Urea Injection Nozzle Crystallization Prevention via Drawing-Back
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Solution Overview
Problem
The urea solution in SCR systems tends to crystallize and clog the injection nozzle when the engine is stopped, leading to faulty injections due to the complex shape of the nozzle, making it difficult to completely draw back the solution and preventing reliable operation upon engine restart.
Innovation Solution
A reduction-causing agent supply device with a controller that operates a drawing-back unit to remove the urea solution from the nozzle while the valve is closed, followed by a compressed gas discharge process to clear any remaining solution, ensuring the nozzle remains free of crystallization and blockages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the injection nozzle is designed with a complex shape to improve injection performance, then the injection efficiency is improved, but the urea solution cannot be completely drawn back and remains in the nozzle, causing crystallization and clogging
Solution Approach 1:
The patent applies preliminary action by performing a drawing-back operation before the engine is restarted. The controller activates the drawing-back pump to suction remaining urea solution from the injection nozzle and supply passage into the collection container, preventing crystallization and clogging before they can occur during storage or shutdown periods.
Solution Approach 2:
The patent extracts the harmful remaining urea solution from the injection system by using the drawing-back pump to remove it from the injection nozzle and supply passage, transferring it to a collection container. This extraction eliminates the source of potential crystallization and clogging problems.
2Loss of energy
If the engine is stopped for extended periods, then fuel consumption is reduced, but the urea solution crystallizes in the injection nozzle, causing faulty injections upon restart
Solution Approach 1:
The system performs a preliminary drawing-back operation when the engine is stopped, actively removing urea solution from the injection nozzle before crystallization can occur during extended shutdown periods. This preliminary maintenance action ensures reliable operation when the engine is restarted after fuel-saving idle periods.
3Reliability
If the drawing-back pump operates continuously to remove all urea solution, then the risk of crystallization is reduced, but the system complexity and energy consumption increase
Solution Approach 1:
The drawing-back pump operates periodically rather than continuously - specifically when the engine is stopped and during maintenance cycles. The controller manages intermittent operation based on engine status and storage duration, reducing system complexity and energy consumption while still preventing crystallization effectively.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively prevents urea solution from remaining in the injection nozzle, preventing crystallization and ensuring reliable urea injection upon engine restart, thereby maintaining the SCR system's functionality.
Implementation Method 1
a drawing-back unit configured to draw back the reduction-causing agent present inside the reduction-causing agent supply passage toward the tank
Implementation Method 2
operate the pumping unit, while the valve of the injection nozzle is closed, to supply the reduction-causing agent into the reduction-causing agent supply passage to compress the gas introduced in the reduction-causing agent supply passage
Implementation Method 3
open the valve of the injection nozzle to discharge the compressed gas into the exhaust pipe through the injection nozzle
Data Source
AI summary
A reduction-causing agent supply device includes a tank to store a reduction-causing agent, a pumping unit to pump the reduction-causing agent, a reduction-causing agent supply passage to supply the reduction-causing agent, an injection nozzle to inject the reduction-causing agent into an exhaust pipe, a drawing-back unit to draw the reduction-causing agent toward the tank, and a controller. After stop of an engine, the controller performs: reduction-causing agent drawing-back process of drawing the reduction-causing agent toward the tank and introducing exhaust gas from the injection nozzle into the reduction-causing agent supply passage; and gas discharge process of supplying the reduction-causing agent to compress the exhaust gas inside the reduction-causing agent supply passage, discharging the compressed exhaust gas from the injection nozzle, and closing a valve of the injection nozzle before the reduction-causing agent reaches the injection nozzle.