Reductant delivery unit for selective catalytic reduction

A reductant delivery system for selective catalytic reduction (SCR) after-treatment for vehicles, the reductant delivery system comprising:

• an exhaust pipe defining a portion of an exhaust gas flow path upstream of a SCR catalytic converter,
• a solenoid fluid injector associated with the exhaust pipe, the fluid injector having a fluid inlet and a fluid outlet, the fluid inlet being constructed and arranged to receive a source of urea solution and the fluid outlet communicating directly with the exhaust flow path so as to control injection of urea solution into the exhaust flow path, and
• an interface between the exhaust pipe and the injector, the interface including a gasket constructed and arranged to seal exhaust gas in the exhaust pipe, and a non-metallic guide constructed and arranged to support an end of the injector with respect to a boss of the exhaust pipe, the gasket and guide defining a thermal barrier constructed and arranged to decoupled a body of the injector from exposure to heat in the exhaust gas flow path.

A method of heating urea solution in a reductant delivery system for selective catalytic reduction (SCR) after-treatment for vehicles, the system including a fluid injector, having a coil and armature, mounted with respect to an exhaust gas flow path so as to inject urea solution directly into the exhaust gas flow path, and a controller operatively associated with the fluid injector to control operation of the fluid injector, the method comprising:

• determining whether urea solution has frozen within the fluid injector, and
• issuing a command, via the controller, to the fluid injector to actuate the coil thereby delivering electrically generated heat to the fluid injector to melt the urea solution.

A method of preventing boiling of urea solution in a reductant delivery system for selective catalytic reduction (SCR) after-treatment for vehicles, the system including a fluid injector mounted with respect to an exhaust gas flow path so as to inject urea solution directly into the exhaust gas flow path, a controller operatively associated with the fluid injector to control operation of the fluid injector and a pump, operatively associated with the controller, for delivering urea solution to the fluid injector, the method comprising:

• delivering urea solution to the fluid injector via the pump,
• determining whether a diesel particulate regeneration event is occurring, and
• if the event is occurring, ceasing delivery of the urea solution to the fluid injector and controlling the pump to increase pressure of the urea solution in the system above a normal operating pressure to prevent boiling of the urea solution.