9th German-Japanese Bridge Symposium, September 10-11, 2012, Kyoto, JAPAN (GJBS09)

Rapporten är en utvärdering av möjligheten att generera elektrisk energi från fjärrvärme med Seebeck-effekten och görs på uppdrag av Skellefteå Kraft. Kursen är examensarbete för högskoleingenjörsexamen i Elkraftteknik, 5EL210 vid institutionen tillämpad fysik och elektronik på Umeå Universitet under vårterminen 2014.En termoelektrisk generator fungerar enligt Seebeck-effekten och genererar en elektrisk spänning som är linjär mot temperaturskillnaden mellan sina två metallytor. För att få en temperaturskillnad så krävs ett kylmedium vilket skapar ett värmeflöde från den varma energikällan till kylmediumet. Utan kylmediumet så kommer temperaturerna gå mot samma värde. Ett kylmedium kan till exempel vara snö, markgrunden eller vattenradiatorer. Eftersom en termoelektrisk generator är väldigt ineffektiv så lämpar det sig inte att använda markgrunden eller snö som kylmedium för att endast generera upp till 4% el av den tillförda värmeenergin och resten går till förluster. Av denna anledning valdes radiatorerna i villan som kylmedium för detta examensarbete.En teoretisk experimentuppställning gjordes med 16 stycken termoelektriska generatorer. Resultatet visade att värmeöverföringen genom de termoelektriska generatorerna begränsades till ca. 250W värmeenergi. Med relativt låga temperaturer så är effektiviteten endast 2% vilket genererar ca. 5W elektrisk energi.Slutsatsen är att med denna experimentuppställning så genereras inte tillräckligt med energi för att driva en cirkulationspump. Effektiviteten av de termoelektriska generatorerna är för dålig och de leder värme dåligt på grund av dess höga termiska resistans.

L’acier 55Cr3 est mis en œuvre dans la fabrication des barres stabilisatrices cambrées (BSC) utilisées dans l’industrie automobile. Le procédé consiste en un cintrage à chaud suivi d’un traitement thermique de trempe/revenu. Les barres ainsi mises en forme subissent ensuite un grenaillage de précontrainte avant peinture et livraison au client final. L’objectif de ce travail est de fiabiliser cette fabrication en vue de garantir des performances optimales quelle que soit la provenance de l’acier. Deux lots d’acier de nuance 55Cr3 élaborés respectivement par la filière électrique et la filière fonte ont été caractérisés métallurgiquement et mécaniquement à chaque étape de la fabrication. Les résultats indiquent une légère différence de trempabilité, conduisant à des écarts inférieurs à 5% de la limite élastique à l’issue du revenu. Le nombre de cycles à rupture d’éprouvettes sollicitées en traction uniaxiale et en torsion est bien corrélé avec les limites élastiques, contrairement aux résultats obtenus sur BSC sur banc de fatigue représentatif des sollicitations de service. L’évaluation des contraintes résiduelles par diffraction des rayons X met en évidence une différence de réponse au grenaillage, qui a été reliée à la microstructure initiale, à réception de l’acier. Un modèle numérique de couplage métallo-thermo-mécanique permettant de simuler le formage des BSC et tenant compte des transformations de phase liées à la trempe a été développé. Ce modèle permet de mettre en évidence l’influence des paramètres matériaux, du process et géométriques et de calculer les contraintes résiduelles introduites par l’opération de trempe. Ceci contribue à l’amélioration de la fiabilité. / 55Cr3 steel grade is used for the manufacturing of stabilizer bars in the automotive industry. Steps in the process are hot bending followed by quench and tempering. After such forming, the bars are submitted to shotpeening before painting and final customer delivering. This work aims at improving the manufacturing reliability in order to get the best performance whatever the steel supply.In this purpose, the microstructure and mechanical properties resulting from each step of the manufacturing process have been characterized for two batches of bars made of 55Cr3 steel grade respectively elaborated by blast furnace route and by electric arc furnace route. A slight difference in quenchability has been found, which is responsible for a 5% variation in the yield strength. Samples fatigue tested under uniaxial tensile stress and torsional stress have reached an amount of cycles to failure that is in agreement with the respective yield strength. Different results have been obtained by fatigue testing complete manufactured bars under representative complex service stresses. The determination of residual stresses by X-ray diffraction shows that both steels respond differently to shotpeening, which results from differences in the as-received microstructure.A metallo-thermo-mechanics coupling model based on finite element method has been created which takes into account phase transformations during the quenching process. This model can simulate the forming process of stabilizer bar, in order to analyze the influence of material properties, processing parameters and sample geometry, to calculate the residual stresses induced by the quenching process, and improve process reliability.

Les échangeurs réacteurs intensifiés (ERI) sont des échangeurs de chaleur utilisés comme réacteurs chimiques afin d'intensifier les procédés de synthèse. L'ERI étudié dans ce travail est composé de plaques en carbure de silicium, lui conférant ainsi des propriétés thermiques et chimiques importantes. En contrepartie, l'utilisation du SiC accentue les risques de rupture fragile, à ajouter aux risques principaux associés aux ERI qui sont les fuites de fluide et l'emballement thermique de la réaction. L'intensification des procédés représente un gain important en terme de productivité, de sécurité et d'impact environnemental, à condition de maîtriser la conception et la mise en œuvre de l'ERI. L'objectif de ce travail est de proposer une démarche d'étude adaptée à ce type de produit en général, et d'optimiser la conception de cet ERI en particulier. Pour cela, les modèles thermo-chimique et thermo-mécanique de l'ERI sont développés puis utilisés dans une étude mécano-fiabiliste, notamment au moyen à la méthode AK-MCS basée sur l'interpolation par krigeage de la fonction de performance. / Intensified heat exchanger reactors (ERI) are heat exchangers used as chemical reactors for process intensification. The ERI studied in this work is composed of silicon carbide (SiC) based plates, giving it interesting thermal and chemical properties. In return, the use of SiC increases the brittle fracture risk, in addition of the main risks that are leaking fluid and thermal runaway reaction. The process intensification represents a significant gain in productivity, safety and environmental impact, provided that the design and the implementation procedure of the ERI are optimized. The objective of this work is to propose a process of study suited to this type of product in general, and to optimize the design of this ERI in particular. For this, the thermo-chemical and thermo-mechanical models are developed and used in a mechano-reliability study, notably using the AK-MCS method based on kriging interpolation of the performance function.

The search for alternative methods of synthesizing cubic boron nitride (cBN), one of the hardest known materials, at low thermo-baric conditions has stimulated considerable research interest due to its great potential for numerous practical industrial applications. The practical applications are motivated by the material’s amazing combination of extraordinarily superior properties. The cBN phase is presently being synthesized from graphite-like boron nitride modifications at high thermo-baric conditions in the presence of catalytic solvents or by ion–beam assisted (chemical and physical) deposition methods. However, the potential and performance of cBN have not been fully realized largely due to central problems arising from the aforementioned synthesis methods. The work reported in this dissertation is inspired by the extensive theoretical investigation of the influence of defects in a ecting the transformation of the hexagonal boron nitride (hBN) phase to the cBN phase that was carried out by Mosuang and Lowther (Phys Rev B 66, 014112 (2002)). From their investigation, using an ab-initio local density approach, for the B, C, N, and O simple defects in hBN, they concluded that the defects introduced into hBN could facilitate a low activation–energy hexagonal-to-cubic boron nitride phase transformation, under less extreme conditions. We use ion implantation as a technique of choice for introducing ‘controlled’ defects into the hot–pressed polycrystalline 99.9% hBN powder samples. The reasons are that the technique is non–equilibrium (not influenced by dilusion laws) and controllable, that is the species of ions, their energy and number introduced per unit area can be changed and monitored easily. We investigate the structural modifications of hBN by ion implantation. Emphasis is given to the possibilities of influencing a low activation–energy hBN-to-cBN phase transformation. The characterization of the structural modifications induced to the hBN samples by implanting with He+ ions of energies ranging between 200 keV and 1.2 MeV, at fluences of up to 1.0 1017 ionscm2, was accomplished by correlating results from X-Ray Di raction (XRD), micro-Raman (-Raman) spectroscopy measurements, and two-dimensional X-Y Raman (2D-Raman) mapping measurements. The surface to pography of the samples was investigated using Scanning Electron Microscopy (SEM). E orts to use Surface Brillouin Scattering (SBS) were hampered by the transparency of the samples to the laser light as well as the large degree of surface roughness. All the implantations were carried out at room temperature under high vacuum. 2D-Raman mapping and -Raman spectroscopy measurements done before and after He+ ion irradiation show that an induced hBN-to-cBN phase transformation is possible: nanocrystals of cBN have been observed to have nucleated as a consequence of ion implantation,the extent of which is dictated by the fluences of implantation. The deviationof the measured spectra from the Raman spectra of single crystal cBN is expected, has been observed before and been attributed to phonon confinement e ects. Also observed are phase transformations from the pre-existing hBN modification to: (a) the amorphous boron nitride (aBN), (b) the rhombohedral boron nitride (rBN) modifications, (c) crystalline and amorphous boron clusters, which are a result of the agglomeration of elementary boron during and immediately after ion implantation. These transformations were observed at high energies. Unfortunately, the XRD measurements carried out could not complement the Raman spectroscopy outcomes probably because the respective amounts of the transformed materials were well below the detection limit of the instrument used in the former case.

Next generation hypersonic cruise vehicle components will be subjected to a collection of loads not achievable in contemporary mechanical test platform. The purpose of this thesis is to demonstrate the design of a unique test platform for combined extreme environment (P-CEEn) needed to replicate thermal, acoustic and mechanical loading to be imparted on hypersonic fuselage panels. The panels are typically subjected to super-imposed cycling from hypersonic shock/impingement and aerodynamic pressure from the usual ascent-cruise-decent motion of the aircrafts combined with mechanical vibration at acoustic frequencies; moreover, these slender components will undergo conventional mechanical fatigue with compressive mean stress due to geometric constraint. Having the ability to precisely replicate the working environment of the fuselage components will help to identify life limiting conditions of the materials. A universal column buckling test frame, an acoustic horn, and a custom-made quartz-lamp furnace have been configured to allow for closed-loop feedback control of cyclic mechanical, thermal, and acoustic loading. The graphical user interface (GUI) associated with this first-of-its-kind test device allows users to design cyclic load profiles that idealize the thermo-acousto-mechanical loading of critical panels. Initial calibration experiments are presented.

One of the major challenges of implementing additive manufacturing (AM) processes for the purpose of production is the lack of understanding of its underlying process-structure-property relationship. Parts manufactured using AM technologies may be too inconsistent and unreliable to meet the stringent requirements for many industrial applications. The first objective of the present research is to characterize the underlying thermo-physical dynamics of AM process, captured by melt pool signals, and predict porosity during the build. Herein, we propose a novel porosity prediction method based on the temperature distribution of the top surface of the melt pool as the AM part is being built. Advance data analytic and machine learning methods are then used to further analyze the 2D melt pool image streams to identify the patterns of melt pool images and its relationship to porosity. Furthermore, the lack of geometric accuracy of AM parts is a major barrier preventing its use in mission-critical applications. Hence, the second objective of this work is to quantify the geometric deviations of additively manufactured parts from a large data set of laser-scanned coordinates using an unsupervised machine learning approach. The outcomes of this research are: 1) quantifying the link between process conditions and geometric accuracy; and 2) significantly reducing the amount of point cloud data required for characterizing of geometric accuracy.

This work presents novel formulations for models describing acoustically forced combustion in three disjoint regimes; highly turbulent, laminar, and the moderately turbulent flamelet regime. Particular emphasis is placed on simplification of the models to facilitate analytical solutions while still reflecting real phenomenology. Each derivation is treated by beginning with general reacting flow equations, identifying a small subset of physics thought to be dominant in the corresponding regime, and making appropriate simplifications. Each model is non-dimensionalized and both naturally occurring and popular dimensionless parameters are investigated. The well-stirred reactor (WSR) is used to characterize the highly turbulent regime. It is confirmed that, consistent with the regime to which it is ascribed for static predictions, the WSR is most appropriate to predict the dynamics of chemical kinetics. Both convection time and chemical time dynamics are derived as explicit closed-form functions of dimensionless quantities such as the Damk\"ohler number and several newly defined parameters. The plug-flow reactor (PFR) is applied to a laminar, burner stabilized flame, using a number of established approaches, but with new attention to developing simple albeit accurate expressions governing the flame's frequency response. The system is studied experimentally using a ceramic honeycomb burner, combusting a methane-air mixture, numerically using a nonlinear FEA solver, and analytically by exact solution of the simplified governing equations. Accurately capturing non-unity Lewis-number effects are essential to capturing both the static and the dynamic response of the flame. It is shown that the flame dynamics can be expressed solely in terms of static quantities. Finally, a Reynolds-averaged flamelet model is applied to a hypothetical burner stabilized flame with homogeneous, isotropic turbulence. Exact solution with a simplified turbulent reaction model parallels that of the plug flow reactor closely, demonstrating a relation between static quantities and the flame frequency response. Comparison with published experiments using considerably more complex flame geometries yields unexpected similarities in frequency scale, and phase behavior. The observed differences are attributed to specific physical phenomena that were deliberately omitted to simplify the model's derivation. / Ph. D.

This thesis describes the coincident prediction and observation of thermo-acoustic instabilities in a turbulent, swirl-stabilized research combustor using a stability model constructed from validated reduced-order component models. The component models included the acoustic response to flame heat release rate at various locations in the combustor, the turbulent diffusion of uneven fuel-air mixing, and the flame's response to perturbations in both inlet velocity and equivalence ratio. These elements are closed in a system-level model to reflect their natural dynamic coupling and assessed with linear stability criteria. The results include the empirical validation of each of the component models and limited validation of the total closed-loop model with a lean premixed gaseous fuel combustor not dissimilar to an industrial burner. The degree of agreement between the predictions and the measurements encourages the conclusion that the reduced-order technique described herein not only includes the relevant physics, but has characterized them with sufficient acuracy to be the basis for design techniques for the passive avoidance of thermo-acoustic instabilities. / Master of Science

Internal combustion (IC) engines used in road transport applications employ pistons to convert gas pressure into mechanical work. Frictional losses abound within IC engines, where only 38- 51% of available fuel energy results in useful mechanical work. Piston-bore and ring-bore conjunctions are fairly equally responsible for circa 30% of all engine friction - equivalent to 1.6% of the input fuel each. Therefore, reduction in piston assembly friction would have a direct impact on specific performance and / or fuel consumption. In motorsport, power outputs and duty cycles greatly exceed road applications. Consequently, these engines have a shorter useful life and a high premium is placed on measures which would increase the output power without further reducing engine life. Reduction of friction offers such an opportunity, which may be achieved by improved tribological design in terms of reduced contact area or enhanced lubrication or both. However, the developments in the motorsport sector are typically reactive due to a lack of relative performance or an ad-hoc reliance, based upon a limited number of actual engine tests in order to determine if any improvement can be achieved as the result of some predetermined action. A representative scientific model generally does not exist and as such, investigated parameters are often driven by the supply chain with the promise of improvement. In cylinder investigations are usually limited to bore surface finish, bore and piston geometrical form, piston skirt coatings and the lubricant employed. Of these investigated areas newly emerging surface coatings are arguably seen as predominate. This thesis highlights a scientific approach which has been developed to optimise piston-bore performance. Pre-existing methods of screening and benchmarking alterations have been retained such as engine testing. However, this has been placed in the context of validation of scientifically driven development. A multi-physics numerical model is developed, which combines piston inertial dynamics, as well as thermo-structural strains within a thermoelastohydrodynamic tribological framework. Experimental tests were performed to validate the findings of numerical models. These tests include film thickness measurement and incylinder friction measurement, as well as the numerically-indicated beneficial surface modifications. Experimental testing was performed on an in-house motored engine at Capricorn Automotive, a dynamometer mounted single-cylinder 'fired' engine at Loughborough University, as well as on other engines belonging to third party clients of Capricorn. The diversity of tests was to ascertain the generic nature of any findings. The multi-physics multi-scale combined numerical-experimental investigation is the main contribution of this thesis to knowledge. One major finding of the thesis is the significant role that bulk thermo-structural deformation makes on the contact conformity of piston skirt to cylinder liner contact, thus advising piston skirt design. Another key finding is the beneficial role of textured surfaces in the retention of reservoirs of lubricant, thus reducing friction.