抄録
Since the oil crises of late about 10 years, the diesel engine fuel tends to be higher in viscosity and lower in quality. As for“high viscosity”and“low quality”, it is learned from many studies that these two words are not always the same meaning. In fact, the influences on the diesel engine performance or on the durability of the engine components are different according to the fuels from different refinery process or crude oil sources even with the same viscosity level. In actual fuel market, however, fuel is classified mainly by the viscosity and the viscosity grade is the first way for the users and the engine manufacturers to discriminate fuel. Therefore it is interesting to know the influence of reference viscosity of the fuel on the diesel engine performance.
From these points of view, a series of experiments has been carried out on a medium speed diesel engine using high viscosity fuels from 380 cSt up to 1000 cSt (@50°C) prepared by blending the same base oil and cutter oil. Marine diesel oil has also been tested in order to compare with the high viscosity fuels.
This paper describes the results of above-mentioned experiments; i.e. combustion characteristics especially on the ignition delay and on the combustion duration as well as the injection characteristics. The problems at low load region such as smoke and deposit formation on the combustion chamber are also discussed in connection with the combustion characteristics.
