Patent ID: 8607546

Claim:
Method for operating a compression-ignition internal combustion engine including an exhaust aftertreatment system comprising an oxidation catalyst fluidly coupled upstream of a catalyzed particulate filter, the method comprising: introducing fuel into an exhaust gas feedstream of the engine upstream of the oxidation catalyst; determining operating parameters associated with the exhaust gas feedstream; determining a hydrocarbon slip rate through the oxidation catalyst corresponding to the operating parameters associated with the exhaust gas feedstream and the introduced fuel into the exhaust gas feedstream, comprising determining an effective hydrocarbon oxidation efficiency through the oxidation catalyst corresponding to the operating parameters associated with the exhaust gas feedstream and the flowrate of fuel introduced into the exhaust gas feedstream and determining the hydrocarbon slip rate through the oxidation catalyst corresponding to the effective hydrocarbon oxidation efficiency; and controlling a flowrate of fuel introduced into the exhaust gas feedstream upstream of the oxidation catalyst in response to the estimated hydrocarbon slip rate through the oxidation catalyst; wherein determining the effective hydrocarbon oxidation efficiency through the oxidation catalyst corresponding to the operating parameters associated with the exhaust gas feedstream and the introduced fuel into the exhaust gas feedstream comprises: determining a present base hydrocarbon oxidation efficiency for the oxidation catalyst corresponding to a temperature of the oxidation catalyst, an oxygen concentration in the exhaust gas feedstream, and an exhaust gas resident time in the oxidation catalyst; determining a diffusion-adjusted hydrocarbon oxidation efficiency for the oxidation catalyst corresponding to the present base hydrocarbon oxidation efficiency and a present base diffusion efficiency for the oxidation catalyst; determining a diffusion-adjusted hydrocarbon oxidation efficiency for the oxidation catalyst adjusted for a hydrocarbon/oxygen ratio in the exhaust gas feedstream; and combining the diffusion-adjusted hydrocarbon oxidation efficiency for the oxidation catalyst adjusted for a hydrocarbon/oxygen ratio in the exhaust gas feedstream with the present base diffusion efficiency to calculate the present effective hydrocarbon oxidation efficiency through the oxidation catalyst.