational cost. Finally, the behavior of the multi-fluid model is assessed in 2D-jets and 3-D Homogeneous Isotropic Turbulence. It illustrates the ability of the method to capture evaporating spray dynamics in more complex configurations. The method is shown to describe accurately the fuel vapor mass fraction, a key issue for combustion applications. Furthermore, the method is shown to be efficient in domain decomposition parallel computing framework, a key issue for simulations at the scale of industrial devices.

Numerical modeling of several turbulent nonreacting and reacting spray jets is carried out using a fully stochastic separated flow (FSSF) approach. As is widely used, the carrier-phase is considered in an Eulerian framework, while the dispersed phase is tracked in a Lagrangian framework following the stochastic separated flow (SSF) model. Various interactions between the two phases are taken into account by means of two-way coupling. Spray evaporation is described using a thermal model with an infinite conductivity in the liquid phase. The gas-phase turbulence terms are closed using the k-� model. In the classical SSF (CSSF) approach the effects of turbulent velocity fluctuations of the gas-phase are modeled stochastically to obtain instantaneous gas-phase velocity, which subsequently is used to estimate droplet dispersion and interphase transport rates. However, in the CSSF model, no such effort is made to model the effects of the fluctuations in the gas-phase reactive scalars, namely temperature and species mass fractions. Instead, the mean value of these scalars is used while solving for the droplet governing equations and estimating various interphase source terms. Also, in flamelet model and conditional moment closure (CMC) applications of turbulent sprays, the mixture fraction is defined using conventional definition, which is no longer a conserved quantity due to associated phase change. Therefore, in this thesis a novel mixture fraction based FSSF approach is used to stochastically model the fluctuating temperature and composition of the gas phase. These gas-phase reactive scalars are then used to refine the estimates of the heat and mass transfer rates between the droplets and the surrounding gas-phase. It is assumed that the fluctuations in the gas-phase reactive scalars are inherently associated with the fluctuation of a single conserved scalar, namely instantaneous mixture fraction. Instantaneous value of the gas-phase reactive scalars seen by individual droplets is then estimated from the instantaneous gas-phase mixture fraction, which is obtained as the Weiner process by randomly sampling a known beta-function probability density function (PDF) of the local mixture fraction field. Finally, Favre mean value of the gas-phase scalars are recovered as appropriate moments of the PDF. The present definition of the mixture fraction based on its instantaneous value facilitate exact calculation of the source terms in the transport equation for variance of the mixture fraction, whereas conventional definition leads to terms which require further modeling and simplifications. The present FSSF model also accounts for the possibility of existence of an envelope flame between the droplet and the bulk gas-phase, which greatly increases the heat and mass transfer rates to the droplet. The present model allows us to treat the occurrence of envelope flame separately which is otherwise neglected in the conventional spray combustion models. The FSSF model is implemented into a numerical code, and different well-defined nonreacting and reacting turbulent spray jets are investigated. For the reacting spray jets, single-step irreversible reaction with infinitely fast chemistry is assumed in the body of the flow. In such cases special care must be taken with modeling the upstream boundary condition. This is because the flow from the spray jet nozzle is unreacted and yet it becomes well reacted shortly downstream. Numerical results are compared against experimental measurements as well as with predictions using the CSSF approach. Numerical results from the FSSF and CSSF model are almost identical for the nonreacting spray jets, where the fluctuations in the gas-phase scalars are relatively low. For the reacting sprays, significant differences are found between the results of the FSSF and CSSF models for the reacting spray jets, where the fluctuations in the reactive scalars are high. The FSSF model reasonably predicts many features of the jet spray flames, such as flame length, gas-phase temperature, and spray droplet velocity/diameter distribution; results appear to be close to the experimental measurements. Finally, the combustion characteristics of the reacting spray jets are studied following classical group combustion theory. It shows that these spray jets have external group combustion mode near the nozzle-exit. Transition to internal group combustion takes place at different downstream locations based on the droplet loading and equivalence ratio at the nozzle-exit, whereas single droplet combustion regime is observed near the tip of the visible flame. Another alternate approach to study the combustion behavior of a cloud is proposed based on fraction of droplets having i) no envelope flame, ii) envelope flame, iii) extinguished envelope flame due to high slip velocity, iv) extinguished envelope flame due to droplet diameter being too small, v) both iii) and iv) above. Based on these, different group combustion behavior of the reacting spray jets are interpreted.

Atomization characteristics of liquid fuel sprays control combustion efficiency and emissions in engines. The present work is motivated by the need to study the atomization and spray structure of vegetable oil biofuels for which no data in the literature exists. In this work, various laser-based diagnostic techniques such as laser shadowgraphy, Particle/Droplet Image Analysis (PDIA) and Laser Sheet Dropsizing (LSD) are applied for studying atomization characteristics, tip penetration, droplet size and liquid volume fraction of Pongamia vegetable oil (SVO) and its blends with diesel. A constant volume high pressure spray visualization chamber is designed and fabricated to study SVO sprays at high gas pressure and temperature conditions. This optical chamber can be used for gas pressures up to 60 bar and temperatures up to 600 K. Optical access inside the chamber is provided through four quartz windows to perform various optical spray diagnostic studies. A high pressure spray injection facility based on components of common rail diesel injection system is designed. This facility can provide an injection pressure of up to 1700 bar with independent control over injection duration and timing. A marked difference is observed between diesel and SVO spray structures under atmospheric gas pressure condition. A very interesting observation related to the behavior of 100% SVO fuel when sprayed into atmospheric pressure is the presence of an intact liquid core even at injection pressure as high as 1600 bar. The presence of liquid core at high injection pressures is attributed to the high viscosity of SVOs and the non-Newtonian behavior of these oils under high pressure and shear. The spray characterization of the oil and its blends at high gas pressure shows that although the atomization is dramatically different from that at atmospheric gas pressure, it is still incomplete even at very high injection pressures. For a gas pressure of 30 bar, it is observed that the Sauter Mean Diameter (SMD) for Pongamia oil is more than twice that of diesel. A new method of simultaneously obtaining two-dimensional droplet size and quantitative liquid volume fraction data in sprays has been developed. Measurements with this method reveal a higher liquid volume fraction at the central axis of spray for Pongamia oil compared to that of diesel indicating potentially poor air-fuel mixing. The experimental data obtained and the spray tip penetration correlations developed for the vegetable oils and blends serve as useful inputs for fuel injection and engine system designers.

Biofuels in civil aviation is actively studied in recent years to identify potential alternative jet fuels to meet stringent environmental regulations imposed to tackle degraded air quality caused by fossil fuel combustion. In this context, the aviation industry prefers to develop ‘drop-in’ fuels which may not require substantial modifications in existing jet engine technologies. The thesis aims at evaluating the atomization characteristics of camelina- and jatropha-derived drop-in biofuels discharging from simplex swirl atomizer used in aircraft gas turbine engines. The test fuels are characterized in detail and all fuels meet current ASTM D7566 specifications. The experiments are conducted by discharging fuel spray into quiescent atmospheric air in a fuel spray booth to obtain spray characteristics such as fuel discharge behaviour, spray cone angle, breakup behaviour of swirling fuel sheet and spray drop size distribution. The characteristics of sheet breakup are deduced from the captured images of biofuel sprays and the measurements of spray droplet size distribution are obtained using Spraytec (laser-diffraction instrument). A systematic comparison is made between the biofuel sprays and the 100% Jet A-1 (conventional aviation kerosene) sprays to evaluate the drop-in feature of the biofuels. All the measured spray characteristics of the biofuel sprays follow the Jet A-1 both in qualitative and quantitative terms which ensure the drop-in nature of the tested biofuels. The minor differences observed in the comparison of the quantitative spray measurements are attributed to the variation in the fuel properties. This claim is supported using the predictions obtained from the liquid film breakup model and the empirical correlation reported in the literature for the determination of sheet breakup characteristics and mean drop size for sprays discharging from simplex swirl atomizers.

Made available in DSpace on 2014-10-09T12:27:23Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:51Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:27:23Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:51Z (GMT). No. of bitstreams: 0 / Os filmes cerâmicos de manganito de lantânio dopado com estrôncio (LSM) e de manganito de lantânio dopado com estrôncio/zircônia estabilizada com ítria (LSM/YSZ) são utilizados como catodos das células a combustível de óxido sólido de temperatura alta (CaCOSTA). Estes filmes cerâmicos porosos foram depositados sobre o substrato cerâmico denso de YSZ, utilizado como eletrólito, componente estrutural do módulo, assim conferindo uma configuração de meia-célula denominada auto-suporte. O estudo da meia-célula é fundamental, pois na interface catodo/eletrólito ocorre a reação de redução do oxigênio, conseqüentemente influenciando no desempenho da CaCOSTA. Neste sentido, o presente trabalho contribui para a síntese de pós de LSM e LSM/YSZ e para o processamento de filmes finos, utilizando a técnica de pulverização de pó úmido, adotada para a conformação dos filmes cerâmicos por permitir a obtenção de camadas porosas com espessuras variadas na ordem de micrômetros. Os pós de LSM foram sintetizados pela técnica de citratos e os pós de LSM/YSZ pela técnica de mistura de sólidos. Na etapa de conformação foram preparadas suspensões orgânicas de LSM e LSM/YSZ alimentada por gravidade em um aerógrafo manual. Para a conformação do substrato de YSZ utilizou-se uma prensa uniaxial hidráulica. Foram possíveis a obtenção das meia-células de óxido sólido catodo/eletrólito de estruturas cristalinas hexagonal para a fase LSM e cúbica para a fase YSZ. E as micrografias das meia-células mostram que o substrato YSZ é denso, suficiente para ser utilizado como eletrólito sólido, e os filmes de LSM e LSM/YSZ apresentam-se porosos com espessura de aproximadamente 30 μm e com boa aderência entre os catodos e o eletrólito. A presença do catodo compósito entre o catodo LSM e o substrato YSZ, possibilitou um aumento no desempenho eletroquímico na reação de redução do oxigênio. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Philosophiae Doctor - PhD / The domesticated apple (Malus x domestica Borkh.) has been distributed into diverse climatic conditions worldwide for commercial production of fruit. Apple trees need exposure to cold temperatures, referred to as chill unit (CU) accumulation during winter, in order for budbreak to occur promptly and uniformly after winter. In warmer production areas the application of dormancy breaking chemicals has enabled successful production of high chilling requiring apple cultivars in suboptimal environmental conditions. In the Western Cape region of South Africa it is common orchard practice to apply dormancy breaking chemicals after winter in order to stimulate vegetative growth. If this is not done prolonged dormancy symptoms (PDS) are experienced which include extended rest, less synchronised breaking of buds and reduced branching. An increasing awareness of both global warming and the negative effects associated with the use of chemical sprays (for both pest and disease resistance and growth regulation) has resulted in the need to breed cultivars better adapted to current and future environmental conditions. The breeding of new cultivars using conventional breeding methods is a time consuming process, especially in perennial tree species with a long juvenile phase such as apple. The implementation of marker-assistedbreeding (MAB) and selection (MAS) will enable the selection of favourable genotypes at a very early seedling stage. Although markers linked to genes involved in disease resistance for a variety of known apple pathogens have been identified and are already in use in breeding programs, the genetic determinants of dormancy related characteristics residing within the bud itself iii (endodormancy) are poorly understood. This hampers the genetic improvement of such characters. Although this study focused on time of initial vegetative budbreak IVB, there are various other characteristics that can be associated with dormancy, such as position and number of budbreak and budbreak duration.

Fuel sprays play a major role in order to achieve the required combustion characteristics and pollutant emissions reduction on internal combustion engines, and thus, an accurate prediction of its behavior is required to perform reliable engine combustion and pollutant simulations. A great effort both on experimental and theoretical studies of spray atomization and dispersion has been performed in the latest years. As a result, Computational Fluid Dynamics (CFD) calculations have become a standard tool not only for spray physics understanding but also for design and optimization of engine spray systems. However, spray modeling in its different uses in the Internal Combustion Engine (ICE) context is still nowadays a challenging task due to the complex interrelated phenomena taking place, some of them still not fully understood. Primary atomization and secondary breakup, droplet collision, coalescence and vaporization, turbulent interactions between phases have to be solved under high Reynolds (so they are turbulent) and Weber numbers conditions due to the high speed (~500 m/s) and small nozzle diameter (~100 µm) imposed by current engine injection systems technologies. Moreover, Taylor numbers cover a wide range, according to the composition of the injected liquid. Those conditions make experimental observations quite challenging and probably insufficient, especially in the very near nozzle region, where primary atomization takes place. Most of the CFD spray models are currently based on the Discrete Droplet Method. The continuous liquid jet is discretized into 'blobs' or 'parcels', which consists in a number of droplets with the same characteristics. A Lagrangian method is applied to track the liquid phase parcels, which are subject to breakup according to atomization models mainly based on the linear instability theory proposed by Reitz and later extended by Huh and Gosman for liquid turbulence effects to be considered. This approach has been successfully applied b / Khuong ., AD. (2012). The Eulerian-Lagrangian Spray Atomization (ELSA) Model of the Jet Atomization in CFD Simulations: Evaluation and Validation [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17237 / Palancia

El modelado CFD se ha convertido en una herramienta aceptada y ampliamente utilizada en el ámbito del diseño de motores de combustión interna alternativos. Los modelos de combustión avanzados ayudan a comprender los fenómenos complejos químicos y físicos del proceso de combustión y aportan información detallada que no se puede obtener con experimentos. Indudablemente, el modelado del proceso de combustión turbulenta parcialmente premezclada característico de los chorros Diesel es particularmente difícil y por lo tanto es un tema de gran interés para la comunidad científica. Los retos más importantes del modelado de este tipo de llamas son la predicción del proceso del auto-encendido, caracterizado por el tiempo de retraso, y la estructura de la llama cuasi-estacionaria con su característica longitud de lift-off. Estos dos parámetros globales de los chorros Diesel son importantes por varios aspectos. Primero, es relativamente sencillo medir estos dos parámetros y por lo tanto utilizarlos para la validación de modelos y segundo, son factores determinantes en el proceso de la combustión en un motor. El auto-encendido marca el inicio de la tasa de liberación de calor y la longitud de lift-off desempeña un papel fundamental en la formación de hollín. El mecanismo de estabilización de la llama en la zona del lift-off todavía no es bien conocido aunque existen diferentes teorías en la literatura, por lo que su modelado es en la actualidad un reto no resuelto. De acuerdo con el contexto descrito previamente, en este trabajo se pretende implementar un modelo de combustión integrado en un solver RANS utilizando la plataforma CFD OpenFOAM de código abierto. El modelo propuesto está basado en el concepto de flamelets usando una química detallada combinado con funciones de probabilidad determinadas a priori (presumed-PDF) para considerar el efecto de interacción entre la química y las características del flujo turbulento, que implica hipótesis importantes. En primer lugar, con el concepto flamelet se asume que una llama Diesel turbulenta quema localmente como un conjunto de llamas laminares de difusión de flujos opuestos. En segundo lugar se asume que las fluctuaciones de las propiedades introducidas por el flujo turbulento, que son las responsables de los fenómenos de interacción entre la química y la turbulencia durante la combustión, siguen un comportamiento estadístico en el tiempo de acuerdo a una distribución de probabilidad conocida a priori. Los fenómenos complejos del auto-encendido de hidrocarburos exigen el uso de mecanismo químicos detallados para recuperar satisfactoriamente los tiempos de retraso del auto-encendido en un rango amplio de condiciones termoquímicas. Una estrategia de interés para mantener los costes computacionales dentro de límites aceptables consiste en pre-tabular los resultados del cálculo de la química en tablas. Los parámetros independientes de estas tablas son la fracción de mezcla, la variable de progreso y la tasa de disipación escalar. Además, la hipótesis de que la distribuciones de probabilidad de las fluctuaciones generadas por la turbulencia sobre las propiedades del flujo son conocidas permite generar una tabla con la información química del problema apta para su aplicación en cálculo CFD en un entorno RANS. Esta aproximación basada en la pre-tabulación de los resultados químicos presenta dos ventajas fundamentales, siendo la primera de ellas la posibilidad de considerar modelos avanzados de interacción química-turbulencia y la segunda el relevante ahorro de tiempo de cálculo. Sin embargo, estas tablas representan un gran espacio de datos cuya gestión eficiente no es trivial. El desarrollo de un almacenamiento adecuado para un acceso de datos rápido y directo así como un esquema de interpolación multidimensional también forma parte del presente trabajo. / Winklinger, JF. (2014). Implementation of a combustion model based on the flamelet concept and its application to turbulent reactive sprays [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48488 / TESIS