Numeric Investigation of Gas Distribution in the Intake Manifold and Intake Ports of a Multi-Cylinder Diesel Engine Refined for Exhaust Gas Stratification

In-cylinder exhaust gas recirculation (EGR) stratification, generally achieved by supplying EGR asymmetrically into intake ports on a four-valve diesel engine, is sensitive to trapped exhaust gas in the intake manifold and intake ports that is caused by the continuous supply of EGR during the valve-close periods of the intake valves. The subject of this study is to evaluate the distribution of trapped exhaust gas in the diesel intake system using commercial Star-CD software (version 4.22.018). Numeric simulations of the intake flow of fresh air and recycled exhaust in the diesel intake system were initialized following previous experiments that were conducted on a reformed six-cylinder diesel engine by supplying CO 2 instead of EGR to the tangential intake port alone to establish CO 2 stratification in the first cylinder. The distributions of the intake CO 2 in the intake manifold and intake ports under the conditions of 1330 r/min and 50% load with different mass flow rates of CO 2 are discussed. This indicates that CO 2 supplied to one intake port alone would escape to another intake port, which not only weakens the CO 2 stratification by diminishing the mass fraction disparity of the CO 2 between the two intake ports of cylinder 1, but also influences the total mass of CO 2 in the cylinder. There is 4% CO 2 by mass fraction in the intake port without CO 2 supply under the condition that the CO 2 mass flow rate is 5 kg/h during the intake process, and 10% CO 2 under the condition of 50 kg/h.