NOx Adsorber Catalyst Oxygen Storage Diagnosis
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Solution Overview
Problem
Current methods are inadequate for accurately determining the NOx reduction efficiency of a NOx adsorber catalyst, particularly in assessing its oxygen storage capacity, which is crucial for diagnosing its operation and aging.
Innovation Solution
A method and system that monitor the operating temperature of the NOx adsorber catalyst, determine its oxygen storage capacity by analyzing oxygen concentration changes in the exhaust gas, and store this information for mapping catalyst aging, using sensors and a control circuit to execute these steps after desulfation is commanded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensors are used to determine oxygen storage capacity, then the diagnosis can be performed with simple equipment, but the measurement precision is insufficient to accurately determine NOx reduction efficiency
Solution Approach 1:
The diagnosis process is segmented into distinct operational phases: desulfation phase and normal operation phase. During desulfation, the system performs calibration by injecting pure oxygen and measuring the breakthrough curve to determine oxygen storage capacity. During normal operation, the system monitors oxygen concentration differences between inlet and outlet. This segmentation allows precise measurement without requiring complex equipment throughout all operating conditions.
Solution Approach 2:
The system performs preliminary calibration action during the desulfation phase before normal operation begins. By injecting pure oxygen and measuring the breakthrough curve during this preliminary phase, the system establishes baseline oxygen storage capacity values that will be used for subsequent diagnostic calculations during normal operation, enabling accurate measurements without complex continuous monitoring equipment.
2Measurement precision
If the system monitors multiple temperatures and parameters to accurately determine catalyst operating temperature, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The system uses exhaust gas temperature as an intermediary parameter to infer catalyst operating temperature. By monitoring temperatures at strategic locations (exhaust manifold, turbine inlet/outlet) and using these as proxies for catalyst temperature, the system achieves sufficient measurement precision without requiring direct catalyst temperature sensors, thus reducing device complexity while maintaining diagnostic accuracy.
Solution Approach 2:
The system creates a thermal model copy of the exhaust system by monitoring temperatures at key points (exhaust manifold temperature, turbine inlet temperature, turbine outlet temperature) and using these measurements to estimate catalyst operating temperature. This copying approach allows accurate temperature determination without placing sensors directly in the catalyst, simplifying the monitoring system.
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 enables precise diagnosis of the NOx adsorber catalyst's operation and aging, allowing for effective monitoring of its remaining useful life and operational efficiency.
Implementation Method 1
determining an oxygen storage capacity of the catalyst as a function of an oxygen concentration of the exhaust gas entering the catalyst and an oxygen concentration of the exhaust gas exiting the catalyst
Data Source
AI summary
A system and method for diagnosing operation of a NOx adsorber catalyst are disclosed. An operating temperature of the catalyst is monitored, and when it exceeds a catalyst desulfation temperature threshold that occurs when the catalyst undergoes a desulfation event, a control circuit determines an oxygen storage capacity of the catalyst as a function of at least an oxygen concentration of exhaust gas exiting the catalyst. The control circuit may further determine the oxygen storage capacity as a function of an oxygen concentration of exhaust gas entering the catalyst. The control circuit may further determine the oxygen storage capacity as a function of a mass flow rate of fresh air entering the internal combustion engine that produces the exhaust gas. The oxygen storage capacity may be mapped to catalyst aging information such as, for example, a remaining useful life of the catalyst.