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The mixture formation by fuel spray impingement (OSKA system) was applied to a small direct-injection diesel engine in order to reduce the wall quenching- induced emissions, i.e., the emissions of THC and soluble organic fractions (SOF). Experiments were carried out using a single-cylinder engine, fitted with various piston cavity geometries, ran under a wide range of compression ratios and fuel injection specifications. The piston cavity was designed as a centrally located reentrant type. The combination of the high squish flow and the weak penetration of the OSKA spray was very effective in reducing harmful emissions. A short ignition delay, under the retarded fuel injection timing, was obtained because of the high compression ratio. The OSKA DI diesel engine showed reduced NOx, smoke, and THC emissions without deterioration of the fuel consumption compared to modern DI diesel engines used in automotive applications.

Considerable amounts (400 ∼ 600 thousand tons) of waste vegetable oil in Japan are still flushed down the drain every year. Utilization of waste vegetable oil for diesel fuel leads to two advantages for environmental protection, to reduce CO2 emission from engines and to avoid water pollution of rivers. In this study, combustion characteristics of waste vegetable oil methyl ester (WME) are investigated in detail by not only engine test run but also observation of burning flames in a visual engine. As results indicate, WME shows rather better combustion state in the visual engine and lower smoke emission from a high-speed DI test engine than gas oil. Moreover, by emulsifying WME with water, further improvement of combustion and more than 18 % reduction of NOx emission is carried out.

This paper details the air-fuel mixing process in a gasoline direct injection (DI) engine. Laser measurement techniques such as particle image velocimetry (PIV) and laser induced fluorescence (LIF) were employed on the optical engine with a transparent cylinder to analyze the in-cylinder flow and fuel vapor concentration. In addition, firing tests were conducted using an actual engine. Test results showed that the multi-stage injection is effective for air-fuel mixing and improvement of combustion stability.