SCR Aftertreatment Control with Ammonia Sensor Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Feedforward control systems for SCR catalysts in internal combustion engines are unable to respond to unmeasured or unmodeled disturbances, limiting their effectiveness in maximizing fuel economy and reducing emissions.
Innovation Solution
A method for controlling an SCR system using a NOx sensor feedback component, which includes a controller with modules for determining an ammonia reference target, error term, and reductant doser command adjustments based on real-time NOx and ammonia measurements, allowing for rate-based and downstream NOx adjustments to optimize SCR performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feedforward control is used for SCR catalysts, then fuel economy is maximized and system responsiveness is improved, but the system cannot respond to unmeasured or unmodeled disturbances
Solution Approach 1:
The patent implements feedback control by continuously monitoring ammonia slip levels downstream of the SCR catalyst and using this information to adjust reductant dosing rates. The controller compares actual ammonia emissions against target levels and dynamically modifies the reductant dose to maintain optimal SCR performance, enabling the system to respond to unmeasured disturbances while preserving fuel economy benefits.
2Speed
If feedforward control is used for SCR catalysts, then system responsiveness is improved, but the system cannot respond to unmeasured or unmodeled disturbances
Solution Approach 1:
The control system incorporates real-time feedback from ammonia sensors positioned downstream of the SCR catalyst. This feedback loop enables the system to detect and respond to disturbances such as catalyst degradation, temperature variations, and unmodeled emissions events, thereby improving adaptability while maintaining the rapid responsiveness characteristic of feedforward control through dynamic adjustment of reductant dosing.
3Adaptability or versatility
If ammonia sensor feedback control is implemented, then the system can adapt to disturbances, but device complexity increases
Solution Approach 1:
The patent employs ammonia slip sensors downstream of the SCR catalyst to provide feedback on actual emissions performance. The controller processes this feedback information and automatically adjusts reductant dosing to compensate for catalyst degradation and unmeasured disturbances. This feedback mechanism enhances adaptability while the automated control logic manages the complexity by providing real-time adjustments without requiring manual intervention or complex mechanical modifications.
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 enhances the responsiveness and efficiency of the SCR system by enabling it to adapt to disturbances, improving fuel economy and reducing emissions by precisely managing reductant dosing and ammonia levels.
Implementation Method 1
a first selective catalytic reduction (SCR) catalyst (108) fluidly coupled to the exhaust conduit
Implementation Method 2
selective catalytic reduction (SCR) catalysts
Implementation Method 3
an ammonia sensor (122) operationally coupled to the exhaust conduit at a position between the first SCR catalyst (108) and the second SCR catalyst (110)
Data Source
AI summary
An exemplary method includes determining an NH3 reference target in an exhaust conduit between a first SCR catalyst and a second SCR catalyst. The method includes determining a present amount of NH3 in the exhaust conduit between the first SCR catalyst and the second SCR catalyst, and determining an NH3 error term in response to the NH3 reference target and the present amount of NH3. The method further includes determining an amount of NOx downstream of the second SCR catalyst, and adjusting one of the NH3 reference target and a reductant doser command in response to the amount of NOx downstream of the second SCR catalyst. The method further includes providing a reductant doser command in response to the NH3 error term.