Purge system for reductant delivery unit for a selective catalytic reduction system

摘要

A purge procedure which is part of an injector, that may be used as part of a reductant delivery unit (RDU), where the RDU is part of a selective catalytic reduction system for injecting diesel exhaust fluid into an exhaust system, to control exhaust emissions. The RDU delivers a reductant carrier to the engine exhaust system. The purge process includes a control strategy to improve the quality of the purge cycle (i.e., increase the amount of fluid evacuated). The sequence of the purge event is adjusted in order to generate a strong vacuum in the fluid supply line and the injector—this enhances the efficiency of the purge by increasing the initial flow rates through the injector. However, upon opening the injector, the pressure inside the fluid path increases to a level just below the ambient pressure outside the injector, therefore the gas flow rate is substantially reduced.

主权项

1. An apparatus, comprising:
a pumping mechanism; an injector in fluid communication with the pumping mechanism, the injector including a valve portion movable between an open position and a closed position; and an injector driver constructed and arranged to cyclically control the valve portion during a single purge event 1) to cause the valve portion to move to the closed position while the pumping mechanism generates a vacuum, and 2) to cause the valve portion to move to the open position while the injector is under vacuum so that fluid is directed away from the injector.