The production of biomass based fuels has long been advocated as a means of utilising solar energy for power generation. The present concern over global warming through the accumulation of carbon dioxide produced from the combustion of fossil fuels gives a further impetus to the consideration of these alternative fuels. They are renewable and photo-synthetically assist to recycle the carbon dioxide they produce on combustion. In particular the plant derived (or vegetable) oils have been shown to be suitable substitutes for hydro-carbon based fuels for use in diesel engines .. The main problems are associated with characteristically low Cetane Numbers and the formation and deposition of residues. However engine tests on both laboratory and commercial type diesel engines show that these oils perform better under normal operating conditions than the Cetane Number would suggest. Furthermore, emulsification with water has been found to reduce emissions of oxides of nitrogen and smoke under certain conditions for both conventional diesel fuel and more particularly for the vegetable oil alternatives and is considered here also as a possible means of reducing residual deposits for the latter. The object of the present work is to study the results of laboratory tests on a single-cylinder diesel engine operating at 750 and 1500 r/min and a four-cylinder diesel engine operating at 2500 and 3500 r/min. Neat diesel and vegetable-oil fuels and their emulsions with 5%, 10% and 15% water, by volume were used in the single-cylinder engine tests at load settings varying from a minimum idling condition to a maximum attainable load condition for each fuel. The single-cylinder engine tests indicated that 10% by volume of water-in-oil in emulsions of both diesel and vegetable oil fuels was the optimum water content. Neat diesel and vegetable-oil fuels and their emulsions with 10% water were thus used in the fourcylinder engine tests. Comparison of the results of the two engines indicates that the trends found in the single-cylinder engine tests also occur in the four-cylinder engine tests. It is shown that both engines perform satisfactorily with vegetable-oil fuel and its emulsion with 10% water, by volume, at a practical running speed despite the low Cetane Number. It is further shown that the Cetane Number. although valid for the conditions of the Cetane test, is not necessarily an appropriate measure of fuel ignitability under different conditions. Ignition-delay values obtained experimentally by analysis of the cylinder-pressure records are compared with calculated values obtained using existing ignition delay correlations. Engine performance parameters and exhaust emissions are not adversely affected when using vegetable-oil fuel or emulsions with 10% water by volume. Indeed the benefits of emulsification on the emissions of smoke and oxides of nitrogen are evident in these tests. This is particularly marked for the vegetable-oil emulsion.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:318937 |
| Date | January 1993 |
| Creators | Kiannejad, F. |
| Publisher | Queen Mary, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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