SI 희박연소 엔진의 연소특성에 미치는 EGR의 영향에 관한 실험적 연구

As an intake process in the conventional spark ignition gasoline engine, the mixture with gasoline and air are inlet through the suction valve into cylinder, compressed and then ignited by an electric discharge, therefore the state of mixture is very important in the characteristics of combustion and emission. Therefore the lean operation is known to decrease the exhaust emission while maintaining a good fuel economy, but at very lean mixtures, the combustion rate has been resulted to reduce. In this experimental study, it is experimented and analyzed the combustion and emission formation according to intake some charge conditions in the lean bum and normal gasoline engine, which is modified the intake system with engine speed, EGR rates and gas temperatures. The following conclusions were drawn out by using the analysis of combustion and emission in this engine with engine speed, flow rates and temperatures of EGR. It is found that the maximum combustion pressure has risen in the condition of lower temperature more than higher temperature of the inflow exhaust gas. And the occurance crank angle of peak pressure has been advanced to the TDC. The brake specific fuel consumption in the cooled EGR gas has enhanced by 7 g/ps-h than that in the hot exhaust recirculation gas of engine charge. It has been verified that NO formation has been reduced as the flow rate of the cooled exhaust recirculation gas, but not reduced clearly the temperature of the hot EGR gas. The formation of unburned hydrocarbon has been reduced more in the case of 10% rate of EGR gas, and then found this phenomenon at lean mixture operation of this gasoline engine.