SCR System NOx Sensor Position Verification via Oxygen Measurement
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Solution Overview
Problem
Current SCR systems face challenges in verifying whether NOx sensors are correctly positioned in the exhaust system, leading to potential manipulation and inaccurate emissions monitoring, which can result in excessive emissions due to the use of cheaper alternatives.
Innovation Solution
A method where the reducing agent is supplied upstream of the SCR catalyst to measure oxygen content using existing NOx sensors, determining if the sensor is in the intended measuring configuration by comparing the measured oxygen content with a modeled value, allowing for quick and accurate verification of the sensor's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a NOx sensor is used to measure NOx content in the exhaust system, then emissions monitoring is enabled, but the sensor can be manipulated by being unscrewed and positioned outside the exhaust system, leading to inaccurate measurements
Solution Approach 1:
The system uses feedback from the NOx sensor measurements to verify sensor position. By continuously monitoring NOx content and comparing it against expected values based on engine operating conditions and SCR catalyst performance, the system can detect when the sensor has been moved or manipulated. If the measured NOx values deviate significantly from the modeled expected values, the system flags a position verification failure, preventing manipulation while maintaining accurate emissions monitoring.
2Reliability
If additional sensors or components are added to verify sensor position, then manipulation detection improves, but system complexity and cost increase
Solution Approach 1:
The system performs self-verification of sensor position using existing components. The control unit utilizes data already being collected by the NOx sensor, engine sensors, and SCR system parameters to calculate expected NOx values and compare them with actual measurements. This self-service approach verifies sensor position without requiring additional sensors or complex verification hardware, maintaining system simplicity while improving reliability.
Solution Approach 2:
The existing NOx sensor serves multiple functions: it measures actual NOx content for emissions monitoring and simultaneously provides data for verifying its own position through comparison with modeled values. This multi-functionality eliminates the need for separate verification sensors or components, reducing system complexity while enhancing reliability through cross-validation of sensor data.
3Reliability
If the system continuously monitors and verifies sensor position, then manipulation detection improves, but processing time and computational load increase
Solution Approach 1:
The system performs preliminary calculations of expected NOx values based on engine operating conditions and SCR catalyst characteristics before actual measurement comparison. By pre-calculating these reference values and having them ready for immediate comparison with sensor readings, the system minimizes processing time during verification while maintaining continuous monitoring capability. This preliminary preparation enables rapid detection of position manipulation without significant computational delay.
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 a robust and cost-effective solution to ensure NOx sensors are correctly positioned, reducing the risk of manipulation and ensuring compliance with environmental regulations without the need for additional sensors or components.
Implementation Method 1
The method comprises the steps of using the NOx sensor to measure an oxygen content at the sensor's measuring position
Implementation Method 2
SCR (selective catalytic reduction) systems which comprise an SCR catalyst in which said reductant and NOx gas can react and be converted to nitrogen gas and water
Data Source
Figure 1~2a
Figure 2b
Figure 3
AI summary
The invention relates to a method, in an SCR system in which reducing agent is supplied to an exhaust flow upstream of an SCR catalyst (260), for deciding whether a NOx sensor (245; 255) is situated in the exhaust duct (241; 251 ) of an engine (240) for NOx measurement according to an intended measuring configuration. The method comprises the steps of using said NOx sensor (245; 255) to measure an oxygen content (Oxmeas) at the NOx sensor's measuring position, and deciding on the basis of the measured oxygen content (Oxmeas) whether said measuring position corresponds to the intended measuring configuration. The invention relates also to a computer programme product comprising programme code (P) for a computer (200; 210; 500) for implementing a method according to the invention. The invention relates also to an SCR system and a motor vehicle (100, 110) which is equipped with the SCR system.