Patent ID: 8720189

Claim:
An engine exhaust treatment system fluidly coupled to an internal combustion engine, comprising: an oxidation catalyst disposed in an engine exhaust stream; a hydrocarbon injector disposed upstream of the oxidation catalyst; a temperature sensor disposed in the exhaust stream upstream of the oxidation catalyst; a temperature sensor disposed in the exhaust stream downstream of the oxidation catalyst; and an electronic control unit in communication with the temperature sensor disposed in the exhaust stream upstream of the oxidation catalyst, with the temperature sensor disposed in the exhaust stream downstream of the oxidation catalyst, and with the hydrocarbon injector, the electronic control unit configured to: inject hydrocarbon fuel into the exhaust stream upstream of the oxidation catalyst; measure a temperature of the exhaust stream on the upstream and downstream sides of the oxidation catalyst during a predetermined period of time following the injection of hydrocarbon fuel into the exhaust stream; calculate a difference in exhaust stream temperature between the upstream and downstream sides of the oxidation catalyst; and determine a value for conversion of NO to NO2 by the oxidation catalyst from the difference in exhaust stream temperature based on a predetermined correlation profile between the temperatures on the upstream and downstream sides of the oxidation catalyst and conversion of NO to NO2.