Axial flux induction machines are attractive solutions for electric vehicle applications nowadays. Thanks to their high torque density and no need for rare-earth material for permanent magnets, axial flux induction machines are the most used electric machine type with good performance and low prices. Research on the thermal characteristics of induction machines can benefit the design development of products. Generally, the finite element analysis (FEA) method is used to conduct a fast thermal simulation of machines. However, a significant disadvantage of the FEA method is that the forced convection heat transfer and the fluid motion are challenging to consider. To solve this problem, the thesis work focuses on conducting a computational fluid dynamics (CFD) model to predict the temperature distribution of the AuraGen induction machine and the velocity distribution of the airflow by accurately considering the forced convection heat transfer and the fluid motion in different operation conditions. The thesis work covers the improvement of 3D cad models of the AuraGen induction machines and airflow fields, evaluation of simulation parameters of the CFD simulation models, and the comparison of results between the CFD simulation, FEA simulation, and physically experimental measurements. Finally, the best CFD simulation model can accurately predict the temperature distribution of all components of the induction machine and the airflow in the 3000, 2000, and 1000 rpm conditions. The accuracy satisfies the desired goal which is within 4℃ of the average error and 8℃ of the maximum error. Velocity distributions of the airflow can also show characteristics of the fluid motion from inlets to the outlet. Compared with simulation results of the FEA method, the CFD simulation model has significantly more accurate results when applied for a wide range of operating speeds to predict the temperature distribution in the forced convection heat transfer condition. The good CFD simulation results can help quickly discover design problems in the early stage of the product development process without making repeated prototype constructions and physical tests. The good CFD simulation results are beneficial to reducing the number of necessary prototypes and therefore reducing development costs and time consumed. / Axial Flux Induktionsmaskiner är attraktiva lösningar för elektriska fordonsansökningar nuförtiden. Tack vare sin höga vridmomentäthet och inget behov av sällsynt jordmaterial för permanenta magneter är Axial Flux-induktionsmaskiner den mest använda elektriska maskintypen med bra prestanda och låga priser. Forskning om induktionsmaskinernas värmekarakteristik kan gynna designutvecklingen av produkter. I allmänhet används metoden Finite Element Analysis (FEA) för att genomföra en snabb termisk simulering av maskiner. Emellertid är en signifikant nackdel med FEA-metoden att den tvungen konvektionsvärmeöverföringen och fluidrörelsen är svåra att ta hänsyn till. För att lösa detta problem fokuserar avhandlingsarbetet att genomföra en CFD-modell för att förutsäga temperaturfördelningen av Auragen-induktionsmaskinerna och luftflödeshastighetsfördelningen genom att noggrant överväga den tvungen konvektionsvärmeöverföring och fluidrörelse i olika driftsförhållanden. Avhandlingsarbetet täcker förbättringen av 3D CAD-modeller av Auragen-induktionsmaskiner och luftflödesfält, utvärdering av simuleringsparametrar för CFD-simuleringsmodellerna och jämförelsen av resultaten av CFD-simuleringen, FEA-simulering och fysiskt experimentella mätningar. Slutligen kan den bästa CFD-simuleringsmodellen noggrant förutsäga temperaturfördelningen av alla komponenter i induktionsmaskinen och luftflödet i 3000, 2000 och 1000 rpm-förhållandena. Noggrannheten uppfyller det önskade målet som är inom 4 ℃ från medelfelet och 8 ℃ från det maximala felet. Velocitetsfördelningar av luftflödet kan också visa egenskaper hos fluidrörelsen från inlopp till utloppet. Jämfört med simuleringsresultat av FEA-metoden har CFD-simuleringsmodellen betydligt mer exakta resultat när det appliceras för ett brett spektrum av driftshastigheter för att förutsäga temperaturfördelningen i det tvångsöverföringstillstånd. De goda CFD-simuleringsresultaten kan hjälpa till att snabbt upptäcka designproblem i ett tidigt skede av produktutvecklingsprocessen utan att göra upprepade prototypkonstruktioner och fysiska tester. De goda CFD-simuleringsresultaten är fördelaktiga för att minska antalet nödvändiga prototyper och därför minska utvecklingskostnaderna och tidsåtgången.

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Este trabalho aborda os conceitos básicos da distribuição de temperaturas e cálculo das tensões térmicas nas estruturas de comportamento linear, utilizando o Método dos Resíduos Ponderados (variante de Galerkin). De modo a sedimentar os conceitos, foram desenvolvidos exemplos de aplicação. / This paper deals with the basic concepts of both temperature distribution and thermal stresses evaluation in structures of linear behavior, by means of the Method of Weighted Residuals (Galerkin\'s approach). Examples of application have been developed in order to sediment the concepts.

名古屋大学博士学位論文 学位の種類:博士(工学) 学位授与年月日:平成19年9月28日

<p>Continuous caster moulds are the last and most important stage in the steelmaking process, where inclusions can either be generated or removed. With increasing casting speed using conventional immersion nozzles critical problems, such as unstable bulk mould flow have been noticed. Mould flux entrapment due to vortex and shearing action from the oscillating surface waves have become of particular concern. It is therefore necessary to have a calm inlet flow at the entrance of the mould. Recently, it has been acknowledged that a swirl blade placed at the upstream of the immersion nozzle effectively resolves the problems arising from unstable bulk mould flow. Therefore, to increase the knowledge of effect of swirling flow on the flow pattern in the mould, fundamental mathematical models of a billet mould equipped with a swirl blade in the nozzle have been developed. The model was used to study the effect of divergent angle of the immersion nozzle and mould aspect ratio on the flow field and temperature distribution inside billets moulds. Data from water model experiments were used to verify the mathematical model predictions. A fairly good agreement was found between physical modeling data and predictions, which ensured that the numerical model is reliable. Thereafter, the differences between square and round billet moulds were studied. Next, the effect of changing aspect ratio of the rectangular mould on the fluid flow and heat transfer, while keeping mould surface area constant, was studied. Two types of immersion nozzles, bottomless and conventional, were also analyzed during the research. The model moulds were changed gradually from a square billet with an aspect ratio of 1x1 to a rectangular billet with an aspect ratio of 3x1. First, the temperature and velocity distributions were calculated. Later, unsteady calculations were done to determine velocity fluctuations on the meniscus level for two types of nozzles and several moulds geometries.</p>

Pirmoje šio darbo dalyje pristatomi temperatūros pasiskirstymo aktyviojoje lazerio terpėje kompiuterinio modeliavimo rezultatai. Skaičiavimai atlikti dviem aktyviosios terpės geometrijoms – plono disko ir plokščiojo kompozitinio elemento. Apžvelgiama skirtingų aktyvios terpės ir kaupinimo parametrų įtaka temperatūros pasiskirstymui. Antroje darbo dalyje pristatomi lazerio pluošto bangos fronto iškraipymų, atsirandančių dėl nevienodo temperatūros pasiskirstymo aktyvioje terpėje ir paviršiaus deformacijų, skaičiavimo rezultatai. / This work presents results of numerical simulation of temperature distribution inside laser active medium. Calculations were performed for two different active medium geometries. First one thin disk geometry and second - composite slab. Influence of different pump and active medium parameters on temperature distribution are presented. Second part of this work presents results of wave front aberrations calculations. Those aberrations were resulted by irregular temperature distribution and surface deformations.

abstract: The operating temperature of photovoltaic (PV) modules is affected by external factors such as irradiance, wind speed and ambient temperature as well as internal factors like material properties and design properties. These factors can make a difference in the operating temperatures between cells within a module and between modules within a plant. This is a three-part thesis. Part 1 investigates the behavior of temperature distribution of PV cells within a module through outdoor temperature monitoring under various operating conditions (Pmax, Voc and Isc) and examines deviation in the temperature coefficient values pertaining to this temperature variation. ANOVA, a statistical tool, was used to study the influence of various factors on temperature variation. This study also investigated the thermal non-uniformity affecting I-V parameters and performance of four different PV technologies (crystalline silicon, CdTe, CIGS, a-Si). Two new approaches (black-colored frame and aluminum tape on back-sheet) were implemented in addition to the two previously-used approaches (thermally insulating the frame, and frame and back sheet) to study temperature uniformity improvements within c-Si PV modules on a fixed latitude-tilt array. This thesis concludes that frame thermal insulation and black frame help reducing thermal gradients and next best viable option to improve temperature uniformity measurements is by using average of four thermocouples as per IEC 61853-2 standard. Part 2 analyzes the temperature data for two power plants (fixed-tilt and one-axis) to study the temperature variation across the cells in a module and across the modules in a power plant. The module placed in the center of one-axis power plant had higher temperature, whereas in fixed-tilt power plant, the module in north-west direction had higher temperatures. Higher average operating temperatures were observed in one-axis tracking as compared to the fixed-tilt PV power plant, thereby expected to lowering their lifetime. Part 3 focuses on determination of a thermal model coefficients, using parameters similar to Uc and Uv thermal loss factors used in PVsyst, for modules of four different PV technologies experiencing hot-desert climate conditions by statistically correlating a year-long monitored data. Thermal models help to effectively quantity factors influencing module temperatures to estimate performance and energy models. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

Este trabalho aborda os conceitos básicos da distribuição de temperaturas e cálculo das tensões térmicas nas estruturas de comportamento linear, utilizando o Método dos Resíduos Ponderados (variante de Galerkin). De modo a sedimentar os conceitos, foram desenvolvidos exemplos de aplicação. / This paper deals with the basic concepts of both temperature distribution and thermal stresses evaluation in structures of linear behavior, by means of the Method of Weighted Residuals (Galerkin\'s approach). Examples of application have been developed in order to sediment the concepts.

Articulated haulers are fundamental equipment to transport material. The load carrying structure on a hauler consists mainly of welded frames. During welding of the frames high residual stress will be introduced. These stresses may have a significant impact on the fatigue life of the frames. This is the reason for having good knowledge of the weld residual stresses. The finite element method was used to calculate the residual stress distributions in a butt weld and a T-join weld. Simulation of the welding process with thermal and mechanical analysis was prepared by means of welding GUI implemented in LS-PrePost. The welding simulation is a computer intensive operation with high CPU time. That is why it is important to investigate which process factors that have the largest impact on welding simulation results. The aim of this thesis is to investigate the correlation between designed models in FEA software with published results of weld residual stress measurements and conclude which parameters should be mainly taken into consideration.