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Exhaust emissions of a test gasoline engine were successfully reduced to 1/30 of the SULEV standards with the aim of minimizing the impact on the atmospheric environment. This reduction was achieved by reducing engine-out emissions from engine startup and by reconciling faster catalyst light-off with suppression of catalyst thermal degradation to avoid a decline in conversion efficiency. Specifically, a new intake gas flow control device and a low heat mass spark plug with high ignitability were developed for promoting post-oxidation of unburned HCs in the combustion chamber thus markedly reducing engine-out emissions, while ensuring acceptable drivability. The conflicting requirements for quicker catalyst light-off and avoidance of catalyst thermal degradation have been achieved at unprecedented levels by developing a new bypass-type exhaust manifold.

This research focused on the light emission behavior of the OH radical (characteristic spectrum of 306.4 [nm]) that plays a key role in combustion reactions, in order to investigate the influence of the residual gas on autoignition. Authors also analyzed on the heat release and thermodynamic mean temperature due to research activity state of unburned gas. The test engine used was a 2-stroke, air-cooled engine fitted with an exhaust pressure control valve in the exhaust manifold. Raising the exhaust pressure forcibly recirculated more exhaust gas internally. When a certain level of internal EGR is forcibly applied, the temperature of the unburned end gas is raised on account of heat transfer from the hot residual gas and also due to compression by piston motion. As a result, the unburned end gas becomes active and autoignition tends to occur.

This research focused on the light emission behavior of the OH radical (characteristic spectrum of 306.4 nm) that plays a key role in combustion reactions, in order to investigate the influence of the residual gas on autoignition. The test engine used was a 2-stroke, air-cooled engine fitted with an exhaust pressure control valve in the exhaust manifold. When a certain level of internal EGR is forcibly applied, the temperature of the unburned end gas is raised on account of heat transfer from the hot residual gas and also due to compression by piston motion. As a result, the unburned end gas becomes active and autoignition tends to occur.