Urea Injection Nozzle Purging System for SCR Clogging Prevention
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Solution Overview
Problem
Clogging of the urea injection nozzle and urea line in internal combustion engines due to high exhaust gas pressure, temperature, and dirt particles, as well as urea crystallization during sudden engine stops, is a persistent issue in selective catalytic reduction systems.
Innovation Solution
A urea injection system that includes a purging line with a purging valve to supply purging air into the urea line and injection nozzle, preventing clogging by flushing the system when urea injection is not in use and recirculating urea to prevent crystallization during engine stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If urea injection is used in the exhaust duct, then nitrogen oxides can be converted into diatomic nitrogen and water, but the injection nozzle and urea line may become clogged due to high exhaust gas pressure, temperature, and dirt particles
Solution Approach 1:
The purging line is connected to the urea line between the valve and the injection nozzle, allowing purging air to be supplied in advance to prevent clogging before it occurs during normal operation. This preliminary action flushes the system periodically to remove dirt particles and prevent crystallization.
Solution Approach 2:
Purging air acts as an intermediary substance that flows through the urea line and injection nozzle to remove harmful deposits. The purging air mediates between the harmful clogging effect and the desired clean state, flushing out dirt particles and preventing crystallization without requiring direct intervention.
2Ease of operation
If the engine is stopped suddenly after emergency stop, then the engine stops operating, but urea may crystallize in the injection nozzle and pipes causing clogging
Solution Approach 1:
The purging line enables preliminary flushing action to be taken before urea crystallization can occur during sudden engine stops. By connecting the purging line between the valve and injection nozzle, the system can rapidly flush out urea to prevent crystallization in the injection nozzle and pipes during emergency stop scenarios.
3Reliability
If the purging line is connected to the urea line near the valve, then the flushing direction is towards the injection nozzle effectively purging the line, but the system complexity increases
Solution Approach 1:
The purging line is segmented into a specific connection point on the urea line between the valve and the injection nozzle. This segmentation allows the purging function to be targeted effectively at the critical section where clogging is most likely to occur, while keeping the overall system configuration relatively simple.
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
Effectively prevents clogging of the urea injection nozzle and line by ensuring continuous purging and recirculation of urea, maintaining system functionality and preventing urea crystallization, even during sudden engine stops.
Implementation Method 1
a purging line for supplying purging air to the urea line, where said purging line is provided with a purging valve for controlling the flow of purging air from said purging line to said urea line
Implementation Method 2
Clogging of the injection nozzle is also problematic when engine have to be stopped suddenly, for example after the emergency stop since urea may crystallize in the injection nozzle and pipes
Data Source
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AI summary
A urea injection system (10) for an internal combustion engine (25), comprising an injection nozzle (1) for injecting urea and air into an exhaust duct (8) of the internal combustion engine (25), a urea inlet (11) connectable to a urea source (12), a urea line (2) for supplying urea from the urea inlet (11) to the injection nozzle (1) and an air line (3) for supplying air to the injection nozzle (1). The system (10) further comprises a purging line (14) for supplying purging air to the urea line (2), which purging line (14) is provided with a purging valve (4) for controlling the flow of purging air from the purging line (14) to the urea line (2).