Abstract: An exhaust valve downstream of a diesel engine splits exhaust gasses between two catalysts. In one position, most of the exhaust gasses go to a first catalyst, and the remaining exhaust gasses, along with injected reductant go to a second catalyst. In a second position, most of the exhaust gasses go to the second catalyst, and the remaining exhaust gasses, along with injected reductant go to the first catalyst. In this way, a reduced cost system is achieved.

Abstract: A system for effective NOx control in a diesel or other lean burn internal combustion engine is presented. The system includes a urea-based SCR catalyst having an oxidation catalyst coupled upstream of it and an ALNC coupled upstream of the oxidation catalyst. This system configuration results in improved NOx conversion due to faster SCR catalyst warm-up and higher operating temperatures. Additionally, placing the ALNC upstream of the oxidation catalyst prevents hydrocarbon slip into the SCR catalyst at low exhaust gas temperatures. Also, system reliability is improved by adding an auxiliary NOx aftertreatment device.

Abstract: A method for diagnosing degradation in a pair of NOx sensors coupled upstream and downstream of a NOx catalyst is presented. The method is performed when catalyst temperature is such that its NOx conversion efficiency is substantially zero, such as when the catalyst temperature is very low (at cold start) or very high (e.g., following regeneration). Under those conditions, sensor degradation can be diagnosed if the upstream and downstream NOx sensor readings are not substantially the same.

Abstract: A method and a system for improving conversion efficiency of a urea-based SCR catalyst coupled downstream of a diesel or other lean burn engine is presented. The system includes an electrically heated vaporizer unit into which a mixture of reductant and air in injected. The mixture is vaporized in the unit and introduced into the exhaust gas prior to its entering the SCR catalyst. Introducing the reductant mixed with air into the reductant delivery system prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process thus reducing system response delays and improving the device conversion efficiency. The reductant delivery system is further improved by adding a hydrolyzing catalyst to it, and by isolating the reductant and air mixture from the heating element.

Abstract: A method for diagnosing degradation in a pair of NOx sensors coupled upstream and downstream of a NOx catalyst is presented. The method is performed when catalyst temperature is such that its NOx conversion efficiency is substantially zero, such as when the catalyst temperature is very low (at cold start) or very high (e.g., following regeneration). Under those conditions, sensor degradation can be diagnosed if the upstream and downstream NOx sensor readings are not substantially the same.

Abstract: A method and a system for improved reductant delivery to an exhaust gas aftertreatment device for a lean burn internal combustion engine exhaust is presented. The system includes a heated evaporator unit into which a mixture of reductant and air in injected, wherein the mixture is vaporized and introduced into the exhaust gas aftertreatment device. Introducing the reductant mixed with air into the heated evaporator unit prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process due to better reductant distribution thus reducing system response delays and improving conversion efficiency of the exhaust gas aftertreatment device. The reductant delivery system is further improved by adding a catalyst to it, and by preventing the reductant and air mixture from coming into direct contact with the surface of the heating element.

Abstract: A system for effective NOx control in a diesel or other lean burn internal combustion engine is presented. The system includes a urea-based SCR catalyst having an oxidation catalyst coupled upstream of it and an ALNC coupled upstream of the oxidation catalyst. This system configuration results in improved NOx conversion due to faster SCR catalyst warm-up and higher operating temperatures. Additionally, placing the ALNC upstream of the oxidation catalyst prevents hydrocarbon slip into the SCR catalyst at low exhaust gas temperatures. Also, system reliability is improved by adding an auxiliary NOx aftertreatment device.

Abstract: A method for improving NOx conversion efficiency of a lean exhaust gas aftertreatment device by determining an accurate amount of reductant required is presented. The method includes calculating a base reductant injection amount based on a steady state amount of NOx in the engine feedgas and adjusting the base amount to compensate for transient NOx emissions. The method further teaches using an air assist heated reductant delivery system to inject the adjusted base reductant amount into the device, thus further improving NOx conversion efficiency of the device.

Abstract: A method and a system for improved reductant delivery to an exhaust gas aftertreatment device for a lean burn internal combustion engine exhaust are presented. The system includes a heated evaporator unit into which a mixture of reductant and air in injected, wherein the mixture is vaporized and introduced into the exhaust gas aftertreatment device. Introducing the reductant mixed with air into the heated evaporator unit prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process due to better reductant distribution thus reducing system response delays and improving conversion efficiency of the exhaust gas aftertreatment device. The reductant delivery system is further improved by adding a catalyst to it, and by preventing the reductant and air mixture from coming into direct contact with the surface of the heating element.

Abstract: A method and a system for improved reductant delivery to an exhaust gas aftertreatment device for a lean burn internal combustion engine exhaust is presented. The system includes a heated evaporator unit into which a mixture of reductant and air in injected, wherein the mixture is vaporized and introduced into the exhaust gas aftertreatment device. Introducing the reductant mixed with air into the heated evaporator unit prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process due to better reductant distribution thus reducing system response delays and improving conversion efficiency of the exhaust gas aftertreatment device. The reductant delivery system is further improved by adding a catalyst to it, and by preventing the reductant and air mixture from coming into direct contact with the surface of the heating element.

Abstract: An exhaust valve downstream of a diesel engine splits exhaust gasses between two catalysts. In one position, most of the exhaust gasses go to a first catalyst, and the remaining exhaust gasses, along with injected reductant go to a second catalyst. In a second position, most of the exhaust gasses go to the second catalyst, and the remaining exhaust gasses, along with injected reductant go to the first catalyst. In this way, a reduced cost system is achieved.

Abstract: A method is presented for estimating an amount of ammonia stored in a urea-based SCR catalyst based on a dynamic model of the catalyst. The model takes into account chemical and physical properties of the catalyst, such as catalyst volume, the number of available ammonia storage cites, adsorption and desorption dynamics, as well as poisoning, thermal aging, and different catalyst operating temperatures, and generates the estimate based on a measured or estimated amount of NOx in an exhaust gas mixture upstream of the catalyst, an amount of reductant injected into the catalyst to facilitate NOx reduction, and on a measured value of NOx in an exhaust gas mixture downstream of the catalyst. The estimated ammonia storage amount is then used to control the amount of reductant injected into the catalyst to maintain desired ammonia storage amount such that maximum NOx conversion efficiency coupled with minimum ammonia slip are achieved.

Abstract: A method is presented for estimating an amount of ammonia stored in a urea-based SCR catalyst based on a dynamic model of the catalyst. The model takes into account chemical and physical properties of the catalyst, such as catalyst volume, the number of available ammonia storage cites, adsorption and desorption dynamics, as well as sulfur poisoning, thermal aging, and different catalyst operating temperatures, and generates the estimate based on a measured or estimated amount of NOx in an exhaust gas mixture upstream of the catalyst, an amount of reductant injected into the catalyst to facilitate NOx reduction, and on a measured value of NOx in an exhaust gas mixture downstream of the catalyst. The estimated ammonia storage amount is then used to control the amount of reductant injected into the catalyst to maintain desired ammonia storage amount such that maximum NOx conversion efficiency coupled with minimum ammonia slip are achieved.

Abstract: A method and a system for improving conversion efficiency of a urea-based SCR catalyst coupled downstream of a diesel or other lean burn engine is presented. The system includes an electrically heated vaporizer unit into which a mixture of reductant and air in injected. The mixture is vaporized in the unit and introduced into the exhaust gas prior to its entering the SCR catalyst. Introducing the reductant mixed with air into the reductant delivery system prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process thus reducing system response delays and improving the device conversion efficiency. The reductant delivery system is further improved by adding a hydrolyzing catalyst to it, and by isolating the reductant and air mixture from the heating element.

Abstract: A method for controlling a temperature of a heated element of a reductant delivery system for a lean exhaust gas aftertreatment device coupled downstream of an internal combustion engine is presented. The method teaches achieving a desired temperature of a heating element by selecting a control signal to the heating element from a predetermined temperature map based on engine operating conditions, such as exhaust gas temperature, engine speed, load, etc. Therefore, durability of the heating element and its power consumption are improved by, for example, controlling its temperature to prevent overheating, and having the ability to turn the heating element off when the exhaust gas temperatures are sufficiently high.

Abstract: A method and a system for improved reductant delivery to an exhaust gas aftertreatment device for a lean burn internal combustion engine exhaust is presented. The system includes a heated evaporator unit into which a mixture of reductant and air in injected, wherein the mixture is vaporized and introduced into the exhaust gas aftertreatment device. Introducing the reductant mixed with air into the heated evaporator unit prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process due to better reductant distribution thus reducing system response delays and improving conversion efficiency of the exhaust gas aftertreatment device. The reductant delivery system is further improved by adding a catalyst to it, and by preventing the reductant and air mixture from coming into direct contact with the surface of the heating element.

Abstract: A method for improving NOx conversion efficiency of a lean exhaust gas aftertreatment device by determining an accurate amount of reductant required is presented. The method includes calculating a base reductant injection amount based on a steady state amount of NOx in the engine feedgas and adjusting the base amount to compensate for transient NOx emissions. The method further teaches using an air assist heated reductant delivery system to inject the adjusted base reductant amount into the device, thus further improving NOx conversion efficiency of the device.

Abstract: A method is presented for estimating an amount of ammonia stored in a urea-based SCR catalyst based on a dynamic model of the catalyst. The model takes into account chemical and physical properties of the catalyst, such as catalyst volume, the number of available ammonia storage cites, adsorption and desorption dynamics, as well as poisoning, thermal aging, and different catalyst operating temperatures, and generates the estimate based on a measured or estimated amount of NOx in an exhaust gas mixture upstream of the catalyst, an amount of reductant injected into the catalyst to facilitate NOx reduction, and on a measured value of NOx in an exhaust gas mixture downstream of the catalyst. The estimated ammonia storage amount is then used to control the amount of reductant injected into the catalyst to maintain desired ammonia storage amount such that maximum NOx conversion efficiency coupled with minimum ammonia slip are achieved.

Abstract: A diesel engine emission control system uses an upstream oxidation catalyst and a downstream SCR catalyst to reduce NOx in a lean exhaust gas environment. The engine and upstream oxidation catalyst are configured to provide approximately a 1:1 ratio of NO to NO2 entering the downstream catalyst. In this way, the downstream catalyst is insensitive to sulfur contamination, and also has improved overall catalyst NOx conversion efficiency. Degradation of the system is determined when the ratio provided is no longer near the desired 1:1 ratio. This condition is detected using measurements of engine operating conditions such as from a NOx sensor located downstream of the catalysts. Finally, control action to adjust an injected amount of reductant in the exhaust gas based on the actual NO to NO2 ratio upstream of the SCR catalyst and downstream of the oxidation catalyst.

Abstract: A diesel engine emission control system uses an upstream oxidation catalyst and a downstream SCR catalyst to reduce NOx in a lean exhaust gas environment. The engine and upstream oxidation catalyst are configured to provide approximately a 1:1 ratio of NO to NO2 entering the downstream catalyst. In this way, the downstream catalyst is insensitive to sulfur contamination, and also has improved overall catalyst NOx conversion efficiency. Degradation of the system is determined when the ratio provided is no longer near the desired 1:1 ratio. This condition is detected using measurements of engine operating conditions such as from a NOx sensor located downstream of the catalysts. Finally, control action to adjust an injected amount of reductant in the exhaust gas based on the actual NO to NO2 ratio upstream of the SCR catalyst and downstream of the oxidation catalyst.