Patent ID: 9726122
Date: 2017-08-08
CPC Classifications: F02D,F02M,Y02T

Claim:
1. A system, comprising: an internal combustion engine having a plurality of cylinders that receive a charge flow from an intake manifold; at least one of the plurality of cylinders comprising a primary EGR cylinder connected to an EGR exhaust manifold that is flow connected to the intake manifold; remaining ones of the plurality of cylinders being in flow communication with an exhaust manifold that is flow connected to an exhaust passage that emits exhaust gas from the remaining ones of the plurality of cylinders; a controller configured to determine an exhaust pressure condition in the EGR exhaust manifold and, in response to the exhaust pressure condition, dynamically increase a compression ratio of the at least one primary EGR cylinder relative to a compression ratio of the remaining ones of the plurality of cylinders to reduce exhaust gas residuals in the at least one primary EGR cylinder; wherein the at least one primary EGR cylinder comprises a first compression ratio, the remaining ones of the plurality of cylinders each comprise a second compression ratio, and the first compression ratio is greater than the second compression ratio; wherein the at least one primary EGR cylinder includes at least one intake valve and at least one exhaust valve that are connected to a variable valve actuation mechanism that is operable to vary an effective compression ratio of the at least one primary EGR cylinder; wherein the effective compression ratio of the at least one primary EGR cylinder is less than the first compression ratio and greater than the second compression ratio; and wherein during operation the at least one exhaust valve of the at least one primary EGR cylinder is closed before top dead center of a piston of the at least one primary EGR cylinder at initiation of an intake stroke in the at least one primary EGR cylinder and the at least one intake valve of the at least one primary EGR cylinder is opened after top dead center of the piston during the intake stroke of the at least one primary EGR cylinder so that an overlap in the opening of the exhaust valve and the opening of the intake valve is less than zero crank angle degrees to reduce backflow of exhaust gases from the EGR exhaust manifold to the intake manifold through the at least one primary EGR cylinder while each of the remaining ones of the plurality of cylinders are operated with an overlap in an intake valve opening and an exhaust valve opening at initiation of an intake stroke of the respective remaining ones of the plurality of cylinders.