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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.
11

Experimental investigation of the performance of a fully cooled gas turbine vane with and without mainstream flow and experimental analysis supporting the redesign of a wind tunnel test section

Mosberg, Noah Avram 16 February 2015 (has links)
This study focused on experimentally determining the cooling performance of a fully cooled, scaled-up model of a C3X turbine vane. The primary objective was to determine the differences in overall effectiveness in the presence and absence of a hot mainstream flowing over the vane. Overall effectiveness was measured using a thermally scaled matched Biot number vane with an impingement plate providing the internal cooling. This is the first study focused on investigating the effect of removing the mainstream flow and comparing the contour and laterally-averaged effectiveness data in support of the development of an assembly line thermal testing method. It was found that the proposed method of factory floor testing of turbine component cooling performance did not provide comparable information to traditional overall effectiveness test methods. A second experiment was performed in which the effect of altering the angle of attack of a flow into a passive turbulence generator was investigated. Measurements in the approach flow were taken using a single wire hot-wire anemometer. This study was the first to investigate the effects such a setup would have on fluctuating flow quantitates such as turbulence intensity and integral length scale rather than simply the mean quantities. It was found that both the downstream turbulence intensity and the turbulence integral length scale increase monotonically with approach flow incidence angle at a specified distance downstream of the turbulence generator. / text
12

Konfigurovatelná vestavná foto/videopast se záznamem dat a samočinnou adaptací na okolí / Configurable Embedded Photo/Video Trap with Storing Data and Self Adaptation to Surroundings

Výborný, Filip January 2015 (has links)
This diploma thesis deals with a design and construction of an embeded camera trap with a video recording and night vision support, which is able to self adapt to surroundings. The device is based on the Raspberry Pi platform and configurable by touch screen control with a user-friendly graphical interface. Also the web-application for easy remote administration was developed in Ruby On Rails framework. The camera trap was built and successfully tested under the real conditions. There are also typical application cases and requirements for camera trap construction described in this thesis.
13

IMPACT BEHAVIOR OF AMMONIUM PERCHLORATE (AP) - HYDROXYL-TERMINATED POLYBUTADIENE (HTPB) COMPOSITE MATERIAL

Saranya Ravva (15353902) 25 April 2023 (has links)
<p>This work investigated the effects of varying the crystal sizes of ammonium perchlorate (AP) when embedded with a polymeric binder, hydroxyl-terminated polybutadiene (HTPB) on impact-induced temperature behavior.  AP and HTPB are the most used oxidizers and fuel binders in the aerospace solid rocket design industry. In this study, samples of 200 µm and 400µm coarse AP crystals in HTPB were constructed using a conventional hand-mixing method. Using a parametric optimization technique such as the Taguchi method, direct-ink-writing as the additive manufacturing process was used for achieving the required shape fidelity in printing HTPB and by introducing ultraviolet polymers to decrease the curing time.</p> <p>A drop hammer experiment in conjunction with an infrared camera was used to study the impact-induced behavior in the conventionally made AP-HTPB samples. The thermal images obtained from the camera at millisecond resolution are invaluable and provide information about distribution across the sample surface, and the evolution of temperature rise observed in the samples which are complex and not easily understood otherwise and therefore help in improving and attaining desired propellant performance. A two-sample t-Test has been utilized to infer the results and statistical nonsignificance has been observed in the highest temperature rises among 200 µm and 400 µm AP-HTPB sample conditions but a difference in temperature distribution has been observed. A much uniform distribution of temperature over the sample surface on impact is observed in thermal images of 200 µm AP-HTPB sample condition compared to 400 µm AP-HTPB sample condition.</p>
14

Monitoring of Partial Discharges on Cable Terminations : An experimental approach to evaluate non-conventional online PD measurement techniques / Övervakning av partiella urladdningar vid kabeländar : En experimentell utvärdering av icke-konventionella mättekniker

Sibo, Tony January 2023 (has links)
The transmission of electric power over long distances has historically posed challenges. However, the advent of high-voltage engineering has not only addressed distance barriers and power losses in electricity transmission and distribution, but it has also significantly improved the efficiency and transmission capacity of power grids. However, the use of high-voltage techniques has presented new challenges in identifying suitable insulator materials capable of withstanding high electrical stresses associated with elevated voltages. A significant issue arising from these extreme electrical stresses is the occurrence of partial discharges (PDs). Those are electrical sparks or pulses in the magnitude order of pico- or nano-coulombs (pC or nC) emitted from high voltage conductors due to the presence of impurities, contaminants or defects in their insulation system. PDs pose a serious threat to the insulation material due to their aggressive nature in breaking down weak points or links inside the insulation system leading to short-circuit and system failure. Means of offline or conventional testing of power assets against partial discharges has proven to be extremely precise but it is often an unavailable option since it requires a total power shutdown. In this paper, the performance of existing online PD detection techniques is tested and evaluated in terms of performance against conventional PD monitoring methods. Five non-intrusive detectors including an infrared camera (IR-camera), an ultrasonic sensor , a temperature and relative humidity sensor (TRH-sensor), high-frequency current transformer (HFCT sensor) and transient earth voltage antenna (TEV-antenna) were tested in a laboratory experiment for detection of PDs emitted by artificially-created defects inside a medium-voltage cable termination. The results showed varying sensitivity levels among the sensors, with the HFCT sensor demonstrating the highest sensitivity to all types and magnitudes of PDs. The IR-camera and ultrasonic sensor also showed potential, while the TRH-sensor exhibited poor sensitivity. The TEV-antenna had limited reliability. The findings of this study are that the HFCT system proved to be highly reliable for online PD monitoring, followed by the IR-camera and ultrasonic sensor, while the TEV-antenna and TRH-sensor showed lower reliability. In future work, further research on testing the HFCT system on-site can be conducted along with performing longer thermographic detection tests using the IR-camera to further investigate their potential in online PD detection. / Överföring av elektrisk kraft över långa avstånd har historiskt sett varit utmanande. Införandet av högspänningsteknik har inte bara övervunnit avståndsbarriärer och effektförluster vid överföring och distribution av elkraft, utan det har också avsevärt förbättrat kraftnätens effektivitet och överföringskapacitet. Användningen av högspänningsteknik har dock också inneburit nya utmaningar såsom utveckling av lämpliga isoleringsmaterial som tål höga elektriska påfrestningar vid höga spänningar. Ett betydande problem som härrör från dessa extrema elektriska spänningar är förekomsten av partiella urladdningar. Dessa urladdningar identifieras vara elektriska gnistor eller pulser i storleksordningen pico- eller nanocoulombs (pC eller nC) som emitteras från högspänningsledare på grund av närvaron av föroreningar eller defekter i närliggande isoleringssystem. PD:er utgör ett allvarligt hot mot isoleringsmaterialet på grund av deras aggressiva natur för att bryta ner svaga punkter eller länkar i isoleringssystemet, vilket kan leda till kortslutningar och systemfel. Konventionella metoder för att testa nätkomponenter mot partiella urladdningar har visat sig vara extremt noggranna, men detta är ofta inte ett tillgängligt alternativ eftersom det kräver ett totalt strömavbrott för att utföras. I denna studie testades och utvärderades prestandan hos befintliga metoder för online-detektering av partiell urladdning i förhållande till konventionella övervakningsmetoder. Fem icke-invasiva detektorer, inklusive en infraröd kamera, en ultraljudssensor, en temperatur- och relativ fuktighetssensor, en högfrekvent strömtransformator och en transient jordspänningsantenn, testades i ett laboratorieexperiment för att upptäcka partiella urladdningar orsakade av artificiellt skapade defekter i en mellanspänningskabelavslutning. Resultaten visade varierande känslighetsnivåer bland sensorerna, där högfrekventa strömtransformatorn visade den högsta känsligheten för alla typer och storlekar av partiella urladdningar. Den infraröda kameran och ultraljudssensorn visade också potential, medan temperatur- och relativ fuktighetssensorn visade låg känslighet. Den transienta jordspänningsantennen hade begränsad tillförlitlighet. Slutsatsen av denna studie är att den högfrekventa strömtransformatorn visade sig vara mycket tillförlitlig för online-övervakning av partiella urladdningar, följt av den infraröda kameran och ultraljudssensorn, medan den transienta jordspänningsantennen, temperatur- och fuktighetssensorn visade lägre tillförlitlighet. I framtida forskning kan ytterligare undersökningar av det högfrekventa strömtransformatorsystemet utföras på plats, tillsammans med längre termografiska detekteringstester med hjälp av den infraröda kameran för att ytterligare undersöka deras potential för onlinedetektering av partiella urladdningar.

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