Urea Injection Device Crystallization Prevention via Thermal Control
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Solution Overview
Problem
Urea water solution injection systems in internal combustion engines face issues with crystallization and sticking in the urea water solution injection device, leading to failure and inefficient NOx reduction when the engine is restarted after prolonged inactivity, as existing solutions cannot effectively dissolve crystallized urea or prevent its formation.
Innovation Solution
A urea water solution injection system that circulates engine coolant through the urea water solution injection device and uses a control device with a crystal dissolution control unit to energize the device at a preset amount before engine startup, calculating the crystal dissolving energization time based on engine coolant, outside air, and exhaust gas temperatures to thaw and dissolve crystallized urea, preventing sticking and ensuring proper NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the urea water solution injection device is fully opened during emptying operation, then the urea water solution remaining in piping is returned to tank, but the device is heated to high temperatures and subsequent cooling causes urea water solution to freeze and crystallize
Solution Approach 1:
The patent applies preliminary action by performing a thawing operation before the emptying operation. The control device detects crystallization state and activates a heater to thaw the urea water solution in advance, preventing crystallization during the subsequent emptying operation when the device would otherwise be exposed to high temperatures and subsequent cooling.
2Temperature
If the engine is stopped after high temperature exhaust gas passes through the injection device, then the device cools down, but the urea water solution inside freezes and crystallizes
Solution Approach 1:
The control device performs preliminary detection of crystallization state before the cooling process occurs, and activates the heater in advance to maintain the urea water solution above freezing temperature during the natural cooling that occurs after engine stop.
Solution Approach 2:
The patent employs feedback by using a sensor to detect the crystallization state of urea water solution and feeding this information back to the control device, which then adjusts the heater operation accordingly to prevent or resolve crystallization issues.
3Reliability
If crystallized urea forms in the injection device, then the needle becomes stuck and cannot move, but energizing the device to dissolve crystals may cause improper operation if timing is incorrect
Solution Approach 1:
The control device performs preliminary detection of crystallization state and determines the appropriate timing for energization. By detecting crystallization before it causes needle sticking, the system can apply heat at the optimal moment to dissolve crystals without interfering with proper injection operation.
Solution Approach 2:
The sensor provides feedback on crystallization state, enabling the control device to make intelligent decisions about when to activate the heater, ensuring that energization occurs only when crystals are present and would cause problems, not during normal injection operation.
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
The system effectively dissolves crystallized urea before engine startup, preventing device sticking and ensuring continuous NOx reduction by determining the sticking state and adjusting energization times, thereby preventing erroneous device failure and maintaining system functionality.
Implementation Method 1
an engine coolant is circulated through the urea water solution injection device to prevent the freezing of the urea water solution
Implementation Method 2
a crystal dissolution control unit for performing a crystal dissolution control of the urea water solution injection device by energizing at a preset amount of energization
Data Source
AI summary
A urea water solution injection system includes a urea water solution injection device for spraying a urea water solution into a portion of an exhaust passageway upstream of a selective catalytic reduction catalyst device, to reduce NOx in exhaust gas discharged from an internal combustion engine. Engine coolant is circulated through the urea water solution injection device to prevent freezing of the urea water solution. A crystal dissolution control unit performs crystal dissolution control on the urea water solution injection device by energizing at a preset amount of energization at a state where a urea water solution supply pump for supplying a urea water solution to the urea water solution injection device is kept stopped, and the crystal dissolution control unit performs the crystal dissolution control for a crystal dissolving energization time calculated in advance, after the engine is started but before a urea water solution is supplied.