Nitrogen dioxide generation diagnostic for a diesel after-treatment system

摘要

A method for assessing NO2 generation efficiency in a diesel engine after-treatment (AT) system having a diesel oxidation catalyst (DOC) downstream of the engine generating the NO2 and a selective catalytic reduction (SCR) catalyst downstream of the DOC converting NOX with the aid of the NO2. Engine exhaust gas flow is passed into the AT system and a reductant is injected into the gas flow between the DOC and the SCR catalyst. SCR inlet gas flow temperature is monitored during transient engine operation and DOC inlet and SCR catalyst outlet NOX concentrations are detected when the SCR catalyst inlet gas flow temperature is in a predetermined range. SCR catalyst NOX conversion efficiency is determined using the detected DOC inlet and SCR catalyst outlet concentrations of NOX. Additionally, whether the NO2 generation efficiency is at or above threshold efficiency is assessed by comparing the determined and threshold NOX conversion efficiencies.

主权项

1. A system for assessing nitrogen dioxide (NO2) generation efficiency in a diesel engine after-treatment (AT) system, the system for assessing NO2 generation efficiency comprising:
an exhaust manifold configured to receive the exhaust gas flow from the engine; a turbocharger connected to the exhaust manifold and configured to pass the exhaust gas flow from the exhaust manifold into the AT system, wherein the AT system includes a diesel oxidation catalyst (DOC) arranged downstream of the engine and configured to generate the NO2, and a selective catalytic reduction (SCR) catalyst arranged downstream of the DOC and configured to convert oxides of nitrogen (NOX) into diatomic nitrogen (N2) and water (H2O) with the aid of the generated NO2; and a controller configured to:
inject a reductant into the exhaust gas flow at a location in the AT system downstream of the DOC and upstream of the SCR catalyst;monitor temperature of the exhaust gas flow at the SCR catalyst inlet during transient engine operation;detect a concentration of NOX at the inlet of the DOC and a concentration of NOX at the outlet of the SCR as the engine continues transient operation and the temperature of the exhaust gas flow at the SCR catalyst inlet is in a predetermined range;determine a conversion efficiency of NOX by the SCR catalyst using the detected concentrations of NOX at the inlet of the DOC and at the outlet of the SCR catalyst; andassess whether the NO2 generation efficiency in the AT system is at or above a threshold NO2 generation efficiency by comparing the determined conversion efficiency of NOX with a threshold conversion efficiency of NOX.