Catalyst light-off for turbocharged internal combustion engine having dedicated EGR cylinder(s)

摘要

A method of decreasing the light-off time of a catalytic exhaust aftertreatment device, using exhaust gas recirculation (EGR) in a turbocharged internal combustion engine. The engine has at least one “dedicated EGR cylinder”, whose entire exhaust is recirculated back to all the engine cylinders. The dedicated EGR cylinder(s) may be operated to produce a differently compositioned exhaust gas than the other cylinders. During light-off, EGR gas is optimized for heat, diverted from the EGR loop and routed to a point directly upstream the aftertreatment device.

主权项

1. A method of using exhaust gas recirculation (EGR) to decrease the light-off time of a catalytic exhaust aftertreatment device, in an internal combustion engine having a number of cylinders, comprising:
using one or more of the cylinders as a dedicated EGR cylinder, such that all of the exhaust produced by EGR cylinder(s), during all or some engine cycles, may be recirculated via an EGR loop when the engine is in normal (non cold start) operation; operating the dedicated EGR cylinder at a first air-fuel ratio that is different from that of the cylinders that are not dedicated; determining whether the engine is in cold start condition; if the engine is in cold start condition, entering a cold start mode that includes the following steps; using an EGR bypass line to divert all or some of the dedicated EGR from the EGR loop to the main exhaust line to a point between the turbine and the exhaust aftertreatment device; operating the dedicated EGR cylinder(s) at a second air-fuel ratio that is also different from that of the cylinders that are not dedicated; and providing supplemental oxygen to the EGR bypass line; determining whether light-off of the aftertreatment device has occurred; and if light-off has occurred, ending the cold start mode.