Cold-start engine loading for accelerated warming of exhaust aftertreatment system

Abstract

The methods of the present invention are adapted to adjust engine loading during catalyst warm up to accelerate heating of the exhaust aftertreatment system and thereby decrease catalyst light-off times. According to a preferred embodiment of the present invention, the method includes: monitoring the current catalyst temperature; determining if the current catalyst temperature is less than a predetermined minimum catalyst temperature; and, if the current catalyst temperature is less than the predetermined minimum catalyst temperature, increasing the current engine load. The current engine load is increased by activating a reducing agent tank heating device and / or a reducing agent line heating device.

Description

TECHNICAL FIELD[0001]The present invention relates generally to exhaust aftertreatment systems. More particularly, the present invention is drawn to methods for accelerated warming of motor vehicle exhaust aftertreatment systems.BACKGROUND OF THE INVENTION[0002]Almost all conventional motorized vehicles, such as the modern-day automobile, include an exhaust aftertreatment system for mitigating the byproducts generated from operation of an internal combustion engine. Most exhaust aftertreatment systems include a catalytic converter for the reduction and oxidation of exhaust gas emissions, and a muffler assembly or similar device for attenuating noise generated by the exhaust emission process. The catalytic converter is normally placed between the engine exhaust manifold and the muffler of the automobile, but can also be integrated into the muffler assembly.[0003]Catalytic converters normally include a monolith substrate, generally of the ceramic honeycomb or stainless steel foil hone...

AI Technical Summary

Benefits of technology

[0006]The methods of the present invention are adapted to adjust engine loading during catalyst warm up to accelerate heating of the exhaust aftertreatment system and thereby decrease catalyst light-off times. In so doing, overall tailpipe nitrogen oxide emissions generated during engine cold-start are significantly reduced.

[0007]According to one embodiment of the present invention, the method includes: monitoring the current temperature of the catalyst; determining if the current catalyst temperature is less than a predetermined minimum catalyst temperature; and, if the current catalyst temperature is less than the predetermined minimum catalyst temperature, increasing the current engine load. The current engine load is increased in accordance with the present invention by activating a reducing agent tank heating device, a reducing agent line heating device, or both. Adjusting the engine load during cold-start using, for example, the urea tank and line heaters will allow for precise calibration of the catalytic converter warm up cycle.

[0012]According to yet another aspect, the method adjusts activation of the reducing agent tank heating device and / or reducing agent line heating device in response to variations in vehicle operating conditions (e.g., changes in vehicle speed, tractive demands, electric system demands, etc.). Adjusting activation of the reducing agent tank heating device and / or reducing agent line heating device in this manner allows the system to shift engine loading into an optimal zone for catalyst warm-up and light-off.

Problems solved by technology

For example, one of the limitations to using an aqueous urea solution in SCR is that it is subject to freezing.

If the urea solution freezes, it will not function in its desired manner as a reducing agent, nor will it freely flow to the reduction site.

As such, a considerable amount of overall tailpipe hydrocarbon emissions is generated during engine cold-start.

During such time, the emissions-reducing catalysts are largely ineffective because they have not reached the temperature at which significant catalytic activity can be maintained, also known as catalytic “light-off”.

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