Potential of Reducing the NOX Emissions in a Spray Guided DI Gasoline Engine by Stratified Exhaust Gas Recirculation (EGR)

In this paper, results of experimental and numerical investigations of stratified exhaust gas recirculation in a single-cylinder gasoline engine are presented. The engine was operated in spray guided direct injection mode. The radial exhaust gas stratification was achieved by a spatial and temporal separated intake of exhaust gas and fresh air. The spatial separation of both fluids was realized by specially shaped baffles in the inlet ports, which prevent an early mixing up to the inlet valves. The temporally separation was performed by impulse charge valves, with one for the fresh air and one for the exhaust gas. From various possible strategies for time-dependent intake of fresh air and exhaust gas, four different strategies for the exhaust gas stratification were examined.