Apparatus and method of operating an injector for an exhaust gas aftertreatment apparatus

Abstract

A method for operating an exhaust aftertreatment system injector to prevent coking includes steps of injecting fuel for heating the aftertreatment devices, when not injecting fuel, flowing air to purge and cool the nozzle to prevent carbon deposits when exhaust gas temperature is low, and substantially stop air flow to allow passive heating of the nozzle by the exhaust for oxidation of any accumulated carbon when exhaust temperature is high enough to support oxidation. Preferably, the nozzle has a catalytic material coating to reduce the temperature necessary for oxidation of the coking material.

Description

FIELD OF THE INVENTION[0001]The invention is directed to exhaust gas aftertreatment apparatuses for internal combustion engines and methods for their operation. More particularly, the invention is directed to an apparatus and method for preventing coke fouling of an aftertreatment injector nozzle of an aftertreatment system.BACKGROUND AND SUMMARY OF THE INVENTION[0002]Exhaust gas aftertreatment apparatuses in automotive vehicles are used to convert or remove targeted substances from the exhaust gas. Aftertreatment devices include, for example, diesel oxidation catalysts (DOC), which can remove particulate matter and oxidize carbon monoxide and uncombusted hydrocarbons in the exhaust gas, diesel particulate filters (DPF), which remove particulate matter from the exhaust gas, and selective catalytic reduction (SCR) systems, that inject an ammonia-based reductant in the presence of a catalyst to convert oxides of nitrogen (NOx) to nitrogen gas and water. Certain aftertreatment devices ...

AI Technical Summary

Benefits of technology

[0002]Exhaust gas aftertreatment apparatuses in automotive vehicles are used to convert or remove targeted substances from the exhaust gas. Aftertreatment devices include, for example, diesel oxidation catalysts (DOC), which can remove particulate matter and oxidize carbon monoxide and uncombusted hydrocarbons in the exhaust gas, diesel particulate filters (DPF), which remove particulate matter from the exhaust gas, and selective catalytic reduction (SCR) systems, that inject an ammonia-based reductant in the presence of a catalyst to convert oxides of nitrogen (NOx) to nitrogen gas and water. Certain aftertreatment devices operate only at or above a threshold temperature, for example, the SCR devices. Other devices, such as the DPF, require the regular removal of collected particulate matter from the filter body. One such process, known as regeneration, occurs by oxidation of the collected particulate matter, which requires the filter body to be at an elevated temperature, typically above 600° C.

Problems solved by technology

At engine start up, aftertreatment components may be at or near ambient temperature, which is typically too low for operation of those devices.

In addition, automotive exhaust, and diesel engine exhaust in particular, is not consistently at temperatures high enough for operation of certain exhaust aftertreatment systems on the vehicle, in particular, regeneration of DPFs.

A problem with hydrocarbon injectors is fouling of the injector nozzle from decomposed liquid hydrocarbon, particulate matter, and other residue collecting on the nozzle, called “coking”.

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