EGR system with dedicated EGR cylinders

A method of operating an internal combustion engine, the engine having an intake manifold and having multiple cylinders, comprising:

• operating at least one cylinder of the engine as a dedicated exhaust gas recirculation (EGR) cylinder, such that the exhaust from the at least one dedicated EGR cylinder is completely recirculated to the intake manifold, and such that none of the exhaust from the remaining cylinders is recirculated to the intake manifold;
• providing the engine with an exhaust gas recirculation loop in which recirculated exhaust flows from the at least one dedicated EGR cylinder into the intake manifold without fluid communication to the exhaust exiting the engine;
• wherein the at least one dedicated EGR cylinder and the remaining cylinders share the same intake manifold, such that the recirculated exhaust is combined with fresh air in the intake manifold;
• using a water-gas shift catalyst in the loop to increase the hydrogen level of the recirculated exhaust received into the intake manifold;
• controlling the amount of the recirculated exhaust, at least in part, by means of variable valve timing of the at least one dedicated EGR cylinder;
• operating the at least one dedicated EGR cylinder at a rich air-fuel ratio that is rich of stiochiometric;
• operating the at least one non dedicated cylinder at a stoichiometric air-fuel ratio;
• and
• controlling the composition of the recirculated exhaust by controlling the rich air-fuel ratio provided to that cylinder;
• wherein the step of controlling the composition is performed to produce exhaust gas from the at least one dedicated EGR cylinder having levels of hydrogen predetermined to provide a desired rate of fuel consumption by all cylinders in accordance with a predetermined relationship between the rich air-fuel ratio and fuel consumption.