The use of exhaust gas recirculation (EGR) systems for recirculating a portion of an internal combustion engine's exhaust gas back to cylinders of the engine is known. In gasoline engines, the relatively inert exhaust gas displaces combustible matter in the cylinder and thereby affords for a reduced heat of combustion with the same pressure produced against the piston at lower temperatures. In diesel engines, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. Since NOx formation is a function of temperature, the EGR systems reduce the amount of NOx produced by the engine due to the lower heat of combustion and thus lower temperatures.
The EGR system typically includes a cooler that cools exhaust gas flowing therethrough, thereby further reducing the heat of combustion within a given cylinder. However, cooling of the exhaust gas can result in the formation of carbon-containing deposits on the cooler. Such deposit formation can reduce the efficiency of the cooler by retarding heat transfer from the exhaust gas to the cooler. In addition, deposit formation can restrict the flow of exhaust gas through the EGR system and/or cause an increase in temperature of the EGR system. Therefore, it is not uncommon for the cooler to be replaced during the warranty period and/or lifetime of a motor vehicle with an EGR system. As such, an internal combustion engine having a self-cleaning EGR system and a process for cleaning the EGR system during operation of the internal combustion engine would be desirable.
USPTO Backgrounds
USPTO Backgrounds