NOx Sensor Scale Factor Diagnosis Using Constant-NOx Exhaust Flow
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Solution Overview
Problem
Existing NOx sensors in exhaust gas aftertreatment systems (EATS) face challenges in reliably diagnosing their performance, particularly in determining scale factors, which affects the functionality and environmental impact of the EATS.
Innovation Solution
A method involving operating the internal combustion engine (ICE) at a constant NOx flow, dosing varying amounts of reductant, and using calculation schemes to determine the scale factor of NOx sensors based on measurement data and predefined conversion ratios, enabling accurate assessment of sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diagnosis scheme is applied to determine the state of NOx sensors by stepped raising of NOx concentrations, then the ability to diagnose sensor performance is improved, but the complexity of the diagnostic process increases
Solution Approach 1:
The patent changes the operational parameters of the engine to maintain constant NOx flow during sensor diagnosis, rather than stepped raising of NOx concentrations. This allows scale factor determination through reductant dosage variations while keeping NOx flow constant, simplifying the diagnostic process while maintaining reliability
Solution Approach 2:
The patent creates a simplified model of the diagnostic process by using calculation schemes that compute scale factors from measurement data and predefined conversion ratios, rather than requiring complex stepped NOx concentration raising procedures
2Use of energy by moving object
If the EATS operates at elevated combustion temperatures to achieve high efficiency, then energy conversion efficiency is improved, but NOx emissions increase
Solution Approach 1:
The patent converts the harmful NOx emissions generated at high combustion temperatures into a useful diagnostic tool. By maintaining constant NOx flow and using reductant dosage variations, the system determines sensor scale factors that ensure accurate NOx measurement and control, turning the presence of NOx from a problem into an opportunity for sensor validation
Solution Approach 2:
The patent changes the operational approach by maintaining constant NOx flow during diagnosis rather than varying it, and uses reductant dosage as the varying parameter instead. This allows accurate sensor characterization under high-temperature operating conditions without changing the fundamental high-efficiency combustion process
3Object-generated harmful factors
If reductant is dosed into the exhaust system to reduce NOx emissions, then NOx conversion is improved, but the complexity of reductant dosing control increases
Solution Approach 1:
The patent uses feedback from NOx sensor measurements combined with predefined conversion ratios to determine scale factors. This feedback mechanism allows the system to characterize sensor performance and adjust reductant dosing control based on actual sensor readings, improving both emissions reduction and control accuracy
Solution Approach 2:
The patent uses predefined conversion ratios as fixed parameters that simplify the reductant dosing control. By establishing known conversion relationships between reductant dosage and NOx reduction, the system reduces the complexity of controlling reductant injection while maintaining effective NOx emissions reduction
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 reliable and efficient means to identify and potentially correct NOx sensor errors, ensuring optimal EATS operation and compliance with legal emission standards.
Implementation Method 1
the ammonia (NH3) may then react with the NOx-molecules to achieve the above desired conversion of the NOx-molecules into e.g. nitrogen and water
Implementation Method 2
a reductant dosing system usually includes a reductant injector which creates a spray of reductant (e.g. a mixture of urea and water)
Implementation Method 3
Due to the high temperature of the exhaust gases, the urea will thermally decompose into ammonia and carbon dioxide (CO2)
Data Source
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AI summary
The present disclosure generally relates to a computer implemented method that has been implemented with the intention to performing sensor analysis in an exhaust gas aftertreatment system (EATS) (204) coupled downstream of an internal combustion engine (ICE) (202). The disclosed methodology is specifically adapted for determining a scale factor for a NOx sensor (214) that is arranged downstream of a position (207) where an amount of a reductant is injected into exhaust gases from the ICE. The present disclosure also relates to a corresponding engine system (200) and a computer program product.