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AssigneeJohnson Matthey Public Limited Company
InventorsEive Tord Ronny Allansson, Anders Klas Andreasson, Claus Friedrich Goersmann, Mats Lavenius, Martyn Vincent Twigg, Andrew Peter Walker
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An exhaust system for a vehicular lean-burn internal combustion engine includes a NOx reduction catalyst, a source reductant, means (20) for contacting the catalyst with the reductant, means for sensing the temperature of the exhaust gas and/or the catalyst bed and means, when in use, for controlling reductant addition. The reductant addition control means supplies an amount of reductant to the catalyst at a rate corresponding to a measured temperature value of the exhaust gas and/or catalyst bed, which temperature value has been pre-determined to correlate, in use, with an amount of NOx in the exhaust gas.
An exhaust system for exhausting a gas composition from a vehicular lean-burn internal combustion engine, which system comprising a catalyst for reducing NOx in an exhaust gas to N2 with a suitable reductant, a source of reductant, means for contacting the NOx reduction catalyst with the reductant, an oxidation catalyst disposed downstream of the NOx reduction catalyst, means for determining a temperature difference (ΔT) across the oxidation catalyst, and means for controlling reductant addition, wherein the reductant addition control means controls reductant addition at a rate sufficient to maintain ΔT within a pre-determined range, wherein the system is configured so that the exhaust gas composition over the oxidation catalyst is lean.
A method of controlling, by feedback, addition of a reductant to a catalyst for reducing NOx to N2 in an exhaust gas of a vehicular lean-burn internal combustion engine having an exhaust gas inlet and an exhaust gas outlet, which method comprises providing an oxidation catalyst for oxidising the reductant in lean exhaust gas downstream of the NOx reduction catalyst, measuring the exhaust gas temperature upstream of the oxidation catalyst, measuring the exhaust gas temperature downstream of the oxidation catalyst, determining a temperature difference (ΔT) between the upstream and the downstream of the oxidation catalyst and adjusting a rate of reductant addition so that ΔT is within a pre-determined range.
Dependencies are inferred from the claim text.