This master thesis deals with design and numerical modelling of piezoceramic sensor, which is placed on a rail, in order to generate electrical energy, which can be used for wireless monitoring of railway traffic and to monitor the condition of the railway. The thesis is divided into three parts. Theoretically background of piezoelectric energy harvesting is described in first part, where some previous application of piezoelectric generator in railway area are shown. In the second part, parametric analysis of numerical model is performed, which directly leads to finding best location on a rail, where piezoelectric generator should be placed. For this analysis the homogenized model of MFC sensor was used. Results of the numerical model were then compared with the results of the conducted experiment. The third part presented own design of piezoceramic sensor, which is placed onto most suitable location on a rail. Results from numerical analysis shown eligibility of using piezoceramic sensor to monitor the railway traffic.

This thesis deals with the influence of balcony glazing to preheat ventilation air. In the first part there are described the ways of passive use of sun radiation and types of ventilation of flats. THESEUS-FE 4.0 is used as a simulation program, for which heat transfer is described. The second part contains description of flat and selected case simulation, followed by a geometric model and description of boundary conditions. Finnaly is done evaluation of case simulations not only in therms of savings in ventilation, but also for heat loss as a whole.

This diploma thesis deals with the impact of changes in operating and geometrical parameters of regenerative heat exchanger on the efficiency of decentralized ventilation units with heat recovery. Decentralized ventilation unit can be used for ventilation of family houses or smaller administration buildings. Output of this work is to determine the efficiency of a particular produced model of decentralized ventilation unit and overview of the possibilities increased efficiency of heat recovery of this units.

This Master thesis focuses on the design of a high efficiency Permanent-Magnet-Assisted Synchronous Reluctance Motor (PMASynRM) intended for pump applications. The new motor is designed to replace an existing Induction Motor (IM) in a pump product. The basic principles of SynRM, and PMASynRM Motors and a good analytical model were introduced. Due to the complexity and high non-linearity of this specific electrical machine, Finite Element Method (FEM) and an analytical model were combined. First, a parameter sensitivity analysis was carried out with the software SPEED. However, SPEED does not give appropriate results for the sensitivity analysis of the distance from the shaft to the first barrier, and in this case, the FEM software FLUX was used instead. Using FEM as well, the risk of demagnetization of the magnets was controlled for the nominal current and for overload conditions. Furthermore, some conclusions were drawn in terms of the losses, and efficiency for the selected design. The design fulfills the required efficiency placing either ferrite or neodymium iron bore magnets in the rotor barriers. However, if ferrite magnets are employed, the maximum current should be controlled to avoid demagnetization. Finally, a ferrite PMASynRM prototype was built and tested in the lab. The simulation results as well as the measurement of other possible technologies including IM and Line Start Permanent Magnets (LSPM) machine were compared with the measurements of the prototype in terms of efficiency, power factor and cost. It is concluded that the designed PMASynRM is a good alternative as it surpassed the required efficiency and the results from the simulation were close to the test measurements. / Detta examensarbete fokuserar på konstruktion av en högverkningsgradmotor av typen Permanent-Magnet-Assisterad Synkronreluktansmotor (PMASynRM) avsedd för pumpapplikationer. Syftet är att asynkronmotorn i befintliga pumpar ska bytas ut mot den nya konstruktionen. På grund av maskinens komplexitet och dess höga olinjäritet kombinerades Finite Element Modelling metoden (FEM) och en analytisk metod. Till en början genomfördes en parameterberoende analys med SPEED för att komma fram till hur modellens olika parametrar påverkar maskinens prestanda. FEM beräkning gav mer pålitligt resultat för parameterstudie när det gällde avståndet från axeln till den första barriären (jämför med SPEED). Detta val hade fördelen att man även kunde studera avmagnetiseringsrisken vid märkström samt undersöka vid vilken ström magneterna faktiskt avmagnetiserades. Därutöver drogs slutsatser om verkningsgrad, prestanda och förluster. PMASynRM uppfyller önskad verkningsgrad med ferrit eller neodymmagneter. Om ferritmagneter används bör den maximala strömmen kontrolleras för att undvika avmagnetisering. Till slut byggdes och testades en PMASynRM prototyp. Resultaten från simulationen samt mätningarna av andra möjliga teknologier, som asynkronmotor och nätstartande permanentmagnetiserad motor (LSPM), jämfördes med mätningarna av prototypen med avseende på verkningsgrad, effektfaktor och kostnad. Slutsatsen är att PMASynRM är ett bra alternativ eftersom den överträffade den önskade verkningsgraden och eftersom resultaten från simulationen låg mycket nära testmätningarna.

One of the early steps in axial turbine design is the use of one-dimensional (1D) mean line calculations to predict the turbine performance and estimate the principal geometric parameters, such as radius and blade heights, that will be needed in further computational fluid dynamic (CFD) studies. This 1D analysis is based on the estimation of the aerodynamic losses expressed as a function of simple blade parameters and the velocity triangles. In this regard, there exist different loss correlations widely used in literature to estimate these losses but at the same time there is a lack of information regarding differentiation between them. Thereafter, the objective in this work was to judge and compare the behaviors of the Kacker- Okapuu, Craig-Cox and Denton loss correlations, all of them widely-used in turbine performance prediction. Present work shows the implementation of these different loss correlations on an existing 1D mean line numerical tool, LUAX-T. Subsequently, once implemented, the correlations were compared and analyzed by the use of a validation process and performing a parametric study. The results show that similar key parameters such as the flow turning, solidity and aspect ratio rule the different loss mechanisms in each correlation. On the other hand, the parametric study shows that the correlations are in agreement with the theory and give similar trends for performance prediction even though they all predict different values of efficiency for the same turbine stage. Moreover, the validation process show the correlations were found to be accurate enough when comparing against two different sets of experimental data. However, it was also proved that the models are only accurate if used within the range of applicability they were developed for, hence a complete knowledge of the limitations of each correlation should be known prior to using them. Finally, the extension of the one-dimensional mean line numerical tool LUAX-T will serve to perform further studies related to turbine design, as there are very few non-confidential turbomachinery design tools available for teaching or researching. Furthermore, a parametric study tool was also developed as part of the program. This last extension and the loss implementation codes are described in this work.

Wood is a complex organic orthotropic viscoelastic material with acellular structure. When stressed, wood will deform over timethrough a process called creep. Creep affects all wooden structureand can be difficult, time-consuming and expensive to measure. For this thesis, a simple computer model of the woodenmicrostructure was developed. The hypothesis was that the modelledmicrostructure would display similar elastic and viscoelasticproperties as the macroscopic material. The model was designed by finding research with cell geometries ofconiferous trees measured. The model considered late- and earlywoodgeometries as well as growth rings. Rays were ignored as they onlycomposed 5-10% of the material. By applying a finite element method, the heterogeneous late- andearlywood cells could be homogenized by sequentially loading thestrain vector and calculating the average stress. The computer model produced stiff but acceptable values for theelastic properties. Using the standard linear solid method to modelviscoelasticity, the computer model assembled creep curvescomparable to experimental results. With the model sufficiently validated, parametric studies on thecell geometry showed that the elastic and viscoelastic propertieschanged greatly with cell shape. An unconventional RVE was alsotested and shown to give identical result to the standard RVE. Although not perfect, the model can to a certain degree predict theelastic and viscoelastic characteristics for wood given itscellular geometry. Inaccuracies were thought to be caused byassumptions and approximations when building the model.

No description available.

No description available.

In recent years, an increase to design slender and aesthetically-pleasing structures have resulted in some structures having a low natural frequency. This is because the design calculation did not meet the requirement of serviceability performance. Structures can experience excessive vibrations when they are subjected to different types of dynamic loading. A device can be installed to prevent these vibrations.In this thesis, we study the response of buildings and lateral vibrations of footbridges equipped with Tuned Liquid Damper. The aim is to mitigate the first mode of vibration. Tuned Liquid Damper consists of a container in rectangular, cylindrical or arbitrary shape partially filled with shallow liquid, most often water is used as a regulating device system. The design properties of Tuned Liquid Damper is introduced and it is based on the analogyof the most popular damper, Tuned Mass Damper.An experimental study of a building frame model with four floors is conducted to validate the numerical results obtained from the simulation of the model in ANSYS. The linear and non-linear analysis are performed through a system coupling between Ansys mechanical and Fluent solver. The simulation results obtained are in good agreement with the experimental results.A parametric study is conducted with a simply supported steel footbridge. It is a 45 m long span with 3 m width and the flexural rigidity is modified to get the lateral vibration mode. The first lateral natural frequency obtained is 0.713 Hz. The load case for the study considered is according to Sétra guide. The variable parameters studied is the Tuned Liquid Damper water mass ratios: 0.7%, 1.0%, 2.0%, 3.0% and 4.0%. The results show a satisfactory performance of the footbridge model equipped with Tuned Liquid Damper. The accelerations are below 0.1 m/s2 which satisfied the requirement of 0.15 m/s2.

In recent years the design of pedestrian bridges has become more slender. As a result the bridges has lower natural frequencies and are more prone to excessive vibrations when subjected to dynamic loads induced by pedestrians. Akademiska Hus are building such a bridge at Nya Karolinska Solna where the bridge will span over Solnavägenconnecting the hospital building, U2, and the research facility BioMedicum. Due to practical reasons, it is not possible to connect one of the bridge ends mechanicallyto the building which increases the risk for lateral modes in the sensitivefrequency range of 0-2.5 Hz. The increased risk of lateral modes of vibrations within the sensitive frequency range as well uncertainties when determining the dynamic response led to this thesis. This thesis covers a frequency analysis of the previously mention bridge and an evaluation of the dynamic response under pedestrian loading by implementation of several design guidelines. A literature review was conducted with the aim of giving a deeper knowledge of human induced vibrations and the relevant guidelines for modelling of pedestrian loading. Furthermore, a parametric study was conducted for parameters which might be prone to uncertainties in data. The investigated parameters were the Young’s modulus for concrete and the surrounding fill materialas well as the stiffness of the connection to BioMedicum. The parametric study yielded a frequency range of 2.20-2.93 Hz for the first lateral mode and 5.96-6.67 Hz for the first vertical mode of vibration. By including nonstructural mass the lower limit for the frequencies were lowered to 2.05 and 5.59 Hzin the first lateral and vertical mode respectively. The parametric study also showed that the largest impact on the natural frequencies were obtained by manipulating the parameters for the supports, both for BioMedicum and the substructure. The implementation of the guidelines resulted in a lateral acceleration between 0.05 and0.599 m/s2. No evaluation was conducted for the dynamic response in the vertical direction due to a natural frequency of 5.59 Hz, which is higher than the evaluation criteria stated in Eurocode 0. The results showed that the design of the Skyway bridge is dynamically sound with regard to pedestrian loading and no remedial actions are necessary.