Bypass controlled regeneration of NOx adsorbers

Abstract

In a method and apparatus for regenerating a lean NOx adsorber, the NOx adsorber treats exhaust gases created during the combustion of gaseous fuels in general. A bypass line maintains a target regeneration flow of exhaust gas through the NOx adsorber during regeneration regardless of operating demands on the engine. Closed-loop and open-loop control are employed. The closed-loop control employs sensors that determine properties of the exhaust gas during regeneration, and the controller uses those properties to provide an efficient regeneration cycle. A regeneration map is also provided that uses creation of in-cylinder regeneration conditions for the exhaust gas in combination with in-line regeneration conditions for the exhaust gas.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S) [0001] This application is a continuation of International Application No. PCT / CA2003 / 001467, having an international filing date of Oct. 2, 2003, entitled “Bypass Controlled Regeneration Of NOx Adsorbers”. International Application No. PCT / CA2003 / 001467 claimed priority benefits, in turn, from Canadian Patent Application No. 2,406,386 filed Oct. 2, 2002, and Canadian Patent Application No. 2,422,188 filed Mar. 14, 2003. International Application No. PCT / CA2003 / 001467 is also hereby incorporated by reference herein in its entirety.FIELD OF THE INVENTION [0002] This invention relates to methods and apparatus for regenerating NOx absorbers used in association with internal combustion engines. BACKGROUND OF THE INVENTION [0003] Emissions controls for internal combustion engines are becoming increasingly important in transportation and energy applications. One class of pollutants of concern is oxides of nitrogen (NOx). NOx form during combustion...

AI Technical Summary

Benefits of technology

[0013] The invention is directed to an efficient method and apparatus for regenerating lean NOx adsorbers. A method is disclosed providing a bypass strategy for regenerating lean NOx adsorbers efficiently.

[0051] In another embodiment of the method of operating an internal combustion engine equipped with an aftertreatment system, the regeneration flow is controlled by at least one valve. In a particular embodiment, the regeneration flow is controlled by a bypass valve in a bypass line and an exhaust valve in an exhaust line. For greater control over the regeneration and bypass flows, each one or both of the bypass valve and the exhaust valve can be a variable control valve.

[0077] The bypass valve can be a variable control valve for improved modulation of flow through the by-pass line. In another embodiment the reductant store can be a fuel system of the engine.

Problems solved by technology

Hydrogen is difficult to store and is generally not readily available.

Further, while hydrogen is an excellent reductant, any regeneration process that takes advantage of hydrogen runs the risk of expelling hydrogen with exhaust gas when regeneration is complete.

This is undesirable due to the flammability of hydrogen.

Also, regeneration using hydrogen from a hydrocarbon source consumes a potential fuel.

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