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The labyrinth seal is widely used in turbo machines to reduce leakage flow. The stability of the rotor is influenced by the labyrinth seal because of the driving forces generated in the seal. The working fluid usually has a circumferential velocity component before entering the seal; the ratio of circumferential velocity and shaft synchronous surface velocity is defined as pre-swirl rate. It has been observed that pre-swirl rate is an important factor affecting driving forces in the labyrinth seal thus affecting the stability of the rotor. Besides the pre-swirl, the eccentricity, the clearance, and the configuration of tooth locations are all factors affecting the rotordynamic properties of the labyrinth seal. So it is of interest to investigate the exact relationships between those factors and the seal's rotordynamic properties. In this research, three types of labyrinth seals have been modeled: the straight eye seal, the stepped eye seal, and the balance drum seal. For the straight eye seal, a series of models were built to study the influence of eccentricity and clearance. The other two seals each have only one model. All models were built with Solid Works and meshed with ANSYS-ICEM. Flows in those models were simulated by numerically solving the Reynolds-Averaged Navier-Stokes (RANS) equations in the ANSYS-CFX and then rotordynamic coefficients for each seal were calculated based on the numerical results. It had previously been very difficult to generate a pre-swirl rate higher than 60% in a numerical simulation. So three ways to create pre-swirl in ANSYS-CFX were studied and finally the method by specifying the inlet velocity ratio was employed. Numerical methods used in this research were introduced including the frame transfer, the k-ε turbulence model with curvature correction, and the scalable wall function. To obtain the optimal mesh and minimize the discretization error, a systematical grid study was conducted including grid independence studies and discretization error estimations. Some of the results were compared with previous bulk-flow or experimental results to validate the numerical model and method. The fluid field in the labyrinth seal must be analyzed before conducting rotordynamic analysis. The predicted pressure distributions and leakages were compared with bulk-flow results. A second small vortex at the downstream edge of each tooth was found in the straight eye seal. This has never been reported before and the discovery of this small vortex will help to improve seal designs in the future. The detailed flows in discharged region and in chambers were also discussed. Radial and tangential forces on the rotor were solved based on the fluid field results. It is shown that the traditional first-order rotordynamic model works well for low pre-swirl cases but does not accurately reflect the characteristics for high pre-swirl cases. For example compressor eye seals usually have pre-swirl rates bigger than 70% and the second order model is required. Thus a second-order model including inertia terms was built and applied to the rotordynamic analysis in this research. The influence of pre-swirl, eccentricity and clearance were studied using the straight eye seal model. The rotordynamic characteristics of the stepped eye seal and the balance drum seal were studied considering high pre-swirl rates. Some relationships between influencing factors and the four rotordynamic coefficients were concluded. The results also showed that for all the three seals higher pre-swirl leads to higher cross-coupled stiffness which is one of the main factors causing rotor instability. The rotor stability analysis was conducted to study the influence of drum balance seal on the stability. The rotor was designed with typical dimensions and natural frequencies for a centrifugal compressor rotor. The parameters for bearing and aerodynamic force were also set according to general case in compressors to minimize the effects from them. The result shows that the high pre-swirl rate in balance drum seal leads to rotor instability, which confirmed the significant effect of pre-swirl on the seal and the rotor system. / Ph. D.

There is a present need for simulation and measuring the inlet swirl distortion generated by airframe/engine system interactions to identify potential degradation in fan performance and operability in a full-scale, ground testing environment. Efforts are described to address this need by developing and characterizing methods for complex, prescribed distortion patterns. A relevant inlet swirl distortion profile that mimics boundary layer ingesting inlets was generated by a novel new method, dubbed the StreamVane method, and measured in a sub scale tunnel using stereoscopic particle image velocimetry (SPIV) as a precursor for swirl distortion generation and characterization in an operating turbofan research engine. Diagnostic development efforts for the distortion measurements within the research engine paralleled the StreamVane characterization. The system used for research engine PIV measurements is described. Data was obtained in the wake of a total pressure distortion screen for engine conditions at idle and 80% corrected fan speed, and of full-scale StreamVane screen at 50% corrected fan speed. The StreamVane screen was designed to generate a swirl distortion that is representative for hybrid wing body applications and was made of Ultem*9085 using additive manufacturing. Additional improvements to the StreamVane method are also described. Data reduction algorithms are put forth to reduce spurious velocity vectors. Uncertainty estimations specific to the inlet distortion test rig, including bias error due to mechanical vibration, are made. Results indicate that the methods develop may be used to both generate and characterize complex distortion profiles at the aerodynamic interface plane, providing new information about airframe/engine integration. / Master of Science

O presente trabalho buscou estudar experimentalmente os efeitos do deslocamento da posição final dos dutos de admissão de um cabeçote no número de swirl e as possíveis consequências nos parâmetros de desempenho do motor diesel (torque, emissão de poluentes e consumo de combustível). Foram construídos protótipos de cabeçotes divididos em quatro grupos de deslocamentos com diferentes direções e sentidos. O valor nominal desses deslocamentos foi de 1 mm. Em seguida os cabeçotes passaram por medição de geometria para verificação da posição real dos dutos de admissão; posteriormente os cabeçotes foram ensaiados em uma máquina de medição do número de swirl. A partir dos dados de posição dos dutos de admissão e do número de swirl de cada cabeçote, foi feita uma regressão linear múltipla para se obter uma equação que correlaciona o número de swirl com os deslocamentos em X e Y dos dois dutos de admissão. Na última parte do trabalho, os cabeçotes de cada grupo de deslocamento foram montados sucessivamente em um motor diesel instalado em dinamômetro para medição dos seus parâmetros de desempenho, a saber: curva de torque; consumo específico e emissão de poluentes. / This work aimed to study experimentally the effects of intake ports displacement of a cylinder head in its swirl number and the possible consequences in the diesel engine performance parameters (torque, emissions and fuel consumption). Cylinder head prototypes were divided into four groups with different displacement directions. The nominal value of these displacements was 1 mm. The cylinder heads were measured to check the real position of their intake ports; then the cylinder heads were tested in a machine to measure the swirl number. From the intake ports position data and swirl number of each cylinder head, a multiple linear regression was performed to obtain an equation that correlates the swirl number with intake ports displacement in X and Y directions. As last step of this work, the cylinder heads of each displacement group were mounted in a diesel engine installed on a dynamometer to measure its performance parameters: torque curve; specific fuel consumption and emissions.

Este estudo pretende avaliar, através de simulações em Computational Fluid Dynamics (CFD), o comportamento do ar frio no interior da câmara de combustão com foco no movimento denominado Swirl. Testes computacionais no cabeçote de um motor de ignição por compressão foram realizados nos quais deslocamentos hipotéticos dos dutos de admissão foram impostos. Posteriormente foram realizadas análises na alteração do número de Swirl e comparados com o comportamento padrão esperado pelo cabeçote. Os resultados indicaram que o Swirl é sensivelmente alterado dependendo do sentido de deslocamento bem como que deslocamentos no eixo cartesiano x são mais impactantes do que deslocamentos no eixo y. Observou-se também, que diferenças expressivas no comportamento do ar ocorrem após a abertura de 73,33% da válvula de admissão. Nas conclusões são apresentados os efeitos causados pelo deslocamento dos dutos de admissão, pontos fortes e fracos deste trabalho e uma breve lista de possíveis desdobramentos desse estudo. / This research evaluates, by Computational Fluid Dynamics (CFD) simulation, the cold air behaviour inside the combustion chamber with focus on a movement named Swirl. Virtual tests were performed on an ignition compression engine overhead where hypothetical shifts on the air intake ducts were imposed. After that analysis were done in the Swirl changes and compared with expected pattern. The results indicated that Swirl is significantly changed depending on the direction of displacement as well as displacements on Cartesian axle x are more expressive than displacements on axle y. It was also observed more expressive changes in air behaviour after valve lifting of 73,33%. In the conclusions are presented the effects caused by displacement on the air intake ducts, strengths and weakness of this research and a list of possible research deployment.

Les travaux présentés dans cette thèse s'inscrivent dans le cadre de la chaire OXYTEC qui regroupe l'entreprise Air Liquide, CentraleSupélec et le CNRS. Ce travail bénéficie également de l'appui de l'ANR. Ce manuscrit fait état des premiers développements et résultats sur le plan expérimental. Un dispositif complet a été développé au laboratoire EM2C pour étudier l'oxy-combustion de flammes stabilisées sur un injecteur tourbillonneur jusqu'à des pressions de 30 bar. Les résultats présentés dans cette thèse ont traits à des prémélanges dont le combustible est du méthane lorsque le foyer opère à pression atmosphérique. Les techniques de LIF-OH, la PIV, la LDV complétées par des mesures de chimiluminescence et de température sont utilisées (1) pour accumuler des données sur la structure de trois flammes de référence CH4/air, CH4/O2/N2 et CH4/O2/CO2 qui sont utilisées pour valider des outils de simulation de la combustion et des transferts thermiques, (2) élucider les mécanismes de stabilisation des oxy-flammes swirlés pré-mélangées à partir d'études paramétriques sur le nombre de swirl, la vitesse débitante, la vitesse laminaire de flamme et l'angle de l'ouvreau de l'injecteur, et (3) comparer la structure des oxy-flammes diluées au CO2 avec des flammes CH4/air en examinant notamment la position de pied de flamme, la topologie générale de la flamme et les températures des parois du foyer. / The work presented in this thesis falls within the framework of the OXYTEC chair, a partnership between Air Liquide, CentraleSupélec and the CNRS. This work also benefits from the support of the ANR. This manuscript reports the first developments and results on the experimental level. A test rig has been developed to study oxy-combustion of swirl-stabilized flames up to pressures of 30 bar. The results presented deal with premixed conditions where the fuel is methaneand the setup is operated at atmospheric pressure. Laser induced fluorescence on the hydroxyl radical, particle imaging velocimetry, Doppler laser velocimetry completed by chemiluminescence imaging and temperature measurements are used to (1) gather data on the structure of three reference flames CH4/air, CH4/O2/N2 and CH4/O2/CO2 which are used to validate simulations of the reacting flow and heat transfer and (2) elucidate the stabilization mechanisms of premixed swirling oxy-flames from parametric studies by varying the swirl number, the bulk injection velocity, the laminar burning velocity and the injector cup angle and (3) compare the structure of CO2 diluted oxy-flames with CH4/air flames by examining the position of the flame leading edge, the general topology of the flame and the temperatures of flow and the combustor walls.

The aerodynamic integration of an aero-engine intake system with the airframe can pose some notable challenges. This is particularly so for many military air- craft and is likely to become a more pressing issue for both new military systems with highly embedded engines as well as for novel civil aircraft configurations. During the late 1960s with the advent of turbo-fan engines, industry became in- creasingly aware of issues which arise due to inlet total pressure distortion. Since then, inlet-engine compatibility assessments have become a key aspect of any new development. In addition to total temperature and total pressure distortions, flow angularity and the associated swirl distortion are also known to be of notable con- cern. The importance of developing a rigorous methodology to understand the effects of swirl distortion on turbo-machinery has also become one of the major concerns of current design programmes. The goal of this doctoral research was to further the current knowledge on swirl distortion, and its adverse effects on engine performance, focusing on the turbo-machinery components (i.e. fans or compressors). This was achieved by looking into appropriate swirl flow descriptors and by correlating them against the compressor performance parameters (e.g loss in stability pressure ratios). To that end, a number of high-fidelity three-dimensional Computational Fluid Dynamics (CFD) models have been developed using two sets of transonic rotors (i.e. NASA Rotor 67 and 37), and a stator (NASA Stator 67B). For the numerical purpose, a boundary condition methodology for the definition of swirl distortion patterns at the inlet has been developed. Various swirl distortion numerical parametric studies have been performed using the modelled rotor configurations. Two types of swirl distortion pattern were investigated in the research, i.e. the pure bulk swirl and the tightly-wound vortex. Numerical simulations suggested that the vortex core location, polarity, size and strength greatly affect the compressor performance. The bulk swirl simula- tions also showed the dependency on swirl strength and polarity. This empha- sized the importance of quantifying these swirl components in the flow distortion descriptors. For this, a methodology have been developed for the inlet-engine compatibility assessment using different types of flow descriptors. A number of correlations have been proposed for the two types of swirl distortion investigated in the study.

O presente trabalho buscou estudar experimentalmente os efeitos do deslocamento da posição final dos dutos de admissão de um cabeçote no número de swirl e as possíveis consequências nos parâmetros de desempenho do motor diesel (torque, emissão de poluentes e consumo de combustível). Foram construídos protótipos de cabeçotes divididos em quatro grupos de deslocamentos com diferentes direções e sentidos. O valor nominal desses deslocamentos foi de 1 mm. Em seguida os cabeçotes passaram por medição de geometria para verificação da posição real dos dutos de admissão; posteriormente os cabeçotes foram ensaiados em uma máquina de medição do número de swirl. A partir dos dados de posição dos dutos de admissão e do número de swirl de cada cabeçote, foi feita uma regressão linear múltipla para se obter uma equação que correlaciona o número de swirl com os deslocamentos em X e Y dos dois dutos de admissão. Na última parte do trabalho, os cabeçotes de cada grupo de deslocamento foram montados sucessivamente em um motor diesel instalado em dinamômetro para medição dos seus parâmetros de desempenho, a saber: curva de torque; consumo específico e emissão de poluentes. / This work aimed to study experimentally the effects of intake ports displacement of a cylinder head in its swirl number and the possible consequences in the diesel engine performance parameters (torque, emissions and fuel consumption). Cylinder head prototypes were divided into four groups with different displacement directions. The nominal value of these displacements was 1 mm. The cylinder heads were measured to check the real position of their intake ports; then the cylinder heads were tested in a machine to measure the swirl number. From the intake ports position data and swirl number of each cylinder head, a multiple linear regression was performed to obtain an equation that correlates the swirl number with intake ports displacement in X and Y directions. As last step of this work, the cylinder heads of each displacement group were mounted in a diesel engine installed on a dynamometer to measure its performance parameters: torque curve; specific fuel consumption and emissions.

Este estudo pretende avaliar, através de simulações em Computational Fluid Dynamics (CFD), o comportamento do ar frio no interior da câmara de combustão com foco no movimento denominado Swirl. Testes computacionais no cabeçote de um motor de ignição por compressão foram realizados nos quais deslocamentos hipotéticos dos dutos de admissão foram impostos. Posteriormente foram realizadas análises na alteração do número de Swirl e comparados com o comportamento padrão esperado pelo cabeçote. Os resultados indicaram que o Swirl é sensivelmente alterado dependendo do sentido de deslocamento bem como que deslocamentos no eixo cartesiano x são mais impactantes do que deslocamentos no eixo y. Observou-se também, que diferenças expressivas no comportamento do ar ocorrem após a abertura de 73,33% da válvula de admissão. Nas conclusões são apresentados os efeitos causados pelo deslocamento dos dutos de admissão, pontos fortes e fracos deste trabalho e uma breve lista de possíveis desdobramentos desse estudo. / This research evaluates, by Computational Fluid Dynamics (CFD) simulation, the cold air behaviour inside the combustion chamber with focus on a movement named Swirl. Virtual tests were performed on an ignition compression engine overhead where hypothetical shifts on the air intake ducts were imposed. After that analysis were done in the Swirl changes and compared with expected pattern. The results indicated that Swirl is significantly changed depending on the direction of displacement as well as displacements on Cartesian axle x are more expressive than displacements on axle y. It was also observed more expressive changes in air behaviour after valve lifting of 73,33%. In the conclusions are presented the effects caused by displacement on the air intake ducts, strengths and weakness of this research and a list of possible research deployment.

The aerodynamic integration of an aero-engine intake system with the airframe can pose some notable challenges. This is particularly so for many military air- craft and is likely to become a more pressing issue for both new military systems with highly embedded engines as well as for novel civil aircraft configurations. During the late 1960s with the advent of turbo-fan engines, industry became in- creasingly aware of issues which arise due to inlet total pressure distortion. Since then, inlet-engine compatibility assessments have become a key aspect of any new development. In addition to total temperature and total pressure distortions, flow angularity and the associated swirl distortion are also known to be of notable con- cern. The importance of developing a rigorous methodology to understand the effects of swirl distortion on turbo-machinery has also become one of the major concerns of current design programmes. The goal of this doctoral research was to further the current knowledge on swirl distortion, and its adverse effects on engine performance, focusing on the turbo-machinery components (i.e. fans or compressors). This was achieved by looking into appropriate swirl flow descriptors and by correlating them against the compressor performance parameters (e.g loss in stability pressure ratios). To that end, a number of high-fidelity three-dimensional Computational Fluid Dynamics (CFD) models have been developed using two sets of transonic rotors (i.e. NASA Rotor 67 and 37), and a stator (NASA Stator 67B). For the numerical purpose, a boundary condition methodology for the definition of swirl distortion patterns at the inlet has been developed. Various swirl distortion numerical parametric studies have been performed using the modelled rotor configurations. Two types of swirl distortion pattern were investigated in the research, i.e. the pure bulk swirl and the tightly-wound vortex. Numerical simulations suggested that the vortex core location, polarity, size and strength greatly affect the compressor performance. The bulk swirl simula- tions also showed the dependency on swirl strength and polarity. This empha- sized the importance of quantifying these swirl components in the flow distortion descriptors. For this, a methodology have been developed for the inlet-engine compatibility assessment using different types of flow descriptors. A number of correlations have been proposed for the two types of swirl distortion investigated in the study.