NOx Sensor Oxygen Correction for Engine Exhaust
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Solution Overview
Problem
Conventional exhaust aftertreatment systems for internal combustion engines rely on physical oxygen sensors to estimate NOx concentrations, increasing system costs and reliability issues due to sensor malfunction.
Innovation Solution
The system uses a NOx sensor positioned downstream of the SCR system to measure both NOx and oxygen concentrations, allowing for the adjustment of estimated NOx amounts without the need for separate oxygen and NOx sensors, thereby reducing operational and maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a physical oxygen sensor is used to adjust estimated engine NOx amount, then measurement accuracy is improved, but system cost and complexity increase
Solution Approach 1:
The patent combines the oxygen sensing function with the existing NOx sensor by utilizing the electrochemical oxygen reduction reaction that occurs within the NOx sensor structure. This merging eliminates the need for a separate physical oxygen sensor while maintaining the ability to measure oxygen concentration for NOx estimation adjustment.
Solution Approach 2:
The NOx sensor is designed to perform multiple functions: it measures both NOx concentration and oxygen concentration in the exhaust gas. This multi-functionality allows the single sensor to provide all necessary measurement data for engine-out NOx estimation without requiring additional dedicated oxygen sensing components.
2Measurement precision
If a physical oxygen sensor is used to adjust estimated engine NOx amount, then measurement accuracy is improved, but reliability decreases due to sensor malfunction
Solution Approach 1:
By merging the oxygen measurement capability into the existing NOx sensor, the system reduces the total number of sensors that can potentially fail. The shared sensor structure means that one robust sensor performs dual measurement functions, improving overall system reliability compared to having multiple separate sensors.
Solution Approach 2:
The NOx sensor utilizes its own electrochemical reaction mechanism (oxygen reduction) to generate the signal needed for both NOx and oxygen measurement. This self-service approach allows the sensor to derive oxygen concentration information from its normal operating reactions without requiring additional measurement infrastructure.
3Measurement precision
If separate oxygen sensor and NOx sensor are used, then measurement accuracy is improved, but operational and maintenance costs increase
Solution Approach 1:
The patent merges the functions of separate oxygen sensing and NOx sensing into a single integrated NOx sensor system. This consolidation reduces component count, simplifies manufacturing, and lowers both initial system cost and ongoing maintenance expenses while maintaining the ability to measure both gases accurately.
Solution Approach 2:
The single NOx sensor is designed with universal sensing capabilities that allow it to measure both NOx and oxygen concentrations. This multi-functional design eliminates the need for multiple specialized sensors, directly reducing hardware costs and simplifying the overall measurement system architecture.
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 provides accurate NOx adjustment and reduces system complexity, ensuring compliance with emission regulations while minimizing sensor-related failures and costs.
Implementation Method 1
a first amount of oxygen in the exhaust gas downstream of the SCR system
Implementation Method 2
a SCR system including at least one catalyst configured to decompose constituents of an exhaust gas flowing through the aftertreatment system
Data Source
AI summary
An aftertreatment system comprises a SCR system including at least one catalyst. A NOx sensor is positioned downstream of the SCR system. A controller is configured to determine an estimated engine NOx amount in the exhaust gas produced by an engine fluidly coupled to the aftertreatment system. The controller interprets an output value indicative of a first amount of oxygen in the exhaust gas downstream of the SCR system. The controller determines an adjusted engine NOx amount in response to the output value. A NOx sensor is positioned downstream of the selective catalytic reduction system and communicatively coupled to the controller. The NOx sensor is structured to provide the output value.