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Low temperature emission control

一种排汽缸、放热反应的技术，应用在发动机的系统领域，能够解决劣化反应效率、慢起燃、加速等问题

Inactive Publication Date: 2008-11-26
FORD GLOBAL TECH LLC
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, in some operating conditions, the LNT is placed too far downstream from the engine (resulting in slower light-off) or the LNT is placed too close to the engine (resulting in degraded acceleration)
Furthermore, even though a balance can be achieved between these extremes where the best efficiency region of the LNT is utilized as much as possible (e.g. the temperature is maintained between approximately 300°C and 500°C), there may also be a region of low temperature where the LNT can be used, but has degraded reaction efficiency during release and reduction

Method used

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Embodiment Construction

[0016] Lean NOx traps are effective for treating NOx emissions from lean burn gasoline or diesel engines at temperatures above about 300°C. However, due to incomplete purge, reduction in NOx conversion efficiency during rich purge, and NO to NO 2 With low conversion rates, the efficiency of the trap decreases at temperatures below 300 °C. In one embodiment, it is proposed to enable more complete purging of the trap at temperatures below 300°C by locally generating an exotherm on the LNT during a rich purge. This can be achieved in a number of ways, such as by providing a reducing agent (e.g., CO, H 2 or HC) and some oxygen (O 2 ) mixtures. In one example, the provided O 2 The level of is less than that required to oxidize all reductants, so the overall mixture is net rich (eg, between 7% and 30%). However, O on the LNT 2 The reaction with some reducing agents generates heat to temporarily and locally raise the LNT temperature and improve the efficiency of the purge. The...

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Abstract

A method of controlling an engine having a lean NOx trap in the exhaust is described. The method comprises during a first mode, at a first temperature, storing NOx at a lean condition and then purging stored NOx from the NOx trap at a rich condition without concurrently supplying oxygen to the trap during the purging and during a second mode, at a second, lower temperature, storing NOx at a lean condition and then purging stored NOx from the NOx, where an exothermic reaction is generated to temporarily raise the temperature of the trap by supplying oxygen and reductants with an overall rich mixture to the trap during the purging.

Description

technical field [0001] The present invention generally relates to a method of controlling an engine having a lean NOx trap in the exhaust and a system for the engine. Background technique [0002] Catalytic converters, such as lean NOx traps (LNTs), may be used to reduce NOx emissions, such as from engines that may operate with an air-fuel ratio leaner than stoichiometry. The performance of LNTs to store, release, and reduce NOx can be affected by various operating conditions including temperature. Specifically, at lower temperature ranges, LNTs may exhibit degraded storage, release, and / or reduction. Accordingly, various approaches have been used to position the LNT at an optimal location along the exhaust path to, for example, balance the need for fast light-off for operation from cold start, and to reduce over-temperature operation during periods of high load. [0003] However, in some operating conditions, the LNT is placed too far downstream of the engine (resulting i...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): F01N3/08F01N3/22B01D53/34
CPCF01N3/0842F02D41/0275F01N3/0814Y02T10/24F01N13/04F02D41/0082Y02T10/26F02D41/3017F02D41/025Y02T10/22F01N13/011Y02T10/12F01N3/0871F01N9/002
Inventor 夏恩·埃尔沃特詹森·亚伦·卢佩斯库约瑟夫·罗伯特·泰斯戈皮昌德拉·苏尼拉
Owner FORD GLOBAL TECH LLC