SCRF Reductant Injection Control via Shrinking Core Model
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Solution Overview
Problem
The degradation of the washcoat in a selective catalytic reduction with filter (SCRF) device reduces its NOx conversion efficacy and physical flow performance, necessitating a system to model soot impact and adjust reductant injection to maintain desirable emissions abatement performance.
Innovation Solution
A method and system that calculates the amount of soot in the SCRF using a processor, determines a shrinking core model, and adjusts reductant injection based on this model to optimize reductant delivery, considering pressure changes and ammonia desorption, ensuring accurate reductant injection and emissions control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reductant injection amount is increased to maintain NOx conversion performance, then emissions abatement performance is improved, but reductant consumption increases and system cost rises
Solution Approach 1:
The system dynamically adjusts the reductant injection amount based on real-time SCRF performance parameters including pressure drop, temperature, and soot load. By continuously monitoring these parameters and modifying reductant delivery accordingly, the system maintains optimal NOx conversion while minimizing unnecessary reductant consumption, thus resolving the contradiction between maintaining performance and reducing substance loss.
Solution Approach 2:
The system implements a feedback control mechanism where sensors monitor SCRF operating conditions (pressure drop, temperature, soot load) and this information is fed back to the control unit. The control unit uses this feedback to adjust reductant injection rates in real-time, ensuring that reductant is injected only when and where needed to maintain NOx conversion performance, thereby reducing overall reductant consumption.
2Reliability
If reductant injection is optimized based on SCRF conditions, then emissions performance is maintained, but system complexity increases due to monitoring and modeling requirements
Solution Approach 1:
The SCRF system performs self-diagnosis and self-adjustment by using its own operating parameters (pressure drop, temperature, soot load) to automatically determine when reductant injection is needed and at what rate. This self-service approach eliminates the need for external complex monitoring systems while maintaining optimal emissions performance, thus reducing overall system complexity.
Solution Approach 2:
The control unit serves multiple functions: it monitors pressure drop, temperature, and soot load; calculates SCRF performance; determines optimal reductant injection rates; and controls the injection system. By consolidating these functions into a single multi-functional control unit, the system achieves optimized emissions performance without proportionally increasing system complexity.
3Quantity of substance
If soot accumulation is allowed to increase, then filter capacity is improved, but flow performance degrades and reductant delivery becomes inefficient
Solution Approach 1:
The system dynamically adapts reductant injection rates based on real-time changes in SCRF flow performance and soot load. As soot accumulates and flow performance degrades, the system automatically adjusts injection parameters to maintain effective NOx conversion despite changing flow conditions, thus resolving the contradiction between filtering capacity and flow performance.
Solution Approach 2:
The system performs preliminary calculations of SCRF performance and predicts future soot accumulation trends based on current operating conditions. By proactively adjusting reductant injection rates before severe flow degradation occurs, the system maintains optimal performance while allowing sufficient soot accumulation for filtration capacity, thus resolving the contradiction between these two parameters.
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
This approach effectively maintains NOx conversion and flow performance by tailoring reductant injection to the current operating conditions of the SCRF, ensuring emissions remain within selected ranges and extending the lifespan of the SCRF device.
Implementation Method 1
A selective catalytic reduction with filter (SCRF) device relies on a catalyst having a washcoat and a gaseous reductant to convert nitrogen oxides (NOx) into nitrogen and water
Implementation Method 2
The SCRF device also includes a soot filter which traps soot that may be entrained in exhaust gases
Implementation Method 3
determining a desorption amount of ammonia in the SCRF
Data Source
AI summary
A method of adjusting reductant injection for a selective catalyst reduction device with a soot filter (SCRF) includes calculating, through a processor, an amount of soot in the SCRF, determining, through the processor, a shrinking core model of the SCRF based on the amount of soot, calculating, with the processor using the shrinking core model, an amount of reductant to inject into the SCRF, and injecting the amount of reductant into the SCRF.