SCR Transient Compensation Control for NOx Efficiency
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Solution Overview
Problem
Selective catalytic reduction (SCR) aftertreatment systems face challenges in managing transient events such as temperature and exhaust flow rate changes, which can lead to undesirable operations and reduced NOx conversion efficiency due to variations in NH3 storage and NOx composition.
Innovation Solution
A method and system that utilize a controller with an NH3 target module, transient adjustment module, and dosing control module to detect transient events and adjust reductant dosing accordingly, ensuring optimal NOx reduction by interpreting reductant targets and providing actuator adjustments to maintain efficient SCR catalyst operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transient events occur in SCR catalyst operation, then temperature and flow rate changes happen, but NOx conversion efficiency decreases and NH3 storage becomes uncontrolled
Solution Approach 1:
The controller detects transient events (temperature changes, flow rate changes) before they significantly impact catalyst performance and proactively adjusts the reductant dosing rate. By anticipating the needs of the SCR catalyst during transient conditions, the system maintains optimal NH3 storage levels and NOx conversion efficiency without waiting for performance degradation to occur.
Solution Approach 2:
The system continuously monitors catalyst temperature, exhaust flow rate, and NOx conversion efficiency, using this feedback to dynamically adjust the reductant dosing rate. This closed-loop control ensures that the NH3 storage level is maintained within optimal ranges even during transient events, resolving the contradiction between maintaining stability and adapting to changing conditions.
2Reliability
If reductant dosing is increased to maintain NH3 storage during transient events, then NOx conversion efficiency improves, but NH3 slip increases
Solution Approach 1:
The system dynamically adjusts the reductant dosing rate based on real-time detection of transient events and current catalyst conditions. Rather than using fixed dosing strategies, the controller modulates the dosing rate to match the instantaneous needs of the SCR catalyst, increasing dosing only when and where needed to maintain NOx conversion efficiency without excessive NH3 storage that would lead to slip.
3Reliability
If transient compensation control is implemented, then NOx conversion efficiency improves, but system complexity increases
Solution Approach 1:
The controller integrates multiple functions into a single device: it detects transient events (temperature changes, flow rate changes), calculates optimal dosing rates, and controls the reductant dosing valve. By consolidating these functions in one multi-functional control unit, the system achieves improved NOx conversion efficiency during transient events without proportionally increasing overall system complexity.
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 compensates for transient events, improving NOx conversion efficiency and reducing NH3 slip, thereby enhancing the overall performance of SCR aftertreatment systems by dynamically adjusting reductant dosing based on real-time catalyst conditions.
Implementation Method 1
An SCR catalyst is a dynamic component that adsorbs reductant (e.g. NH3) and NOx from the exhaust gas
Implementation Method 2
reacts the reductant with the NOx to reduce the NOx
Data Source
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AI summary
A system includes an internal combustion engine, an exhaust conduit fluidly coupled to the internal combustion engine and an SCR catalyst, and a reductant doser operationally coupled to the exhaust conduit at a position upstream of the SCR catalyst. The reductant doser is responsive to a reductant doser command. The system includes a controller having a number of modules functionally structured to execute operations to compensate for transient operation of the system. An NH3 target module interprets a reductant amount target that is a target amount of reductant in the exhaust conduit at a position upstream of the SCR catalyst. A transient adjustment module detects a transient event in the SCR catalyst and provides an adjusted reductant amount target in response to the transient event and the reductant amount target. A dosing control module provides the reductant doser command in response to the adjusted reductant amount target.