An exhaust aftertreatment system and associated method for purifying an exhaust gas feedstream of a lean-burn or other compression-ignition internal combustion engine is described. An instruction set is executable to determine an engine-out NO2 concentration upstream of an oxidation catalyst and determine a first parameter associated with O2 concentration. A consumption of oxygen in the oxidation catalyst due to oxidation reactions is determined, and a concentration of NO2 generated by the oxidation catalyst is determined based upon the consumption of oxygen in the oxidation catalyst. A concentration of NO2 downstream of the oxidation catalyst is determined. A NO2/NOx ratio in the exhaust gas feedstream downstream of the oxidation catalyst is determined based upon the concentration of NO2 downstream of the oxidation catalyst and the NOx concentration measured by the downstream NOx sensor. The oxidation catalyst is evaluated based upon the NO2/NOx ratio.

An aftertreatment system comprises a housing defining a first and a second internal volume fluidly isolated from each other. A first aftertreatment leg extends from the first to the second internal volume and includes an oxidation catalyst and a filter. The oxidation catalyst receives exhaust gas from an inlet conduit and the filter emits exhaust gas into the second internal volume. A second aftertreatment leg extends from the second to the first internal volume and includes at least one SCR catalyst disposed offset from the first aftertreatment leg. A decomposition tube is disposed offset from the SCR catalyst and the oxidation catalyst. The decomposition tube is configured to receive the exhaust gas from the second internal volume and communicate it to the inlet of the at least one SCR catalyst. A reductant injection inlet is defined proximate to the inlet of the decomposition tube for reductant insertion.

A lean-burn internal combustion engine and an exhaust aftertreatment system having an oxidation catalyst are described. A controller determines a fueling rate and a mass flowrate of the exhaust gas feedstream. An inlet temperature of the exhaust gas feedstream upstream of the oxidation catalyst is determined via the first temperature sensor, and an in-use outlet temperature of the exhaust gas feedstream is determined downstream of the oxidation catalyst via the second temperature sensor. An expected outlet temperature from the oxidation catalyst is determined based upon the inlet temperature, the fueling rate, and the mass flowrate of the exhaust gas feedstream. The oxidation catalyst is evaluated based upon the expected outlet temperature and the in-use outlet temperature.

An aftertreatment system for treating an exhaust gas comprises an exhaust conduit, a preheating oxidation catalyst, a primary oxidation catalyst disposed downstream of the preheating oxidation catalyst, and a selective catalytic reduction system disposed in the exhaust conduit downstream of the primary oxidation catalyst. A controller is configured to determine a temperature of an exhaust gas at an inlet of the selective catalytic reduction system. In response to the temperature being below a threshold temperature, the controller generates a hydrocarbon insertion signal configured to cause hydrocarbons to be inserted into or upstream of the preheating oxidation catalyst so as to increase a temperature of the exhaust gas to above the threshold temperature.

An oxidation catalyst for treating an exhaust gas produced by a diesel engine comprises a catalytic region and a substrate, wherein the catalytic region comprises a catalytic material comprising: bismuth (Bi) or an oxide thereof; a Group 8 metal or an oxide thereof; a platinum group metal (PGM) selected from the group consisting of (i) platinum (Pt), (ii) palladium (Pd) and (iii) platinum (Pt) and palladium (Pd); and a support material, which comprises alumina, silica, a mixed oxide of alumina and a refractory oxide, a mixed oxide of silica and a refractory oxide, a composite oxide of alumina and a refractory oxide, a composite oxide of silica and a refractory oxide, alumina doped with a refractory oxide or silica doped with a refractory oxide.

Engine systems and methods use a dual air injection approach to control exhaust reactions and to maintain temperatures below a maximum limit of exhaust system components during engine enrichment operation conditions. Dual air injectors are disposed in the exhaust system with one upstream from, and another downstream from, the catalytic converter. Providing air injection before and/or after the converter helps convert all HC, CO, and PM emissions while keeping the catalyst temperature below the catalyst protection temperature limit. Air injection quantity may be controlled and diagnosed by monitoring the temperatures before and after the catalytic converter. The catalytic converter may be a three-way catalytic converter for lower cost or a downstream two-way catalytic converter may be added if further emission reduction is necessary.

A mixing conduit for use within an exhaust treatment system of a work vehicle. The mixing conduit is configured to receive engine exhaust and a mixture of engine exhaust and reductant. The mixing conduit includes an outer tube and an inner tube within the outer tube. Each tube extends lengthwise from upstream ends to downstream ends of the inner and outer tubes, respectively. The inner tube includes an exterior surface, and the outer tube includes an interior surface. The inner tube defines an inner flowpath within the inner tube. The outer tube and inner tube also define an outer flowpath radially between the exterior surface of the inner tube and the interior surface of the outer tube. The mixing conduit further includes one or more swirler vanes extending radially between the exterior surface of the inner tube and the interior surface of the outer tube and within the outer flowpath.

A system for providing microwave energy to aftertreatment devices that treat the exhaust of an internal combustion engine. The system has a microwave generator and a transmission network for delivering the microwaves to one or more of the aftertreatment devices. The transmission network comprises a combination of solid and hollow waveguides. Antenna(s) transmit microwave energy into the working chamber the aftertreatment device(s), with at least one of the devices having antenna(s) capable of distributing microwave energy throughout its chamber.

A system and method for a variable displacement internal combustion engine using different types of pneumatic cylinder springs on skipped working cycles to control engine and aftertreatment system temperatures are described. The system and method may be used to rapidly heat up the aftertreatment system(s) and/or an engine block of the engine following a cold start by using one or more different types of pneumatic cylinder springs during skipped firing opportunities. By rapidly heating the aftertreatment system(s) and/or engine block, noxious emissions such as hydrocarbons, carbon monoxide, NO.sub.x and/or particulates, following cold starts are significantly reduced.

An exhaust aftertreatment system for an internal combustion engine includes an outer casing defining an exhaust flow path for exhaust gases from the internal combustion engine, a selective catalytic reduction unit provided in the exhaust flow path for reducing nitrogen oxides, a urea dosing device for adding urea to the exhaust flow upstream of the selective catalytic reduction unit, and a rotatable mixer device for mixing the urea with exhaust gases upstream of the selective catalytic reduction unit. The exhaust aftertreatment system further comprises an air inlet valve provided upstream of the mixer device for introducing air into the exhaust flow path, and an electric motor arranged for rotating the mixer device to create a suction of air into the exhaust flow path via the air inlet valve.