SCR Catalyst Failure Detection via Composite ACN Value
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Solution Overview
Problem
Existing SCR catalyst failure detection methods in internal combustion engines often result in false positives due to reliance on single signals, leading to unnecessary catalyst replacement and potential NOx emissions, as they fail to accurately differentiate between catalyst degradation and operational issues.
Innovation Solution
A system and method utilizing multiple parameters such as ammonia to NOx ratio (ANR), deNOx conversion inefficiency, and NH3 slip indicator to generate a composite ACN value, which, when exceeding a predetermined threshold, indicates SCR catalyst failure, thereby reducing false positives and enhancing detection robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single parameter monitoring is used for SCR catalyst failure detection, then the detection system is simple, but false positives increase and detection accuracy decreases
Solution Approach 1:
The patent combines three separate monitoring parameters (ammonia to NOx ratio, deNOx conversion inefficiency, and NH3 slip indicator) into a unified ACN diagnostic value. This merging approach allows the system to maintain relatively simple implementation while significantly improving detection accuracy by considering multiple factors simultaneously rather than relying on a single parameter that may produce false positives.
2Measurement precision
If multiple parameters are used to generate composite ACN value, then false positives are reduced and detection accuracy improves, but system complexity increases
Solution Approach 1:
The patent introduces an intermediary computational layer that processes three separate sensor signals through a standardized algorithm to produce the ACN diagnostic value. This intermediary approach allows multiple parameters to be integrated without directly increasing hardware complexity, as the combination logic can be implemented through software or control unit processing rather than additional physical components.
3Speed
If single parameter threshold monitoring is used, then the response time is fast, but false alarms occur leading to unnecessary catalyst replacement
Solution Approach 1:
The patent transforms the diagnostic approach from monitoring single parameter thresholds to evaluating a composite ACN value that integrates three parameters. This parameter transformation allows the system to maintain fast response by using real-time sensor data while improving reliability through multi-parameter correlation analysis, where false alarms are reduced because all three parameters must indicate failure conditions simultaneously rather than relying on a single potentially erroneous threshold crossing.
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 use of multiple parameters to calculate a composite ACN value effectively reduces false positives and ensures accurate SCR catalyst failure detection, minimizing unnecessary replacements and maintaining NOx emission reduction efficacy.
Implementation Method 1
a selective catalytic reduction (SCR) process may be implemented to convert the NOx compounds into more neutral compounds, such as diatomic nitrogen, water, or carbon dioxide, with the aid of a catalyst and a reductant
Implementation Method 2
an NH3 sensor positioned relative to the exhaust system to detect an amount of NH3 slip downstream of at least a portion of the SCR catalyst
Implementation Method 3
a NOx sensor positioned relative to the exhaust system and acquiring the ANR value is based on a detected amount of NOx by the NOx sensor
Data Source
AI summary
Implementations of systems and methods for detecting the failure of an selective catalytic reduction (SCR) catalyst may include a controller or one or more circuits for acquiring an ammonia to NOx ratio (ANR) value for exhaust gas flowing through an exhaust system, acquiring a conversion inefficiency value indicative of a conversion inefficiency of the SCR catalyst, acquire an NH3 slip value indicative of an amount of NH3 slip through the exhaust system downstream of the SCR catalyst, calculate a combined ANR/conversion inefficiency/NH3 slip (ACN) value based on the ANR value, conversion inefficiency value, and NH3 slip value, and indicating a failure of the SCR catalyst responsive to the calculated ACN value exceeding a predetermined threshold value.