Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 182-190). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 144-152).

Thesis (M.S.)--Rochester Institute of Technology, 2004. / Typescript. Includes bibliographical references (leaves 65-66).

Les turbines à gaz modernes deviennent de plus en plus compactes, ce qui augmente les interactions entre leurs différents composants. Les interactions chambre de combustion-turbine sont particulièrement critiques car elles peuvent changer le champ aérothermique dans la turbine et réduire la durée de vie du moteur. Aujourd’hui, ces deux composants sont traités de façon indépendante, ce qui ne permet pas de prendre en compte leurs interactions. Cette thèse propose une approche couplée, basée sur les Simulations aux Grandes Échelles (SGE), une technique qui permet de prendre en compte toutes les interactions chambre de combustion-turbine. Dans la première partie de cette thèse, une méthode, compatible avec le code SGE AVBP, est proposée pour traiter les configurations rotor/stator de manière rigoureuse. Une série de cas test académiques vient prouver que l’interface respecte les propriétés des schémas numériques du code. Cette étude est suivie par une validation de l’approche dans le cas d'une turbine haute-pression mono-étage. Les résultats sont comparés avec des mesures expérimentales et l’influence des différents paramètres et modèles est établi. La deuxième partie de cette travail est dédiée à la prédiction des interactions chambre de combustion-turbine en utilisant les méthodes précédemment décrites et validées. Le premier type d’interaction étudié est la génération du bruit de combustion indirect dans une turbine haute pression. Ce bruit est créé lorsque des hétérogénéités de température, générées dans la chambre de combustion, sont accélérées dans la turbine. Pour simplifier les calculs, les hétérogénéités sont modélisées par des fluctuations de température sinusoïdales, injectées dans la turbine par les conditions limites. Les mécanismes de génération de bruit sont mis en évidence et le bruit de combustion indirect est mesuré et comparé avec une théorie analytique et des prédictions 2D. La deuxième application est un calcul couplé chambre de combustion-turbine qui analyse les interactions entre ces deux composants d’un point de vue aérothermique. Les caractéristiques instationnaires de l’écoulement à l’entrée de la turbine et la migration des hétérogénéités de température dans la turbine sont étudiées. Un calcul de la turbine seule est aussi effectué pour comparaison avec le calcul couplé. / Modern gas turbines are characterized by compact designs that enhance the interactions between its different components. Combustion chamber-turbine interactions, in particular, are critical as they may alter the aerothermal flow field of the turbine which can drastically impact the engine life duration. Current state-of-the-art treats these two components in a decoupled way and does not take into account their interactions. This dissertation proposes a coupled approach based on the high-fidelity Large Eddy Simulation (LES) formalism that can take into account all the potential paths of interactions between components. In the first part of this work, an overset grid method is proposed to treat rotor/stator configurations in a rigorous fashion that is compatible with the LES solver AVBP. This interface treatment is shown not to impact the characteristics of the numerical schemes on a series of academic test cases of varying complexity. The approach is then validated on a realistic high-pressure turbine stage. The results are compared against experimental measurements and the influence of different modeling and simulation parameters is evaluated. The second part of this work is dedicated to the prediction of combustion chamber-turbine interactions using the developed methodologies. The first type of interactions evaluated is the indirect combustion noise generation across a high-pressure turbine stage. This noise arises when combustor-generated temperature heterogeneities are accelerated in the turbine. To simplify the simulations the heterogeneities are modeled by sinusoidal temperature fluctuations injected in the turbine through the boundary conditions. The noise generation mechanisms are revealed by such LES and the indirect combustion noise is measured and compared to an analytical theory and 2D predictions. The second application is a fully-coupled combustor-turbine simulation that investigates the interactions between the two components from an aerothermal point of view. The rich flow characteristics at the turbine inlet, issued by the unsteady combustion in the chamber, are analyzed along with the migration of the temperature heterogeneities. A standalone turbine simulation serves as a benchmark to compare the impact of the fully coupled approach.

Récemment, les sources d’énergie renouvelables telles que l’énergie éolienne et solaire, sont devenues des éléments essentiels des réseaux électriques en tant qu’alternatives d’énergie propre aux combustibles fossiles. Cependant, la qualité de la production de telles ressources énergétiques dépend de différents facteurs incertains, tels que les conditions météorologiques. Par conséquent, la gestion intermittente des sources d’énergie renouvelables est l’un des principaux défis à relever pour une utilisation à plus grande échelle.Une solution possible pour réduire les effets de l'intermittence des ressources énergétiques sur la production d'énergie et la stabilité du réseau consiste à utiliser les technologies de stockage d'énergie. Les stations de transfert d’énergie par pompage (STEP) semblent être la méthode de stockage propre unique qui peut être utilisée pour lutter contre la nature intermittente de l’énergie éolienne et solaire. Les STEP utilisent des pompes-turbines réversibles pouvant fonctionner comme des pompes pour stocker l'excès d'énergie électrique dans le réseau et comme des turbines pour générer de l'énergie électrique, lorsque davantage d'énergie électrique est nécessaire. Ainsi, les STEP aident à stabiliser le réseau en présence de ressources en énergies renouvelables intermittentes.Ce travail met l’accent sur les conditions de fonctionnement de la turbine pour le démarrage des STEP. Dans les STEP, la condition de fonctionnement de démarrage est généralement visitée plusieurs fois, à la suite d'un basculement entre les modes de pompage et de turbine. Ainsi, l'amélioration des performances des régulateurs de vitesse utilisés pour le démarrage devient plus importante lorsque l'on traite avec des STEP afin de permettre une récupération rapide de la tension.Cette thèse s'inscrit dans le cadre du projet pluridisciplinaire INNOVHYDRO, qui regroupe différents laboratoires et entreprises tels que, GIPSA-lab où cette thèse a été préparée, G2Elab, GE et EDF.Dans cette thèse, une architecture de contrôleur prenant en compte les limitations informatiques des microcontrôleurs existants utilisés chez GE est proposée. Elle apporte une solution au problème du démarrage rapide de la turbine tout en évitant l'excitation de fortes oscillations de pression. De plus, les contraintes de couple s'intègrent facilement pour permettre un démarrage en douceur, ce qui réduit la fatigue des composants mécaniques, résultant du démarrage répétitif des turbines.Des solutions sont proposées pour ajuster les gains du contrôleur, tout en tenant compte de la dynamique non linéaire de l'actionneur utilisé chez GE. Pour commencer, une méthodologie de réglage est décrite pour garantir la stabilité asymptotique et les performances en boucle fermée, tout en minimisant la limite supérieure de l'erreur de suivi en sortie. De plus, une approche d'optimisation systématique est développée pour sélectionner les gains du contrôleur afin de minimiser le temps nécessaire pour obtenir une connexion stable au réseau, tout en respectant les contraintes de couple maximales. De plus, des algorithmes sont utilisés pour choisir les paramètres du contrôleur de sorte que des certificats de robustesse soient obtenus sur le contrôleur résultant.De plus, un simulateur a été développé pour les centrales hydrauliques et utilisé pour tester le contrôleur proposé. Le simulateur est constitué d’un système d’équations différentielles continues qui modélisent systématiquement le comportement des différents composants de la centrale hydraulique, tels que les conduites forcées, les tunnels, les réservoirs et les cheminées d’équilibre. De plus, le comportement non linéaire et les caractéristiques en S des régions instables des turbines hydrauliques, généralement modélisées par des diagrammes de Hill, sont pris en compte avec succès. De plus, la dynamique non linéaire de l'actionneur est incluse dans le modèle mathématique complet. / Recently, renewable energy resources such as, wind and solar energy, have become integral parts of electric grids as clean energy alternatives to fossil fuels. However, the quality of production of such resources of energy depends on different uncertain factors, for instance, weather conditions. Therefore, dealing with the intermittent nature of renewable energy resources is one of the main challenges when using them on a larger scale.A possible solution to reduce the effects of energy resources intermittency on energy production and grid's stability, is to use energy storage technologies. Pumped storage power plants (PSPs) seem to be the unique clean storage method that can be used to counteract the intermittent nature of wind and solar energy. PSPs make use of pumps-turbines which are capable of working as pumps to store excess electric energy in the grid, and as turbines to generate electric energy, when more electric energy is needed. Thus, PSPs help in stabilizing the grid in the presence of intermittent renewable energy resources.The emphasis in this work is on turbine start-up operating mode for PSPs. In PSPs, the start-up operating mode is usually visited multiple times, as a result of switching back and forth between pumping and turbine modes. Thus, enhancing the performance of the speed governors used for starting-up becomes more important when dealing with PSPs to enable a rapid voltage recovery.This PhD thesis is part of the multidisciplinary INNOVHYDRO project that includes different laboratories and enterprises such as, GIPSA-lab where this thesis was prepared, G2Elab, GE and EDF.In this thesis, a controller architecture that takes into account the computational limitations of existing microcontrollers in use at GE, is proposed. It provides a solution to the problem of fast turbine start-up, while avoiding the excitation of sharp pressure oscillations. In addition, torque constraints are easily integrated to achieve smoother start-up, which reduces the fatigue of the mechanical components, resulting from repetitive start-up of turbines.Different approaches are proposed to tune the controller gains, while taking into account the nonlinear dynamics of the actuator used at GE. To begin with, a tuning methodology is outlined to guarantee the asymptotic stability and the closed-loop performance, while minimizing the guaranteed upper bound on the output tracking error. In addition, a systematic optimization approach is developed to select the controller gains to minimize time needed to get a stable start-up, while respecting maximum torque constraints. Moreover, randomized algorithms are used to choose the controller parameters such that robustness certificates are obtained on the resulting controller.Furthermore, a simulator has been developed for hydraulic power plants and used to test the proposed controller. The simulator constitutes of a system of continuous differential equations, which systematically model the behavior of the different components of the hydraulic power plant such as, penstocks, tunnels, reservoirs and surge tanks. In addition, the nonlinear behavior and unstable regions 'S-characteristics' of hydraulic turbines, usually modeled by Hill charts, are successfully taken into consideration. Moreover, the actuator's nonlinear dynamics are included in the overall mathematical model.

Thesis (M. Sc. ( Physics)) -- University of Limpopo, 2020 / In this work, we present first-principles calculation on the structural, thermodynamic, mechanical and electronic stabilities of Fe-Al and FeAl-X (X: Pt, Pd, Ru and Ag) alloys at lower and high temperatures. These systems have recently attracted a lot of attention for both scientific and possible technological application in turbines, Steel-It coating, energy sector, boilers, pipes and automotive parts as a potential replacement of steel due to their excellent resistance to oxidation at high temperatures. However, they suffer limited room temperature ductility and a sharp drop in strength above 873 K. We determined the lattice parameters, heats of formation, elastic constants, bulk to shear moduli, density of states, phonon dispersion curve and X-ray diffraction pattern for binary and ternary system at various concentrations between 0 ≤ x ≤ 10. Furthermore, the lattice expansion, elastic constants, Gibbs free energy, X-ray diffraction pattern and radial distribution function were done on the most stable systems to determine the melting point of FeAl-X ternary systems. A systematic investigation was performed on the stability of the Fe-Al alloys at zero K. We employed CASTEP code to evaluate the thermodynamic, elastic and electronic stability. Virtual crystal approximation was used to determine various atomic concentrations (0 ≤ x ≤ 5) of both Pt and Ru; this allowed more precise predictions on the materials’ behaviour. Further analysis was done on the density of states to describe the behaviour of each phase near the Fermi level; these phases were observed at different percentage compositions. A supercell approach, DMol3 was also used to evaluate these systems at a larger scale (0 ≤ x ≤ 50). VASP and LAMMPS codes were used to determine the stability of these FeAl-X ternary systems at concentrations (0 ≤ x ≤ 10). It was found that the equilibrium lattice parameters of the binary systems are in good agreement to within 2% with the available experimental data. The heats of formation showed that β2 FeAl phase was the most energetically stable system since it displayed the lowest value compared to all other binary systems. This observation accord well with the experimental phase diagram. It was also confirmed from the corresponding electronic DOS behaviour near the Fermi level. Furthermore, the shear modulus (C’) of these Fe-Al binary systems, i.e. FeAl, Fe2Al5, Fe4Al13, Fe5Al8, Fe2Al and FeAl3 were found to be positive fulfilling the condition of stability. The Fe2Al5 system was found to be the second most stable phase, followed by the monoclinic structure Fe4Al13. This observation was confirmed from the total DOS (where the Fermi level falls in the pseudogap, condition of stability). We further employed virtual crystal approximation and supercell approaches to model various atomic compositions at 0 ≤ x ≤1 and 0 ≤ x ≤ 50 for Ag, Pt, Pd and Ru. The heats of formation, density of states and elastic constants were determined to describe the structural, thermodynamic and mechanical stability of these systems. It was found that the addition of Ag, Pt, Pd and Ru enhances the stability at lower atomic percentage composition below 0.5%. Interestingly, the addition of Pt and Ru was found to significantly improve the ductility of the ternary FeAl-X compound for 0.2 and 0.5 at. % compositions. These systems showed that the Fe-sublattice was the preferred doping site with promising improvement in strength on the properties. It was further deduced that Ag and Pd stabilize the FeAl-X system at atomic percentage compositions of 0.5 and 0.7 respectively. Furthermore, a molecular dynamics-based LAMMPS-EAM was employed to model Fe50-XXXAl doped systems with either Ag, Pt or Pd. The lattice site preferences of the dopant were deduced from their energy landscape. More importantly, Ag and Pd doped systems gave comparable transition temperatures to experimental findings of 1273 K and 1073 K, respectively. Their thermodynamic and mechanical stability trends showed promising properties for industrial applications, displaying stability at a high temperature below 1300 K. This was evident for Ag, Pt (0.5 at %) and Pd (0.7 at %) doping as was the most stable systems with respect to Cij, ΔG, and RDF’s which indicated to influence the elastic instability above 1200 K as well as the ductility of these systems. The XRD confirmed that the doped systems preserved the structural symmetry as expected.

A facility for the investigation of stall flutter in aircraft engine compressors and fans was designed. Stall flutter was achieved in the test fan and verified through sonic and photographic methods. The frequency components of the sonic output during flutter were determined using a real-time analyzer. This frequency analysis indicated a dominant peak within 7 percent of the theoretical torsional natural frequency of the blades. Photographs taken during stall flutter indicated the presence of an interblade phase angle. The effect of blade stagger angle, flow incidence angle and solidity on flutter speed was determined. / Master of Science

The aerodynamic and thermodynamic performance of an aircraft gas turbine directly affects the fuel consumption of the engine and the life of the turbine components. Hence, it is important to be able to understand and predict the fluid flow and heat transfer in turbine blades to enable the modifications and improvements in the design process. The use of numerical experiments for the above purposes is becoming increasingly common. The present thesis is involved with the development of a flow solver for turbine flow and heat transfer computations. A 3-D Navier-Stokes code, the Moore Elliptic Flow Program (MEFP) is used to calculate steady flow and heat transfer in turbine rotor cascades. Successful calculations were performed on two different rotor profiles using a one-equation q-L transitional turbulence model. A series of programs was developed for the post-processing of the output from the flow solver. The calculations revealed details of the flow including boundary layer development, trailing edge shocks, flow transition and stagnation and peak heat transfer rates. The calculated pressure distributions, losses, transition ranges, boundary layer parameters and peak heat transfer rates to the blade are compared with the available experimental data. The comparisons indicate that the q-L transitional turbulence model is successful in predicting flows in transonic turbine blade rows. The results also indicate that the calculated loss levels are independent of the gridding used while the heat transfer rate predictions improve with finer grids. / Master of Science

M.S.