Student Number : 9506932W - MSc research report - School of Mechanical Engineering - Faculty of Engineering and the Built Environment / In this research project, the performance and emissions of a conventional compression ignition engine fuelled on ethanol as main fuel and dimethyl ether as ignition promoter were investigated. Tests were first conducted on diesel fuel, then on ethanol fuel with dimethyl ether and compared. All tests for both fuelling techniques were conducted at the same engine speed and injector pressure. However, engine settings with specific reference to injection timing and injector pressure were optimised to suit diesel fuel, and were left unaltered when the engine was fuelled on ethanol and dimethyl ether. The injector nozzle configuration used for diesel fuel was a standard three-hole type nozzle, whereas for ethanol fuel with dimethyl ether a standard three-hole nozzle as well as a four-hole type nozzle was used. Also investigated was the effect a catalytic converter would have on exhaust emissions, from both fuelling techniques. The performance results of ethanol/dimethyl ether fuel compared favourably to that of diesel fuel. The brake power attained for both fuelling techniques was approximately the same, however the only penalty incurred to this desired result was the simultaneous increase in the brake specific fuel consumption of ethanol/dimethyl ether fuel. The fuel conversion efficiency of ethanol/dimethyl ether fuel was also found to be lower than that of diesel fuel, this largely attributed to the difference in energy release patterns between the two fuels. The emissions results obtained showed that ethanol/dimethyl ether fuel burns cleaner, mainly due to its chemical structure containing oxygen molecules. The NOx, THC, CO and CO2 emissions, produced before the catalytic converter, of ethanol/dimethyl ether fuel were lower than those of diesel fuel. The catalytic converter further produced lower emissions, with the four-hole type nozzle producing the most desired results. In terms of catalytic converter efficiency, THC and CO emissions were more readily removed compared to NOx. In addition, virtually no smoke emissions were detected for ethanol/dimethyl ether fuel combustion.

The aim of this diploma thesis is to design two different switching power supply circuits with integrated circuits suitable for controlling of LED. The theoretical part describes the principles of two main switching converters topologies – buck and boost. Furthermore, a universal H-bridge structure of switching supply is described. This is compared with the typical switching supply design. Based on specified requirements, two circuits are designed with selected IO which are suitable for using in the automotive industry. Their function and typical schema are described. In the practical part is realized design with both selected IC, choosing components and layout PCB. Set of tests are carried out with manufactured samples. Based on measured results are performed optimalization of samples, which are tested also. In the end of this thesis both samples are compared in terms of function, efficiency and EMC.

The master‘s thesis deals with DC/DC converters for power LED diodes. Gives an overview of the field of LED lighting technology, analyzes various types of converters and shows their principle of operation. Furthermore presents some possible circuit designs for three different voltage levels and the calculations for each part. As an approval of their functionality the results of their measurements are plotted followed by the data evaluation.

The Modular Multilevel Converter (MMC) is one of the most commonly used active converters in the high-/medium-voltage sector due to its many advantages such as high scalability, high efficiency, modularity and low harmonic contents. However, in low-voltage and high-current applications, classical MMC designs are not very economical. Recently there has been interest in a new design of modular multilevel converter with interleaved submodules (ISM-MMC) capable of using lower cost, lower current switches. The aim of this study is to compare several different design configurations for a given ISM-MMC topology including classical MMC and to give the best design approach taking into account the efficiency and energy density of the system. The power loss of ISM-MMC influence the final efficiency. The loss studied in this thesis mainly consists of conduction losses and switching losses in the semiconductor devices and inductor losses. An analytical calculation method is summarized and validated by the simulation result. The simulation result is carried out in PLECS model with different system components. Power density is determined by the output power and the converter dimension. The volume of semiconductor devices and passive components determine the general dimension of the converter. This thesis discusses the selection of semiconductor devices, inductor and capacitor in the system, with semiconductor devices constraining interleaved leg current and submodule voltage, inductor constraining output current ripple and capacitor constraining capacitor voltage fluctuation. After the specific components are designed, their dimensions are evaluated, and thus the power density of different configurations can be compared. / Den modulära multinivåomvandlaren (modular multilevel converter, MMC) är en av de mest använda aktiva omvandlarna inom hög-/mellanspänningssektorn på grund av dess många fördelar som hög skalbarhet, hög verkningsgrad, modularitet och lågt övertonsinnehåll. Men i lågspännings- och högströmsapplikationer är konventionella MMC-konstruktioner inte särskilt ekonomiska. Nyligen har det funnits intresse för en ny design av modulär flernivåomvandlare med interfolierade submoduler (ISM-MMC) som kan uppnå lägre kostnad, och använda mindre halvledarelement. Syftet med denna studie är att jämföra flera olika designkonfigurationer för en given ISM-MMC-topologi inklusive konventionell MMC och att ge den bästa designmetoden med hänsyn till systemets verkningsgrad och energitäthet. Effektförlusten för ISM-MMC påverkar den slutliga verkningsgraden. Förluster som studeras i denna avhandling består huvudsakligen av ledningsförluster och kopplingsförluster i halvledarenheterna och induktorförluster. En analytisk beräkningsmetod sammanfattas och valideras av simuleringsresultatet. Simuleringsresultatet utförs men en PLECS-modell med olika systemkomponenter. Effekttätheten bestäms av uteffekten och omvandlardimensionen. Volymen av halvledarenheter och passiva komponenter bestämmer omvandlarens allmänna dimension. Denna avhandling diskuterar valet av halvledarenheter, induktor och kondensator i systemet, med halvledarenheter som begränsar interfolierad benström och submodulspänning, induktor som begränsar utströmsrippel och kondensatorbegränsande kondensatorspänningsfluktuationer. Efter att de specifika komponenterna har valts utvärderas deras storlek, och därmed kan effekttätheten för olika konfigurationer jämföras.