Stratified exhaust gas recirculation strategy for internal combustion engine

Abstract

A four-stroke reciprocating internal combustion engine that uses stratified exhaust gas recirculation to improve combustion is disclosed. The engine includes at least one combustion chamber defined by a cylinder, a reciprocating piston contained within the cylinder, and a cylinder head. Each combustion chamber is in fluid communication with at least one intake port and at least one exhaust port. At least one intake port includes an associated intake valve, an intake flow motion generating device and an associated intake flow direction control device for creating an intake fluid flow near the center of the cylinder. At least one exhaust port includes an exhaust valve that opens during the intake stroke at part load, an exhaust flow motion generating device and an associated exhaust flow direction control device for creating an exhaust fluid flow near the outer periphery of the combustion chamber during the intake stroke at part load. An engine controller processes signals from at least one sensor and outputs a control signal to a variable valve lift and timing system for operating each intake valve and each exhaust valve such that an exhaust residual flow is inducted through at least one exhaust port into the combustion chamber and air or an air/fuel mixture is simultaneously inducted through at least one intake port into the combustion chamber. If air is inducted into chamber, fuel is directed into the air in the chamber. The engine produces a stratified exhaust gas and air-fuel mixture that includes recirculated exhaust gas which rotates about the cylinder axis and remains substantially along an interior wall of the cylinder and a stoichiometric air-fuel mixture which rotates about the cylinder axis and occupies a portion of the piston surface and the remaining portion of the combustion chamber. Because of the stoichiometric operation of the engine, conventional three-way catalysts can be used for emission control.