Diesel Engine Aftertreatment Control Operation with Waste Heat Recovery

Abstract

A diesel engine exhaust gas aftertreatment system is described. The system may comprise a heat transfer device comprising a first side and a second side; a heater downstream of the first side of the heat transfer device, a filter downstream of the heater; and, an exhaust path downstream of the filter leading to the second side of the heat transfer device, wherein the exhaust path is isolated from an external surface of the filter to inhibit heat transfer from the heated exhaust gas exiting the filter to the external surface of the filter.

Description

BACKGROUND AND SUMMARY[0001]The effectiveness of a diesel particulate filter (DPF) in an exhaust after treatment system for a lean-burn internal combustion engine can be improved by periodically regenerating the particulate filter. Regeneration typically involves elevating the temperature of the particulate filter, thereby combusting adsorbed particulates. While regeneration is exothermic and may produce enough energy to be self-sustaining after initiation, lean-burn internal combustion engines typically have an exhaust gas temperature that is lower than that required to activate regeneration. Thus, many particulate filter devices incorporate heat sources such as catalysts or heaters to initiate the regeneration process. On the other hand, the particulate filter can be damaged at excessive temperatures. For example, catalyst particles incorporated into the particulate filter may sinter (reducing the activity of the catalyst), the structural integrity of the filter element may be dam...

AI Technical Summary

Benefits of technology

The patent text describes a system for improving the effectiveness of a diesel particulate filter in an exhaust after treatment system for a lean-burn internal combustion engine. The system includes a heat transfer device, a heater, a filter, and an exhaust path. The heat transfer device isolates the exhaust path from the external surface of the filter to prevent excessive heat transfer. This system allows for recycling of waste heat from the regeneration process without directly subjecting the particulate filter to the thermal load of the heated exhaust gases, reducing the potential for self-sustained regeneration and degradation of the filter. The system also allows for low-temperature combustion processes that generate less particulate matter, reducing the risk of over-temperature and the need for smaller particulate filters.

Problems solved by technology

On the other hand, the particulate filter can be damaged at excessive temperatures.

For example, catalyst particles incorporated into the particulate filter may sinter (reducing the activity of the catalyst), the structural integrity of the filter element may be damaged, etc.

The inventors herein have recognized that these thermal limitations may force a trade-off between the efficiency and reliability of a particulate filter.

Particulate filter devices that attempt to conserve energy by reusing waste heat from the regeneration reaction to directly heat the particulate filter risk potentially self-sustained reactions, especially without a separate cooling mechanism to manage excessive temperatures.

Alternatively, particulate filter devices that do not recycle waste heat from the regeneration reaction may also lower fuel economy, leading to increased operating costs.

Moreover, additional heat shielding and / or cooling may be used if the temperature of the particulate filter effluent is too high to safely pass to downstream devices, adding to manufacturing and / or maintenance costs.

For example, the after treatment system may permit waste heat from the regeneration to be recycled without directly subjecting the particulate filter to the thermal load of the heated exhaust gases exiting the particulate filter, thereby reducing potential of self-sustained regeneration resulting in over-temperature conditions that may degrade the particulate filter or other components.

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