I dagsläget finns det en mängd olika storlekar på vindkraftverk, allt från små landbaserade vindkraftverk på några hundra kilowatt till havsbaserade kraftverk på upp till 14 MW. Bland de största vindkraftverken ute till havs, är direktdrivna vindkraftverk dominerande på grund av en högre driftssäkerhet och livslängd på komponenterna. En stor nackdel med dessa direktdrivna vindkraftverk är att för att få ut en hög effekt ur en relativt låg rotationshastighet, behöver generatorerna vara väldigt stora och blir då väldigt tunga. Syftet med det här arbetet var att titta närmare på vilka fördelar som potentiellt finns med att halvera vikten på nacellen som innehåller drivlinan och generatorn. De delarna som utreds i den här rapporten är viktens inverkan på vindkraftverkets torn och fundament men även kostnader för att transportera och montera vindkraftverk. Då allting som rör vindkraftverk är väldigt komplext, har en hel del förenklingar fått göras. För det första förenklades vindkraftverks torn till en fast inspänd balk med en punktmassa på toppen, vilket motsvarar massan för nacellen, hubben och bladen. När det kommer till transporter och montering har det inte gått att få fram exakt vad det kostar att transportera och montera en nacell, men utifrån en del data kunde uppskattningar göras för att skapa en bild av vad kostnaderna låg på och vilka kostnadsfördelar som skulle kunna finnas av att minska vikten.För att få bra data på olika vindkraftverk användes data för olika referenskraftverk som finns tillgängliga för forskningssyfte. De som användes var NREL 5 MW, LW 8 MW, DTU 10 MW och IAE 15 MW. Efter beräkningar på dessa vindkraftverk kan det konstateras att en minskning av krafterna som verkar på fundamenten är den stora fördelen men en halverad vikt på nacellen. I de beräkningar som gjordes låg minskningarna på mellan 13 – 17%. När det kommer till viktens inverkan på tornet är det svårare att dra några klara slutsatser. Enligt beräkningarna minskade de maximala tryckspänningarna med ungefär 1.5 – 2.5%, medan dragspänningarna istället ökade med 0.6 – 2.1 %. Tryckspänningarna i tornet var de största och därav minskar de största spänningarna i tornet, men då till exempel vissa vindkraftverks torn är gjorda i betong, som är sämre på att ta upp dragspänningar, kan ökande dragspänningar vara något som vill undvikas. När beräkningar gjordes för egenfrekvenserna på tornet visade de att egenfrekvensen ökar med ungefär 20 % vid en halverad vikt, vilket både kan vara en fördel och en nackdel. När det kommer till kostnader för transporter och montering är det svårt att ge en exakt siffra eller procentsats över hur mycket billigare det blir. Det kan vara allt från några tiotusentals kronor per nacell i vissa delar, upp till miljontals kronor för ett helt projekt i andra delar. / Today there is a large amount of different wind turbines, from small onshore turbines with an effect of only a few kilowatts to huge offshore turbines with an effect of 14 MW. The largest offshore turbines are dominated by turbines with a direct drive drivetrain due to a higher operational reliability and longer life span of the components. A major disadvantage of these direct-drive wind turbines is that in order to have a high power output from a relatively low rotational speed, the generators become very large and heavy.For this project, the purpose is to analyze the potential benefits of lowering the weight of the nacelle, which contains the drivetrain and the generator. The parts discussed in this report are the nacelle’s weight’s impact on the wind turbine’s tower and its foundation and the costs for transporting and assembling wind turbines. Since everything that concerns wind turbines is very complex, a lot of simplifications had to be made. First of all, the wind turbine’s tower was simplified as a cantilever beam with a mass at the top corresponding to the mass of the nacelle, hub and blades. When it comes to transportations and installations, it has not been possible to find out the exact costs to transport and install a nacelle, but based on some data, estimations could be made of what the costs are and what benefits there could be of reducing the weight. To get reliable data on different wind turbines, reference turbines were used. These are turbines used for research and almost all information is accessible online. The reference turbines that were used were the NREL 5 MW, the LW 8 MW, the DTU 10 MW and the IAE 15 MW. After calculations on these wind turbines, it became clear that the forces affecting the foundations are the biggest advantages (regarding forces) with a reduced weight on the nacelle. In the calculations that were made, the forces were reduced by between 13 - 17% if the nacelle weighs 50% less. When it came to the impact of weight of the nacelle had on the tower, it was more difficult to come to any clear conclusions. The calculations shows that the maximum compressive stresses decreased by approximately 1.5 – 2.5% while the tensile stresses increased by 0.6 – 2.1 %. The compressive stresses in the tower were the largest and hence, the largest forces on the tower decrease. But since some wind turbines are made of concrete, which isn’t as good on taking tensile forces, therefor increasing tensile stresses may be undesirable. When analyzing the natural frequencies of the different towers, calculations showed that the natural frequency were raised by approximately 20%.When it comes to costs of transportations and installations, it is difficult to give an exact figure or percentage of how much cheaper it will be. It could range from a couple of thousand US dollars per nacell in some instances, up to a several hundred thousand US dollar for an entire project in other instances.

Modeling the flight conditions of an aircraft that utilizes an airbreathing propulsion system necessitates a method to account for the increase in energy introduced into the flow. Current methods for modeling engines either assign fixed conditions on flat faces on the intake and exhaust through a manual process with the use of external models or attempt to model the flow through the engine within the simulation using complex and computationally expensive geometry and solvers. The method presented attempts to provide an intermediate option to model airbreathing engines through coupling the intake and exhaust boundary conditions with a parametric engine model. This enables the intake conditions within the finite volume simulation to assign the exhaust boundary conditions as the solution iterates, allowing for engines to be dynamically simulated in transient cases and for continuity in the simulation to be better maintained. This method of modeling airbreathing engines could also prove useful in nacelle optimization studies and in modeling aircraft with long engine intakes. The NASA Common Research Model and an axisymmetric nacelle geometry are used to demonstrate the functionality of the developed coupled engine model and its implementation in a finite volume solver.

Due to a trend towards Ultra High Bypass Ratio engines the corresponding engine/airframe interference is becoming a key aspect in aircraft design. The present economic situation increases the pressure on commercial aviation companies to reduce the Direct Operating Cost, and the environmental situation requires a new generation of aircraft with a lower environmental impact. Therefore detailed aerodynamic investigations are required to evaluate the real benefits of new technologies. The presented research activity is part of a long-term project with the main objective of generating a reliable and accurate tool to predict the performance of an aircraft over the whole flight domain. In particular the aim of this research was to perform advanced CFD in order to establish a tool able to evaluate engine installation effects for different configurations and attitudes. The developed tool can be provided with correlations of the Net Propulsive Force (NPF), the force exerted by the power-plant to the aircraft, as a function of position. This can be done in principle at cruise, hold, climb, descent, take-off and landing, to model the different integration effects at different phases. Due to the complexity of the problem it was only possible at an initial stage to determine these correlations at cruise condition. Two parametric test cases were evaluated, showing that the engine horizontal positioning can influence the mission fuel burn by up to 6.4%. According to the extensive literature review that has been done, this study can be regarded as the first open literature engine position-NPF parametric study using CFD. Even though no correlations were extracted for other conditions; a deployed high-lift wing configuration was also studied in detail, defining the main aerodynamics effects of the engine integration at high angle of attack. A topological study of the high-lift installation vortices is presented in this work and it can be considered the first in the open literature. It should be pointed out that extensive research is currently underway to correctly evaluate the high-lift aerodynamic using CFD. The Propulsive System Integration (PSI) in high-lift conditions is adding flow features to an already demanding problem, making it a real challenge for the numerical methods. Nevertheless the additional effects of a nacelle chine on the maximum lift were also evaluated. The main outcomes of this PhD research were: a coupled performance modelling tool able to handle the effects of engine-airframe integration as a function of geometry and attitude, and a topological study of the high-lift installation vortices. During the course of the work, this research was successfully suggested as an extra activity for the European NEWAC project (New Aero Engine Core Concepts), and resulted in a new deliverable for that project.

Due to a trend towards Ultra High Bypass Ratio engines the corresponding engine/airframe interference is becoming a key aspect in aircraft design. The present economic situation increases the pressure on commercial aviation companies to reduce the Direct Operating Cost, and the environmental situation requires a new generation of aircraft with a lower environmental impact. Therefore detailed aerodynamic investigations are required to evaluate the real benefits of new technologies. The presented research activity is part of a long-term project with the main objective of generating a reliable and accurate tool to predict the performance of an aircraft over the whole flight domain. In particular the aim of this research was to perform advanced CFD in order to establish a tool able to evaluate engine installation effects for different configurations and attitudes. The developed tool can be provided with correlations of the Net Propulsive Force (NPF), the force exerted by the power-plant to the aircraft, as a function of position. This can be done in principle at cruise, hold, climb, descent, take-off and landing, to model the different integration effects at different phases. Due to the complexity of the problem it was only possible at an initial stage to determine these correlations at cruise condition. Two parametric test cases were evaluated, showing that the engine horizontal positioning can influence the mission fuel burn by up to 6.4%. According to the extensive literature review that has been done, this study can be regarded as the first open literature engine position-NPF parametric study using CFD. Even though no correlations were extracted for other conditions; a deployed high-lift wing configuration was also studied in detail, defining the main aerodynamics effects of the engine integration at high angle of attack. A topological study of the high-lift installation vortices is presented in this work and it can be considered the first in the open literature. It should be pointed out that extensive research is currently underway to correctly evaluate the high-lift aerodynamic using CFD. The Propulsive System Integration (PSI) in high-lift conditions is adding flow features to an already demanding problem, making it a real challenge for the numerical methods. Nevertheless the additional effects of a nacelle chine on the maximum lift were also evaluated. The main outcomes of this PhD research were: a coupled performance modelling tool able to handle the effects of engine-airframe integration as a function of geometry and attitude, and a topological study of the high-lift installation vortices. During the course of the work, this research was successfully suggested as an extra activity for the European NEWAC project (New Aero Engine Core Concepts), and resulted in a new deliverable for that project.

Les applications de pick-and-place à hautes cadences requièrent des caractéristiques très élevées en terme de performances dynamiques, que seuls les robots parallèles sont capables d'atteindre. Les robots à quatre degrés de liberté proposent le plus de flexibilité, mais l'amplitude de la rotation permettant l'orientation de l'objet est souvent le point faible de ces architectures. Cependant, le concept de nacelle articulée permet de dépasser cet inconvénient. Ainsi, trois nouvelles architectures de robots de pick-and-place à quatre degrés de liberté sont présentées dans ce manuscrit : les architectures Par4, Héli4 et Dual4. Pour chacun des robots présentés, une étude complète est effectuée et un démonstrateur est réalisé afin de valider les concepts et de les évaluer. Une méthode de modélisation dynamique simplifiée appliquée aux robots à nacelle articulée est ensuite présentée. Cette méthode est appliquée au robot Par4 et permet de mettre en avant un déséquilibre des couples moteurs sur ce mécanisme. Il est alors démontré qu'un changement mineur dans la cinématique de la nacelle permet de réduire de 30% les couples mis en jeux lors de trajectoires de prises-déposes. Une nouvelle version "équilibrée" du robot est donc proposée en se fondant sur l'étude dynamique présentée précédemment. Enfin, deux types d'optimisations appliquées aux robots de pick-and-place sont présentés. Tout d'abord, une méthode de recherche des paramètres géométriques dédiée aux robots de pick-and-place est présentée et appliquée au robot Par4. De plus, une génération de trajectoire utilisant les clothoïdes et une loi horaire adaptative est proposée afin d'optimiser les déplacements du robot lors de mouvements de pick-and-place à très hautes accélérations

Strides in modern computational fluid dynamics and leaps in high-power computing have led to unprecedented capabilities for handling large aerodynamic problem. In particular, the emergence of adjoint design methods has been a break-through in the field of aerodynamic shape optimization. It enables expensive, high-dimensional optimization problems to be tackled efficiently using gradient-based methods in CFD; a task that was previously inconceivable. However, adjoint design methods are intended for gradient-based optimization; the curse of dimensionality is still very much alive when it comes to design space exploration, where gradient-free methods cannot be avoided. This research describes a novel approach for reducing dimensionality in large, computationally expensive design problems to a point where gradient-free methods become possible. This is done using an innovative application of Principal Component Analysis (PCA), where the latter is applied to the gradient distribution of the objective function; something that had not been done before. This yields a linear transformation that maps a high-dimensional problem onto an equivalent low-dimensional subspace. None of the original variables are discarded; they are simply linearly combined into a new set of variables that are fewer in number. The method is tested on a range of analytical functions, a two-dimensional staggered airfoil test problem and a three-dimensional Over-Wing Nacelle (OWN) integration problem. In all cases, the method performed as expected and was found to be cost effective, requiring only a relatively small number of samples to achieve large dimensionality reduction.

This diploma thesis is focused on CFD analysis of M-601 turboprop engine nacelle mounted on L-410 commuter aircraft. Calibrating exercise is performed at the beginning of the thesis in order to be more familiar with CFD problems. Next parts of the thesis are chronologically divided with respect to project progress, namely suitable geometrical model creation, mesh creation in order to obtain computational model, calculation using CFD methods, results evaluation and proposal of possible construction transformation at the conclusion.

No description available.