Patent ID: 8291695
Filing Date: 2012-10-23
Classification: F01N,F02D,Y02T

Abstract:
1. Method for controlling exhaust emissions from a spark-ignition, direct-injection internal combustion engine, comprising: connecting an aftertreatment system to an exhaust outlet of the engine to entrain an exhaust gas feedstream, the aftertreatment system comprising a first aftertreatment device fluidly connected upstream of a second aftertreatment device fluidly connected upstream of a third aftertreatment device and a reductant injection system configured to inject urea upstream of the third aftertreatment device, wherein the first aftertreatment device comprises an oxidation catalytic device, the second aftertreatment device comprises a three-way catalytic device including cerium, and the third aftertreatment device comprises an ammonia-selective catalyst reduction device having a capacity to store ammonia reductant; operating the engine to generate reformates reformable into ammonia reductant storable on the third aftertreatment device; and then operating the engine lean of stoichiometry and reducing nitrides of oxygen in the exhaust gas feedstream using ammonia reductant stored on the third aftertreatment device under low engine load conditions; operating the engine lean of stoichiometry and employing the reductant injection system to inject urea into the exhaust gas feedstream under low engine load conditions when the ammonia reductant stored on the third aftertreatment device is depleted; operating the engine and employing the reductant injection system to inject urea into the exhaust gas feedstream and using the ammonia reductant stored on the third aftertreatment device to reduce nitrides of oxygen in the exhaust gas feedstream across the third aftertreatment device under high engine load conditions; and operating the engine at stoichiometry and employing the second aftertreatment device to reduce nitrides of oxygen in the exhaust gas feedstream upon detecting a fault in the reductant injection system.