This thesis identifies the benefits offered by combustion pressure measurement in petrol engines to real-time engine control. Benefits include reduced exhaust emissions and better engine performance. The various techniques used for combustion pressure measurement are reviewed, and thick-film piezoresistive technology is identified as a technology capable of producing a low cost sensor. Two possible locations for. the thick-film pressure sensor are experimentally investigated, both on the spark plug. The piezoresistive material chosen is Heraeus 8241, a widely used material based on jt ruthenium dioxide particles in a glass matrix. Properties relevant to the construction of a combustion pressure sensor are evaluated; the elastic modulus is measured for the first time between 173 and 573K, and piezoresistivity is measured for the first time between 77 and 533K. The response of thick-film piezoresistors to hydrostatic pressure is investigated. A spark plug sensor is constructed, calibrated and engine tested. The detection of the angle of peak pressure, magnitude of peak pressure and knock is demonstrated.

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This thesis describes the development of a microprocessor based control system for a parallel hybrid petrol/electric vehicle. All the fundamental systems needed to produce an operational vehicle have been developed and tested using a full sized experimental rig in the laboratory. The work begins with a review of the history of hybrid vehicles, placing emphasis on the ability of the petrol electric design to considerably reduce the consumption of oil based fuels, by transferring some of the load to the broad base of fuels used to generate electricity. Efficient operation of a hybrid depends on the correct scheduling of load between engine and motor, and correct choice of gear ratio. To make this possible torque control systems using indirect measurements provided by cheap sensors, have been developed. Design of the control systems is based on a theoretical analysis of both the engine and the motor. Prior to final controller design, using the pole placement method, the transfer functions arising from the theory are identified using a digital model reference technique. The resulting closed loop systems exhibit well tuned behaviour which agrees well with simulation. To complete the component control structure, a pneumatic actuation system was added to a 'manual gearbox' bringing it under complete computer control. All aspects of component control have been brought together so that an operator can drive the system through simulated cycles. Transitions between modes of operation during a cycle are presently based on speed, but the software is structured so that efficiency based strategies may be readily incorporated in future. Consistent control over cycles has been ensured by the development of a computer speed controller, which takes the place of an operator. This system demonstrates satisfactory transition between all operating modes.

In 2004, the Municipal Property Rates Act 6 of 2004 (MPRA) was promulgated which repealed all the Valuation Ordinances that existed in South Africa. This introduced a single piece of legislation for the purposes of conducting municipal valuations. This study concentrated on the Cape Town Metropolitan 2006 General Valuation that, at the time, was the first local authority to conduct municipal valuations in terms of the new legislation. The research explored the extent to which local authorities intervened in the valuation process, the in dependent judgment of property valuers as well as non-co-operation by oil companies during the valuation process, which was evident by them not responding to the survey questions. The manner in which petrol filling stations were valued, the most frequently used methodology applied and the application of the MPRA in the process were explored. The research was supplemented with a survey of property valuers employed by the local authorities as well as in private practices. This culminated in a holistic overview of the shortcomings in the legislation, the methodology and practice by interested parties in arriving at the municipal valuation in order to provide a critical review. From the critical review, the shortcomings in the valuation processes were identified, the methodology was addressed and recommendations made to the local authority.

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This thesis presents an ethnographic study of the downstream petroleum industry in Ghana focusing on trade, infrastructure, flow, politics and social relationships. In 2010, the West African Republic of Ghana started pumping crude oil from the offshore Jubilee-field. The rapid development from discovery to extraction, along with economic expectations generated by the development of the new upstream industry, led to exponential growth in the downstream industry. A liberalisation reform of the downstream industry was initiated in 2005 and the state started to redefine its role in the petroleum industry, allowing a range of private entrepreneurs to participate in the downstream sector. On the back of these key transformations of the industry, this thesis demonstrates the continuous politicisation of petroleum products on a national level and the significance of this politicisation on infrastructure, networks and social relationships throughout the industry. This thesis argues that the trade, distribution and price of petroleum products in Ghana facilitates and shapes political and economic reciprocity between the government, the publics and profitable economic networks. Even though there was adequate infrastructure such as refinery, pipelines and petroleum storage depots, petroleum products in Ghana were distributed in a way that allowed the most number of people to come into contact with petroleum, by having access to the actual product, but also through enabling job creation and profitable economic activities. The petroleum infrastructure would obstruct profitable networks and informal markets. I propose the term ‘Politics of Petrol’ to emphasise how the industry and the commodities were part and parcel of the political and social fabric in Ghana. Reflecting the negotiable nature of politics and reform alongside the changeable practices and networks in the industry - Politics of Petrol - demonstrates the productive purpose of petroleum in Ghana’s democracy.

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