Dynamic SCR NH3 Storage Management for Cold Start Emissions
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Solution Overview
Problem
Active Selective Catalytic Reduction (SCR) systems in heavy vehicles face challenges during cold starts due to insufficient heat for thermolysis and hydrolysis of the liquid reducing agent, leading to reduced NH3 storage and potential NH3 slip, which is exacerbated by stringent emission regulations.
Innovation Solution
A method to increase NH3 storage by modifying the limiting curve and using engine-off air circulation through electric turbines or recirculation means to preheat the SCR, ensuring sufficient NH3 is available for subsequent cold starts without additional NOx storage devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the SCR storage capacity is increased to improve cold start performance, then NH3 availability improves, but NH3 slip risk increases during sudden acceleration
Solution Approach 1:
The SCR target storage is made dynamic by adjusting it as a function of SCR temperature. During cold start, the target storage is increased to maximize NH3 availability when the SCR temperature is low. During sudden acceleration, the target storage is reduced to prevent NH3 slip. This dynamic adjustment allows the system to optimize NH3 storage based on real-time operating conditions, resolving the contradiction between cold start performance and slip prevention.
Solution Approach 2:
The invention changes the parameter of SCR target storage from a fixed value to a variable parameter that depends on SCR temperature and engine operating conditions. By modifying the storage target parameter dynamically, the system can increase NH3 storage during cold start to improve performance while reducing storage during acceleration to prevent slip, thus resolving the technical contradiction.
2Object-affected harmful factors
If additional NOx storage devices (NSC or PNA) are implemented to store NOx during cold start, then emissions compliance improves, but device complexity increases
Solution Approach 1:
The invention makes the existing SCR system self-sufficient for cold start emissions compliance by optimizing its control strategy. Instead of adding external NOx storage devices, the system uses dynamic adjustment of the SCR target storage based on temperature and operating conditions to achieve emissions compliance. This self-service approach resolves the contradiction by meeting regulatory requirements without increasing device complexity.
Solution Approach 2:
The invention makes the SCR system perform multiple functions: it handles both cold start emissions compliance and sudden acceleration slip prevention through dynamic control. By making the SCR system universal in its functionality, the invention eliminates the need for additional dedicated NOx storage devices, thus resolving the contradiction between emissions compliance and device complexity.
3Object-affected harmful factors
If the SCR target storage is reduced to prevent NH3 slip during acceleration, then emissions compliance improves, but cold start performance deteriorates
Solution Approach 1:
The SCR target storage is dynamically adjusted based on engine operating conditions. During acceleration, the target storage is reduced to prevent NH3 slip and maintain emissions compliance. During cold start, the target storage is increased to ensure sufficient NH3 availability for emissions control. This dynamic behavior resolves the contradiction by optimizing NH3 storage for different operating phases.
Solution Approach 2:
The system applies periodic or phase-based control strategies where the SCR target storage is adjusted according to the engine operating phase. During cold start phase, higher storage is maintained; during acceleration phase, storage is reduced. This periodic adjustment resolves the contradiction between NH3 availability and slip control by adapting to the temporal sequence of different operating conditions.
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
Enhances NH3 storage capacity during engine shutdowns, maintaining emissions compliance by optimizing reducing agent hydrolysis and storage, even at cold temperatures, thereby improving durability and reducing NH3 slip.
Implementation Method 1
The NH3 is generated by thermolysis and subsequent hydrolysis of a liquid reducing agent
Implementation Method 2
The NH3 is generated by thermolysis and subsequent hydrolysis of a liquid reducing agent
Implementation Method 3
Internal combustion engine, especially, Diesel type implement active SCR to neutralize NOx produced by the respective internal combustion engines
Data Source
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AI summary
Method for managing an active SCR (Selective Catalytic reduction) of an ATS (After-treatment system), wherein the ATS is connected to an exhaust manifold (EP) of an internal combustion engine (E), the method comprising the step of increasing an NH3 storage (vii) when an engine shut off command is detected (i), such that, said increased NH3 storage is ready for a subsequent engine cold start