This report investigates methods to reduce fuel consumption in SAAB's prototype hybrid car. It is primarily concerned with changes in the final drive ratio (FDR) of the gearbox. Reducing the FDR lowers the engine speed, allowing the engine to run at a more efficient operating point. However, this has a negative impact on engine power and vehicle performance. It was thought that the hybrid's eXWD (electric cross wheel drive) system could make up for this loss of performance. Computer simulations showed significant improvements in fuel economy when the FDR was reduced. This was confirmed by real world tests on a chassis dynamometer, although the number of tests were too low to establish the precise fuel consumption reduction. The effects on performance were evaluated by creating a quasi static model of the drivetrain and calculating which combinations of speed and acceleration corresponded to the engine's torque limits. The loss of acceleration was found to be lower than the increase in acceleration made possible by eXWD for most choices of FDR. It is therefore possible to reduce the FDR in the hybrid version of the car and still maintain a performance advantage compared to the front wheel drive version. No other major disadvantageous effects were found. The conclusion was therefore that a reduction of the final drive ratio is a feasible method to improve the fuel economy of the prototype car, given that maximizing performance is deemed less important than increasing fuel economy.

In a nuclear reactor core there are fuel assemblies with different age (i.e. how long the assembly has been in the core) and burnup (i.e. how much energy that has been extracted from the assembly). The fresh assemblies have higher reactivity, which means they generate more thermal power, and therefore need a higher coolant flow rate than the older assemblies. In order to redistribute the coolant flow from the older assemblies to the fresher assemblies, the core can be divided into different throttling zones. The older assemblies are placed in the periphery of the core which has higher throttling, while the fresher assemblies are placed in the central parts of the core which has lower throttling. This type of throttling is done in the core inlet. However, there is also an opportunity to throttle the flow into each separate fuel assembly, which is done in the bottom nozzle of the assembly. This type of throttling is usually constant during the whole time the assembly is in the core and is specific for the assembly type, which means that it does not contribute to the redistribution of coolant flow from older to fresher assemblies. In this project, so called variable throttling was studied. This means that the throttling of each assembly is increased after the assembly has been in the reactor core for a specific time (e.g. one or two years) and the need of coolant flow hence has decreased. By doing this, while also decreasing the total coolant flow rate through the core, the amount of void (steam) in the core increases but enough coolant flow is supplied to the fresher assemblies due to the increased redistribution of the flow. An increased amount of void leads to a shift of the neutron spectrum to higher energies (“hardening” of the spectrum), which in turn leads to better breeding. Better breeding means that more fissile material, mainly Pu-239, is produced in the core during operation. A lower enrichment can therefore possibly be used, which would reduce the fuel costs. The results show that, by implementing variable throttling, the breeding is improved and the relevant safety requirements are also fulfilled. According to the calculations, the enrichment in the fresh fuel could possibly be lowered with up to 0.068 weight percent, which means that the fuel costs would be reduced with up to approximately 8 MSEK per fuel cycle.

Detta är en studie med syfte att visa vid vilka driftsförhållanden fartyget M/T Ramonas framdriftsmotor driver fartyget som mest bränsleeffektivt och på så sätt även med minst miljöpåverkan genom avgasutsläpp (Havsmiljöinstitutet, 2017). Dessa två driftsförhållande är lastad samt olastad kondition. Fartyget har under studien körts med så kallat combinator mode och har haft sin strömförsörjning via en axelgenerator. Resultatet baseras på 12 veckors datainsamling.Efter att all data samlats in och uträkningar analyserats, har ett resultat per kondition kunnat presenteras med hjälp utav figurer. Den slutsats som kunde dras var att, vid lastad kondition driver framdriftsmotorn fartyget som mest effektivt vid en belastning på 46 till 48 procent och en hastighet på 10.5 knop. Dock finns en felmarginal då tester inte tilläts vid lägre belastningar på framdriftsmotorn vid tiden för studien. Slutsatsen som drogs för den olastade konditionen var att framdriftsmotorn driver fartyget som mest bränsleeffektivt vid en belastning på 34 till 38 procent och en hastighet på 8.3 knop. / This is a study aimed at showing the operating conditions at which the M/T Ramonas propulsion engine is operated most fuel efficient and thus also with the least environmental impact through exhaust emissions (Havsmiljöinstitutet, 2017). These two operating conditions are loaded and unloaded condition. During the study, the ship has been run in so-called combinator mode and has had its electricity generated via a shaft generator. The result is based on 12 weeks of data collection. After all the data has been collected and calculations has been analyzed, a result per condition has been presented using figures. The conclusion that could be drawn was that, at loaded condition, the propulsion engine is driven most fuel efficiently at a load of 46 to 48 percent and at a speed of 10.5 knots. However, there is a margin of error as tests were not allowed at lower loads on the propulsion engine at the time of the study. The conclusion reached for the unloaded condition was that the propulsion engine is driven most fuel-efficient at a load of 34 to 38 percent and at a speed of 8.3 knots.

Denna studie handlar om den fartförlust och därmed den ökade energiförbrukningen som drabbar fartyg på grunt vatten. Syftet var att ta reda på hur mycket kortare en grund passage behöver vara för att den ska vara ett bättre alternativ än en lång och djup rutt med hänsyn till bränsleförbrukning och tidsåtgång. Resultatet av detta blev att det inte går att dra några generella slutsatser som gäller för alla fartygstyper men att det går att se tydliga tendenser. Studien hade även som målsättning att skapa ett underlag som skulle kunna användas av nautiker vid planering av resor, detta presenterades i form av en sammanställning av de resultat som erhållits vid beräkning av fartförlust i öppet vatten. Någon sammanställning gjordes inte för begränsat vatten eftersom exempelfartygen där fick likadana resultat vilket skulle ha gjort en sådan överflödig. Syftet uppnåddes genom användande av kvantitativa studier i form av matematiska beräkningsmetoder för att beräkna fartförlust, bränsleförbrukning och tidsåtgång för ett antal exempelfartyg. / This study concerns the speed loss and thereby the increased energy consumption which affects ships in shallow water. The aim of the study was to gain knowledge of how much shorter a shallow passage is required to be in order to be the better alternative compared to a long and deep route with regard to fuel and time consumption. The result was that it is not possible to draw any definitive conclusions which are applicable to all ship types, however, there are clear patterns. Moreover, the goal of the study was to aid mariners facing a choice between a long and deep route and a short and shallow route, this was done by creating a compilation of the results for speed loss in open water. Due to the results for confined waters being the same for all the ships in the study, no compilation was done for confined waters as it was deemed excessive. The aim of the study was achieved by quantitative research in the form of mathematical models to calculate speed loss, fuel consumption and time consumption for a number of fictitious ships.