Au cours des dernières années, le transport aérien de passagers connaît un développement sans cesse croissant et continue ainsi d’accroire sa contribution aux émissions mondiale de CO2. Par conséquent, un effort commun entre les avionneurs est fait pour diminuer les émissions de CO2 et de polluants. Pour encourager cet effort, les réglementations deviennent de plus en plus drastiques en terme d'émissions et de polluants tels que le CO2, les NOx mais aussi le bruit. Ces nouvelles limitations sont à la fois définies à court et moyen-long termes pour inciter les motoristes à travailler sur les technologies de plus en plus efficientes.Pour concevoir des moteurs toujours plus performants tout en respectant ces réglementations à court terme, les motoristes travaillent sur l'optimisation de leurs technologies conventionnelles, en améliorant des leviers bien identifiés comme l'augmentation du taux de compression. Cependant, cette optimisation des turbomachines actuelles a déjà atteint un niveau de maturité très élevé. Il semble ainsi difficile de continuer indéfiniment leurs optimisations. Par conséquent, pour atteindre les objectifs à moyen-long terme, les motoristes sont dès aujourd'hui en train d'étudier des nouveaux systèmes propulsifs avancés comme les chambres de Combustion à Volume Constant (CVC) qui peuvent accroître le rendement thermique. Contrairement aux chambres de combustion traditionnelles, qui fonctionnent à flux continu, les chambres CVC opèrent de façon cyclique afin de créer un volume constant pendant la phase de combustion et libérer les gaz chauds dans les étages de turbines.Pendant cette thèse, une approche numérique permettant d'évaluer ce type de chambres est développée. Tout l'enjeu est de pouvoir étudier des chambre de combustion intégrant des parties mobiles, qui permettent de créer le volume constant dédié à la combustion tout en évitant les fuites à travers ces systèmes mobiles lors de l'élévation de la pression dans la chambre. Cette modélisation doit aussi prédire correctement les phases transitoires comme l'admission des gaz frais, qui pilote la phase de combustion. Cette étude utilise des objets immergés pour modéliser les parties mobiles. Les objectifs de cette thèse sont de rendre ces objets immergés imperméables et adapter la méthode aux différents modèles utilisés pour étudier les milieux réactifs tels que le modèle de combustion ECFM-LES ou encore l'injection liquide Lagrangienne utilisée pour résoudre l'injection du fuel.Dans cette étude, une nouvelle formulation est développée puis testée sur différents cas tests de plus en plus représentatifs des chambres CVC. Cette approche numérique est ensuite évaluée sur une chambre réel étudiée expérimentalement au laboratoire PPRIRME de Poitiers. Dans cette dernière étude, deux cas non réactifs permettent de comparer les évolutions de pression à deux endroits dans la dispositif expérimental, ainsi que les champs de vitesse au sein de la chambre de combustion, aux simulations réalisées. Pour ces cas complexes, l'utilisation des objets immergés permet de prédire les résultats expérimentaux à un coût attractif.Un des cas non réactif est ensuite carburé et allumé pour confronter l'évolution pression et les champs de vitesse dans la chambre de combustion des résultats numériques obtenus aux mesures expérimentales. L'approche numérique développée a permis d’enrichir les données expérimentales, d'analyser les variabilités cycle-à-cycle rencontrées au banc et d'identifier les leviers qui permettraient d'optimiser ce type d’architecture. / Over the past few years, aircrafts have become a common means of transport, thus continuously increasing their contribution to global CO2 emissions. Consequently, there is a common effort between aircraft manufacturers to reduce CO2 and pollutant emissions. To encourage this effort, regulations are becoming more and more stringent on the emissions and pollutants like CO2, NOx and noise. These regulations are both defined in the short and medium-long terms to urge aircraft manufacturers to work on more and more efficient technologies.In order to design more efficient engines while respecting the short term objectives, engine manufacturers are working on the improvement of conventional architectures by using well-known levers like the increase of the Overall Pressure Ratio (OPR). However, the optimization of the present turbomachinery has already reached a high level of maturity and it seems difficult to continuously enhance their performances. Consequently, to reach the medium-long term objectives, engine manufacturers are working on new advanced propulsion systems such as the Constant Volume Combustion (CVC) chambers, which can increase the thermal efficiency of the system. Contrary to present turbomachinery which are burning fresh gases continuously, CVC chambers operate cyclically so as to create the constant vessel dedicated to the combustion phase and to expand the burnt gases into turbine stages.In this PhD thesis, a numerical approach is developed to allow the evaluation of these kind of combustors. The challenge is to be able to evaluate CVC chambers by taking into account the moving parts which create the constant volume and avoid mass leakages through these moving parts during the increase of the combustion chamber pressure when the combustion occurs. This approach also has to correctly predict unsteady phases like the intake, which directly controls the combustion process.These moving parts are modeled with a Lagrangian Immersed Boundary (LIB) method .The main goals of this thesis is to make the LIB as airtight as possible and to render this approach compatible with the different models which are adapted to analyse reactive flows such as the ECFM-LES combustion model or Lagrangian liquid injection, used for fuel sprays. In this study, a new formulation is developed and tested on several test cases from very simple ones to cases more representative of CVC chambers.Then, this approach is evaluated on a real chamber experimentally analysed in PPRIME laboratory in Poitiers. Two non-reactive operating points are used to compare the experimental pressure at two positions in the apparatus and the experimental velocity fields in the combustion chamber with the numerical results. In this complex configuration, the LIB method allows the prediction of the experimental results with a low CPU cost. As in the experiment, one non-reactive case is carburized and ignited to compare the measured pressure and the velocity fields in the combustion chamber with the simulations. The proposed numerical approach allows the data enhancement of the experiment and then the analysis of the cycle-to-cycle variability encountered during the experimental measurements. Last but not least, this method enables the identification of the different levers that could decrease the variability and then could improve operability of this type of combustors.

La conception des moteurs aéronautiques est soumise à de nombreuses contraintes telles que les gains de performance ou les normes environnementales de plus en plus exigeantes. Face à ces objectifs souvent contradictoires, les nouvelles technologies de moteur tendent vers une augmentation de la température locale et globale dans les étages chauds. En conséquence, les parties solides comme les parois du brûleur sont soumises à des niveaux de température élevés ainsi que d’importants gradients de température, tous deux critiques pour la durée de vie du moteur. Il est donc essentiel pour les concepteurs de caractériser précisément la thermique locale de ces systèmes. Aujourd’hui, la température de paroi est évaluée par des essais de coloration. Pour limiter ces essais relativement chers et complexes, des outils numériques haute fidélité capables de prédire la température de paroi des chambres de combustion sont actuellement développés. Cet exercice nécessite de considérer tous les modes de transfert de chaleur (convection, conduction et rayonnement) ainsi que la combustion au sein du brûleur. Ce problème multi-physique peut être résolu numériquement à l’aide de différentes approches numériques. La méthode utilisée dans ce travail repose sur une approche partitionnée qui inclut la résolution de l’écoulement turbulent réactif par un code de simulation aux grandes échelles (LES), un solveur radiatif basé sur la méthode aux ordonnées discrètes ainsi qu’ un code de conduction solide.Les diverses questions et difficultés liées à la répartition des ressources informatiques ainsi qu’à la méthodologie de couplage employée pour traiter les disparités d’échelles de temps et d’ espace présentes dans chacun des modes de transfert de chaleur sont discutées. La performance informatique des applications couplées est étudiée à travers un modèle très simplifié ainsi que sur une application industrielle. Les paramètres importants sont identifiés et des pistes potentielles d’amélioration sont proposées. La méthodologie de couplage thermique est ensuite étudiée du point de vue physique sur deux configurations distinctes. Pour commencer, l’équilibre thermique entre un fluide réactif et un solide est étudié pour une configuration académique d’accroche flamme. L’influence de la température de paroi de l’accroche flamme sur la stabilisation de flamme est mise en évidence sur des simulations fluideseul. Ces résultats indiquent trois états d’équilibre théorique différents. La pertinence physique de ces trois états est ensuite évaluée à l’aide de diverses simulations de transfert de chaleur conjugué réalisées pour différentes solutions initiales et conductivités solides. Les résultats indiquent que seulement deux états d’équilibre ont un sens physique et que la bifurcation entre les deux états possibles dépend à la fois de la condition initiale et de la conductivité solide. De plus, pour la gamme de paramètres testés, la méthodologie de couplage n’a pas d’effet sur les solutions obtenues. Une méthodologie similaire est ensuite appliquée à une chambre de combustion d’hélicoptère pour laquelle le rayonnement est de plus pris en compte. Diverses simulations sont présentées afin d’évaluer l’impact de chacun des processus de transfert de chaleur sur le champ de température : une simulation fluide-seul adiabatique de référence, de transfert de chaleur conjugué, d’interaction thermique fluide-rayonnement ainsi qu’une simulation incluant toutes les physiques. Ces calculs montrent la faisabilité d’un couplage LES/conduction solide dans un contexte industriel et fournissent de bonnes tendances de distribution de température. Pour finir, pour cette géométrie de brûleur et la condition d’opération simulée, les divers résultats montrent que le rayonnement joue un rôle important dans la distribution des températures de paroi. De ce fait, les comparaisons aux essais de coloration sont globalement en meilleur accord quand les trois modes de transfert sont pris en compte / The design of aeronautical engines is subject to many constraints that cover performance gain as well as increasingly sensitive environmental issues. These often contradicting objectives are currently being answered through an increase in the local and global temperature in the hot stages of the engine. As a result, the solid parts encounter very high temperature levels and gradients that are critical for the engine lifespan. Combustion chamber walls in particular are subject to large thermal constraints. It is thus essential for designers to characterize accurately the local thermal state of such devices. Today, wall temperature evaluation is obtained experimentally by complex thermocolor tests. To limit such expensive experiments, efforts are currently performed to provide high fidelity numerical tools able to predict the combustion chamber wall temperature. This specific thermal field however requires the consideration of all the modes of heat transfer (convection, conduction and radiation) and the heat production (through the chemical reaction) within the burner. The resolution of such a multi-physic problem can be done numerically through the use of several dedicated numerical and algorithmic approaches. In this manuscript, the methodology relies on a partitioned coupling approach, based on a Large Eddy Simulation (LES) solver to resolve the flow motion and the chemical reactions, a Discrete Ordinate Method (DOM) radiation solver and an unsteady solid conduction code. The various issues related to computer resources distribution as well as the coupling methodology employed to deal with disparity of time and space scales present in each mode of heat transfer are addressed in this manuscript. Coupled application high performance studies, carried out both on a toy model and an industrial burner configuration evidence parameters of importance as well as potential path of improvements. The thermal coupling approach is then considered from a physical point of view on two distinct configurations. First, one addresses the impact of the methodology and the thermal equilibrium state between a reacting fluid and a solid for a simple flame holder academic case. The effect of the flame holder wall temperature on the flame stabilization pattern is addressed through fluid-only predictions. These simulations highlight interestingly three different theoretical equilibrium states. The physical relevance of these three states is then assessed through the computation of several CHT simulations for different initial solutions and solid conductivities. It is shown that only two equilibrium states are physical and that bifurcation between the two possible physical states depends both on solid conductivity and initial condition.Furthermore, the coupling methodology is shown to have no impact on the solutions within the range of parameters tested. A similar methodology is then applied to a helicopter combustor for which radiative heat transfer is additionally considered. Different computations are presented to assess the role of each heat transfer process on the temperature field: a reference adiabatic fluid-only simulation, Conjugate Heat Transfer, RadiationFluid Thermal Interaction and fully coupled simulations are performed. It is shown that coupling LES with conduction in walls is feasible in an industrial context with acceptable CPU costs and gives good trends of temperature repartition. Then, for the combustor geometry and operating point studied, computations illustrate that radiation plays an important role in the wall temperature distribution. Comparisons with thermocolor tests are globally in a better agreement when the three solvers are coupled.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Actually in Brasil there there is a fleet around 1500 agricultural aircraft working on different aplications. The spray aplication by na airplane of crop defenses is increasing on the last years, generating a demand on spraying airplanes, pilots, spare parts for maintenance, fuel and, first of all, operational cost reduction. Base on this, the present master thesis is working as knowledge generator ans presenting results for, in the future, to project an ethanol aeronautical engine that will use on agricultural/spraying airplanes. Operational costs for agricultural airplanes is based on maintenance and in the fuel, that the major part uses aviation gasoline AvGas as fuel. Ethanol comes with a great chance to reduces such costs, due to the price of this fuel is only around 25% of AvGas. The aeronautical engines that flies nowadays with ethanol as fuel are a conversions from AvGas engines, wich generates some problems, the main is consumption increasing. The possibility to reduces operational costs with using a fuel from renewable source and challenge to get an aeronautical engine dedicated to run with ethanol as fuel is what motivates and derecting this research. Development process of a technical system, as an ethanol engine, is complex and requires human and material resources administration, information colect, research and a strenght management of whole development process. Methodology for this work development is based on exploratory research of existing bibliography about development product process, technical systems, aeronautical engines, agricultural aviation and homologation standards for aeronautical engines and your parts and components. Information acquired are presented to provide a data base to meet the need of companies, engineers and designers on a future development. After organization and threatment the data supply the base of influence factors for a project of aeronautical ethanol engine for agricultural airplane. The knowledge about brasilian agricultural airplane fleet and engines used on such airplanes provide detailed information about size and capacity of each airplane and their aplications, including information about their technical and operating characteristics. With this, was able to make entire influence factors for a project of aeronautical ethanol engine for agricultural airplane, such influence factors are divided in four groups that is: Project Scope, Benchmarking, Operating Characteristics and Standards & Homologation. Technical data and information of aeronautical engines and their characteristics was evaluated and compared to observ the tendency of engines with power in a range beetween 151 and 300kW, where more than 80% of those engines in whole brasilian fleet is inside of this range, the major part using AvGas as fuel. Engines running with ethanol generates more power if compared the same engine running with AvGas, for other side, there is a consumption increasing, aorund 40% more and the emissions are decreased, what is a positive point with ethanol use as fuel. / No Brasil, hoje, há uma frota aproximada de 1500 aeronaves agrícolas efetuando operações diversas. A aplicação aérea de defensivos nas culturas agrícolas tem sido crescente nos últimos anos, gerando uma necessidade maior de aeronaves, pilotos agrícolas, peças de reposição e combustível, bem como, e principal quesito, a necessidade de redução dos custos operacionais. É neste ponto que este trabalho entra como gerador de conhecimento apresentando dados e resultados para a obtenção, no futuro, de um motor projetado para o uso de etanol equipar aeronaves de aplicação agrícola.Os custos operacionais das aeronaves agrícolas está baseado na manutenção e no combustível que ela utiliza, na grande maioria é a AvGas gasolina de aviação. O etanol vem com grande chance de reduzir significativamente estes custos, pois seu preço é inferior ao da AvGas, podendo chegar apenas 25% do preço desta. Os motores de aeronaves que voam atualmente com etanol são conversões, o que gera alguns problemas, dentre eles o mais significativo que é o aumento de consumo de combustível. A possibilidade de redução dos custos operacionais com a utilização de combustível produzido de fonte renovável e o desafio de se ter um motor projetado especificamente para o uso de etanol como combustível é o que motiva o estudo e direciona a pesquisa. O processo de desenvolvimento do projeto de sistema técnico, como o de um motor a etanol, é complexo e exige administração dos recursos humanos e materiais, coleta de informações, pesquisa e um rígido gerenciamento de todo o processo para tal desenvolvimento. A metodologia para desenvolvimento do estudo está baseada na pesquisa exploratória de bibliografia existente acerca de desenvolvimento de produtos e sistemas técnicos, motores aeronáuticos, aviação agrícola e normas para homologação de produtos e peças aeronáuticas para aplicação em aeronaves agrícolas. As informações obtidas estão apresentadas de maneira a fornecer uma base de dados capaz de suprir a necessidade de empresas, engenheiros e projetistas num desenvolvimento futuro. Os dados compilados e organizados formam a base para a apresentação dos fatores de influência no projeto de um motor a etanol para aplicação em aeronaves agrícolas. O conhecimento sobre a frota brasileira de aeronaves e os motores utilizados fornecem informações detalhadas sobre o tamanho e capacidade de cada aeronave e suas aplicações, bem como os motores necessários em cada uma destas aeronaves e suas características técnicas e operacionais. Obtêve-se a elaboração completa de todos os fatores de influência para o projeto de um motor aeronáutico a etanol direcionado para aplicação agrícola, tais fatores de influência estão subdivididos em quatro grupos que são: Escopo do projeto, análise comparativa dos motores, características da operação e normas e homologação. Informações e dados técnicos de motores e suas características foram avaliadas e comparadas entre si, de maneira a observar a tandência de utilização de motores na faixa de 151 à 300kW, onde mais de 80% dos motores empregados estão dentro desta faixa e na grande maioria consumindo AvGas. Motores a etanol geram maior potência em detrimento de aumento de consumo, da ordem de 40%, porém, as emissões de gases tóxicos são reduzidas, o que é fator positivo no uso do etanol como combustível.