Urea Injection Nozzle Choking Prevention via Pressure Equilibrium
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Solution Overview
Problem
The urea injection nozzle in SCR systems is prone to choking during after-run operations due to crystallization of urea, which can lead to system damage, especially in winter conditions, as existing methods fail to effectively detect and prevent this issue.
Innovation Solution
A method that involves comparing pressures and rates of pressure increase within the supply module with predetermined thresholds to control the opening and closing of the urea injection nozzle, ensuring pressure equilibrium and preventing choking by maintaining optimal nozzle operation, which includes repeated open/close control based on pressure and rate of pressure changes, and stopping after-run operations when conditions are not met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the urea injection nozzle is kept open during after-run operation to withdraw urea, then urea can be withdrawn from the system, but crystallization occurs in the nozzle causing choking
Solution Approach 1:
The urea injection nozzle is controlled to open and close periodically during after-run operation. The nozzle opens for a predetermined time to allow urea withdrawal, then closes to prevent crystallization. This periodic cycling continues until pressure equilibrium is detected, resolving the contradiction between maintaining productivity (urea withdrawal) and reliability (preventing nozzle choking).
2Quantity of substance
If the urea injection nozzle is opened 100% during after-run operation, then urea flow is maximized, but crystallization is generated in the nozzle
Solution Approach 1:
Instead of keeping the nozzle 100% open continuously, the system applies periodic opening/closing control where the nozzle opens for a predetermined time period then closes. This reduces the total exposure time to crystallization-prone conditions while still achieving sufficient urea withdrawal, thereby preventing crystallization damage.
Solution Approach 2:
The system detects pressure equilibrium before crystallization occurs and stops the after-run operation at that point. This preliminary detection and response prevents the harmful crystallization effect from developing in the first place.
3Duration of action of stationary object
If pressure equilibrium is not monitored during after-run operation, then the operation can continue indefinitely, but the urea injection nozzle may become choked without detection
Solution Approach 1:
The supply module incorporates pressure sensors that continuously monitor pressure changes during after-run operation. When pressure equilibrium is detected (indicating urea withdrawal is complete), the system receives feedback and automatically stops the after-run operation. This prevents prolonged operation that would lead to nozzle choking, solving the detection difficulty.
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 urea injection nozzle choking during after-run operations without the need for additional defrosting devices, ensuring system integrity and preventing damage from backward urea flow, even in winter conditions.
Implementation Method 1
comparing pressure within the supply module with a first predetermined pressure (Pa), open controlling the urea injection nozzle when the pressure in the supply module is higher than the first predetermined pressure (Pa) or repeating open/close controlling the urea injection nozzle when the pressure in the supply module is lower than the first predetermined pressure (Pa)
Data Source
AI summary
A method for preventing choking of a urea injection nozzle in after run operation on a SCR system which supplies urea stored in a urea tank through a supply module, a urea injection nozzle and a urea line connecting the supply module and the urea injection nozzle, the method for preventing choking of a urea injection nozzle includes comparing pressure within the supply module with a first predetermined pressure (Pa), open controlling the urea injection nozzle when the pressure in the supply module is higher than the first predetermined pressure (Pa) or repeating open/close controlling the urea injection nozzle when the pressure in the supply module is lower than the first predetermined pressure (Pa), pressure equilibrium which recovers pressure in the supply module and stopping the after run operation when the balancing pressure is completed.