Method and system for reducing particulate emissions

Abstract

The present invention relates to methods and systems for reducing particulate emissions. Methods and systems are provided for filtering particulate matter in an exhaust passage of an engine system. In one example, a method may include directing engine exhaust to an exhaust particulate filter during cold start conditions including an engine temperature less than a threshold engine temperature, and directing engine exhaust to bypass exhaust particulates during warm engine conditions The filter, wherein the warm engine condition includes an engine temperature greater than or equal to a threshold engine temperature, and fuel burning in the engine. In this way, the exhaust particulate filter may be reliably regenerated during engine shutdown events such as DFSO while reducing filter degradation and lowering PM emissions.

Description

technical field [0001] The present invention generally relates to the design and use of engine exhaust systems for reducing particulate emissions from combustion engines. Background technique [0002] Engine combustion using diesel or gasoline fuel can produce particulate matter (PM) such as soot and aerosols that can be emitted into the atmosphere. For emissions compliance, particulate filters such as Diesel Particulate Filters (DPF) and Gasoline Particulate Filters (GPF) are included inline in the engine exhaust stream to filter out exhaust gases before they are released PM. A particulate filter clogged with PM may be regenerated in situ during a deceleration fuel cut off (DFSO) event by supplying excess oxygen to the filter and increasing filter temperature to oxidize PM. One example approach shown by Bidner et al. in US 8,424,295 discloses adding excess oxygen to the particulate filter during engine shutdown conditions and regenerating the particulate filter during at ...

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Problems solved by technology

[0003] However, the inventors herein have recognized potential disadvantages of using the above approach

Oxygen flow to the filter during DFSO or other engine shutdown events can excessively increase filter temperature, leading to premature filter degradation

Additionally, employing strategies to limit DFSO duration to mitigate excessive exhaust particulate filter temperature increases and premature filter degradation can reduce fuel economy and can also reduce drivability

Furthermore, still during short periods of engine operation (eg, during short vehicle trips), the particulate filter temperature may not reach a high enough temperature for regeneration

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