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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Better design of wheel-loaded decks

Berg, Johan January 2012 (has links)
This study treats the design of secondary structures for wheel-loaded decks. It concludes that significant savings in structural weight, overall cost and environmental impact can be obtained by an improved design. The rules of three classification societies are examined and their principle differences are discussed. Weight and cost optimal solutions of rule-based design are identified for a deck of a typical short-sea RoRo-vessel. The rule-optimal designs are assessed and further improved on the basis of FEcalculations and the economic and environmental benefits associated with the best solutions are approximated.
42

Modeling of fatigue in RORO ships

Amundin, Eskil January 2012 (has links)
The largest modern Pure Car and Truck Carriers (PCTC’s) are typically 230 meters long and have 13 cargo decks. In order to facilitate rapid loading and unloading these ships have been subject to a development of reducing any obstructing structures in the cargo hold, meaning that the transversal shear preventing structures, i.e. the racking bulkheads, has been taken to a minimum. Previous studies have concluded that some points on the racking bulkheads, as a result of the stripped down design, are subject to high stresses resulting from wave induced accelerations of the ship. In this M.Sc. Thesis the fatigue life of a corner of a transverse bulkhead opening in a 230 meter long PCTC with a capacity of 7200 cars is calculated with different methods. •Fatigue life is calculated from recorded ship motion data with the notch stress method in conjunction with rain flow counting and the cumulative damage principal. • Fatigue life is calculated according to (DNV CN. 30.7, 2010), based on a Lloyd’s Register FE model load case. • Actual findings on the ship are compared to the calculated results. Due to the lack of inspection data this comparison is not very extensive and only more briefly discussed. It is concluded that the fatigue life of the examined point, calculated from recorded motion data is 9.6 years and the fatigue life according to DNV is 8.0 years. It is also found that the fatigue damage is cumulated in almost discrete portions and thus the calculated fatigue life can be inaccurate when a short period of time is evaluated as is done in this thesis. A modification to the racking bulkhead with respect to fatigue life is also analyzed and it is concluded that the fatigue life in the examined point could be extended significantly by some simple modifications to the geometry.
43

Modelling of Elastic Ship in Waves

Manohara Ranganath, Draksharam January 2012 (has links)
Ships in the seas undergo different distortions like bending, twisting or combined bending and twisting. The demand for increase in length and speed of the ships is increasing due to this the study for flexibility of structures is becoming important. Usually the structural excitations or natural frequencies of structure are given less priority since the natural frequencies of the structure are higher than encounter frequencies but since the length and speeds are increasing the encounter frequencies are closer to the fundamental frequencies. The structural behavior can be analyzed by semi-empirical formulation developed by classification societies but the flexibility of its application is limited. The present thesis work deals with the vertical motions of the ship structure. The thesis work is divided in to two parts the first part deals with the literature review of the global loads and Hydroelasticity and the second part deals with the modeling of the structural dynamic problem. In the modeling part Hydro-elasticity theory proposed by Bishop and Price on Euler Bernoulli beam is used for solving the structural dynamic problem and the illustration of springing and whipping is presented. An attempt has also been made to study the dynamic structural responses for a particular hull with the hydrodynamic forces and added mass from high speed strip program developed at KTH and the study has been performed to analyze the influence of various parameters like added mass, damping and stiffness.
44

Conceptual design and investigation of hydrogen-fueled regional freighter aircraft

Seeckt, Kolja January 2010 (has links)
This thesis presents the conceptual design and comparison of five versions of regional freighter aircraft based on the ATR 72. The versions comprise four baseline designs differing in their propulsion systems (jet/turboprop) and the fuel they use (kerosene/hydrogen). The fifth version is an improved further development of the hydrogen-fueled turboprop aircraft. For aircraft modeling the aircraft design software PrADO is applied. The criteria for the overall assessment of the individual aircraft versions are energy use, climate impact in terms of global warming potential (GWP) and direct operating costs (DOC). The results indicate that, from an aircraft design perspective, hydrogen is feasible as fuel for regional freighter aircraft and environmentally promising: The hydrogen versions consume less energy to perform a reference mission of 926 km (500 NM) with a payload of 8.1 t of cargo. The climate impact caused by the emissions of hydrogen-fueled regional freighter aircraft is less than 1 % of that of kerosene-fueled aircraft. Given the circumstance that sustainably produced hydrogen can be purchased at a price that is equivalent to kerosene with respect to energy content, hydrogen-fueled regional freighter aircraft are also economically competitive to current kerosene-fueled freighters. In consequence, regional freighters appear especially favorable as first demonstrators of hydrogen as aviation fuel, and cargo airlines and logistics companies may act as technology drivers for more sustainable air traffic. The potential of regional freighter aircraft alone to mitigate climate change is marginal. The share of national and regional air cargo traffic in global manmade climate impact lies in the region of 0.016 % to 0.064 %, which also represents the maximum reduction potential. The presented work was to a large extend performed during the joint research project "The Green Freighter" under the lead of Hamburg University of Applied Sciences (HAW Hamburg). / QC 20101123
45

Methods for Modelling and Characterization of In-Duct Sources

Rämmal, Hans January 2005 (has links)
Methods to characterize acoustic sources in flow ducts have been investigated. In the first part of this thesis a measurement procedure to characterize an air terminal device using an acoustic one-port source model based on the two microphone technique has been tested and validated. In order to provide a prediction of flow noise generation at different operating points for the device a scaling law was derived. Successful validation experiments were performed. In the second part a new method based on the multi-load technique was developed and used to characterise the source data of various piston-engines with non-linear behaviour. The source characterisation results were compared to results obtained using the well-known linear two-load technique. It was shown that the new non-linear multi-load technique gave improved results when the source was slightly non-linear. In the third part an improved method to characterize noise sources in high temperature flowducts has been suggested. As a test environment for the standard two microphone technique a helium-air mixture has been used to simulate acoustical conditions similar to hot exhaust gas systems. In order to test the method the passive acoustic properties of automotive diesel engine and an unflanged flow duct termination have been experimentally determined. The experimental results for duct termination have been compared to theoretical predictions. Keywords: Acoustic source, one–port, source model, duct termination, source impedance, reflection coefficient, source strength, IC-engine, flow duct, multi-load method, non-linear / QC 20120208
46

Exploring force allocation control of over actuated vehicles

Edrén, Johannes January 2011 (has links)
As the concern for environmental changes and diminishing oil resources grows more and more, the trend of new vehicle concepts now includes full electric or partly electric propulsion systems. The introduction of electric power sources enables more advanced motion control systems due to electrification of the vehicle's actuators, such as individual wheel steering and in wheel hub motors. This can enable a control methodology that uses different chassis control strategies into a system that will be able to fully utilise the vehicle. Due to this, future vehicles can be more optimised with respect to energy consumption, performance and active safety. Force allocation control is a method that distributes the wheel forces to produce the desired response of the vehicle. In order to evaluate if this methodology can be implemented in future series production vehicles, the aim of this work is to explore how force allocation control can be utilised in a real vehicle to improve vehicle dynamics and safety. In order to evaluate different approaches for generic vehicle motion control by optimization, modelling and simulation in combination with real vehicle experiments will be needed to fully understand the more complex system, especially when actuator dynamics and limitations are considered. The use of a scale prototype vehicle represents a compromise between development cost, efficiency and accuracy, as it allows realistic experiments without the cost and complexity of full vehicle test. Moreover since the vehicle is unmanned it allows studies of at-the-limit situations, without the safety risks in full vehicle experiments. A small scale prototype vehicle (Hjulia) has been built and equipped with autonomous corner module functionality that enables individual control of all wheels. A cost effective force allocation control approach has been implemented and evaluated on the prototype vehicle, as well as in vehicle simulation. Results show improvement of stopping distance and vehicle stability of a vehicle during split-m braking. The aspects of vehicle dynamic scaling are also discussed and evaluated, as it is important to know how the control implementation of small scale prototype vehicles compares with full size vehicles. It is shown that there is good comparison between vehicles of different scales, if the vertical gravitational acceleration is adjusted for. In Hjulia, gravity compensation is solved by adding a specific lifting rig. Studies of vehicles considering optimal path tracking and available actuators are also made to evaluate control solutions of evasive manoeuvres at low and high friction surfaces. Results show differences in how the forces are distributed among the wheels, even though the resulting global forces on the vehicle are approximated to be scaled by friction. Also it is shown that actuator limitations are critical in at-the-limit situations, such as an obstacle avoidance manoeuvre. As a consequence these results will provide good insights to what type of control approach to choose to handle a safety critical situation, depending on available actuators. The built prototype vehicle with implemented force allocation control has shown to be a useful tool to investigate the potential of control approaches, and it will be used for future research in exploring the benefits of force allocation control. / QC 20111202
47

Första steget mot ett egenutvecklat litet vindkraftverk : Framtagning av ett vindkraftsblad

Skyllermark, Emelie January 2012 (has links)
Wind power is a mature market for large wind turbines but the small wind turbine market is still an open one. There is only one player of considerable size on the small wind market: the market leader Southwest Windpower. Now Skyllermarks Pressar AB (hereafter referred to as Skyllermarks) wants to develop a more competitive turbine than Southwest Windpower’s Skystream 3.7. The first step in this project is to develop a blade for injection moulding for FuturEnergy’s FE10XX turbine. Skyllermarks is a reseller for the English small wind turbine manufacturer FuturEnergy. As a first step towards developing a new turbine the aim of this theisis is to provide the backbone for developing a new wind turbine blade for FuturEnergys FE10XX turbine. The turbine is a fixed pitch, variabel speed machine with a rotordiameter of 1.75 m. It uses furling for overspeed protection. Southwest Windpower is Skyllermarks’s main competitor as the market leader in the small wind sector. Because of this, Southwest Windpower’s turbine Skystream 3.7 is used as a basis for comparsion for the FE10XX. It is found that the FE10XX turbine should be able to provide the desired annual energy production of 2000 kWh for a average wind speed of 4 to 6 m/s if the rotordiameter is expanded to 3.6 m. The blade profile family S822 or S833 from NREL should be used for the new blade. To make the turbine quieter the optimal tip speed ratio of the blades should be reduced from the present 5.5 to 4.5. The tip shape of the blade also has an impact on the sound and therefore a tip shape with a sweept leading edge is recomended. Is is concluded that the new blade can be produced in the largest injection moulding machine at Skyllermarks’s plastic mouldning partner Accenta Plast. At the price of added complexity the rotor can be improved further by adding vortex generators to make the blades more efficient and quiet and by using PETD technology for de-icing the blades.
48

Development and on-Track Tests of Active Vertical Secondary Suspension for Passenger Trains

Qazizadeh, Alireza January 2014 (has links)
<p>QC 20150204</p>
49

Model Based approach to Predict Boundary Conditions of a Single  Cylinder Test Engine

Reddy, Goutham, Khambaty, Murtaza January 2016 (has links)
Huvudämnet i denna avhandling är användningen av prediktiva modeller för att styra randvillkori en encylindrig motor. Encylindriga motorer används i utvecklingen av nya motorer för att studeraförbränningskoncept. De utgör en modulär plattform för utveckling av bland annat nyaventilkoncept, förbränningsmetoder, bränsleinsprutningsmetoder och portkonstruktioner. I enproduktionsmotor representeras turboaggregatet och motorn av ett kopplat dynamiskt system därmotorns driftspunkt bestämmer avgasmottryck och insugstryck. Det är nödvändigt att utföraexperiment på encylindriga motorer med rätt insug- och avgasmottryck för att studierna ska vararealistiska. Dessa encylindriga motorer har dock oberoende ventilstyrda insug- och avgassystemdär driftspunkten för en produktionsfärdig flercylindrig motor simuleras. Därför finns det ett behovav att använda modellbaserade tekniker för att styra inlopps- och utloppstryck. I denna avhandling har en metod utvecklats för att förutsäga randvillkor med hjälp av en skaladversion av den encylindriga modellen tillsammans med en modell av ett turboaggregat. Endetaljerad 1D modell av en encylindrig provcell skapades i AVL Boost. Modellen har sedanvaliderats med hjälp av mätdata och skalats till en flercylindermodell. En 0D Simulinkmodell harutvecklats utöver 1D modellen för att jämföra deras användning i en realtidsapplikation. Samtidigttas det hänsyn till de avvikelser från verkliga processer som sker i båda modellerna. 0D modellenrepresenterar en enkel motormodell för att förutsäga stationär prestanda genom att förutsätta kvasistationär strömning. Motivationen bakom att använda en sådan modell är att de förutsagdamedelvärden av inlopps- och utloppstryckspår ger en mer realistisk referensparameter som kananvändas för att styra randvillkoren på en encylindermotor. Avgasturbinen har också modellerats i syfte att studera volutets dämpande effekt på det pulserandeavgasflödet. Olika extrapoleringsmetoder för turbinmappar studerades där fysiskt baseradealgoritmer användes för att extrapolera turbindata. Turbinvolutet och dess effekter påturbinprestanda har diskuterats tillsammans med uppskattning av effektiviteten hos turbinen underostadiga flödesförhållanden. Dessa modeller har sedan kalibrerats och validerats motvevaxelupplösta cylindertryck och cykelmedelvärderade parametrar från mätdata som erhållitsfrån den encylindriga provmotorn. De fel och avvikelser mellan 0D- och 1D modellerna ochmätdata identifierades och diskuterades. En styralgoritm baserad på den encylindriga 1D Boostsimuleringen utvecklades för att reglera insug- och avgastryck och jämfördes sedan mellan 0D-och 1D modellerna för att utvärdera prestanda och noggrannhet. / The main topic of study in this thesis is the use of predictive models to control the boundaryconditions of a single cylinder engine. Single cylinder engines are used to study combustionconcepts in the development cycle of new engines. They provide a modular research platform todevelop new valve train concepts, combustion methods, fuel injection methods, port designsamong other things. In a production engine the turbocharger and engine represents a coupleddynamic system where the operating point of the engine sets the cylinder exhaust back pressureand the inlet pressure. Hence, it is necessary to provide single cylinder engines with correctcharged air input and exhaust back pressure for the studies to be realistic. These single cylinderengines however have independent charging systems and valves to simulate the operating point ofa production multi cylinder engine. Therefore, there is a need to use model-based techniques tocontrol the inlet and outlet pressure. In this thesis a method was developed to predict the boundary conditions of the single cylinder testengine using a scaled version of the single cylinder model along with a turbocharger model. Adetailed 1D model of the single cylinder test cell was created using AVL Boost. This model wasthen validated using measured data and scaled to a multi cylinder model. A 0D model, in theSimulink environment, was also developed together with the 1D model in order to compare theiruse in real time application. The 0D model represents a simple approach to engine modelling inorder to provide steady state performance prediction, assuming quasi-steady flow. The motivationbehind using such a model is that the predicted mean values of inlet and outlet pressure tracesprovide a more realistic reference parameter that can be used to control the boundary conditionsin the single cylinder engine. The turbine volute was also modelled in order to capture the dampening effect it has on thepulsating flow. Different turbine map extrapolation methods were also studied and physics basedalgorithms were used to extrapolate the turbine data. The turbine volute and its effects on theturbine performance have been discussed along with some thoughts on estimating the efficiencyof the turbine during unsteady flow conditions. These models were then calibrated and validatedagainst crank angle resolved cylinder pressures and cycle averaged parameters from measured dataobtained from the single cylinder test engine. The errors and deviations between the 0D and 1Dmodel as well as from the measured data were identified and discussed. A control algorithm usingthe Single cylinder 1D Boost simulation, as the plant model, was developed in order to control theinlet and exhaust pressures. The algorithms were then compared between 0D model and 1D modelfor evaluating the performance and accuracy.
50

Towards Efficient Vehicle Dynamics Evaluation using Correlations of Objective Metrics and Subjective Assessments

Gil Gómez, Gaspar January 2015 (has links)
<p>QC 20150611</p>

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