The combustion of “A/C” blend fuels in a high speed, four-stroke, direct-injection engine have been investigated by using a high speed photo-system.
Three kinds of fuel (A heavy oil, 70% A heavy oil + 30% C heavy oil and 30% A heavy oil + 70% C heavy oil) were used. The combustion performance was measured in this experiment, also the influence of injection timing and of fuel temperature was discussed.
It is shown that the ignition lag of blend fuels mixed with 30% C heavy oil was almost the same as that of A heavy oil. In the range of tests, only small differences of ignition lag were found by heating the fuels.
Up for the 30% C heavy oil in blend fuel, the combustion phenomena showed almost the same as A heavy oil, but for 70% C heavy oil, the different combustion phenomena were observed in the growth of initial flame and termination of combustion in the cylinder.
With increasing the content of C heavy oil in blend fuels, the combustion efficiency and the concentration of NOx in exhaust gas decreased.
For the three kinds of fuel above, the combustion phenomena and combustion performance had the same tendency with changing of injection timing.

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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.

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An extensive investigation was carried out to evaluate the feasibility of using Exxon Donor Solvent (EDS) coal-derived liquid fuel for marine diesel engines.
The characterization analyses and the thermogravimetry were first performed predicting the nature of the fuels and their properties relevant to diesel engine performance, and also compatibility of EDS coal liquid and marine diesel oil (MDO) was tested. The combustion test of several blending fuels of EDS and MDO was carried out with two laboratory engines of high and medium speed type. The test clarified the available maximum ratio of bleding in unmodified engines and the effect of modification such as higher compression ratio and higher intake air temperature was confirmed.
As the result, the characteristics of EDS coal liquid have been clarified and the performance of EDS and its blending fuels with MDO in diesel engines was found. And then, the investigation found that the existing high speed engine, which was used in this test, as well as medium speed ones can use EDS blended with MDO in the ratio 50 to 50 with small modification and some countermeasures.

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This paper deals with trouble occurrence cases of machinery by degraded fuel oil using the questionnaire reports from the companies belong to the Japanese Ship-owners' Association during 1984, and the situations of troubles experienced at our company's ships.

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オイルショック以後, 船舶発電用中速ディーゼル機関にあってもC重油を燃料とする技術はいちじるしく向上し, 当社では1982年にIF380, 1984年にIF700C重油機関を開発している.
これと並行して, 船主や造船所においてもディーゼル主機関と補機関に同一のC重油を適用するモノフュエル船を建造するようになったが, 就航船における長時間の実績としては, まだIF380モノフュエル船を調査できるという段階である.
本稿は当社のIF380C重油 (以下C重油と言う) 機関6PL-24を発電機関としているモノフュエル実船の追跡調査結果を報告するものである.
舶用機関の機能を十二分に発揮させるには, 機関自身の性能, 耐久性とともに, その周辺の機関室設備とシステムにも十分な配慮が必要であり, C重油機関にあっては特にそうであると考える.
本報告では, 就航後の追跡調査結果だけでなく, 6PL-24機関の概要, 本船計画段階において, 船主, 造船所, エンジンメーカである我々との間で十分意見をかわして決定した機関室システムの考え方も紹介する.
今回調査した船は西ドイツHDWキール造船所196, 200, 201番船として建造された3隻中の第1船で船名はカルタゴ号 (M/VCALTHAGO) , 船主は西ドイツのクリスティアンフ・アーレンキール社, 1984年5月就航の26140DWt, 1328TEUコンテナ船で550kW発電機を駆動する当社6PL-24形機関3台を搭載している (表1) .発電機関の発停・低負荷運転も含めすべての負荷において主機関燃料と同一のIF380C重油を使用して15000時間ピストン無開放の目標をたて, その可能性調査を第1号発電機関について, 船主・造船所協力のもとに実施した.
また, これと比較のため発停・低負荷運転をA重油で行う別の実例について, その訪船調査も報告する.この船は韓国現代造船所319, 320, 321番船の第1船で1985年1月就航の32000DWt貨物船スター・フロリダ号 (M/VSTAR・FLORIDA) で船主はノルウエーのビラボン社である.
750kW発電機を駆動する当社6PL-24形機関3台を搭載しており定常負荷における燃料はIF380C重油である.

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As the specific gravity of the marine fuel oil increases, catalytic fines of high hardness have come to be seen in the fuel oil in addition to high viscosity and low combustability.
In order to meet these trends, improvements of fuel treatment, startability, combustability, durability, etc. have been taken up as the main study themes these days. Among them the study concerned with the wear has been thought difficult to deal with, in spite of its importance, because of requirements of spending much time for the evaluation, large fluctuation and scarce repeatability among the data. However, as far as no further improvements in the marine fuel characteristics are available in the prospect for the years to come, the study on the wear could not help being taken up among the study themes.
Under the circumstances, it is the writer's eager desire to introduce and offer for the readers' reference, not only improvements of several kinds of methods to know the wear of the cylinder liner and piston rings which are apt to be effected by the fuel oil characteristics, but also a new method developed by us for the purpose.

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