The phase relations, electrical properties and structural characteristics of doped cubic stabilised Zirconia based electroceramic materials have been investigated using a number of characterisation techniques. The phase relations of the ternary systems ZrO2 -Y2O3 -TiO2 and ZrO2 -Gd2 O3 - TiO2 at 1500°C have been investigated. Electrical characterisation in air and in low oxygen partial pressures has been carried out using 2-probe A.C. Impedance Spectroscopy and 4-probe D.C. resistivity measurements to ascertain whether compositions within these systems could be utilised as the anode materials in Solid Oxide Fuel Cells. The effect of porosity on the ionic and electronic conducting properties of the ZrO2 -Y2 O3 -TiO2 system has been investigated to provide a clearer understanding of the effect of the porosity within candidate anode materials. The effect of Al2O3 additions on the electrical properties and stability of the Solid Oxide Fuel Cell material of choice, 8 mol% Yttria stabilised Zirconia, has been investigated. Al2 O3 has been found to remain primarily as a second phase within the 8YSZ, however a small quantity of Al3+ does dissolve into the fluorite matrix. Al2 O3 has been found to have a negligible effect on the high temperature ionic conductivity of 8YSZ and improves the resistance of 8YSZ to hydrothermal degradation by stabilising the cubic structure. High temperature Time of Flight Neutron Diffraction has been used to link the change in activation energy observed in 8YSZ to a break down in local ordering of oxygen ions. Extended X-ray absorption Fine Structure Spectroscopy has been used to characterise the local structure of the cations in 8 mol% Yttria-stabilised Zirconia. Analysis of the high temperature data reveals that the local structure is quite different from the average crystallographic structure. The oxygen vacancies were determined to be associated with Zirconium ions and found to disorder at high temperatures.

The purpose of this work was to examine vehicle fuel consumption in urban areas and provide a means by which consumption in various situations could be expressed. A review of previous work has been made, including details of the models used for overall consumption in urban areas. The models used are examined and compared with a simple model based on journey distance, journey time, and number of stops. The value of kinetic energy change as a predictive variable is also examined. An explanation of commercial vehicle consumption is provided, but there are difficulties in generalising this to include the whole vehicle fleet. Minimum estimates of consumption related to gross vehicle weight and functions of journey speed are therefore given for overall consumption and for urban conditions. The effect on fuel consumption of changing the area traffic signal control regime from TRANSYT to SCOOT is examined. The method used is to compare complete journeys of several kilometres rather than short lengths of road near each signal. Significant improvements are found for those routes which are mainly inside the control areas. Consumption at roundabouts, in queues, at simple curves and at part stops are considered in detail. The roundabout data and queueing data were collected on street, and the test track results for part stops and simple curves are compared with limited on street data. Predictive equations are given for the consumption of a 2. 2 litre car.

Hydrogen is considered a possible alternative to fossil fuels. Hydrogen can be produced through dark fermentation with 1 mol hexose yielding a maximum of 4 mol hydrogen in association with acetate production, and 2 mol hydrogen in association with butyrate production. However, an economically and technically feasible process is yet to be established. So far research into fermentative hydrogen production has focused on pure and soluble carbohydrates, particularly glucose. To reduce substrate costs, use of more complex low-cost co- and waste products of the food industry or biomass crops which have undergone minimum pre-treatment would be desirable. Also, whilst much research to date has focused on use of pure bacterial strains, an easily obtainable mixed microflora would be preferable to avoid costs of substrate sterilisation. Therefore this research project focused on fermentative hydrogen production from three abundant (in the UK) low cost substrates, namely a wheat starch co-product, sugarbeet and perennial ryegrass. Anaerobic digester sludge obtained from the local sewage works was used as inoculum in a continuously stirred tank reactor. Production of hydrogen and other fermentation products was measured to gain information about the main metabolic pathways used. To lower hydrogen partial pressure the reactor was sparged with nitrogen and the effect on hydrogen production observed. It was demonstrated that stable fermentative hydrogen production from the wheat starch co-product and sugarbeet water extract was possible in continuous operation. Hydrogen production from grass extract was demonstrated in batch mode. Sparging with nitrogen significantly increased hydrogen yields, by 46% for the wheat starch co-product, by 67% for sugarbeet water extract, and by 184% for ryegrass extract. Maximum yields achieved were 1.9 mol hydrogen per mol hexose converted for 16 days on starch, 1.7 mol per mol hexose converted for 5 days on sugarbeet water extract and 0.8 mol hydrogen per mol hexose converted in batch from grass extract. Therefore up to 48% of the maximum theoretical hydrogen yield was produced. Various factors were identified as preventing higher hydrogen yields. Hydrogen production was more closely related to butyrate than acetate concentration. Also, lactate, ethanol and propionate, which are products of carbohydrate fermenting metabolic pathways that do not produce hydrogen, were detected, as were signs of hydrogen consuming homoacetogenesis in continuous operation.

The work presented in this thesis includes experimental investigation using a basic fluidised bed to gasify woodchips and cold modelling studies to improve the fluid bed reactor dynamics incorporating bed internals, such as draft tubes and jets. Low grade fuel gas was produced from woodchips as feedstock, in a 154 mm i/d fluidised bed as the main experimental part of the project using air as the gasifying medium. The influence of a number of process variables on the gasification process were studied including fuel feedrates, temperatures and bed heights, with respect to their effects on quality and quantity of the fuel gas produced. It was found that fuel gas of about 6 MJ/Nm3 can be obtained with temperatures in excess of 700 °c and with fuel feedrates in excess of 3.5 times stoichiometric. The process also benefitted from increasing the static bed heights of the fluidised bed, which was due to the better separation of the combustion and gasification zones. The cold modelling studies coducted using a 2-D glass model employing a draft tube a nd jet system, and using a novel photographic technique produced more realistic data. This showed that both the systems in question produced induced recirculation rates which can be controlled by the process variables such as bed height, bed and jet velocities. Further studies employing these systems for biomass conversion should prove that a better fuel gas quality and quantity can be achieved. In addition a variety of feedstocks can be utilised using the same reactor configuration.

Dans un contexte de réduction des émissions de polluants et de gaz à effet de serre, mais aussi d’enjeux économiques liés aux ressources en pétrole brut, la nécessité de se diversifier énergétiquement a imposé l’apparition et l’utilisation dans des quantités sans cesse croissantes de carburants de substitution. Ces carburants provenant de nombreuses sources primaires, produits à partir de diverses techniques, possèdent des propriétés physico-chimiques différentes. Les effets de chaque propriété sur le comportement du moteur Diesel (émissions, rendement, etc.) ne sont pas encore compris de manière détaillée. La présente thèse porte sur une étude expérimentale de l’influence des propriétés physico-chimiques des carburants sur les processus physiques se déroulant dans la chambre de combustion pour des applications sur moteurs Diesel. L’originalité de l’approche réside par la définition d’une matrice de carburants (20 carburants au total) dont les propriétés varient de manière indépendante. De plus, les différentes étapes de l’injection Diesel ont été considérées. On s’intéresse par la mise en oeuvre de huit techniques de mesures avancées, à la caractérisation de l’hydraulique dans les orifices de l’injecteur, de la structure du spray, de son atomisation, sa vaporisation et enfin la combustion du mélange résultant. Ces expériences ont été conduites dans des cellules adaptées et sur moteur à accès optiques permettant de reproduire des conditions de fonctionnement représentatives. L’analyse porte essentiellement sur la phase quasi-stationnaire de l’injection pendant laquelle les résultats expérimentaux sont corrélés à des modèles basés sur la physique issus de la littérature et de nouvelles corrélations empiriques sont proposées. / In a context of pollutant emission and green house gas reduction, but also economic issues related to crude oil ressources, the necessity for energy diversification has imposed the emergence and the use in growing quantities of substitute fuels. These fuels derived from numerous feedstocks, produced by several manufacturing processes, have different physico-chemical properties. The effects of each individual property on the Diesel engine behavior (emissions, efficiency, etc) are not well fully understood yet. The present thesis focuses on an experimental study about the influence of physico-chemical properties of the fuels on the processes occuring in the combustion chamber for Diesel engine application. The originality of the approach concerns the definition of a fuel matrix (a total of 20 fuels) for which properties are independently varied. Moreover every stages of the Diesel injection are considered. The interest focuses by the setting of eight advance measurement technics on the caracterization of the flow into the injector orifices, the spray structure and atomization, the spray vaporization and finally the Diesel combustion. Experiments were conducted in dedicated vessels and in an optical access engine allowing to reproduce representive operating conditions. The analysis mainly focuses on the quasi-stationnary phase of the injection event and experimental results are scaled to physic-based models and new empirical correlation are proposed.

The aim of this thesis is to propose the design process and considerations to be employed in the fabrication of a high-volumetric-power-density intermediate temperature solid oxide fuel cell (IT-SOFC), as well as the necessary characterization and analysis techniques for such a device. A novel hexagonal honeycomb design will be proposed with functionally graded electrodes and an alternative electrolyte – a previously unexplored configuration based on attained research. The potential use of CFD software to investigate mass and heat transport properties of an SOFC having such a design shall be discussed, as well as the utility of experimental methods such as the generation of a polarization curve and the use of SEM to characterize electrochemical performance and microstructure, respectively. Fabrication methods shall also be evaluated, and it will be shown that the proposed design is not only feasible but meets the goal of designing an SOFC with a power density of 2 W/cm3 operating at or below 650 C.

Solid Oxide Fuel Cells (SOFC) as the heat source for a heat engine power cycle can greatly increase the overall efficiency. The maximum efficiency is limited in at least the following ways. All thermal heat engine power cycles are limited by the Carnot efficiency which is a function of the hot and cold reservoirs the cycle operates between. Another irreversibility that limits the maximum efficiency of a fossil fuel cycle is the combustion reaction. In a boiler or combustion chamber, the chemical reaction of combustion happens spontaneously, meaning that the reaction happens without being used to generate power. A fuel cell decreases this irreversibility because it generates work as the combustion reaction happens. A SOFC can do this without an expensive catalyst due to the higher operating temperature. The power generated by the fuel cell can be added to the power generated by the thermal power cycle operating from the exhaust of the SOFC. The total work generated would be more than the system would have generated from just the heat engine resulting in a higher overall efficiency for the cycle. A SOFC and a recovery power cycle was simulated in Engineering Equation Solver (EES) to solve for ideal operating conditions. The fuel cell and gas turbine system had a net power output of 136 MW and had an efficiency of 60.84%, assuming the fuel cell had an 85% fuel utilization.

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