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Air velocities in the cylinder of motored engine were measured by laser Doppler anemometer (LDA) and particle image velocimetry (PIV) to make the standard database that will be used for verification of the numerical simulation. A 4-stroke, 4-valve test engine with transparent cylinder was operated with engine speed of 600rpm. The velocities on that condition were measured individually in vertical- and swirl-direction. The distributions of mean- and RMS- velocities are obtained from the measured data. Flow velocity through the intake valve was also measured at the top of the cylinder. As the results, the flow structure by each crank angle can be clarified. The present data can be commonly used for some numerical research group of RC238 in JSME for verification of numerical simulation results. The effect of the tumble generation valve (TGV) is evaluated by velocity distributions.

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.

Some SI (spark-ignition) engines fueled with gasoline for industrial machineries are designed based on the conventional diesel engine in consideration of the compatibility with installation. Such diesel engine-based SI engines secure a combustion chamber by a piston bowl instead of a pent-roof combustion chamber widely applied for SI engines for automobiles. In the development of SI engines, because knocking deteriorates the power output and the thermal efficiency, it is essential to clarify causes of knocking and predict knocking events. However, there has been little research on knocking in diesel engine-based SI engines. The purpose of this study is to elucidate knocking phenomena in a gasoline engine with a re-entrant piston bowl and swirl flow numerically and experimentally. In-cylinder visualization and pressure analysis of knock onset cycles have been experimentally performed. Locations of autoignition have been predicted by 3D-CFD analysis with detailed chemical reactions.

To drastically improve thermal efficiency of a gasoline spark-ignited engine, super-lean burn is a promising solution. Although, studies of lean burn have been made by so many researchers, the realization is blocked by a cycle-to-cycle combustion variation. In this study, based on the causes of cycle-to-cycle variation clarified by the authors’ previous study, a unique method to reduce the cycle-to-cycle variation is proposed and evaluated. That is, a bulk quench at early expansion stroke could be reduced by making slight fuel stratification inside the cylinder using the twin-tumble of intake flows. As a result, the lean limit was extended with keeping low NOx and moderate THC emissions, leading to higher thermal efficiency.

The chemiluminescence emission intensity can be measured with high temporal resolution, leading to understanding the chemical reaction. Time-series chemiluminescence measurements of OH*, CH* and C2* were carried out to understand flame propagation speed, its thickness and A/F ratio of combustion status. The optical piston head (quartz) allows us to visualize combustion chamber. It is found that the chemiluminescence intensity ratio of CH*/OH* and C2*/OH* can estimate local A/F. The A/F measured by O2 sensor was used for evaluation and the results indicate this method can be applicable to estimate A/F.