Cette thèse présente la conception, la fabrication et l'étude analytique d'un nouveau concept basé sur la barre de Hiller pour réaliser la commande du rotor sans plateau cyclique. Les pales sont couplées à des palettes. Un aileron, commandé par des actionneurs piezo-électriques, est situé derrière le bord de fuite de chaque palette. L'aileron est incliné par l'actionneur, et génère ainsi une portance. Le moment en pas de la palette change ainsi que le pas, la portance et le battement de la palette. L'angle de battement de la palette et l'angle de pas de la pale étant couplés, ce dernier varie. Chaque ensemble {pale palette aileron} est indépendant d'un autre. La palette peut donc générer du pas collectif et cyclique en entrée de la pale. Comparé aux rotors conventionnels, un tel système présente divers avantages tels la réduction de la complexité mécanique, de la traînée et du poids. La consommation en fuel de l'hélicoptère devrait donc décroître fortement et la disponibilité de l'aéronef augmenter. Un hélicoptère de modélisme a été piloté en milieu extérieur et sert à valider le concept de couplage. Le système a pu maintenir un vol stationnaire stable malgré la présence de vent. Une analyse comprenant la dynamique de l'aileron et quatre degrés de liberté est développée pour évaluer le comportement dynamique et apprécier la faisabilité d'un tel concept de rotor sans plateau cyclique. L'analyse est utilisée pour investiguer l'effet des paramètres du système sur l'influence que la palette et l'aileron peuvent exercer sur la pale. Des tests en stationnaire ont été réalisés sur un banc rotor principal qui représente un environnement plus maîtrisé. Le but de ces tests est de valider l'étude théorique et d'évaluer l'effet de différentes variables de conception sur la réponse en pas de la pale. Pour ce faire, le système est équipé de capteurs. Dans le cas des essais en vol comme au banc rotor principal, la commande en pas de la palette est réalisée par de petits plateaux cycliques assurant une conception rapide, simple et peu coûteuse. Le reste du système est inchangé. Pour une palette d'envergure égale à 40% du rayon de la pale, avec un pas cyclique de g o, un angle de pas cyclique de pale de 5° a été obtenu.

<p><p>This paper is the result of a master thesis project on helicopter rotor downwash effects using computational fluid dynamics (CFD). The work was performed at the department of Aerodynamics and Flight Mechanics at Saab AB, Linköping in 2008. It completes the author’s studies for a M.Sc degree in Applied Physics and Electrical Engineering at the Department of Electrical Engineering at the Linköping institute of technology (LiTH), Linköping, Sweden.</p><p> </p><p>The aim of the project was to study the rotor downwash effects and its influence on the helicopter fuselage. To fulfil this purpose, several CFD calculations were carried out and the aerodynamic forces and moments resulting from the calculations were implemented in an existing simulation model, developed in-house at Saab. The original (existing) model was compared to the updated model by studying step responses in MATLAB, Simulink. For some step commands, the comparisions indicated that the updated model was more damped in yaw compared to the original model for the hovering helicopter. When the helicopter was trimmed for a steady turn, the states in the updated model diverged much faster than the states in the original model for any given step command.</p><p> </p><p> </p><p>In order to investigate the differences between the original helicopter model and the updated model from a controlling perspective, a linear quadratic (LQ) state feedback controller was synthesized to stabilize the vehicle in a steady turn. The LQ method was chosen as it is a modern design technique with good robustness and sensitivity properties and since it is easily implemented in MATLAB.  Before synthesising, a simplification of the helicopter model was made by reducing states and splitting them into lateral and longitudinal ones. Step responses from simulations with the original and the updated model were studied, showing an almost identical behavior.</p><p> </p><p>It can be concluded that the aerodynamic coefficients obtained from the CFD calculations can be used for determining the aerodynamic characteristics of the helicopter. Some further validation is needed though, for example by comparing the results with flight test data. In order to build an aerodynamic data base that covers the whole flight envelop, additional CFD calculations are required.</p><p> </p></p>

<p>Major part of the current work describes the development of the update methodology for onedimensional code (TML) currently used at Volvo Aero Corporation during turbine design process. The methodology is then applied and tried out in a general engine analysis (GESTPAN).</p>

Depuis ses débuts, la conception des convertisseurs électromécaniques se limitait à l'optimisation, par l'électrotechnicien, de la conversion d'énergie électrique en énergie mécanique. Cette énergie, alors fournie sous la forme quasi exclusive d'un mouvement à un seul degré de liberté, le plus souvent rotatif, devait ensuite être adaptée, par les mécaniciens, aux besoins du système à actionner. Aujourd'hui, grâce aux évolutions récentes dans des domaines aussi variés que l'électronique de puissance, l'informatique ou encore la conception et la fabrication assistées par ordinateur, il est devenu possible de concevoir de nouveaux actionneurs directement en fonction des besoins des applications auxquelles ils sont destinés. Ainsi, des actionneurs pouvant posséder plusieurs degrés de liberté, tant en rotation qu'en translation, ont été développés. Dans ce contexte, cette thèse poursuit deux objectifs. Le premier est de proposer une démarche de conception intégrant au mieux les aspects électriques et mécaniques de systèmes électromécaniques tels que ces nouveaux actionneurs. Plus largement, elle a pour vocation de s'appliquer à tous types de problèmes multidisciplinaires où la prise en compte des différentes disciplines et de leurs interactions est indispensable pour assurer les performances globales du produit final. Plus particulièrement, elle est adaptée aux cas de recherches qui, contrairement aux cas de développements, font parfois intervenir des concepts mal maîtrisés. Le second objectif est d'appliquer cette démarche à la conception d'un actionneur électrique dont le rotor, de forme sphérique, est actionné avec un débattement illimité selon deux des trois degrés de liberté qu'il possède en rotation. Suivant les différentes étapes constituant cette démarche, divers concepts de solution sont d'abord générés, tant pour les aspects électriques d'actionnement que pour les aspects mécaniques de guidage. Ces concepts sont ensuite caractérisés, via une série de modélisations et d'expérimentations, avant d'être combinés en vue de produire une solution globale, dimensionnée, fabriquée et validée sur un banc d'essai. / From the outset, the design of electromechanical converters was limited to the optimization, by electrical engineers, of the conversion of electrical energy to mechanical energy. The latter was at that time nearly exclusively provided under the form of single degree of freedom motion, more often rotary, and had to be adapted, by mechanical engineers, to the needs of the system to be actuated. Today, thanks to recent evolutions in fields as various as power electronics, computer capabilities or computer-aided design and manufacturing (CAD-CAM), it has become possible to design new actuators by taking directly into account the needs of the applications they are intended for. As a result, actuators with several degrees of freedom, both in rotation and in translation, have been developed. Within this context, this thesis pursues two objectives. The first consists in proposing a new design method integrating as best as possible the electrical and mechanical aspects of electromechanical systems such as these new actuators. More broadly, its vocation is to be applicable to all multidisciplinary problems where taking into account each discipline and their interactions are necessary to ensure the global performances of the final product. More particularly, this method is adapted to the case of researches that, contrary to the case of other developments, sometimes includes badly mastered concepts. The second aim is to apply this approach to the design of an electrical motor with a spherical rotor actuated, with an unlimited angular range, along two of the three degrees of freedom it possesses in rotation. Following the basic steps involved in this approach, various solution concepts were first generated both for the electrical actuation aspects and the mechanical guiding aspects. These concepts were then characterized, via a number of modeling and experimentation phases, before being combined in order to obtain a global solution, which was then sized, manufactured and validated on a test bench.

The thesis deals with finite element method simulations of the two-degree of freedom spherical induction actuator performed using the 2D and 3D models. In some cases non-linear magnetization curves, rotor movement and existence of higher harmonics are taken into account. The evolution of the model leading to its simplification is presented. Several rotor structures are tested, namely the one-layer, two-layers and two-layers-with-teeth rotor. The study of some rotor parameters, i.e. teeth number and size, external and internal layer thickness, in order to improve the actuator electromechanical conversion and reduce the torque ripple is performed. The influence of the rotor teeth geometrical form on the electromechanical conversion is shown. General actuator parameters such as the airgap, source current and parameters of the magnetic material are verified as well. Finally the superiority of the two-layers-with-teeth rotor structure over the one-layer and two-layers structures is confirmed.

This thesis presents numerical predictions for the leakage and direct stiffness coefficients of pocket damper seals. Modifications made to earlier flow-prediction models are discussed. Leakage and static pressure measurements on straight-through and diverging configurations of eight-bladed and twelve-bladed seals were used for code validation and for calculation of seal discharge coefficients. Higher than expected leakage rates were measured in the case of the twelve-bladed seal, while the leakage rates for the eight-bladed seals were predicted reasonably accurately. Results are presented for shake tests conducted on the seals at pressures of up to 1000 Psi (6.90 MPa). Test variables included pressure drop across the seals and rotor speed. The experimentally obtained stiffness coefficients are compared to results of a rotordynamic damper seal code, which uses the corrected mass flow-rate calculation method. Results show that the code under-predicts the magnitude of the seal's stiffness for most test cases. However, general trends in the frequency dependency of the direct stiffness are more accurately predicted. The expectation of high values of negative stiffness in diverging seals is confirmed by the results, but the frequency at which the sign of the stiffness becomes positive is considerably lower than is predicted. In addition to presenting high-pressure test data, this thesis also attempts to provide some insight into how seal parameters can be modified to obtain desired changes in seal stiffness.

In this thesis, a novel approach is presented for blade loss simulation of an aircraft gas turbine rotor mounted on rolling element bearings with squeeze film dampers, seal rub and enclosed in a flexible housing. The modal truncation augmentation (MTA) method provides an efficient tool for modeling this large order system with localized nonlinearities in the ball bearings. The gas turbine engine, which is composed of the power turbine and gas generator rotors, is modeled with 38 lumped masses. A nonlinear angular contact bearing model is employed, which has ball and race degrees of freedom and uses a modified Hertzian contact force between the races and balls and for the seal rub. This combines a dry contact force and viscous damping force. A flexible housing with seal rub is also included whose modal description is imported from ANSYS. Prediction of the maximum contact load and the corresponding stress on an elliptical contact area between the races and balls is made during the blade loss simulations. A finite-element based squeeze film damper (SFD), which determines the pressure profile of the oil film and calculates damper forces for any type of whirl orbit is utilized in the simulation. The new approach is shown to provide efficient and accurate predictions of whirl amplitudes, maximum contact load and stress in the bearings, transmissibility, thermal growths, maximum and minimum damper pressures and the amount of unbalanced force for incipient oil film cavitation. It requires about 4 times less computational time than the traditional approaches and has an error of less than 5 %.

The thesis is focussed on low consistency (LC) refining of mechanical pulp. Theresearch included evaluations of energy efficiency, development of pulpproperties, the influence of fibre concentration on LC refining and effects of rotorposition in a two-zoned LC refiner. Trials were made in mill scale in a modern TMP line equipped with an MSDImpressafiner for chip pre-treatment, double disc (DD) first stage refining and aprototype 72-inch TwinFlo LC refiner in the second stage. Tensile index increasedby 8 Nm/g and fibre length was reduced by 10 % in LC refining at 140 kWh/adtgross specific refining energy and specific edge load 1.0 J/m. Specific lightscattering coefficient did not develop significantly over the LC refiner. The above mentioned TMP line was compared with a two stage single disc highconsistency Twin 60 refiner line. The purpose was to evaluate specific energyconsumption and pulp properties. The two different process solutions were testedin mill scale, running similar Norway spruce wood supply. At the same tensileindex and freeness, the specific energy consumption was 400 kWh/adt lower in theDD-LC concept compared with the SD-SD system. Pulp characteristics of the tworefining concepts were compared at tensile index 47 Nm/g. Fibre length was lowerafter DD-LC refining than after SD-SD refining. Specific light scattering coefficientwas higher and shive content much lower for DD-LC pulp. The effects of sulphite chip pre-treatment on second stage LC refining were alsoevaluated. No apparent differences in fibre properties after LC refining werenoticed between treated and untreated pulps. Sulphite chip pre-treatment iniiicombination with LC refining in second stage, yielded a pulp without screeningand reject refining with tensile index and shives content that were similar to nonpre-treated final pulp after screening and reject refining. A pilot scale study was performed to investigate the influence of fibreconcentration on pulp properties in LC refining of mechanical pulps. MarketCTMP was utilised in all trials and fibre concentrations were controlled by meansof adjustments of the pulp consistency and by screen fractionation of the pulp. Inaddition, various refiner parameters were studied, such as no-load, gap and baredge length. Pulp with the highest fibre concentration supported a larger refinergap than pulp with low fibre concentration at a given gross power input. Fibreshortening was lower and tensile index increase was higher for long fibre enrichedpulp. The results from this study support the interesting concept of combiningmain line LC refining and screening, where screen reject is recycled to the LCrefiner inlet. It has been observed that the rotor in two-zoned refiners is not always centred,even though pulp flow rate is equal in both refining zones. This leads to unequalplate gaps, which renders unevenly refined pulp. Trials were performed in millscale, using the 72-inch TwinFlo, to investigate differences in pulp properties androtor positions by means of altering the pressure difference between the refiningzones. In order to produce homogenous pulp, it was found that uneven plate gapscan be compensated for in LC refiners with dual refining zones. Results from thedifferent flow rate adjustments indicated that the control setting with similar plategap gave the most homogenous pulp.

The heat dissipation and thermal performance of ventilated brake discs strongly depends on the aerodynamic characteristics of the air flow through the rotor passages. In this thesis, the thermal convection is analyzed using an analytical method, and the velocity distribution, temperature contours and Nusselt number are determined. Then numerical models for different rotors, pillar post rotors and vane rotors are generated and numerical simulations are conducted to determine the desired parameters. To analyze more realistic vane and pillar post rotor models, commercial CFD software packages, Fluent and Gambit, are used to simulate the heat flux rate, air flow rate, velocity distributions, temperature contours, and pressure distributions inside the rotors. Furthermore, sensitivity studies have been performed, to determine the effects of a different number of vanes or pillar posts, inner and outer radii and various angles of vanes. To automate the tedious and repetitive design process of the disc rotor, a design synthesis framework, iSIGHT, is used to integrate the geometrical modeling using GAMBIT and numerical simulations based on FLUENT. Through this integrated design synthesis process, the disc rotor geometrical optimization is performed using design of experiment studies. / UOIT

This paper is the result of a master thesis project on helicopter rotor downwash effects using computational fluid dynamics (CFD). The work was performed at the department of Aerodynamics and Flight Mechanics at Saab AB, Linköping in 2008. It completes the author’s studies for a M.Sc degree in Applied Physics and Electrical Engineering at the Department of Electrical Engineering at the Linköping institute of technology (LiTH), Linköping, Sweden.   The aim of the project was to study the rotor downwash effects and its influence on the helicopter fuselage. To fulfil this purpose, several CFD calculations were carried out and the aerodynamic forces and moments resulting from the calculations were implemented in an existing simulation model, developed in-house at Saab. The original (existing) model was compared to the updated model by studying step responses in MATLAB, Simulink. For some step commands, the comparisions indicated that the updated model was more damped in yaw compared to the original model for the hovering helicopter. When the helicopter was trimmed for a steady turn, the states in the updated model diverged much faster than the states in the original model for any given step command.     In order to investigate the differences between the original helicopter model and the updated model from a controlling perspective, a linear quadratic (LQ) state feedback controller was synthesized to stabilize the vehicle in a steady turn. The LQ method was chosen as it is a modern design technique with good robustness and sensitivity properties and since it is easily implemented in MATLAB.  Before synthesising, a simplification of the helicopter model was made by reducing states and splitting them into lateral and longitudinal ones. Step responses from simulations with the original and the updated model were studied, showing an almost identical behavior.   It can be concluded that the aerodynamic coefficients obtained from the CFD calculations can be used for determining the aerodynamic characteristics of the helicopter. Some further validation is needed though, for example by comparing the results with flight test data. In order to build an aerodynamic data base that covers the whole flight envelop, additional CFD calculations are required.