SCR Nozzle Temperature Control via Reductant Injection
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Solution Overview
Problem
Selective catalytic reduction systems face thermal deformation of reducing agent injection nozzles due to high exhaust gas temperatures, leading to reduced NOx conversion efficiency and potential engine output limitations and regulatory violations.
Innovation Solution
A selective catalytic reduction system with a temperature calculator and controller that monitors and adjusts the reducing agent injection amount and cooling fan speed to maintain the nozzle temperature within safe limits, including increasing the reducing agent injection during engine operation and using an extra cooling fan after engine stoppage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reducing agent injection module is exposed to high temperature exhaust gas during high load operation, then the exhaust gas treatment function is maintained, but the injection nozzle undergoes thermal deformation and nozzle hole blockage
Solution Approach 1:
The system performs preliminary cooling action by increasing reducing agent injection before thermal deformation occurs. The control unit detects high exhaust gas temperature and proactively increases the reducing agent injection amount to cool the injection nozzle, preventing thermal deformation and nozzle hole blockage before they happen.
Solution Approach 2:
The system converts the harmful high temperature exhaust gas into a beneficial cooling mechanism by injecting additional reducing agent. The endothermic evaporation and reaction of the reducing agent absorbs excess heat from the exhaust gas, cooling the injection nozzle while simultaneously maintaining NOx reduction function.
2Temperature
If the reducing agent injection amount is increased to cool the injection nozzle, then the nozzle temperature is reduced, but the engine output power is limited
Solution Approach 1:
The system dynamically adjusts the reducing agent injection amount based on real-time exhaust gas temperature conditions. During high load operation with high exhaust temperature, the injection amount is temporarily increased for cooling, while during normal operation it returns to the stoichiometric ratio for optimal power and emission control, creating a dynamic balance between cooling and power output.
3Temperature
If a cooling fan is added to cool the reducing agent injection module, then the nozzle temperature is controlled, but the device complexity increases
Solution Approach 1:
The system uses the reducing agent itself as the cooling medium, eliminating the need for separate cooling systems like cooling fans or coolant circuits. The reducing agent injection serves dual purposes: maintaining NOx reduction chemistry and cooling the injection nozzle through evaporative and reaction cooling, making the system self-sufficient.
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
Prevents thermal damage to the reducing agent injection module, ensuring stable NOx conversion efficiency and compliance with emission regulations by effectively managing nozzle temperature through real-time monitoring and adaptive control measures.
Implementation Method 1
an injection nozzle of the reducing agent injection module is exposed frequently to the exhaust gas of high temperature in a high load work during hot season, the injection nozzle may be thermally deformed
Implementation Method 2
a proper amount of urea for NOx reduction may not be injected, thereby deteriorating NOx conversion efficiency
Implementation Method 3
a cooling fan installed in a side of the reducing agent injection module and configured to cool the reducing agent injection module
Data Source
Figure 1
Figure 2
Figure 3~4A
AI summary
A selective catalytic reduction system includes a reducing agent injection module installed in an exhaust pipe through which an exhaust gas is discharged from an engine and configured to inject a reducing agent into the exhaust pipe, a temperature calculator configured to calculate a temperature of the reducing agent injection module using temperature-related information of the reducing agent injection module, and a temperature controller configured to control to increase a reducing agent injection amount of the reducing agent injection module when the calculated temperature.