【作者】

Koji Takasaki

【摘要】

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。The trend of shifting from HFO to alternative fuels is promoted by two circumstances: tighter regulations for emissions from ships imposed by the IMO including the SOx and NOx regulation; and the benefit for cost-effectiveness in operation achieved by the more affordable fuels. This paper investigates the potential of a number of alternative fuels as future environmentally-friendly marine fuels using a world-largest class visual combustion test facility, RCEM (Rapid Compression & Expansion Machine). Contents of the liquid fuel part are as follows: 1. Low sulfur but high aromatic fuel CLO (Clarified Oil = heavy cycle oil) is a residual from the FCC (Fluid Catalytic Cracking) process in the oil refinery, and is mainly composed of 2-3 ring aromatics. However, it has rather low-sulfur content and will be fit for the Global Cap of marine fuel from 2020. As a measure to improve the poor ignition quality of CLO, high CN (Cetane Number) component like GTL (Gas to Liquid) is mixed and the effect as an ignition improver is confirmed. 2. Large amount of water emulsion In this test, large amounts of water, even more than fuel (cracked gas oil) itself is mixed and ignited by a pilot injection. About twice the volume of emulsified fuel is injected from larger nozzle hole than the normal pure fuel case to obtain the same heat. This method is effective, not only to reduce NOx drastically to even clear the Tier3 regulation (-75%) but also to promote spray combustion to achieve shorter after-burning. The reason for improvement of spray combustion is examined according to the momentum theory of fuel spray. 3. Methanol As a zero-sulfur fuel, the combustion characteristics of methanol are investigated. Methanol spray combustion displays extremely short after-burning and reduced NOx, which can be explained in the same way as for the wateremulsion technology. As the gaseous fuel study, gases suitable for the GI (high pressure Gas Injection) type engine are investigated. Contents are as follows: 4. Natural gas Image of air-fuel mixture formation by high pressure natural gas jet is fundamentally near to that of liquid spray. Effect of gas injection pressure on GI combustion is investigated by raising it from the conventional 30 MPa level, and improvement of air-fuel mixture formation that leads to faster diffusive combustion is studied. 5. Ethane Ethane will be used as a marine fuel in the near future and GI combustion of ethane instead of methane is here demonstrated. Results indicate that ethane jet burns with more luminous flame because of higher C/H ratio at a little slower burning speed than methane. 6. Hydrogen-admixture to natural gas Adding hydrogen is one way to reduce CO2 further from the natural gas level. Moreover, the prominent effect to improve the natural gas diffusive combustion by added hydrogen is visualized. 7. Low calorie gas Since air entrainment into a gas jet depends on the injected gas momentum, adding even inert gas thus increases the momentum and could improve the diffusive combustion. It is the same theory as for the above-mentioned water emulsion. The admixture of natural gas and inert gas, equivalent to a low calorie gas shows a rather higher combustion rate during the injection than pure methane does. This is a unique feature of GI combustion, which is not seen in the lean-burn type engine. In addition, the inert gas, in contrast to hydrogen addition, has the merit of not increasing NOx.

【会议名称】

第28届CIMAC会议

【会议地点】

芬兰 赫尔辛基

【下载次数】

2

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