EGR 변화에 따른 CAI 엔진 연소 소음 저감에 관한 연구

Controlled Auto Ignition (CAI) engine, which is still on developmental stage, is widely known to have higher efficiency and lower emission than conventional gasoline engine. A few problems (such as ignition control and operational range) are still holding back the CAI engine from commercialization, and combustion noise, which is the main subject of this study, is one of them. Since a significant portion of the CAI engine combustion process is similar to that of a conventional SI engine under knocking condition, large noise just might seem inevitable. Although self-ignition of gasoline in CAI engine is different from SI engine in that it is intentional, the fact that self-ignition occurs almost simultaneously in several different locations within the clearance volume and causes large pressure gradient, is the same. To achieve possible noise reduction in CAI combustion, cooled EGR was used as the potential sound reducing additive in the experiments of this study. In order to simulate the effects of cooled EGR in our experiment, commercially charged carbon dioxide with 99% purity was used. In the various cases of our experiment, CO₂ gas was injected through the intake port at various volumetric percentages ranging from 0 to 2%. As a result, correlation between pressure gradient and effect of cooled EGR was found in this research while IMEP was maintained at a similar level.