Proposition of a Stratified Charge System by Using In-Cylinder Gas Motion

A new idea for controlling the in-cylinder mixture formation in SI engines is proposed. This concept was developed by applying the results of numerical calculations. Fuel that is directly injected into the cylinder is transferred toward the cylinder head to form a mixture stratification by using the in-cylinder gas motion that is generated by the interaction between the swirl and squish flows inside a combustion chamber. At first, the flow characteristics were measured in the whole in-cylinder space using an LDV system. Also, numerical calculations of the in-cylinder flow were made using measured data as the initial conditions. Secondly, the local equivalence ratio at several points inside the combustion chamber was measured by using a fast gas sampling device. The results showed that this idea generates the desired stratified charge when the fuel is injected with a higher injection pressure (about 1.3 MPa) at near the intake-BDC timing than with a usual pressure of 0.2 MPa in the port-injection case. Further numerical calculations were performed to examine other factors that might enhance mixture stratification during the compression stroke.