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Diesel engine has been used as a power source in many fields, because of its high thermal efficiency and durability. But its exhaust gas emissions, such as NOx or Particulate Matter, are considered as the matter which brought the air pollution. Thus, it is needed to reduce such harmful matters to agree with the level set by the legislation. In this study, the engine performance of the mixed fuel comprised of DME (Dimethyl Ether) and marine diesel oil was experimentally examined. Because of the molecule properties of DME, it emits no soot in combustion. At the atmospheric condition, DME can be liquefied with rising in its pressure. When liquefied DME is injected in combustion chambers, the flashing energy is supposed to be useful as the atomization of other liquid fuels. A small high-speed direct injection diesel engine was used as the test engine. Its bore and stroke were 92mm and 96mm, and the compression ratio was 17.7.

Some volumes of gas oil and ethanol were mixed to the rape-seed oil to examine the engine performance characteristics. A 4-cycle indirect injection diesel engine was used as the test engine, and exhaust emissions were measured together with cylinder pressure history in variation of the engine loads. The single droplet combustion test was also carried out. Combustion processes in the heated constant volume vessel were observed by using of a high-speed video camera. From the experiments, it is obtained that rape-seed oils take longer combustion duration compared with gas oils. And addition of ethanol promotes the micro explosion of fuel droplets. These features affect to the properties of exhaust emissions from the engine.

Diesel engine has fuel combustion capability in various high density oil such as residual fuels or biofuels derived from fossil or living matter. But for commercial use, these fuels except bio diesel fuel (BDF) should be heated, separated and filtered by equipment and dosed or mixed with additive or distillate oil etc. before being supplied to the engine in order to improve combustibility. This study aims to illuminate fuel characteristic of blend contained woody pyrolysis oil (WPO) which is high viscosity and incombustible, and dimethyl ether (DME) whose emission of combustion has no soot particle. This paper describes thermo-physical property of neat WPO and the blend on the basis of the evaluation of fuel fluidity by measurement and calculation of viscosity. According to the result, it was confirmed that the fluidity of WPO was improved by mixing DME and the approximate viscosity expressions at any temperature of WPO and the blend were good accuracy.