Urea Injection Systems Wash Cycles

A method comprising:

• providing a system configured to selectably provide urea solution to a first inlet of a blending chamber and selectably provide pressurized gas to a second inlet of the blending chamber;
• operating the system to provide urea solution to the first inlet, provide gas to the second inlet, and output a combined flow of pressurized gas and urea solution from the blending chamber;
• monitoring pressure of the combined flow at a location downstream from the first inlet and the second inlet;
• turning off the gas flow when the monitored pressure is below a first value;
• providing urea solution to the first inlet with the gas flow off when the monitored pressure is below a second value effective to fill at least a portion of the blending chamber with urea solution;
• and
• turning on the gas flow to expel urea solution from the blending chamber.

A method comprising:

• providing an SCR urea injection system configured to provide urea solution to a first inlet of a blending chamber and provide pressurized gas to a second inlet of the blending chamber;
• operating the system to provide urea solution to the first inlet, provide pressurized gas to the second inlet, and provide a combined flow of pressurized gas and urea solution from the blending chamber to an SCR catalyst;
• initiating a wash cycle based upon pressure of the combined flow meeting a predetermined pressure criterion and a timer meeting a predetermined time criterion, the wash cycle including providing urea solution to the first inlet with the gas flow off, and turning on the gas flow to expel urea solution from the blending chamber;
• and
• resuming the operating the system to provide urea solution to the first inlet, provide pressurized gas to the second inlet, and provide the combined flow of pressurized gas and urea solution from the blending chamber to the SCR catalyst.