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Diesel combustion and emissions with four kinds of oxygenated agents as main fuels were investigated. Significant improvements in smoke, particulate matter, NOx, THC, and thermal efficiency were simultaneously realized with the oxygenates, and engine noise was also remarkably reduced for the oxygenates with higher ignitability. The improvements in the exhaust emissions and the thermal efficiency depended almost entirely on the oxygen content in the fuels regardless of the oxygenate to diesel fuel blend ratios and type of oxygenate. The unburned THC emission and odor intensity under starting condition with an oxygenate were also much lower than with conventional diesel fuel.

Remarkable progress has been made in recent years on pressure measuring techniques and apparatuses, yet they seem not necessarily successful in achieving accurate pressure diagrams at the high frequency range. The primary cause of difficulty lies in the occurrence of undesirable vibrations in the connecting passages which diminishes the accuracy of pressure diagrams. In order to prevent such vibration, the authors have attempted to increase the natural frequency in the connecting passages by enclosing heat resisting silicon oil, to analyse the frequency characteristics of the passages, and to ensure the propriety of the analysis through comparison with experiments. As a result, it is proved that the natural frequency of the silicon oil enclosed passage increases twice as high as that of the passage filled with working gas.