Abstract:
The present invention is particularly applicable to lean burn engines that produce exhaust containing insufficient amounts of unburned hydrocarbons to satisfactorily reduce NOx emissions without undermining engine performance. In the exhaust purification system (10), ethanol or another suitable hydrocarbon (19) is injected into the exhaust stream at an appropriate location between the engine and the catalytic converter (12). A deNOx catalytic converter (22, 122, 222) is positioned within the exhaust downstream from the ethanol injection point. The combination engine application, ethanol injection and suitable deNOx catalyst combine to reduce NOx to satisfactory levels without producing significant amounts of undesirable secondary nitrogen containing compounds. An oxidation catalytic converter (24, 124, 224) is positioned in the exhaust downstream from the deNOx catalytic converter (22, 122, 222). The oxidation catalyst serves to convert any remaining unburned hydrocarbons (19) into carbon dioxide and water. At the same time, only small amounts of secondary nitrogen compounds are converted back into NOx compounds upon passage through the oxidation catalyst. The end result being an overall reduction in both HC and NOx compounds particularly for lean burn engines to satisfactory levels.
Abstract:
The present invention is particularly well suited for purifying exhaust from relatively large lean burn diesel engines. A computer controlled injector (20) intermittently injects an optimal amount of NOx reducing fluid into the exhaust passageway (11) from the engine (12). The optimal amount corresponds to an amount that will achieve optimal NOx reduction rates for the given engine operating condition and exhaust temperature. A computer (16) periodically senses the engine operating condition and the exhaust temperature, and calculates the appropriate injection amount. With appropriate deNOx and oxidation catalysts located downstream from the injector (20), the exhaust purification system (10) of the present invention has the ability to greatly reduce NOx content of the exhaust while maintaining HC emissions at acceptable levels.
Abstract:
A catalytic converter exhaust section (10, 50) comprises a first mounting plate (11, 51), a second mounting plate (12, 52), a hollow cylindrically shaped metallic tube (14, 54) and a plurality of substantially identical metallic catalytic converter substrates (13, 53) arranged in a honeycomb pattern. Each of the catalytic converter substrates (13, 53) has a regular hexagonal cross section (30) and an inlet end separated from an outlet end by six planar walls (31). The metallic substrates (13, 53) are attached in parallel to form a compound heneycomb cross section (30) with an inlet side, an outlet side, and an outer border defined by a portion of the planar walls (31). The compound heneycomb cross section (30) is affixed within the tube (14, 54) between the first mounting plate (11, 51) and the second mounting plate (12, 52). The individual substrates (13, 53) are coated with an appropriate catalyst for treatment of a particular exhaust component. The present invention finds particular applicability to treating exhaust from relatively large internal combustion engines that require a catalytic converter cross section larger than that currently possible with monolithic catalytic converter substrates.