Fuel efficient ammonia generation strategy for lean-burn engines utilizing passive NH3-SCR for the control of NOx

摘要

A method and system for operating an ammonia generation cycle in an internal combustion engine and a connected aftertreatment system includes monitoring a parameter of engine operation, comparing the parameter of engine operation to a threshold delineating operation of the engine in one of a stoichiometric operation and rich operation, and operating the ammonia generation cycle based upon the comparing indicating the parameter of engine operation exceeding the threshold.

主权项

1. A method for operating an ammonia generation cycle in an internal combustion engine and a connected aftertreatment system, the method comprising:
operating a deceleration fuel cut-off function command during normal operation of the engine, the deceleration fuel cut-off function command depriving the engine of fuel during deceleration events; monitoring operation of the engine and the aftertreatment system; determining a need to generate ammonia based upon the monitored operation; based upon the determined need and prior to executing the deceleration fuel cut-off function command for an impending deceleration event:
determining a present oxygen storage amount in the aftertreatment system based upon the monitored operation;monitoring driver commands to the engine;determining a predicted deceleration time for the impending deceleration event based upon the monitored operation and the monitored commands;determining a predicted air to fuel ratio in the aftertreatment system if the deceleration fuel cut-off function command is executed during the impending deceleration event;determining a predicted oxygen storage content in the aftertreatment system after the deceleration event based upon the predicted air to fuel ratio in the aftertreatment system if the deceleration fuel cut-off function command is executed and the present oxygen storage amount;determining a predicted air to fuel ratio in the aftertreatment system if the deceleration fuel cut-off function command is not executed during the impending deceleration event;determining a predicted oxygen storage content in the aftertreatment system after the deceleration event based upon the predicted air to fuel ratio in the aftertreatment system if the deceleration fuel cut-off function command is not executed and the present oxygen storage amount;comparing the predicted oxygen storage contents; andselectively overriding the deceleration fuel cut-off function command based upon the comparing indicating an ability to reduce oxygen storage in the aftertreatment system during the impending deceleration event.