Compression-ignition engine with exhaust system

摘要

A compression-ignition engine (10) comprises an exhaust system (16) with an exhaust gas after-treatment assembly, the after-treatment assembly comprising a three-way catalyst device (30) and an SCR device (34), the three-way catalyst device being arranged upstream the SCR device in close-coupled position with respect to the engine. An engine control unit (47) is provided for controlling operation of the engine. The engine control unit is configured to monitor the temperature of the SCR device and to control the engine to change over from an operation with a lean air/fuel mixture to an operation with a stoichiometric or a rich air/fuel mixture in response to the temperature of the SCR device dropping below a temperature threshold.

主权项

1. A compression-ignition engine comprising
an exhaust system with an exhaust gas after-treatment assembly, said after-treatment assembly comprising a three-way catalyst device and an SCR device, said three-way catalyst device being arranged upstream said SCR device in close-coupled position with respect to said engine; and an engine control unit for controlling operation of said engine; wherein said engine control unit is configured to monitor a temperature of said SCR device and to control said engine to change over from an operation with a lean air/fuel mixture to an operation with a stoichiometric or a rich air/fuel mixture when the temperature of said SCR device drops below a temperature threshold; and said engine control unit further being configured to temporarily prevent or delay the change over to the stoichiometric or rich air/fuel mixture if said engine control unit determines that engine-out NOx emissions will remain below a certain threshold even if the engine continues operating with a lean air/fuel mixture.