Urea injection system treating exhaust gases from lean burn engine, comprises air-cooling jacket surrounding injector valve to keep it cool, so that a petrol injection valve may be used

摘要

The dosing unit has an injection valve (14). This has a double-walled valve casing (17) connected to an air compressor (19) for cooling. It blows into the gap (144) between outer- (173) and inner- (172) walls of the casing, cooling at least that section close to the exhaust pipe. An Independent claim is included for the corresponding method of secondary treatment for exhaust gases. Preferred Features: Mounting design in the double-walled casing brings the injection valve outlet close to the passage into the exhaust system. The mounting is funnel-shaped so that the tip of the injector valve (143) is surrounded by an air gap (144). The outer wall of the valve mounting casing is fixed to the wall (41) of the exhaust pipe. The valve axis is normal to the exhaust pipe wall, or is at an acute angle. The mounting is metallic, ceramic or temperature-resistant plastic. The air compressor is an electrically-controlled pump (19), or is driven mechanically from the engine. An air reservoir (20) and non-return valve (21) is included in the air line.