Method and system for reducing engine exhaust emissions

Abstract

Methods and systems are provided for addressing engine cold-start emissions while an exhaust catalyst is activated. In one example, a method for improving exhaust emissions may include flowing ionized air into an engine exhaust, downstream of an exhaust catalyst, to oxidize exhaust emissions left untreated by the catalyst. The approach reduces the PM load of the exhaust as well as of a downstream particulate matter filter.

Description

technical field [0001] The present description generally relates to methods and systems for reducing engine cold start exhaust emissions and particulate matter emissions. Background technique [0002] Engine-out cold-start emissions generated prior to ignition of an exhaust system emission control device (eg, a catalytic converter) can account for a majority of total exhaust emissions. Various schemes may be used by the engine control system to expedite reaching the catalyst light-off temperature. For example, expensive electrocatalyst heaters can be used to generate heat. As another example, various combinations of spark timing retard, valve overlap, and increased fuel injection may be used to accelerate catalyst warm-up. [0003] In another approach shown by Shimoda in US Pat. No. 7,331,170, the plasma generator is coupled to the emission control device downstream of the oxidation catalyst and upstream of the diesel particulate filter. The exhaust flow is discharged by ...

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Problems solved by technology

As another example, after the upstream addition of ionized air, the engine may need to run rich to maintain the exhaust catalyst at stoichiometry, thereby degrading fuel economy

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