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The effects of ethyl tertiary butyl ether (ETBE) and ethanol (EtOH) blending in gasoline on particulate matter (PM) emissions were investigated for a direct-injection spark ignition vehicle running on a chassis dynamometer. The test was performed under constant-speed conditions and 10.15-mode and 11-mode cycles. The total number of particles was measured by using a condensation particle counter (CPC). It was observed that the number of particles was affected by the amount of aromatics in the fuel and T90 (the distillation temperature where 90 vol.% of the fuel is evaporated), which was caused by the blending of the oxygenated compounds. The impact of T90 on the number of particles was greater for the 11-mode cycle than for the 10.15-mode one.

The effects of octane number on stratified charge combustion were investigated with single cylinder direct injection gasoline engine. Two tests were conducted. First, combustion characteristics of stratified charge combustion were studied by changing fuel octane number. Second, auto-ignition characteristics of stratified charge combustion were compared with that of homogeneous charge combustion by changing fuel component. Three types of fuels were used to change octane number and fuel component. They were single-component fuel, multi-component fuel and refinery feedstock, Unique combustion characteristics concerning octane number was found on stratified charge combustion. The increase of indicated thermal efficiency and decrease of unburned hydrocarbon were observed as octane number decreased. The difference of octane number influence between stratified charge combustion and homogeneous charge combustion was discussed.

A constant volume combustion chamber (CVCC) was used to measure the flame speeds for various kinds of liquid hydrocarbon fuels, and an engine test was also carried out to obtain the relationship between combustion characteristics on the CVCC and the engine performance in an SI engine. In the engine test, it was confirmed that the fuel composition significantly affected the combustion stability under lean-burn conditions. From the relationship between the flame speed in the CVCC and the combustion duration in the test engine, we could find out the possibility of various kinds of fuels as the future fuel base.