Method for supplying EGR in an i.c. engine

摘要

Each cylinder of the engine has at least one intake valve and one exhaust valve operating on a four stroke cycle. The method comprises selectively interchanging in timing relative to the engine strokes the opening events of the intake and exhaust valves of one or more cylinders when EGR is required so that the exhaust valve is opened during a downward stroke drawing exhaust gases from the exhaust system into the cylinder and the intake valve is opened during a upward stroke discharging exhaust gases from the cylinder into the intake. The cylinder (EGR cylinder) thereby operates as a positive displacement exhaust gas charger with two gas exchange strokes and two non gas exchange strokes during the four stroke cycle delivering exhaust gases for mixing with the intake air supplied to the remaining cylinders (power cylinders). Fuel may be injected into the EGR cylinder for pre-conditioning the fuel in the hot exhaust gases in the EGR cylinder, and the EGR gases and pre-conditioned fuel may be subsequently mixed with the intake air supplied to the power cylinders of the engine for combustion within the power cylinders.