Browsing by Author "Yates, Andrew David Bennett"

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    Abnormal combustion - methanol versus gasoline
    (1988) Yates, Andrew David Bennett; Bennett, Kevin
    The maximum efficiency of conventional gasoline engines is largely determined by the compression ratio, and this is limited by the onset of kno8k. The maximum cylinder size is similarly constrained. The relatively higher knock resistance of methanol opens up possibilities for increased efficiency or engine size. The auto-ignition of methanol and gasoline was characterised in terms of fundamental parameters and the results were compared. The research findings were used in the analysis of a particular combustion chamber design to assess the potential of using squish as a means of avoiding knock in a large, spark-ignition methanol engine.
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    An estimation of the performance of spark ignition methanol engines
    (1981) Yates, Andrew David Bennett; Dutkiewicz, Ryszard Karol; Bennett, Kevin Frank
    The possibility of using methanol as an alternative fuel for petrol and diesel engines has been investigated at the University of Cape Town in recent years by the Energy Research Institute. Engines, taken from existing road vehicles, were converted to methanol operation and evaluated. During the planning phase of each conversion, it was apparent that there was a need for a method of estimating the probable performance of the converted engine. The objective of this thesis was therefore to develop a generally applicable formula for predicting the rated performance of a methanol-fuelled, spark-ignition engine given only the bore, stroke, number of cylinders and maximum rated engine speed. The prediction was based on an estimate of the indicated efficiency, the volumetric efficiency and the frictional losses of a methanol engine, from which the shaft power and overall efficiency could be determined. The performance of three engines, which were converted to methanol operation, was used to test the theory. The conversions were each of a very different nature: - a) An automotive petrol engine of which only the carburettor was modified. b) An automotive petrol engine that was modified to take advantage of the properties of methanol to improve the performance. c) A truck diesel engine that was converted to spark ignition for operation on methanol. The predicted results were found to compare favourably with the experimental results, with the exception of one spurious reading. An analysis of the range of error in the theoretical estimate was used as the basis for comparison: Range of error in predicted overall efficiency ± 6%. Range of error in predicted shaft power ± 10%. The work of this thesis would be applicable in situations where a quick answer was required and few details were available. With the aid of a programmable calculator, the anticipated performance map could be obtained in a few minutes.