The ignition performance of fuel oils in marine diesel engines

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The ignition performance of fuel oils in marine diesel engines

Zeelenberg, A.P. / Fijn van Draat, H.J. / Barker, H.L.

The traditional parameters defining ignition performance of distillate fuels, cetane number, calculated cetane index and diesel index, are difficult to apply or of uncertain relevance to residual fuel oil. So far residual fuels have shown satisfactory ignition performance in low-speed and medium-speed diesel engines under most operational conditions. Cases of poor ignition performance are rare in practice; they have been encountered mainly in laboratories by the selection of test fuels not representative of what normally is available in the marine market. Research by engine manufacturers has mainly centred upon operating conditions and has resulted in useful practical recommendations such as increasing the intake air temperature at low load for improving ignition performance. The supplementary effect of the chemical nature of the fuel oils, which is beyond their control, has now been studied at Koninklijke Shell-Laboratorium, Amsterdam in test engines in an attempt to relate ignition performance to physical, chemical and preferably inspection properties of the fuels themselves. While several specification data, such as Conradson carbon residue proved to be of little use in predicting ignition quality, the aromaticity of the fuel seems to determine the length of the ignition delay to a much greater extent. This rather scientific criterion is not easily determined in the field, but a function of normal inspection properties has been developed which correlates very well with the above aromaticity.