System and method for controlling exhaust gas temperatures for

Abstract

A system for adjusting the temperature of the exhaust emissions from an internal combustion engine so that it is at a temperature that maintains one or more catalysts at their effective operating temperature. This has particular application for NOx control from any lean-burn engine. The system includes a heat exchanger that cools the exhaust emissions by forced air from a variable speed fan. The cooled exhaust emissions are directed from the heat exchanger to the catalyst for conversion. The fan speed is controlled to adjust the amount of cooling of the exhaust emissions in response to various input data, such as the temperature of the exhaust emissions at different locations in the exhaust pipe, engine speed, engine load and the catalyst being used. Two or more catalysts can be incorporated at different locations along the exhaust path and have different operating temperatures so as to control the effectiveness of exhaust emissions conversions for increased efficiency and reduced energy consumption. The incorporation of a temperature-controlled catalytic conversion system allows the catalysts to be placed closer to the exhaust manifold, thus reducing cold-start emissions and extending catalyst durability and long-term emissions control for any heat engine application.