Diesel particulate traps

Abstract

A bypass blower provides air for combustion and scavenging purposes to a two-stroke diesel engine having an exhaust port from which an exhaust conduit ducts exhaust materials through a particulate trap and then to the atmosphere. An air atomizing nozzle is provided for introducing atomized supplemental fuel into the exhaust conduit upstream of the trap and a supply of supplemental fuel and compressed air is provided. A microprocessor-based control unit is adapted to operate the bypass blower under a condition of reduced bypass during normal operation of the engine. However, when backpressure in an exhaust conduit rises to a predetermined level due to particulate build-up, the bypass blower setting is changed to increase the amount of bypass of scavenging air in order to reduce the trapped air/fuel ratio and raise the temperature of the exhaust materials. Compressed air and supplemental fuel are then delivered to the nozzle to promote burning of the exhaust materials and regeneration of the respective trap. When either the backpressure in the exhaust conduit falls or the temperature of the trap rises, the engine is returned to normal operation. In one variation, the diesel engine does include a bypass blower, but the trap regeneration temperature is lowered by operating the engine on fuel having an additive which includes one or both of manganese and copper. In a simplified version, only the bypass blower is provided, and this is operated as described above to increase the temperature of the exhaust materials when particlate build-up is detected through increased backpressure, thus initiating regeneration of the trap.