The design of a prototype Otto-Atkinson engine and evaluation of the part load fuel efficiency
Master Thesis
1992
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University of Cape Town
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Abstract
This thesis is an investigation into the application of the hybrid Otto-Atkinson cycle, as a means of improving the part load fuel efficiency of spark-ignition engines. The primary objective of this thesis was to investigate the technical feasibility of the modified Atkinson cycle as a spark-ignition engine concept and thus to quantify the associated potential for greater fuel efficiency. The modified Atkinson cycle is a hybrid cycle which approximates the Otto cycle at full load but tends to emulate the Atkinson cycle at part load, and therefore it is referred to as the Otto-Atkinson cycle. In order to fulfil this objective, a single cylinder engine which operated on the Otto-Atkinson cycle, was designed and constructed. This unusual cycle was achieved by a crank linkage which allowed the power output to be controlled by varying the inlet and compression strokes rather than by the more conventional method of throttling the induced fuel-air mixture. Thus the pumping losses associated with throttled part-load operation are eliminated. Furthermore, the expansion stroke is always greater than the compression stroke, the difference being greatest at part loads. This results in a cycle which approximates the Atkinson cycle for part-load operation. A simplified thermodynamic simulation of the cycle was formulated. Theoretical predictions were made based on this simulation.
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Bibliography: page 71.
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Van Binsbergen, P. 1992. The design of a prototype Otto-Atkinson engine and evaluation of the part load fuel efficiency. University of Cape Town.