Methods for engine exhaust nox control using no oxidation in the engine

Method for reducing NOx emissions in a powertrain comprising an internal combustion engine including a combustion chamber and an aftertreatment system, the method comprising:

• monitoring operation of the engine;
• determining an actual exhaust gas feedstream ratio of NO2 to NO;
• determining a desired engine NOx aftertreatment device based upon the operation of the engine;
• selecting a desired exhaust gas feedstream ratio of NO2 to NO based on the desired engine NOx aftertreatment device;
• comparing the actual and the desired exhaust gas feedstream ratios of NO2 to NO;
• injecting a fuel mass into the combustion chamber after a primary combustion event to generate HO2;
• and
• utilizing the generated HO2 to oxidize NO present in the combustion chamber to generate NO2 sufficient to establish the actual exhaust gas feedstream ratio of NO2 to NO at the desired exhaust gas feedstream ratio of NO2 to NO.

Apparatus for reducing NOx emissions in a powertrain comprising an internal combustion engine including a combustion chamber, the apparatus comprising:

• an aftertreatment system;
• and
• an aftertreatment system control module:
• monitoring an actual exhaust gas feedstream ratio of NO2 to NO;
• monitoring a desired exhaust gas feedstream ratio of NO2 to NO;
• comparing the actual and the desired exhaust gas feedstream ratios of NO2 to NO;
• selectively initiating NO2 generation by injecting a fuel mass into the combustion chamber after a primary combustion event sufficient to establish the actual exhaust gas feedstream ratio of NO2 to NO at the desired exhaust gas feedstream ratio of NO2 to NO.